2024-03-28T11:07:05Zhttps://research-repository.st-andrews.ac.uk/oai/requestoai:research-repository.st-andrews.ac.uk:10023/119622019-06-07T15:43:01Zcom_10023_51com_10023_18col_10023_53
2017-10-31T14:14:38Z
urn:hdl:10023/11962
Layered perovskites as cathode materials for IT-SOFC
Satapathy, Akshaya Kumar
Irvine, John T. S.
SUPERGEN
Commonwealth Scholarship Commission in the United Kingdom
T* based La₀.₉Ln₀.₉Sr₀.₂CuO₄ (Ln = Sm & Gd) has been investigated as cathode material for intermediate temperature solid oxide fuel cell using Ce₀.₉Gd₀.₁O₁.₉₅ (GDC) and La₀.₉Sr₀.₁Ga₀.₈Mg₀.₂O₃-δ (LSGM-9182) as the electrolyte material. Both oxides crystallize in tetragonal P4/nmm symmetry. The structural and phase stability has been confirmed up to 800 °C by High temperature XRD studies. The coefficient of thermal expansion (CTE) and oxygen content decrease with decreasing size of the Ln³+ ions from Ln = Sm to Gd. While the decrease in CTE is due to the increasing co-valence of the Ln–O bond, the decrease in electrical conductivity at high temperature is due to the increasing oxide ion vacancies and a bending of the O–Cu–O bonds. The highest value of DC conductivity has been observed for the LSSCu, which showed a metal like temperature dependence. LGSCu showed a semiconductor to metallic temperature dependence of conductivity with a maximum of 25 Scm-¹. From the microstructural characterization and the polarisation resistance measurement of the symmetric cells at temperature ranges from 700 - 800 °C, 900 °C has been chosen as the most suitable sintering temperature and LGSCu has shown the minimum polarization resistance of 0.35 Ωcm² and 0.09 Ωcm² at 800 °C using GDC and LSGM-9182 electrolytes respectively under OCV condition. To improve the ASR of LGSCu, the composite of LGSCu and GDC with varying wt. % of GDC has been optimised and it shows the ASR of 0.12 Ωcm² using GDC as the electrolyte because it enhance the triple phase boundary region. The maximum power density of single-cell SOFCs fabricated with the La₀.₉Ln₀.₉Sr₀.₂CuO₄ (Ln= Sm & Gd) cathodes, La₀.₉Sr₀.₁Ga₀.₈Mg₀.₂O₃-δ (LSGM-9182) electrolyte, and Ni–Ce₀.₉Gd₀.₁O₁.₉₅ cermet anode exhibit 720 and 824 mWcm-² at 800 °C respectively.
The phase pure T* Nd₁.₃₂Ce₀.27Sr₀.₄₁CuO₄-δ (NCSCu) has been synthesized by combustion method and its crystal chemistry, thermal and electrochemical properties, and catalytic activity in SOFC were evaluated using LSGM-9182 as the electrolyte. It shows promising performance and can be used as potential cathode materials for IT-SOFC.
The effect of B-site Ni and Co substitution for Cu on the structural and electrochemical properties of the T* La₀.₉Gd₀.₉Sr₀.₂CuO₄ has been investigated as cathode materials for intermediate temperature solid oxide fuel cells using LSGM-9182 as the electrolyte. At a given temperature, the electrical conductivity gradually increases with increasing Ni content and the CTE gradually decreases. Ni doping has also improved the electrochemical performance.
Sr doped A /A //B₂O₅+δ (A / = Rare Earth, A // = Ba or Sr and B = Transition Metals) layered perovskites improves the electrochemical performance due to the increase in electrical conductivity and smaller size difference between Ln+³ and Sr+². However these layered perovskites suffer from high thermal expansion coefficient (20-23 x 10-6 K-1) which does not match with the state of the art electrolyte materials. B-site transition metal doped layered perovskites of compositions SmBa₀.₅Sr₀.₅Co₂-ₓO₅+δ (M = Cu, Ni, Fe) have been investigated as cathode material for intermediate temperature solid oxide fuel cell using LSGM-9182 as the electrolyte material. Phase purity has been confirmed by XRD technique. The crystal cell parameters have been found out using Rietveld refinement by FULLPROF software. The substitution of Cu, Ni and Fe for Co lowers the CTE of Co-based materials by suppression of the spin state transition of Co³+ which will be highly advantageous for long term SOFC application. The introduction of transition metals exhibit inferior electrochemical performance to pristine cathode using LSGM-9182 as the electrolyte but still shows reasonable power density with advantage of lower CTE value thereby can be explored as promising cathode material for IT-SOFCs.
2017-10-31T14:14:38Z
2017-10-31T14:14:38Z
2015-02
Thesis
http://hdl.handle.net/10023/11962
en
2020-01-02
Thesis restricted in accordance with University regulations. Electronic copy restricted until 2nd January 2020
xxi, 124 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/3622019-07-01T10:05:12Zcom_10023_51com_10023_18col_10023_53
2007-07-06T16:06:27Z
urn:hdl:10023/362
Synthesis and evaluation of β-fluoro-γ-aminobutyric acid enantiomers
Deniau, Gildas
O'Hagan, David
The impact of fluorine in medicinal chemistry is reviewed in the first chapter of
this work and the fluorine gauche effect, which has not been fully exploited in
medicinal chemistry, is also discussed. GABAA and GABAB receptors are then
presented and the synthesis of neurosteroid antagonists acting at GABAA receptors is
reported. The synthesis of such compounds was motivated to explore the mode of action
of neurosteroids at GABA receptors.
The observation that the C-F bond has a strong preference to align gauche to the
C-N+ bond in protonated β-fluoroamines stimulated the enantioselective synthesis of 3-fluoro-GABA enantiomers. This was achieved from L- and D- phenylalanine in six steps
and in an overall yield of 31%. The preferred conformations of 3-fluoro-GABA in
solution are then explored by NMR analysis and ab initio calculations. The biological
evaluation of 3-fluoro-GABA enantiomers on GABA aminotransferase was then investigated and showed that the (R)-enantiomer undergoes HF elimination ten times more rapidly than the (S)-enantiomer, suggesting a preferred binding conformation of GABA on GABA aminotransferase. This study demonstrates that the C-F bond can be used as a chemical probe to reveal the binding conformation of a bioactive amine and this offers exciting prospects for future research.
The synthesis of 3-fluoro-GABA from phenylalanine indicated that amino acids
are practical starting materials for the preparation of β-fluoroamines. This methodology is applied to L-lysine to generate (2R)-fluorohexane-1,6-diamine. The formation of a
diamine of potential interest for catalysis is also observed in this synthesis.
2007-07-06T16:06:27Z
2007-07-06T16:06:27Z
2007
Thesis
http://hdl.handle.net/10023/362
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
xi, 271
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/129272019-03-29T11:18:56Zcom_10023_51com_10023_18col_10023_53
2018-03-13T10:54:33Z
urn:hdl:10023/12927
Magnetic ordering in systems of reduced dimensionality
Purdie, Stuart
The magnetic behaviour of thin films of (111) FCC structures and (0001) corundum structured materials were studied by the mean field analysis and some Monte Carlo simulation. These models were conditioned on a mapping from first principles calculations to the Ising model. The effect of the suggested octopolar reconstruction for the polar (111) surfaces of FCC was also examined.
2018-03-13T10:54:33Z
2018-03-13T10:54:33Z
2005
Thesis
http://hdl.handle.net/10023/12927
en
177 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/17052019-07-01T10:12:36Zcom_10023_51com_10023_18col_10023_53
2011-03-21T12:00:08Z
urn:hdl:10023/1705
Applications of ordered mesoporous metal oxides : energy storage, adsorption, and catalysis
Ren, Yu
Bruce, Peter G.
EaStCHEM
Engineering and Physical Sciences Research Council (EPSRC)
EU
SUPERGEN
Mesoporous metal oxides
Energy storage
Adsorption
Catalysis
Li-ion battery
Rate capability
CO oxidation
The experimental data and results demonstrated here illustrate the preparation and application of mesoporous metal oxides in energy storage, adsorption, and catalysis.
First, a new method of controlling the pore size and wall thickness of mesoporous silica was developed by controlling the calcination temperature. A series of such silica were used as hard templates to prepare the mesoporous metal oxide Co₃O₄.
Using other methods, such as varying the silica template hydrothermal treatment temperature, using colloid silica, varying the materials ratio etc., a series of mesoporous β-MnO₂ with different pore size and wall thickness were prepared. By using these materials it has been possible to explore the influence of pore size and wall thickness on the rate of lithium intercalation into mesoporous electrode.
There is intense interest in lithium intercalation into titanates due to their potential advantages (safety, rate) replacing graphite for new generation Li-ion battery. After the preparation of an ordered 3D mesoporous anatase the lithium intercalation as anode material has been investigated.
To the best of our knowledge, there are no reports of ordered crystalline mesoporous metal oxides with microporous walls. Here, for the first time, the preparation and characterization of three dimensional ordered crystalline mesoporous α-MnO₂ with microporous wall was described, in which K+ and KIT-6 mesoporous silica act to template the micropores and mesopores, respectively. It was used as a cathode material for Li-ion battery. Its adsorption behavior and magnetic property was also surveyed.
Following this we described the preparation and characterization of mesoporous CuO and reduced Cu[subscript(x)]O, and demonstrated their application in NO adsorption and delivery.
Finally a series of crystalline mesoporous metal oxides were prepared and evaluated as catalysts for the CO oxidation.
2011-03-21T12:00:08Z
2011-03-21T12:00:08Z
2010-11-30
Thesis
http://hdl.handle.net/10023/1705
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
116 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/151932019-03-29T11:18:58Zcom_10023_51com_10023_18col_10023_53
2018-07-10T14:20:33Z
urn:hdl:10023/15193
Some studies on the formation and interconversion of iron-sulfur nitrosyl complexes
Blyth, Debra F.
Glidewell, Christopher
Studies on the effect of substituting iron(III) for iron(II) or nitrate for nitrite in the reaction of cysteine with iron(II) salts and nitrite with and without sodium ascorbate present demonstrated the formation of the tetranuclear Na[Fe₄S₃(NO)₇] complex when iron(III) is substituted for iron(II), albeit in smaller yield; but no iron-sulfur-nitrosyl clusters were detected when nitrite was replaced with nitrate. Similarly in the case of reaction of methionine with iron(II) salts and nitrite in the presence of sodium ascorbate, the dinuclear complex Fe₂(SMe)₂(NO)₄ is formed in reduced yield when iron(III) is substituted for iron(II) and no iron-sulfur-nitrosyl complexes are detected when nitrite is replaced with nitrate. The effect of pH on the reactions of cysteine and methionine with iron(II) salts and nitrate, with and without sodium ascorbate present in the case of cysteine, were studied. The cysteine reactions showed that in the presence of sodium ascorbate, the yield of Na[Fe₄S₃(NO)₇] fell slightly as pH was decreased due to formation of the less soluble ascorbic acid from acidification of sodium ascorbate. At very low pH both cysteine reactions with and without sodium ascorbate present did not yield Na[Fe₄S₃(NO)₇] due to the formation of nitric oxide from nitrite, which would rapidly oxidise to give nitrogen dioxide, and to the instability of the Na[Fe₄S₃(NO)₇] complex itself at very low pH. The dinuclear complex Fe₂(SMe)₂(NO)₄ is very stable to conditions of low pH but its formation at very acidic conditions was hindered, again due to the formation of nitric oxide from nitrite. A range of iron-sulfur containing amino acid complexes of the general type [Fe₃o(amino acid)₆(H₂0)₃]X₇, were synthesised and their reactions with nitrite studied. In the presence of sodium ascorbate, when the amino acid is methylcysteine, both [Fe₄S₃(NO)₇]' and Fe₂(SMe)₂(NO)₄ were isolated after reaction with nitrite. However no identified iron-sulfur-nitrosyl complexes could be detected when the amino acid was methionine. In the absence of sodium ascorbate both the methylcysteine and methionine complexes yielded a range of unidentified complexes which infra-red spectroscopy demonstrated absorbed strongly in the nitrosyl stretching region and it was postulated that the species observed were inorganic nitrosyl complexes. FTIR analysis of Fe₄S₄(NO)₄ in the polar coordinating solvents THF, DMF and DMSO demonstrated conversion to [Fe₄S₃(NO)₇]⁻. No such conversion was observed using the solvents diethyl ether or dichloromethane. An intermediate species was observed in THF and DMSO using FTIR spectroscopy which was postulated to be a [Fe(solvent)₆][Fe₄S₄(NO)₄]₂ complex. Another peak observed in the latter stages of the conversion was believed to be that of a dinuclear Fe(SR)₂(NO)₄ type complex. ESR analysis of Fe₄S₄(NO)₄ in THF and DMSO however demonstrated formation of a mononuclear species of type [Fe(NO)₂(X)₂]ⁿ⁺. Thus in the dilute solutions required for ESR analysis, mononuclear species of the type [Fe₂(NO)₂(X)₂]ⁿ⁺ are favoured but in the more concentrated solutions needed for FTIR analysis polynuclear species of the type [Fe₄S₄(NO)₄] are predominant.
2018-07-10T14:20:33Z
2018-07-10T14:20:33Z
1996
Thesis
http://hdl.handle.net/10023/15193
en
170 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/36462019-03-29T11:19:00Zcom_10023_51com_10023_18col_10023_53
2013-06-10T10:47:31Z
urn:hdl:10023/3646
Pyrazolidinones as templates in asymmetric catalysis
Gould, Eoin
Smith, Andrew David
This thesis principally focuses on the development of a novel series of asymmetric iminium ion organocatalysts, based on the pyrazolidin-3-one template. Also described is the development of a novel asymmetric Steglich rearrangement with pyrazolyl carbonates. The pyrazolidin-3-one framework has been identified as a potentially effective new scaffold for iminium ion organocatalysis. The development of a synthetic route to racemic pyrazolidinone
catalysts is outlined which allows for systematic variation of key substituents. The influence of these groups on reactivity and diastereoselectivity in the Diels-Alder reaction of (E)-cinnamaldehyde and cyclopentadiene is described and an optimised catalyst identified.
A method for the resolution of a simple pyrazolidinone precursor was then investigated in order to access an enantioenriched catalyst for asymmetric reaction. Resolution was achieved by amide coupling to a chiral acid, chromatography to separate the subsequent diastereoisomers
and acid cleavage. The initial enantioenriched catalyst gave modest enantioselectivity in the Diels-Alder reaction. The diastereoisomeric intermediates in the resolution process were themselves identified as active and enantioselective iminium ion organocatalysts. In general, one diastereoisomer was superior in terms of enantioselectivity, indicating a ‘matching’ of the two catalyst stereocentres. An optimised asymmetric diastereoisomeric catalyst derived from a trifluoromethyl-substituted pyrazolidinone and Cbz-protected proline gave good diastereo- and enantioselectivities in Diels-Alder reactions with a range of aryl aldehydes. Mechanistic investigations with this
compound then found that fast ring-opening occurs under catalysis conditions creating a new chiral hydrazide which was catalytically active at catalyst loadings as low as 1 mol%.
Also explored was the Steglich rearrangement of structurally related pyrazolyl carbonates.
Rearrangement was observed with a range of Lewis base organocatalysts, with N-heterocyclic carbenes (NHCs) generally superior. Chiral NHCs were also effective in an asymmetric reaction, particularly with methyl substituted pyrazolyl carbonates.
2013-06-10T10:47:31Z
2013-06-10T10:47:31Z
2012
Thesis
http://hdl.handle.net/10023/3646
en
iii, 219
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/186102019-11-27T15:11:38Zcom_10023_51com_10023_18col_10023_53
2019-10-04T13:39:24Z
urn:hdl:10023/18610
Tetra- and penta-vicinally fluorinated cyclohexane ring motifs
Bykova, Tetiana
O'Hagan, David
Organofluorine compounds have had an important influence on the advances in the
healthcare and agricultural industries. Selective substitution with fluorine can produce a
significant impact on the pharmacokinetic properties of bioactive compounds; generally this
is through stereoelectronic effects that the fluorine atom can confer. As such, there is a
continuous interest in the development of novel organofluorine compounds and the
incorporation of fluorine into bioactive compounds and natural products.
The all-cis-1,2,4,5-tetrafluorocyclohexane motifs were the first examples of facially polarised
cyclohexane rings which possess a dipolar nature arising from two 1,3-diaxial C-F bonds. The
fluorine face, which possesses a negative electrostatic profile, along with the positively
polarized methylene hydrogens on the opposite face give a unique facial polarity to this
motif.
These highly polarized fluorinated ring systems present as novel building blocks for use in
drug development and agricultural programs; hence the aim of this study was the
development of functionalised derivatives of these all-cis tetrafluoro-cyclohexanes.
Transformations of previously reported phenyl all-cis-2, 3, 5, 6-tetrafluoro-cyclohexane were
explored in a variety of directions and new pathways towards partially fluorinated
cyclohexanes were investigated. The range of all-cis-tetrafluorocyclohexane motifs
produced, with functional groups attached directly to the fluorinated cyclohexane ring,
varied from methyl substituted all-cis-tetrafluorocyclohexane alcohols, aldehydes, nitriles
and amines to all-cis-tetrafluorocyclohexane amino acid, pentafluoro carboxylic acid and
alcohol derivatives.
These novel derivatives were then used in liquid-phase peptide synthesis, incorporated into
peptidomimetic systems through Ugi multi-component reactions and utilised in the
formation of bis-systems, in order to demonstrate their reactivity and to gain an insight into
their possible intramolecular conformational preferences and supramolecular
arrangements.
2019-10-04T13:39:24Z
2019-10-04T13:39:24Z
2019-06-26
Thesis
http://hdl.handle.net/10023/18610
en
198 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/25852019-07-01T10:10:37Zcom_10023_51com_10023_18col_10023_53
2012-05-04T14:14:52Z
urn:hdl:10023/2585
Towards new catalytic systems for the formation of methyl methacrylate from methyl propanoate
Coetzee, Jacorien
Cole-Hamilton, D. J. (David John)
Lucite International
Methyl methacrylate
Methyl propanoate
Propanoic acid
Methanol dehydrogenation
Aliphatic C-H activation
Irdium PNP pincer complexes
Mixed anhydride complexes
Alpha process
Homogeneous catalysis
Alpha methylenation of esters
The two stage Lucite Alpha Process for the industrial manufacturing of methyl methacrylate (MMA) represents one of the most efficient technologies currently available for the large scale production of this important chemical commodity. The second stage of this process, which involves the condensation of methyl propanoate (MeP) with formaldehyde over a heterogeneous fixed bed catalyst, however, still shows great scope for improvement. Herein the development of a novel homogeneous catalytic system that would promote the condensation of either propanoic acid or MeP with formaldehyde is explored. Since C–C bond forming reactions which proceed via C–H activation pathways typically display high atom efficiency, our efforts were particularly focussed on employing a functionalisation strategy that is mediated by C–H activation.
In the case of propanoic acid, the possibility of achieving regioselective α-methylenation by linking the substrate to phosphorus was evaluated. Thus, a series of acyloxyphosphines and acylphosphites derived from either propionic acid or phenylacetic acid was prepared and, where stability allowed, fully characterised. Some of the resultant simple mixed anhydrides posed problems relating to their stability, and the stabilisation of such ligand systems by using electronic and / or steric effects was therefore explored. In addition, the coordination chemistry and in solution behaviour of Rh(I) and Ru(II) complexes containing these ligands was examined. Similar to the free ligands, complexes derived from these mixed anhydrides rearranged in solution via a number of decomposition pathways, with the specific pathway dependent on the nature of the auxiliary ligands. For most of these complexes, however, ligand decarbonylation was the route of preference for decomposition. Despite the instability of these complexes, a selection of Rh(I) mixed anhydride complexes were assessed for their potential as C-H activation catalysts in reactions aimed at the α-methylenation of saturated carboxylic acids.
Furthermore, the stabilisation of Rh(I) mixed anhydride complexes with chelating auxilary ligands, such as bisphosphines or N-substituted diphosphinoamines, was explored. In particular, a series of new Rh(I) mixed anhydride complexes containing dppe, dppb and dppbz as secondary ligands were prepared and the effects of these secondary ligands on the in solution stability of these complexes assessed.
As MeP represents the final product in the first stage of the Alpha process and not propanoic acid, the utilisation of PNP iridium pincer complexes in the regioselective sp³ C–H activation of MeP and related esters was also examined. The factors that govern the regioselectivity of such reactions were of great interest to us and, in particular, the effects of water on the reactivity and regioselectivity of these reactions were explored. For MeP, preferential C–H activation of the methoxy group was found to proceed under anhydrous conditions and the catalytic functionalisation of this site with ethene using this activation approach was considered.
Formaldehyde, employed in the second stage of the Alpha process, is a difficult substance to manufacture and handle, especially on a large scale. A preliminary study on the in situ production of anhydrous formaldehyde via the catalytic dehydrogenation of methanol was therefore performed. During this study, catalytic systems based on carbonate salts and / or transition metal complexes were considered. In the hope of reducing the number of steps required in the production of MMA, a new one-pot cascade reaction for the indirect α-methylenation of MeP with methanol was developed. Although the production of MMA using this system only proceeded with low efficiency, the obtained results serve as an important proof of concept for future developments in this area.
Finally, the capacity of a series of simple bases to catalyse the condensation of MeP with formaldehyde was assessed as part of a fundamental study directed towards determining the factors that govern the efficiency of this reaction. In addition, the extent to which each base effects the deprotonation in the α-position of MeP was determined with the aid of deuterium labelling experiments. Similarly, using sodium propanoate as model base a rough estimate of the kinetics of deprotonation could be made based on the degree of deuterium incorporation over time. These studies suggested that the low efficiency of this condensation reaction is not caused by ineffective deprotonation but rather by the weak nucleophilicity of the generated carbanion. For this reason, attempts to increase the electrophilicity of formaldehyde through Mannich-type condensations reactions involving secondary amine and carboxylic acid additives were made.
2012-05-04T14:14:52Z
2012-05-04T14:14:52Z
2011-11-30
Thesis
http://hdl.handle.net/10023/2585
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
253
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/285922024-03-04T11:45:04Zcom_10023_51com_10023_18col_10023_53
2023-10-30T15:26:15Z
urn:hdl:10023/28592
Computational insights into catalytic mechanism and thermostability of the enzyme Is-PETase
Shrimpton-Phoenix, Eugene
Mitchell, John B. O.
Bühl, Michael
Biotechnology and Biological Sciences Research Council (BBSRC)
Enzymes
QM/MM
PETase
The field of study surrounding the PETase class of enzymes has gained a great deal of popularity in
the past five years. PETases are enzymes capable of degrading poly(ethylene) terephthalate and
presents an opportunity to bioanalytically recycle this common pollutant. The most extensively
researched PETase is the enzyme Is-PETase, which originates from the organism Idonella
sakaiensis and was discovered near a recycling plant in 2016. To further the utility of Is-PETase in
the industrial recycling of poly(ethylene) terephthalate, improvements in desirable properties
such as catalytic rate and thermostability must be achieved via introduction of amino-acid
substitutions to the enzyme.
In order to further improve the activity of Is-PETase, it would be informative to have a deeper
understanding of its catalytic mechanism. To this end, we have investigated the catalytic
mechanism of the degradation of poly(ethylene) terephthalate via Is-PETase. We applied hybrid
quantum mechanical/ molecular mechanical to generate several independent reaction profiles.
From these reaction profiles we have concluded that this reaction proceeds with an overall
activation barrier of 35.6 kJ mol-1
. This relatively low activation barrier suggests that the ‘true’
rate-limiting step for this reaction is a physical process such as substrate binding or product
dissociation. Our calculations provide preliminary evidence for the product dissociation step being
rate-limiting.
We have also investigated modifications to wild-type Is-PETase that contribute to the enzyme’s
thermostability. We have created our own mutant of Is-PETase, DISU-PETase, through the in silico
introduction of a novel disulfide bond. We generated reaction profiles for DISU-PETase using the
same quantum mechanical/ molecular mechanical techniques as applied to wild-type Is-PETase.
We found that introduction of the novel disulfide bond in DISU-PETase had no adverse effect upon
the reaction profile of the degradation of poly(ethylene) terephthalate. We have also applied
molecular dynamics techniques to investigate the intramolecular interactions that contribute
toward the thermostability of the most highly active variants of Is-PETase in the literature.
We have also used our quantum mechanical/ molecular mechanical techniques to generate
reaction profiles for the degradation of an alternate substrate, poly(ethylene) furanoate via wildtype Is-PETase.
2023-10-30T15:26:15Z
2023-10-30T15:26:15Z
2023-11-29
Thesis
https://hdl.handle.net/10023/28592
https://doi.org/10.17630/sta/643
BB/M010996/1
en
https://doi.org/10.17630/486acc90-3be5-43c2-aa08-17c02096bb85
Computational Insights into the Catalytic Mechanism of Is-PETase: An Enzyme Capable of degrading poly(ethylene) terephthalate (thesis data)
Shrimpton-Phoenix, E., Mitchell, J. B. O., and Buehl, M., University of St Andrews, 27 Oct 2022. DOI: 10.17630/486acc90-3be5-43c2-aa08-17c02096bb85
247
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/219272022-02-01T11:25:13Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:59:27Z
urn:hdl:10023/21927
Ab initio SCF-MO calculations on linear triatomic molecules
Wishart, B.J.
Thomson, Colin
Single configuration wave functions for the ground states of several small species have been calculated – 0CC ³Σ⁻ ; CNC ²π ; NCO ²π ; NC ²Σ⁺ ; PC ²Σ⁺ ; OBO ²π Extended, Slater function basis sets were used in these calculations, allowing the wave functions so calculated to approach the Hartree-Fock limit. One-electron properties have been calculated for the species; and, where possible, compared with the experimental results. Conclusions are drawn that the near Hartree-Fock wave function gives good predictions of one-electron properties. These investigations were continued for species containing second-row atoms – SCC ³Σ⁻ ; PCC ²π ; SCN ²π ; PC ²Σ⁺ The single configuration approximation has been used in the calculation of wave functions for excited states of some of these species - OCC; HCC; HNC; NCO; CNC. Conclusions are drawn that the single configuration wave function is not an adequate model of excited states. For the ground state species, HBO, a configuration interaction investigation was undertaken.
2021-04-08T08:59:27Z
2021-04-08T08:59:27Z
1981
Thesis
http://hdl.handle.net/10023/21927
en
213 p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/153102019-03-29T11:19:07Zcom_10023_51com_10023_18col_10023_53
2018-07-12T13:13:07Z
urn:hdl:10023/15310
Chitose
Grant, Archibald Bradshaw
New Zealand. Government
2018-07-12T13:13:07Z
2018-07-12T13:13:07Z
1951
Thesis
http://hdl.handle.net/10023/15310
en
201 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/34702020-04-01T02:02:57Zcom_10023_51com_10023_18col_10023_53
2013-04-05T14:25:05Z
urn:hdl:10023/3470
Carbon monoxide hydrogenation using ruthenium catalysts
Blank, Jan Hendrik
Eastman Chemical Company
Ionic liquids
Homogeneous catalysis
Ruthenium
Syngas
Phosphonium salts
Oxygenates
High pressure
In this dissertation we investigate aspects of the Ru/[PBu₄]Br mixture in the
homogeneous conversion of CO and H₂ as pioneered by Knifton, Dombek and Gresham. In chapter 1 we present a current overview of the literature on this subject.
In chapter 2 we establish benchmark reactions and a full analysis of the liquid
products that are generated during catalysis. The product mixture consists primarily of small
alcohols (linear), acetic acid ethers, esters, and ethylene glycol. Both methanol and EG are
formed independently, but methanol is then converted into almost all other products that we
find.
In chapter 3, the gas phase activity is assessed, and it is found that the Ru/[PBu₄]Br
system is highly active for the WGS reaction, and as a result the reactor gas phase changes in
composition over time. Following this, in chapter 4 the orders in p[sub](H2) and p[sub](CO) are determined
for both the methanol formation reaction and the methanol homologation reaction. In order to
achieve this, a simple kinetic model is developed to assess the relative reactivity of the
system for each reaction. Using these orders and the knowledge of fast Water-Gas-Shift
activity, we iteratively model the conditions in the reactor to closely fit and predict the
methanol levels during the reaction.
In chapter 5 the discovery of a promoter, [HPBu₃]Br is discussed. The promoter
dissociates under catalysis conditions into HBr and PBu₃. The HBr then proceeds to improve
catalysis by changing the catalyst composition, while the PBu₃ inhibits the homologation
reaction selectively.
In chapter 6 we proceed to test the activity of the system for a range of different
promoters and solvents. The effect of bromide concentration, changing the halide, and using
various acid promoters is tested. At last we attempt to expand on the scope of this reaction by
using different ruthenium precursors and by using dimethyl ether as a reagent instead of
methanol. Both seem effective.
Notably, the conversion of CO₂ to methanol in a one-pot reaction was observed.
2013-04-05T14:25:05Z
2013-04-05T14:25:05Z
2012-11-30
Thesis
http://hdl.handle.net/10023/3470
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
283
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/148152019-03-29T11:19:08Zcom_10023_51com_10023_18col_10023_53
2018-07-02T15:26:17Z
urn:hdl:10023/14815
The pyrolysis of triphenyimethane, carbazole and toluene
Ferguson, Charles Urquhart
Horrex, Charles
Shell Research Limited
University of St Andrews
In all the studies reported in the subsequent sections a common method of approach has been followed. As a preliminary to the kinetic work, detailed investigations have been made of the precise nature and stoichiometry of the decompositions occurring. Since the conditions chosen for the work involve low concentrations of reactants as a means of minimising secondary processes, the analytical techniques to determine the precise stoichiometry have faced considerable difficulties peculiar to each case investigated. The general techniques of gas analysis, ultra violet spectrophotometry, mass spectrometry, and chromatography have been enlisted to solve the problems involved. Although many of these techniques have been common to all three substances, the problems were sufficiently individual to merit their discussion in separate sections.
1. Triphenyl Methane
a. The pyrolytic decomposition of this substance yielded 9-phenyl fluorine and hydrogen in equimolecular proportions. A hydrocarbon C₂₃H₁₈ was also produced in a very small amount.
b. The decomposition proceeded by a first order mechanism, obeying the rate equation k=1.26 x 10¹⁴ e ⁻⁷¹, ¹°°/RT.
2. Carbazole
a. The thermal decomposition of this compound has been shown not to give the dimer 9:9’ of dicarbazyl under usual pyrolytic conditions.
b. It is more probably that hydrogen and a phenazine type of compound are produced by the reaction of two carbazyl radicals.
c. There appeared to be some heterogenous decomposition on the walls of the reactor during carbazole pyrolysis and a carbon coated surface is necessary.
d. The kinetic data obtained were rather scattered due to poor reproducibility, but first order rate constants are of a magnitude given by k = 10¹³e ⁷⁵,°°°/RT.
e. If the energy of activation is ascribed to the dissociation of the N-H link in the molecule, it is shown that the resonance energy of the radical is in rough agreement with expectations from other data.
3. Toluene.
a. Since two values for the energy of activation of the primary decomposition of toluene have been reported, a brief re-examination of the problem has been made, using the nitrogen carrier gas technique.
b. The value of 77.5 k.cals./mole found was in agreement with the previous work of Szwarc, and the products were those anticipated on the basis of his proposed mechanism
c. An examination is made of the papers by Szwarc³¹ and Steacie ⁴°
2018-07-02T15:26:17Z
2018-07-02T15:26:17Z
1956
Thesis
http://hdl.handle.net/10023/14815
en
163 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/108262019-10-21T13:43:58Zcom_10023_51com_10023_18col_10023_53
2017-05-24T08:29:32Z
urn:hdl:10023/10826
Development of a biotechnological toolkit for the synthesis of diverse cyclic peptides
Mann, Gregory
Naismith, James
Cyanobactins
Patellamides
Biosynthesis
Macrocycles
Cyclic peptides possess desirable characteristics as potential pharmaceutical scaffolds.
The cyanobactin family of cyclic peptide natural products boast diverse structures and
bioactivity. Exemplars are the patellamides, which have attracted attention due to
their ability to reverse the effects of multi-drug resistance in human leukemia cells. In
addition to their macrocyclic architecture patellamides contain azol(in)e heterocycles
and d-amino acids. This structural complexity makes them challenging targets for
chemical synthesis. Understanding their biosynthesis will enable the development
of a biotechnological ‘toolkit’ for the synthesis of new pharmaceutical compounds.
Patellamides are ribosomally-synthesised and post-translationally modified peptides
(RiPPs) and much of their biosynthesis has been elucidated, however there are still
elements of their biosynthesis that are not yet fully understood.
PatA and PatG contain C-terminal domains of unknown function (DUFs). The
crystal structure of PatG-DUF has been solved and subsequent to biochemical and
biophysical investigation PatG-DUF was found not to constitute an essential part of the
biotechnological ‘toolkit’ and can be excluded from in vitro enzyme-based synthesis of
cyanobactin-like cyclic peptides.
The cyanobactin heterocyclases are able to introduce heterocycles into a peptide
backbone, seemingly irrespective of the neighbouring residues; however a molecular
rational governing substrate recognition is unknown. Additionally the mechanism of
heterocyclisaton is disputed. Analysis of crystal structures of LynD in complex with
cofactor and substrate (solved by Dr Jesko Koehnke) enabled the active site and
substrate recognition site to be located. A new mechanism for heterocyclisation has
been proposed. Guided by the substrate recognition observed in complex structures
a constituently active heterocyclase (AcLynD) has been engineered, which is able to
process short, leaderless peptide substrates.
Epimerisation in cyanobactin biosynthesis is believed to be spontaneous, but its precise
timing is uncertain. NMR analysis of selectively labelled peptide substrates processed by
the modifying enzymes, identified epimerisation to be spontaneous on the macrocycle,
regardless of whether the neighbouring heterocycles have been oxidised.
A one-pot in vitro synthesis of cyanobactins has been developed, and employed to create
a number of patellamide D analogues to ascertain structural-activity relationships.
2017-05-24T08:29:32Z
2017-05-24T08:29:32Z
2017-06-21
Thesis
http://hdl.handle.net/10023/10826
en
xxi, 256 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/149992019-03-29T11:19:10Zcom_10023_51com_10023_18col_10023_53
2018-07-05T13:40:41Z
urn:hdl:10023/14999
Some addition reactions of thiazoles
Skelton, Frederick Stevens
Reid, D. H.
University of St Andrews
Possible synthetic approaches to the pyrrolo[2,1-b]thiazole system have been investigated involving the mode of addition of thiazoles to dimethyl acetylenedicarboxylate. A number of thiazoles were allowed to react with the ester and the reactions were found to be remarkably solvent dependent. Dimethylformamide and methanol (or acetonitrile) were found to be specific for the formation of a particular class of adduct. The structures of the various adducts were extensively investigated by proton magnetic resonance spectroscopy. It was found that the proton magnetic resonance spectra of the unsubstituted and monosubstituted thiazole adducts, prepared in dimethylformamide, were different from the resonance spectra of the 2,4-disubstituted thiazole adducts. Various compounds were prepared for use as proton magnetic resonance reference compounds giving strong support for the structures proposed. Various degradative methods were employed in order to gain additional evidence for the proposed structures. Trimethyl pyrrolo[2,1-b] thiazole-5,6,7-tricarboxylate v/as isolated in low yield from thiazole and dimethyl acetylenedicarboxylate in methanol. Various attempts to decarboxylate the 6-carboxylic acid and isolate the parent pyrrolo[2,1-b] thiazole in good yield were unsuccessful. The 6-carboxylic acid methyl ester was reduced to 6-methyl-pyrrolo[2,1-b] thiazole with the lithium aluminium hydride/aluminium chloride complex. 2-Methylthiazoliiie formed isolable adducts with dimethyl acetylenedicarboxylate but the proton magnetic resonance spectra showed that they possessed a different structure from the corresponding 2-methylthiazole adducts. Thiazoles did not react with ditetrahydropyranyl acetylene-dicarboxylate nor with a saturated solution of acetylene in N-methyl-2-pyrrolidone. The addition reactions of thiazoles were extended to methyl propiolate which was found to be less reactive than dimethyl acetylenedicarboxylate. Adducts could only be isolated in low yield from thiazole, 2,4-dimethylthiazole and 2-methylthiazole. The structures proposed for these adducts did not bear analogy to those isolated from dimethyl acetylenedicarboxylate. Further investigations into the preparation of pyrrolo[2,1-b] thiazoles were attempted using other methods. Low yields of 6-substituted pyrrolo[2,1-b] thiazoles were obtained from the cyclisation of acetonyl and phenacyl-2-alkylthiazolium salts in aprotic solvents. Attempted cyclisations of 3-acetonyl-2-niethyl-thiazolium perchlorate with thionyl chloride and 3-formylmethyl-2-methylthiazolium chloride with sodium acetate and acetic anhydride gave only traces of the corresponding pyrrolo[2,1-b]thiazoles.
2018-07-05T13:40:41Z
2018-07-05T13:40:41Z
1965
Thesis
http://hdl.handle.net/10023/14999
en
180 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/21552019-07-01T10:16:15Zcom_10023_51com_10023_18col_10023_53
2012-01-04T15:55:36Z
urn:hdl:10023/2155
Inorganic organic composite polymer coatings based on functionalised polyhedral oligomeric silsesquioxanes
Robertson, Duncan J.
Morris, Russell Edward
Silsesquioxane
POSS
Coatings
Ambient-cure
Epoxy
A study has been undertaken with the aim of preparing appropriately functionalised polyhedral oligomeric silsesquioxane (POSS) compounds to be used in ambient-cure chemistry. Numerous epoxy-functionalised compounds have been designed and synthesised and these materials have been characterised in order to determine their chemical structure. These compounds have also been incorporated into existing polymerisation reactions to test whether these materials could be used in the protective coatings industry. A glycidyl-functionalised POSS compound was prepared and reacted with a series of amines to produce ambient-cured polymers which could be used in the coatings industry. There were also a series of experiments undertaken on these polymers to identify the processes at work and to test how they compare to industry standards. As a direct comparator to this work, another set of results was obtained with a cyclic-siloxane material incorporated into the systems in place of the POSS. A linear analogue was also tested. The reactions proved to be a success and an appropriate data-set was yielded.
During the synthesis of POSS precursors there are a series of residual materials produced. These materials have also been studied in this project. It was anticipated that these would behave in a similar way to the POSS compounds however the same functionality was never achieved as had been with the POSS. Ambient-cured polymers have also been targeted from a basic hydride-functionalised POSS compound and a polybutadiene system. The appropriate reactions unfortunately never took place as anticipated but there were a series of tests undertaken to identify the processes at work.
A study has also been undertaken using near-I.R. to track the curing reactions. From this data, the extent of cure could be studied and the make-up of the reaction could be investigated in more detail.
2012-01-04T15:55:36Z
2012-01-04T15:55:36Z
2011-06
Thesis
http://hdl.handle.net/10023/2155
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
170
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/218122021-10-21T13:31:30Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:56:58Z
urn:hdl:10023/21812
Syntheses and properties of liquid crystalline macrocyclic complexes
McGregor, Alan
Crayston, Joe A.
Investigations are conducted into substituted tetraazaannulenes with the objective of forming novel liquid crystalline compounds. Various synthetic strategies are devised and the compounds tested by differential scanning calorimetry and heated-stage polarised optical microscopy. The electrochemistry and variable temperature solid state NMR properties of certain of these compounds were also investigated. A series of novel compounds was prepared utilising the active (3-methine site of the 7,16-dihydro-6,8,15,17-tetramethyldibenzo[b,i]-[ 1,4,8,1 l]tetraazacyclotetradecinato(2-) Ni(II)) complex starting material, commonly known as nickel tetramethyltetraazaannulene. Long aliphatic chains were joined to this macrocycle in an attempt to induce mesogenic properties in the crystals. Diazo functional groups were utilised as the link. However, the bulky nature of the benzene side groups on the macrocycle prevented liquid crystalline behaviour. The ability to replace the nickel centre in these macrocycles was demonstrated. The electrochemistry of the cobalt rod shaped complex was investigated on gold electrodes.
A further series of compounds based on a macrocycle with less bulky side groups was prepared. The dibenzo groups were replaced by ethylenediamine groups. Diazo linked compounds exhibited mesogenic behaviour for the longer chain length, the molecules displaying smectic A mesophases at high temperatures. Once liquid crystalline properties had been established by reducing the bulk of the molecules the effect of the linkage was examined. The diazo linkage was replaced with a dibenzoyl linkage while keeping all other factors constant. However, this small alteration was sufficient to destroy the mesogenic properties for the entire range of chain lengths. In V addition to the liquid crystal transitions several solid state crystalline transitions were observed for these compounds. The effect of making the inner core of the molecules more planar by removing the peripheral methyl groups was investigated. Results suggested that the methyl groups have opposing roles, i.e. they increase the steric bulk of the molecules, but at the same time prevent strong interactions between molecules. Unfortunately, the best synthetic route to such molecules also left the unsymmetrical mono substituted complex as an impurity which could not be easily removed. This impurity was likely to be liquid crystalline in its own right. Variable temperature solid state NMR studies of these compounds were begun by investigating the metal-free parent macrocycles and the intramolecular proton transfer which takes place between the four inner nitrogen atoms. Comparison with X-ray data and 15N isotope enriched studies revealed that the αC¹³C CP / MAS spectra was a valid probe for this tautomerism. This was then extended to TAA which had not been studied by solid state NMR. The results were consistent with an equal population of both tautomers, apparently in conflict with the evidence from the original crystal structure. Later crystallographic work by revealed that the packing in the crystal structure is dependent on the method of formation (recrystallisation or vacuum sublimation).
2021-04-08T08:56:58Z
2021-04-08T08:56:58Z
1997
Thesis
http://hdl.handle.net/10023/21812
en
171p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/76902019-07-01T10:08:49Zcom_10023_51com_10023_18col_10023_53
2015-10-26T14:27:41Z
urn:hdl:10023/7690
Gene mining of biosynthesis genes and biosynthetic manipulation of marine bacteria for the production of new antibiotic candidates
Zarins-Tutt, Joseph Scott
Goss, Rebecca J.
Medical Research Council (MRC)
Aquapharm
Biosynthesis
Antibiotics
Natural products
Actinomycetes
Marine bacteria
iPCR
Echinomycin
Cryptic secondary metabolism
Natural product drug discovery has traditionally been the corner stone of medicine having provided cures to many of today’s most common diseases. In particular, antibiotics have revolutionised healthcare and extended human lifespan. However, since their introduction into the clinic, resistance to these drugs has arisen. With the number of new antibiotics being discovered in recent years declining, and fewer drugs making it past clinical trials, we have reached the point where antibiotic resistant infections have become common place and a serious threat to health and society. There is now an urgent requirement for the discovery of new antibiotics and in particular those with unexploited mode of action.
This thesis details the different areas of natural product drug development from discovery through to analogue generation. In Chapter one, the history of natural products as therapeutics is explored with a particular focus on antibiotics and how resistance arises against these agents. It outlines why the discovery of new antibiotics is so important and new methods used to facilitate this search. Chapter two follows with the development of a screening platform for antibiotic induction, using the model Streptomyces; Streptomyces coleiolor M145. A variety of culture additives are explored for their ability to induce secondary metabolism production. Chapter three then details the sampling and identification of microbes from a pseudo-marine environment and their screening for their ability to produce secondary metabolites with antibiotic properties.
The second half of this thesis centres on the non-ribosomal peptide echinomycin. Collaborators Aquapharm supplied the marine derived strain AQP-4895, capable of producing echinomycin. Chapter four details the establishment of AQP-4895 culturing conditions and the shift observed in production profile. Next Chapter five looks at producing echinomycin analogues through precursor directed biosynthesis. A range of halogenated quinoxaline carboxylic acids are synthesised and fed to AQP-4895, and the respective echinomycin analogues monitored by LC-MS. Chapter Six then aims to direct biosynthesis of the halogenated analogues, using mutasynthesis. Due to the lack of genetic data available surrounding the strain, an unusual approach was taken, using iPCR to create a template for homologous recombination.
2015-10-26T14:27:41Z
2015-10-26T14:27:41Z
2015-11-30
Thesis
http://hdl.handle.net/10023/7690
en
http://creativecommons.org/licenses/by-nc-nd/4.0/
Print and electronic copy restricted until 25th September 2020
Thesis restricted in accordance with University regulations
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
211
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/21562019-07-01T10:06:03Zcom_10023_51com_10023_18col_10023_53
2012-01-04T16:16:42Z
urn:hdl:10023/2156
Crystalline polymer and small molecule electrolytes
Ainsworth, David A.
Bruce, Peter G.
Crystalline polymer electrolytes
Lithium-ion batteries
Poly (ethylene oxide)
Glymes
The research presented in this thesis includes a detailed investigation into factors influencing ionic conductivity in the crystalline polymer electrolyte PEO₆:LiPF₆. It has previously been shown that preparing PEO₆:LiPF₆ with PEO modified with larger –OC₂H₅ end groups increases ionic conductivity by one order of magnitude [¹],primarily due to disruption of the crystal structure caused by the inclusion of the larger end groups. In this study it is shown that by reducing PEO molecular weight in crystalline PEO₆:LiPF₆ ionic conductivity is also increased. This was attributed to an increasing concentration of polymer chain end regions upon lowering molecular weight resulting in the creation of more defects, as well as possible increases in
crystallite size resulting in longer continuous pathways for ion transport. Similar results were observed using both polydispersed and monodispersed PEO to prepare complexes.
In addition, it is demonstrated here that ionic conductivity in crystalline polymerelectrolytes is not confined to PEO₆:LiXF₆ (X=P, As, Sb)[²][³] type materials. The structures and ionic conductivity data are reported for a series of new crystalline polymer complexes: the alkali metal electrolytes. They are composed of low molecular weight PEO and different alkali metal hexafluoro salts (Na⁺, K⁺ and Rb⁺), and include the best conductor poly(ethylene oxide)₈:NaAsF₆ discovered to date [⁴], with a conductivity 1.5 orders of magnitude higher than poly(ethylene oxide)₆:LiAsF₆.
A new class of solid ion conductor is reported: the crystalline small-molecule
electrolytes. Such materials consist of lithium salts dissolved in low molecular weight glyme molecules [CH₃O(CH₂CH₂O)[subscript(n)]CH₃, n=1-12], forming crystalline complexes [⁵][⁶].
These materials are soft solids unlike ceramic electrolytes and unlike polymer
electrolytes they are highly crystalline, are of low molecular weight and have no
polydispersity. By varying the number of repeat units in the glyme molecule, many
complexes may be prepared with a wide variety of structures. Here, ionic conductivity and cation transference number (t₊) data for several such complexes is presented [⁷][⁸][⁹].These complexes have appreciable ionic conductivities for crystalline complexes and their t₊ values vary markedly depending on the glyme molecule utilized. The differences in t₊ values can be directly attributed to differences in their crystal structures.
[¹] Staunton, E., Andreev, Y.G. & Bruce, P.G. Factors influencing the conductivity of crystalline polymer electrolytes. Faraday Discussions 134, 143-156 (2007).
[²] Gadjourova, Z., Andreev, Y.G., Tunstall, D.P. & Bruce, P.G. Ionic conductivity in crystalline polymer electrolytes. Nature 412, 6846 (2001).
[³] Stoeva, Z., Martin-Litas, I., Staunton, I., Andreev, Y.G. & Bruce, B.G. Ionic Conductivity in the Crystalline Polymer Electrolytes PEO₆:LiXF₆, X = P, As, Sb. J. Am. Chem. Soc. 125, 4619-4626(2003).
[⁴] Zhang, C., Gamble, S., Ainsworth, D., Slawin, A.M.Z., Andreev, Y.G. & Bruce, P.G. Alkali metal crystalline polymer electrolytes. Nature Materials 8, 580-584 (2009).
[⁵] Henderson, W.A., Brooks, N.R., Brennessel, W.W. & Young Jr, V.G. Triglyme-Li⁺ Cation Solvate Structures: Models for Amorphous Concentrated Liquid and Polymer Electrolytes (I). Chem. Mater. 15, 4679-4684 (2003).
[⁶] Henderson, W.A., Brooks, N.R. & Young Jr, V.G. Tetraglyme-Li⁺ Cation Solvate Structures: Models for Amorphous Concentrated Liquid and Polymer Electrolytes (II). Chem. Mater. 15, 4685-4690
(2003).
[⁷] Zhang, C., Andreev, Y.G. & Bruce, P.G. Crystalline small-molecule electrolytes. Angewandte Chemie, International Edition 46, 2848-2850 (2007).
[⁸] Zhang, C., Ainsworth, D., Andreev, Y.G. & Bruce, P.G. Ionic Conductivity in the Solid Glyme Complexes [CH₃O(CH₂CH₂O)[subscript(n)]CH₃]:LiAsF₆ (n = 3,4). J. Am. Chem. Soc. 129, 8700- 8701 (2007).
[⁹] Zhang, C., Lilley, S.J., Ainsworth, D., Staunton, E., Andreev, Y.G., Slawin, A.M.Z. & Bruce, P.G. Structure and Conductivity of Small-Molecule Electrolytes [CH₃O(CH₂CH₂O)[subscript(n)]CH₃]:LiAsF₆ (n = 8-12). Chem. Mater. 20, 4039-4044 (2008).
2012-01-04T16:16:42Z
2012-01-04T16:16:42Z
2010-06-23
Thesis
http://hdl.handle.net/10023/2156
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
2
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/31082019-07-01T10:17:10Zcom_10023_51com_10023_18col_10023_53
2012-09-20T20:42:30Z
urn:hdl:10023/3108
Investigations into the role of α-amino acids as chiral modifiers for Ni-based enantioselective heterogeneous hydrogenation catalysts
Wilson, Karen E.
Baddeley, Christopher J.
Heterogeneous
Catalysis
Enantioselectivity
Chirality
Nickel
Gold
Aspartic acid
Ultra-high vacuum
Liquid-solid interface
Lysine
The hydrogenation of β-ketoesters over chirally modified Ni catalysts is a celebrated and thoroughly researched example of an enantioselective heterogeneous catalytic reaction. Enantioselective heterogeneous processes, although extremely attractive in terms of fewer complications in the separation of products from the catalyst, are hindered in their viability as industrial applications due to the lack of detailed knowledge on how chirality is conferred to the metal surface. Surface science techniques have afforded substantial progress into determining mechanisms between modifier, reactant and catalyst to explain the source of enantioselectivity of the system. In this study, a combination of solution and ultra-high vacuum (UHV)-based experiments allow a more realistic interpretation of the surface chemistry underpinning the catalytic reaction as the key step in achieving enantioselective performance is the adsorption of chiral modifiers from solution. The behaviour of (S)-aspartic acid and (S)-lysine on Ni{111} and their interaction with the prochiral β-ketoester methylacetoacetate is investigated in this study to understand their potential as chiral modifiers for the system. In UHV, scanning tunnelling microscopy (STM), reflection absorption infrared spectroscopy (RAIRS), and temperature programmed desorption (TPD) are used to analyse the conformation and order of the amino acids on the metal, and their thermal stability. Additionally, liquid-solid interface RAIRS and X-ray photoelectron spectroscopy (XPS) are used to examine the modified Ni surface, prepared under aqueous conditions, to give an accurate representation of the catalytic studies. It has been found highly likely that, for (S)-aspartic acid modified Ni{111}, enantioselective sites exist at step or step/kink defects, formed by corrosive leaching of the Ni substrate. Conversely, lysine appears to bind with a high sticking probability to Ni, in the form of lysine islands, and does not appear to etch the Ni chirally. Finally, similar experiments have been carried out on Au{111}, where lysine was found to chiral restructure the surface and form nanofingers, and 2D Ni clusters grown on Au{111} in order to investigate the formation of possible metal-organic frameworks.
2012-09-20T20:42:30Z
2012-09-20T20:42:30Z
2011-11-30
Thesis
http://hdl.handle.net/10023/3108
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
262
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/152702019-03-29T11:19:13Zcom_10023_51com_10023_18col_10023_53
2018-07-12T08:19:33Z
urn:hdl:10023/15270
The synthesis and chemical properties of some compounds containing the perinaphthene nucleus
Bonthrone, William
Reid, D. H.
Carnegie Trust for the Universities of Scotland
This thesis comprises three parts, Parts A, B and C. Part A commences with a very brief survey based on the chemical literature of the concept of aromaticity. A number of excellent reviews covering both the historical and theoretical aspects of this subject have appeared recently and, in view of this, a more detailed consideration of aromaticity was deemed unnecessary. This is followed by a discussion of the chemistry of the mulenes with particular emphasis on the theoretical aspects of the subject. The chemistry of perinaphthene and its derivatives is then reviewed in detail and this leads logically to a reasoned description of the aims of the experimental investigation.
Part B is a discussion of the results achieved in the course of investigations centred on the perinaghtene nucleus. Part C is devoted entirely to a description of experimental details, and is the complement to part B.
2018-07-12T08:19:33Z
2018-07-12T08:19:33Z
1958
Thesis
http://hdl.handle.net/10023/15270
en
161 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/218222021-10-25T08:24:22Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:57:02Z
urn:hdl:10023/21822
Synthetic studies towards new pigments
Garnett, Alasdair Nathan
Riddell, Frank G.
Phthalate ester synthesis. An investigation into various methods of synthesising phthalate esters suitable as precursors for phthalocyanine and other pigment synthesis was conducted. This was achieved via thermal Diels-Alder reactions between 2-substituted furans and dimethyl acetylenedicarboxylate (DMAD), proceeding in high yield. Subsequent aromatisation of the resulting adducts by either sulphuric acid or low-valence titanium also proceeded in good yields. The phenols generated by the acid aromatisation were further reacted in high yields with a range of haloalkanes to form the expected aryl ethers.
Latent pigment investigation Work was also carried out on the synthesis of reversibly soluble "latent" DPP (1,4-diketo-pyrrolo[3,4-c]pyrrole) pigments. The aim was to synthesise a moiety that could be incorporated into a DPP pigment, increasing its solubility in various media. The solublised DPP pigment should then be treatable in situ to precipitate a considerably less soluble aromatic DPP pigment.
2X X-DPP-X Ar-DPP-Ar
It was necessary for the moiety X to be stable to the DPP forming conditions (1), but once it was incorporated into the soluble DPP it had to be easily converted without significant degradation to produce the less soluble aromatic DPP pigment under reasonably mild conditions (2). A variety of methods and moieties were investigated, the main efforts concentrating on two areas: heterobicycloheptadiene "norbornadiene" analogue containing groups, which could aromatise to phenyl-type groups under thermal conditions while extruding various gases, and upon both cis and trans-stilbenyl containing groups which could cyclise to planar phenanthryl groups under suitably oxidative photochemical conditions.
2021-04-08T08:57:02Z
2021-04-08T08:57:02Z
1998
Thesis
http://hdl.handle.net/10023/21822
en
119p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/147052019-03-29T11:19:13Zcom_10023_51com_10023_18col_10023_53
2018-06-28T11:21:12Z
urn:hdl:10023/14705
The nature of the ferric thiocyanate complexes
Mitchell, Kenneth McLean
Macdonald, J. Y.
Department of Scientific and Industrial Research (DSIR)
2018-06-28T11:21:12Z
2018-06-28T11:21:12Z
1951
Thesis
http://hdl.handle.net/10023/14705
en
200 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/70422018-03-05T15:10:08Zcom_10023_51com_10023_18col_10023_53
2015-07-28T08:28:18Z
urn:hdl:10023/7042
The location of active sites in microporous solids
Eschenröder, Eike Christian Viktor
Wright, Paul Anthony
The location of heteroatoms within porous materials was examined in chosen zeolite
and zeotype materials. For zeolites, the substitution of aluminium (mainly, but also
gallium and boron) for silicon was examined in materials with the AFX and EUO
topology types. For the zeotypes, magnesium and zinc substitution for aluminium was
studied in MAPO STA-2 (SAT framework) as well attempts to include silicon into the
material. In addition to the investigation of heteroatoms within the framework, the role
of templating has been explored in (Cu-)SAPO STA-7 and phosphonium cation
templated materials, where calcination leaves extra-framework Cu²⁺ cations and
phosphorus species, respectively. Solid-state NMR spectroscopy, X-ray diffraction
(single-crystal and powder) and IR spectroscopy were used for the characterisation of
these structures.
For MAPO and ZnAPO STA-2, the location of the heteroatoms in the framework was
confirmed and their role in charge balancing established. Additionally, for MgAPO STA-2, the NMR indicates preferential substitution of Mg in one of the two
crystallographically distinct Al sites. The zeolite SSZ-16 (AFX structure type, which like
SAT has two topologically-distinct Al sites) was synthesised with two closely related
diquaternary templates The synthesis was optimised with respect to purity,
crystallisation conditions, and time, giving a range of materials with different Si/Al
contents. Based on ²⁷Al and ¹¹B MAS NMR, it was not possible to resolve between the
two crystallographic sites. Full details are given of the crystallisation using these
organic structure directing agents. Other templated materials crystallised included
mordenite, EU-1, L and offretite. For the more complex and higher Si/Al EUO materials
(10 crystallographically-distinct tetrahedral sites), it was attempted to locate heteroatom
positions in the isostructural EU-1 and ZSM-50, which are prepared with
hexamethonium and dibenzyldimethyl ammonium cations, respectively. These zeolites
show considerable charge-balancing of the charged template by framework defects
over the Si/Al range. These defects can be healed by post-synthetic treatment with
aqueous NH₄F solutions. In all samples examined, the ²⁷Al MAS NMR shows
significant differences between the EU-1 and ZSM-50 materials, which is attributed to
the role of the different charge distribution of the templates.
With focus on extra-framework species, the calcination and subsequent dispersion of
Cu²⁺ cations throughout the pore space of Cu-SAPO STA-7 was examined by
Synchrotron IR spectroscopy of microcrystals at the Diamond Light Source. Applying
polarised IR radiation, direction-dependent information was extracted. Combining IR
spectroscopic data with complementary techniques such as EPR spectroscopy, X-ray
diffraction and computational modelling, the dehydration state of the templating Cu-cyclam complex and the change in orientation of the complex was determined based
on the characteristic N-H stretching vibration.
Additionally, a range of commercially-available and custom-made phenylphosphonium-
based organics have been examined as templates for MAPO based materials. A
layered phase based on tetraphenylphosphonium and methyltriphenylphosphonium
cations was synthesised and the structure was confirmed by Rietveld refinement on
powder X-ray diffraction data. For diphenylphosphonium templates, framework MAPOs
have successfully been prepared, including those with the ATS topology type (MAPO-36). The phosphonium-based templates were removed by calcination, leaving
phosphate species in the pores behind according to solid-state NMR.
2015-07-28T08:28:18Z
2015-07-28T08:28:18Z
2014
Thesis
http://hdl.handle.net/10023/7042
en
2019-01-11
Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 11th January 2019
xi, 295 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/151752019-03-29T11:19:15Zcom_10023_51com_10023_18col_10023_53
2018-07-10T11:21:41Z
urn:hdl:10023/15175
Glyceride studies of selected seed oils
Qureshi, Muhammad Ilyas
Gunstone, F. D.
1. The component glycerides of J. curcas, J. inultifida, J. gossypifolla and sunflower seed oils are determined by a new method of crystallisation and column chromatography on silica-silver nitrate. 2. The component glycerides of nine seed oils (safflower, tobacco, A. mexieana, maize, cotton, gi-oundnut, M. ternifolia, G. asiatica and M. latifolia) are determined by thin layer argentation procedure. 3. The results agree with those obtained by lipolysis on" calculated directly from the component acids on the basis of the theory of positional distribution. Moreover, the distribution of oleic, linoleic, hexadec-9 and 11-enoic, lauric and myristic acids in vegetable triglycerides are studied by hydrolysis with pancreatic lipase. The results, discussed in terms of a "selectivity factor", indicate that these unsaturated acids do not compete equally for the secondary hydroxyl group of glycerol.
2018-07-10T11:21:41Z
2018-07-10T11:21:41Z
1966
Thesis
http://hdl.handle.net/10023/15175
en
176 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/42932019-03-29T11:19:16Zcom_10023_51com_10023_18col_10023_53
2013-12-13T16:20:43Z
urn:hdl:10023/4293
Investigations into surface-confined covalent organic frameworks : towards developing novel enantioselective heterogeneous catalysts
Greenwood, John
Baddeley, Christopher J.
There is an increasing necessity for the pharmaceutical industry to develop
enantiomerically pure drugs. Up till now, production of enantiomerically pure
molecules has been provided by harvesting them from plants or utilising homogeneous
catalysis and biocatalysis. None of these methods are efficient means of production,
and attention is now being directed towards heterogeneous enantioselective catalysis
as the preferred technique. This is on account of the high product yield and ease of
separation of catalyst from the reaction mixture.
Over the past few decades, a great deal of research has been conducted into
investigating the Ni catalysed hydrogenation of β-ketoesters and Pt catalysed
hydrogenation of α-ketoesters. These are the most successful systems for
enantioselective heterogeneous catalysis. However, they are unsuitable for industrial
purposes due to the low thermal and mechanical stability of the modified surfaces.
The main goal throughout this project has been the investigation of surface-confined
covalent reactions. The motivation of this research is to develop enantioselective
heterogeneous catalysis; covalent networks are believed to infer the necessary
thermal and chemical stability required to chirally modify catalytic surfaces for docking
interactions with reactant species. Covalent organic frameworks (COFs) on surfaces
hold potential for a number of chemical applications, and not just in the field of
heterogeneous catalysis; for example in areas such as molecular electronics and
templating.
2013-12-13T16:20:43Z
2013-12-13T16:20:43Z
2013
Thesis
http://hdl.handle.net/10023/4293
en
xi, 214
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/36842019-03-29T11:19:16Zcom_10023_51com_10023_18col_10023_53
2013-06-13T09:52:48Z
urn:hdl:10023/3684
Polymer precursors from catalytic reactions of natural oils
Furst, Marc R. L.
Cole-Hamilton, D. J. (David John)
Green chemistry
Natural oils
Palladium
Ruthenium
Methoxycarbonylation
Hydrogenation
Polymers
NHC
The bidentate ligand 1,2-bis(ditertbutylphosphinomethyl)benzene has been shown to be a very efficient catalyst for operating the alkoxycarbonylation of alkenes and unsaturated
esters and carboxylic acids giving a very high selectivity to the linear product with very few exceptions to this general rule.
Due to the increasing prices of petroleum feedstock and petroleum-derived chemicals, the preparation of chemicals starting from renewable resources and waste products from the industry becomes an interesting alternative. Fatty acids and fatty esters, due to the
existence of one or more unsaturation in their alkyl chain are subjected to the alkoxycarbonylation
reactions in presence of 1,2-bis(ditertbutylphosphinomethyl)benzene, palladium,
methane sulfonic acid, carbon monoxide and methanol, yielding diesters with
a long carbon chain (up to 19 carbon atoms). The diesters are shown to be readily
prepared from unpurified olive, rapeseed or sunflower oils as well as from tall oil. In
the last case triesters are also formed. The diesters are subjected to hydrogenation in
the presence of 1,1,1-tris(diphenylphosphinomethyl)ethane, ruthenium and hydrogen, in
a mixture of dioxane and water at high temperature, yielding the corresponding diols.
The resulting products of the reactions are monomers for preparing polyesters having the
potential to replace some existing petroleum-based polymers (for instance polyethylene).
The aminocarboxylation reaction in the presence of the same palladium/1,2-bis(ditertbutylphosphinomethyl)
benzene catalyst, in the presence of aniline, 2{naphthol and potassium
iodide in diethylether, is employed for preparing esteramides, which are subjected
to hydrogenation. Aromatic polyamides are prepared by melting together an aromatic
diamine and diacids obtained from methoxycarbonylation.
Finally, N-Heterocyclic Carbene (NHC) ligands are employed for preparing new palladium
complexes which are used in the Suzuki-Miyaura cross-coupling reaction in a
water/isopropanol mixture. Other complexes based on copper are employed for developing
an inexpensive transmetallation reaction for transferring a NHC ligand from
copper to palladium and gold.
2013-06-13T09:52:48Z
2013-06-13T09:52:48Z
2013-06-26
Thesis
http://hdl.handle.net/10023/3684
en
144
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/1462019-10-21T13:49:16Zcom_10023_51com_10023_18col_10023_53
2006-12-18T18:01:03Z
urn:hdl:10023/146
PyrH and PrnB crystal structures
De Laurentis, Walter
Naismith, James
Enzymes
FADH dependent tryptophan halogenases
Determination of the three-dimensional structure of enzymes at atomic resolution is a key prerequisite for elucidation of molecular mechanisms of catalysis and catalysis mechanism prediction. X-ray protein crystallography is the most widely used method today for determining protein structures.
In this thesis we describe the expression, purification, crystallization and structure
solution of two new enzymes: PyrH and PrnB.
PyrH is a member of the new emerging family of FADH dependent tryptophan halogenases. It catalyzes the regioselective halogenation of tryptophan at the C-5 position of the indole ring. Elucidation of its structure (Chapter 2) and comparison with PrnA, aregioselective 7th tryptophan halogenase whose structure has already been solved confirmed the proposed mechanism of action for this class of enzymes.
PrnB is the only enzyme known to perform exquisite and peculiar ring rearrangement chemistry: it converts 7-Cl-tryptophan and tryptophan into respectively
monodechloroaminopyrrolnitrin and aminophenylpyrrole. We developed a method for
expression and purification of milligrams of pure and homogeneous recombinant PrnB
(Chapter 3). We identified suitable crystallization conditions and determined PrnB structure
(Chapter 4). Analysis of the PrnB structure helped us to propose a reaction mechanism for
this unique enzyme.
2006-12-18T18:01:03Z
2006-12-18T18:01:03Z
2006-12
Thesis
http://hdl.handle.net/10023/146
en
http://creativecommons.org/licenses/by-nc-nd/2.5/
Creative Commons Attribution-NonCommercial-NoDerivs 2.5 Generic
vi, 6-157 leaves
University of St Andrews
The University of St Andrews
Centre for Biomolecular Sciences
oai:research-repository.st-andrews.ac.uk:10023/166192021-07-27T02:00:52Zcom_10023_51com_10023_18col_10023_53
2018-12-04T12:15:16Z
urn:hdl:10023/16619
Studies of enzymes relevant to the biotransformation of fluorinated natural products
Bandaranayaka, Nouchali
O'Hagan, David
This thesis is focused on enzymes related to the biosynthetic pathway of fluorometabolite
synthesis in S.cattleya. The first native fluorinating enzyme, fluorinase was isolated from a
soil bacterium, Streptomyces cattleya in 2002. Fluorinase catalyses the reaction between
S-adenosyl-L-methionine and inorganic fluoride to produce 5′-fluoro-5-deoxyadenosine (5′FDA) and L-methionine as the first step of the fluorometabolite biosynthetic pathway.
Fluorinase has been an attractive tool for incorporating ¹⁸F into a limited number of
substrates for applications in positron emission tomography (PET). This thesis describes
a preparation of the fluorinase for PET, and then the production of [¹⁸F]-5-fluoro-5-deoxy-
D-ribose ([¹⁸F]-FDR) via fluorinase mediated enzymatic synthesis. S. cattleya fluorinase
has been the only fluorinase identified until recently when four more fluorinases have been
identified by gene mining. These new fluorinase isolations are presented in the thesis. In
addition this thesis describes the crystallisation of 5-deoxy-5-fluoro-D-ribose 1-phosphate
isomerase (FDRPi), an aldose-ketose isomerase involved in the biosynthetic pathway of
fluorometabolite biosynthesis in S.cattleya.
Chapter 1 presents the background of this research focusing on the enzymes involved in
the biosynthesis of the two fluorometabolites; fluoroacetate and 4-fluoro-L-threonine,
produced by S.cattleya.
Chapter 2 describes the development of a practical, ‘off the shelf’ method of producing
[¹⁸F]-FDR in remote radiochemistry labs. Enzymes, fluorinase and nucleoside hydrolase,
isolated from Trypanosoma vivax (TvNH) were freeze-dried in their buffers to produce a
shelf stable, potentially portable kit, where rehydration on site, would then provide catalysts
on demand for radiochemical synthesis of [¹⁸F]-FDR. This kit was practical enough to
conduct a successful tumour imaging using a mouse model at Vrije University in
Amsterdam.
Chapter 3 presents the over-expression and purification of fluorinase gene product (FLA1)
from a newly isolated soil bacterium Streptomyces sp. MA37. The gene was identified by
sequence mining of the Streptomyces sp. MA37 genome. This fluorinase shared high
homology to S.cattleya fluorinase and the flA1 was cloned into E.coli, over-expressed,
purified, assayed and shown to be a fluorinase. The FlA1 was also crystallized and the
structure solved.
Chapter 4 describes the successful crystallisation of FDRPi, an enzyme involved in the
fluorometabolite synthesis of S. cattleya. The FDRPi was over expressed, purified,
crystallised and the structure was solved.
2018-12-04T12:15:16Z
2018-12-04T12:15:16Z
2018-06-27
Thesis
http://hdl.handle.net/10023/16619
en
xii, 155 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/152932019-03-29T11:19:17Zcom_10023_51com_10023_18col_10023_53
2018-07-12T09:54:26Z
urn:hdl:10023/15293
Some new heterocyclic thermosets
Nicolson, Neil James
Smith, D. M.
The original aim of this project was to investigate the possibility of synthesising a novel polymer system combining the best features of cyanate ester resins and epoxy resins. Chapter 1 presents the historical background for both types of resin. The remaining three chapters describe attempts to achieve this aim by a) finding a cyanate ester that cures at a lower temperature than those in current commercial use (Chapter 2); b) using mixed epoxy and cyanate ester resins (Chapter 3); and c) designing chemically completely novel polymers from knowledge of the existing ones (Chapter 4). In Chapter 2 it was revealed that different cyanate esters cure at different temperatures, but that no obvious correlation exists between curing temperature and either steric or electronic effects of the ring substituents. The mixing of two dicyanate esters, one of which cures at a lower temperature than the other, leads to some reduction in the overall curing temperature required, but not sufficient to warrant further study at this stage. In Chapter 3 the usefulness of a previously proposed co-reaction between cyanate esters and epoxides was examined. Previous work in this area is full of inconsistencies that put many of the proposed conclusions in doubt. Further examination of the alleged co-reaction reveals that any such co-reaction is unpredictable, can vary significantly with reaction conditions and is in any case a minor reaction pathway by comparison with the self-reactions of the two individual reactants. It was therefore decided that further pursuit of this strategy was also likely to prove unrewarding in the short term. In Chapter 4 a study was made into the effects of including novel monomers in a standard epoxy resin system. These novel monomers had a cyanurate backbone with epoxide functionality, and can be cured at the lower temperatures of epoxy resins. Tests on the properties (mechanical, dielectric, water absorption, fracture toughness etc.) of these polymers were of a preliminary "scouting" nature, but are sufficiently promising to encourage further study.
2018-07-12T09:54:26Z
2018-07-12T09:54:26Z
1996
Thesis
http://hdl.handle.net/10023/15293
en
136 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/112452019-03-29T11:19:18Zcom_10023_51com_10023_18col_10023_53
2017-07-18T14:13:46Z
urn:hdl:10023/11245
Studies on absorption from mammalian intestine
Wood, Helen Ogilvie
Garry, R. C.
2017-07-18T14:13:46Z
2017-07-18T14:13:46Z
1945-02
Thesis
http://hdl.handle.net/10023/11245
en
133 leaves
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/44772019-10-21T13:43:32Zcom_10023_51com_10023_18col_10023_53
2014-02-27T14:52:15Z
urn:hdl:10023/4477
The application of the fragment-based screening approach to RmlA protein and PA1645 structure
Boulkeroua, Wassila Abdelli
Naismith, James
P. aerguinosa is a serious human bacterial pathogen. This thesis describes attempts to use
structural biology to identify new starting points for drugs against P. aerguinosa .A number of
fragment-based screening techniques were used in order to identify potential inhibitors to P.
aerguinosa RmlA protein, the first enzyme in the L-Rhamnose pathway. A 500 “Rule of 3”
Fragment Library (Maybridge) was investigated. The first approach was the application of
Differential Scanning Fluorimetry (DSF) approach to detect ligands that bind and stabilize
RmlA protein. The stabilisation of RmlA was determined by thermal unfolding in the presence
of each of the 500 compounds. 21 of those compounds were found to increase the protein
stability. The library was then screened by NMR spectroscopy for binding to RmlA. Two
techniques were evaluated STD and WaterLOGSY. 106 compounds gave positive results in
both NMR experiments. These hits were then tested by a simple STD competition binding with
dTTP, a natural RmlA substrate, in order to identify those binding at the active or allosteric
site. 21 out of the 106 compounds were observed to compete with dTTP. The results were
compared to the results of the DSF screening. Compounds that tested positive in the dTTP
competition binding STD experiment and in the DSF screening were tested for their ability to
inhibit RmlA in a biological assay. A coupled enzyme assay was used to monitor RmlA
activity. Only one compound, 3-pyridin-3-ylaniline, showed significant inhibition of the
enzyme activity.
The PA1645 protein from P. aerguinosa has been identified as essential. The protein was
overexpressed, purified and crystallised. Data were collected at Diamond on beamline IO3 and
phases were determined by S-SAD at a wavelength of 1.6Å. Final coordinates have been
deposited in the protein data bank under entry code 2XU8. The structure has 3 molecules in the asymmetric unit. There is some ambiguity as to the validity of the proposed trimeric
arrangement, with results from solution and crystal disagreeing.
Fragment-based screening approach has been applied to RmlA protein, using the DSF
technique, a number of ligand-based NMR experiments and a coupled enzyme biological
assay. 3-pyridin-3-ylaniline was the only compound that showed significant inhibition of the
enzyme activity. The structure of PA1645 from P. aerguinosa has been solved. This work will
help to design new drugs to combat multi-drug resistant P. aerguinosa and MTB.
2014-02-27T14:52:15Z
2014-02-27T14:52:15Z
2013
Thesis
http://hdl.handle.net/10023/4477
en
265
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/218372021-10-25T14:10:05Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:57:07Z
urn:hdl:10023/21837
Enzyme-catalysed carbohydrate biosynthesis and modification
Merkel, Alexandra B.
Naismith, James
Glycopeptides are regarded as the last line of defence antibiotics. Since their peptide backbone has no biological activity, these compounds depend on attached carbohydrates for their antibacterial potency, as well as for their selectivity and specificity. In Amycolatopsis orientalis, five enzymes are responsible for the synthesis of the L-epivancosamine deoxysugar from dTDP-glucose in the chloroeremomycin biosynthesis. This thesis discusses the structural characterisation of two of these enzymes: EvaD, a 5-epimerase; and EvaA, a 2,3-dehydratase. Structural data on EvaD crystals have been obtained to 1.5Å resolution for apo- and to 1.4Å resolution for a dTMP co-complex. The M131F/L135A mutant of EvaD was also crystallised and data to 2.lÅ collected. Kinetic analysis and deuterium incorporation studies with wild-type and mutant EvaD allowed the identification of all residues involved in catalysis and showed that this enzyme is naturally a mono-epimerase, despite being structurally similar to RmlC-type epimerases. The main reason for this anomaly is the orientation of the catalytic acid, Tyr133. EvaA and several homologues from other Actinomycetales have been cloned, expressed and purified; and the activity of EvaA has been confirmed. Initial crystallisation conditions have been identified for EvaA, but no diffraction has been obtained. A second part of this thesis deals with the investigations into the reaction mechanism of KDPG aldolase from E. coli. This enzyme is useful for the enzymatic synthesis of C-C bonds; however, its substrate profile is too limited for chemical synthesis. To engineer this enzyme to accept non-natural substrates, the reaction mechanism and basis for selectivity have to be understood. Prior to this study, the aldolase had been crystallised, but citrate contained in these conditions bound to the active site preventing co-crystallisation and soaking experiments. Several new crystal forms without citrate were identified facilitating substrate soaks; however, no clear results were obtained.
2021-04-08T08:57:07Z
2021-04-08T08:57:07Z
2005
Thesis
http://hdl.handle.net/10023/21837
en
239, 22 p : ill. (some col.) 30 cm.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/148372019-03-29T11:19:19Zcom_10023_51com_10023_18col_10023_53
2018-07-03T10:48:32Z
urn:hdl:10023/14837
Studies of some aliphatic constituents of shellac
Prentice, Hugh Graham
Gunstone, F. D.
Indian Lac Research Institute
Hydrolysis of lac resin yields a mixture of acids among which only two - aleuritic (up to 40%) and shellolio (up to 5%) - have been adequately characterised and examined by several investigators. The work embodied in this thesis represents some studies of the aliphatic acids in lac hydrolysate. The presence of a range of non-hydroxy acids (1.1%) 6-hydroxytetra- decanoic acid (not less than 8%), l6~hydroxyhexadecanoic acid and snother monohydroxyhexadecanoic acid has been demonstrated. The 6-hydroxytetradecanoic acid has been shown to be identical with butolic acid recently isolated by chemists of the Indian Lac Research Institute but considered by them to be a C1B hydroxy acid. The other acids have not previously been reported as constituents of lac resin. Reversed-phase chromatography was found to be unsuitable for the examination of lac acids, probably due to their highly hydroxylated nature. Dehydroxylation experiments on lac acids by lodlnatlon- deiodination and by bromination-debrominatlon revealed the presence of hydroxylated tetradecanoic and hexadecanoic acids; brominatlon- debrominatlon reactions also showed the presence of small amounts of vicinal dihydroxy acids of these two series. Partition of lac acids between petroleum ether and 80% aqueous methanol and subsequent examination of the petroleum other-soluble material (1.1%) revealed the presence of dodecanoic (trace). tetradec-9-onoic and tetradecanoic acids (25%), hexadec-9-enoic acid (13%), hexadecanoic acid (53%), octadec-9-enoic acid (7%) and octadecanoic acid (2%). Examination of lac acids by adsorption, gas-liquid and thin layer chromatography showed the presence of 6-hydroxy-tetradecanoic acid (8% or more of lac acids), 16-hydroxy-hexadeoanoic acid and another monohydroxyhexadeoanoic acid.
2018-07-03T10:48:32Z
2018-07-03T10:48:32Z
1962
Thesis
http://hdl.handle.net/10023/14837
en
118 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/3602019-07-01T10:20:08Zcom_10023_51com_10023_18col_10023_53
2007-07-06T15:52:45Z
urn:hdl:10023/360
Designing hypercyclic replicating networks
Wood, Evan A.
Philp, Douglas
Templated synthesis
Minimal replication
Reciprocal replication
Organic supramolecular chemistry
In the last 20 years there has been a number of synthetic and natural product based molecular replicators published in the literature. The majority of these systems have focused on the minimal model with only a few examples of cross-catalytic or reciprocal replication. Of the cross-catalytic systems investigated the majority focus around the use of natural products, oligonucleotides, peptides etc. This thesis will investigate the design, synthesis and kinetic analysis of both synthetic minimal and reciprocal replicating systems, and how these two forms of replication interact in a complex hypercyclic network.
Chapter 1 introduces key concepts such as molecular recognition, intramolecularity/ enzyme kinetic, bisubstrate systems and the work conducted into replication systems to date.
Chapter 2 describes the design, synthesis and kinetic analysis of a reciprocal replicating system, based on Diels-Alder and 1,3-dipolar cycloadditions, before going on to discuss what we have learned and how this system can be improved.
Chapter 3 focuses on the design, synthesis and kinetic analysis of a replicating network (minimal and reciprocal replication), based on 1,3-dipolar cycloadditions. Initial individual systems are examined in isolation to determine their behavior and nature. After which the systems are combined to observe how each species interacts in a potential complex hypercyclic network.
Chapter 4 investigates the redesign of the replicating network in Chapter 3 in order to overcome the problems identified from its kinetic analysis.
Chapter 5 introduces the shift in direction away from kinetically controlled replicating networks towards systems in thermodynamic equilibrium.
2007-07-06T15:52:45Z
2007-07-06T15:52:45Z
2007-11-30
Thesis
http://hdl.handle.net/10023/360
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
327
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/220262022-04-13T16:00:03Zcom_10023_51com_10023_18col_10023_53
2021-04-08T09:04:22Z
urn:hdl:10023/22026
A combinatorial approach to glycotherapeutics : template synthesis
Gibson, Darren
In this thesis, general synthetic methods applicable to the development of carbohydrate mimetics were achieved. With such methodology in hand we turned to the development of inhibitor libraries for: a) Trypanosoma cruzi trans-sialidase, an essential enzyme involved in the onset of South American Chagas' disease. Octyl galactoside is recognised by the enzyme so chemical modifications of this structure would be possible. The synthesis of octyl 6- azido-6-deoxy galactoside has been achieved by using two different chemical methods.
b) E. coli 0157 (verotoxin) is a food poisoning toxin (Wishaw, central Scotland). The minimum active component for interaction of sugar and toxin is galabiose [αGal-(1-4)- βGal-(l-4)-OMe] In this thesis, the synthesis of galabiose and various galabiose template mimics are described. Modification of the galabiose structure at the 2 position (methoxycarbonylmethyl) and at the 6 position (amine) or both was successfully achieved. These structures are ready to be incorporated onto a solid-support or a dendrimer base for further evaluation. A small array of 6-amino functionalised galabiose compounds has been successfully achieved.
2021-04-08T09:04:22Z
2021-04-08T09:04:22Z
2001
Thesis
http://hdl.handle.net/10023/22026
en
178p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/219892022-03-10T14:31:57Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:59:49Z
urn:hdl:10023/21989
Quantum chemical studies of intermediates in nitrosamine carcinogenesis
Reynolds, Christopher Arthur
N-Nitrosamines are chemical compounds which are frequently carcinogenic. They may be formed from naturally occurring precursors under a variety of conditions. Despite much experimental study, many of these intermediates in nitrosamine carcinogenesis have not been identified; this thesis describes quantum chemical calculations on these intermediates.
The majority of the calculations have been performed using ab-initio self-consistent-field gradient techniques with a 4-21G split valence basis set. Some calculations have used polarised basis sets; estimates of the correlation energy have also been made. The strategy has been to locate stationary points on the potential energy surfaces for proposed intermediates; the calculation of energies of reaction and energy barriers has made a critical evaluation of alternative pathways possible. A large number of fully optimised ab-initio transition structures are reported.
The nitrosating agent in acidic solution - the nitrous acidium ion has never been observed. However, calculations show that it may exist as a number of different structures. The nitrosation of tertiary amines by the nitrous acidium ion is discussed. Enzymic activation of nitrosamines usually yields an α-hydroxynitrosamine; the calculations suggest that this decomposes either to the diazohydroxide or to the diazotate. The interconversion of monomethylnitrosamines and methyldiazohydroxides is studied. It is proposed that both the (V-hydroxynitrosamines and the diazohydroxides may have sufficient stability to diffuse across the cell. The nature of the alkylating agent is discussed and reasons for reconsidering the diazoalkane are presented. Acid catalysis may be important in the formation of the diazohydroxide. Experiments are suggested which may shed light upon the nature of the alkylating agent.
2021-04-08T08:59:49Z
2021-04-08T08:59:49Z
1986
Thesis
http://hdl.handle.net/10023/21989
en
267p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/286292023-11-24T15:11:54Zcom_10023_51com_10023_18col_10023_53
2023-11-03T12:20:28Z
urn:hdl:10023/28629
Design and synthesis of red thermally activated delayed fluorescence emitters for OLEDs, sensors and bioimaging
Si, Changfeng
Zysman-Colman, Eli
China Scholarship Council (CSC)
University of St Andrews. School of Chemistry
Thermally activated delayed fluorescence
Red TADF
OLEDs
Sensors
Bioimaging
N-doped polycyclic aromatic hydrocarbons (PAH)-acceptor
Developing efficient red thermally activated delayed fluorescence (TADF) emitters remains a formidable challenge due to their low photoluminescence quantum yield governed by the energy-gap law. This thesis concerns the study of orange-to-red TADF materials, focusing on their molecular design, synthesis and photophysics. In addition to OLEDs, these materials were employed as sensors and bioimaging reagents.
Chapter 1 introduces fundamental principles of photoluminescence, electroluminescence, and provides a review of red TADF emitters for OLEDs and TADF emitters for bioimaging.
Chapter 2 documents the relationship between different N-doped polycyclic aromatic hydrocarbons (PAH)-acceptor compounds (DMACBP, DMACPyBP, DMACBPN and DMACPyBPN), their photophysics and OLED performance.
Chapter 3 focuses on a molecular design strategy that combines a p-conjugated acceptors with a TPA donor. By modulating the solid-state solvatochromism and adjusting the p-p stacking interactions, a deep red emission was obtained from both the TPAPyBPN-doped films and its OLED. Furthermore, we demonstrated the first TADF optical sensor for ZnCl₂ based on TPAPyBP.
Chapter 4 explores four new yellow-to-red TADF dendrimer emitters, which were designed to be solution processable. We systematically investigated the effect of substitution position and the strength of the donors on the optoelectronic properties of these four dendrimers. Finally, we employed these emitters in solution-processed OLEDs.
Chapter 5 continues the work on TADF dendrimer emitters by investigating the effect of extending the p-conjugation of the acceptor on the photophsics of the compound. 2GCzBPPZ, with a much larger planarity and p-conjugation acceptor, shows unusual dual emission that is both concentration-dependent and temperature-dependent in solution. 2GCzBPPZ is the first small molecule TADF compound used for colorimetric temperature sensing.
Chapter 6 presents three tetra(donor)-acceptor compounds TCzPhCor, TDMACPhCor, and TPXZPhCor employing corannulene, a curved PAH, as the acceptor. These three emitters exhibit room-temperature phosphorescence from different excited triplet states. While TPXZPhCor doped film can act as an optical temperature sensor in the range from 77 K to 298 K. We also fabricated solution-processed afterglow OLEDs using TPXZPhCor.
Chapter 7 explores the use of D-A TADF emitters in bioimaging. We discussed two types of water-soluble materials: nanoparticles and water-soluble sodium-salt emitters. We also document our first attempt to study these compounds in vitro.
2023-11-03T12:20:28Z
2023-11-03T12:20:28Z
2023-11-29
Thesis
http://hdl.handle.net/10023/28629
https://doi.org/10.17630/sta/650
201806890001
en
https://doi.org/10.17630/54b79926-d8ae-4019-ad10-d2bbf1777816
https://doi.org/10.1039/D3TC02352D
https://doi.org/10.1002/anie.202309718
https://doi.org/10.1002/adma.202300997
https://doi.org/10.1002/anie.202215522
https://doi.org/10.1021/acs.orglett.3c02167
https://doi.org/10.1002/adpr.202200203
https://doi.org/10.1039/D1TC04918F
https://doi.org/10.1002/adma.202003911
https://doi.org/10.1039/C9SC05404A
https://doi.org/10.1039/D0QM00190B
Design and Synthesis of Red Thermally Activated Delayed Fluorescence Emitters for OLED, Sensors and Bioimaging (thesis data). Si, C., University of St Andrews, 1 Nov 2024. DOI: 10.17630/54b79926-d8ae-4019-ad10-d2bbf1777816
Si, C., Hu, Y-N., Sun, D., Wang, K., Zhang, X., & Zysman-Colman, E. (2023). The influence of nitrogen doping of the acceptor in orange–red thermally activated delayed fluorescence emitters and OLEDs. Journal of Materials Chemistry C, 11(36), 12174-12184. https://doi.org/10.1039/D3TC02352D.
Si, C., Wang, T., Gupta, A. K., Cordes, D. B., Slawin, A. M. Z., Siegel, J. S., & Zysman-Colman, E. (2023). Room-temperature multiple phosphorescence from functionalized corannulenes: temperature sensing and afterglow organic light-emitting diode. Angewandte Chemie International Edition, 62(43), [e202309718]. https://doi.org/10.1002/anie.202309718. https://doi.org/10.1002/adma.202300997.
Madayanad Suresh, S., Zhang, L., Matulaitis, T., Hall, D., Si, C., Ricci, G., Slawin, A. M. Z., Warriner, S., Beljonne, D., Olivier, Y., Samuel, I. D. W., & Zysman-Colman, E. (2023). Judicious heteroatom doping produces high-performance deep blue/near-UV multiresonant thermally activated delayed fluorescence OLEDs. Advanced Materials, 35(33), [2300997]. https://doi.org/10.1002/ange.202215522.
Madayanad Suresh, S., Zhang, L., Hall, D., Si, C., Ricci, G., Matulaitis, T., Slawin, A. M. Z., Warriner, S., Olivier, Y., Samuel, I. D., & Zysman-Colman, E. (2023). A deep-blue-emitting heteroatom-doped MR-TADF nonacene for high-performance organic light-emitting diodes. Angewandte Chemie International Edition, 62(8), [e202215522]. https://doi.org/10.1002/ange.202215522.
Yuan, K., Gupta, A. K., Si, C., Uzelac, M., Zysman-Colman, E., & Ingleson, M. J. (2023). Brominated B1-polycyclic aromatic hydrocarbons for the synthesis of deep-red to near-infrared delayed fluorescence emitters. Organic Letters, 25(31), 5880-5884. https://doi.org/10.1021/acs.orglett.3c02167.
Sun, D., Si, C., Wang, T., & Zysman-Colman, E. (2022). 1,3,5-Triazine-functionalized thermally activated delayed fluorescence emitters for organic light-emitting diodes. Advanced Photonics Research, 3(11), [2200203]. https://doi.org/10.1002/adpr.202200203.
Hong, G., Si, C., Gupta, A. K., Bizzarri, C., Nieger, M., Samuel, I. D. W., Zysman-Colman, E., & Bräse, S. (2022). Fluorinated dibenzo[a,c]-phenazine-based green to red thermally activated delayed fluorescent OLED emitters. Journal of Materials Chemistry C, 10(12), 4757-4766. https://doi.org/10.1039/D1TC04918F.
Li, W., Li, Z., Si, C., Wong, M. Y., Jinnai, K., Gupta, A. K., Kabe, R., Adachi, C., Huang, W., Zysman-Colman, E., & Samuel, I. D. W. (2020). Organic long persistent luminescence from a thermally activated delayed fluorescence compound. Advanced Materials, 32(45), [2003911]. https://doi.org/10.1002/adma.202003911.
Ingleson, M. J., Yuan, K., Kahan, R. J., Si, C., Williams, A., Kirschner, S., Uzelac, M., Zysman-Colman, E., & Ingleson, M. J. (2020). The synthesis of brominated-boron-doped PAHs by alkyne 1,1-bromoboration: mechanistic and functionalisation studies. Chemical Science, 11(12), 3258-3267. https://doi.org/10.1039/c9sc05404a.
Sun, D., Suresh, S. M., Hall, D., Zhang, M., Si, C., Cordes, D. B., Slawin, A., Olivier, Y., Zhang, X., & Zysman-Colman, E. (2020). The design of extended multiple resonance thermally activated delayed fluorescence emitter based on polycyclic amine/carbonyl system. Materials Chemistry Frontiers, 4(7), 2018-2022. https://doi.org/10.1039/d0qm00190b.
http://creativecommons.org/licenses/by/4.0/
2024-11-01
Thesis restricted in accordance with University regulations. Restricted until 1 November 2024
Creative Commons Attribution 4.0 International
406
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/292552024-02-15T12:00:22Zcom_10023_51com_10023_18col_10023_53
2024-02-15T11:30:32Z
urn:hdl:10023/29255
Design and development of a deoxyfluorination method using transition metal fluorides
Sood, D. Eilidh
Watson, Allan John Bell
GlaxoSmithKline
University of St Andrews
The installation of a C–F bond in organic molecules is of significant importance to the scientific community due to its ability to modulate a compound’s physicochemical properties. For this reason, organofluorine compounds are valuable and widespread in the medicinal, agrochemical, and material industries.
Accordingly, research into developing new methods of C–F bond formation is a fast-paced field. A popular way of installing C(sp³)–F bonds is by deoxyfluorination whereby alcohols are converted to the corresponding fluorides. This particular transformation is attractive due to the fact that alcohols are readily available and inexpensive starting materials, and the reaction can proceed in a stereospecific manner. There have been a vast range of bespoke deoxyfluorination reagents which have been designed to facilitate this reaction, and whilst they are effective, they often have drawbacks associated with them such as cost and stability.
Of particular interest with regards to C–F bond formation is the use of metal fluorides. This poses a major challenge to organic chemists as the inherent properties of metal fluorides render them difficult to utilise as the fluoride is not easily accessible. Whilst this is an underdeveloped field, recently strategies are emerging which successfully aid the poor reactivity of metal fluorides such as hydrogen bonding catalysis, allowing them to successfully participate in fluorination reactions.
Enclosed is the development of a stereospecific deoxyfluorination reaction using CuF₂ enabled by a Lewis base activating group. The reaction design means that through a ligation approach, the inherent properties of metal fluorides can be circumvented which in turn allows for the chelate-directed delivery of fluoride. Ultimately, the development of this methodology and its generality towards a wide range of alcohol substrates will be discussed. In order to showcase the utility of this strategy, the translation of the system into a ¹⁸F-radiolabelling protocol is demonstrated.
2024-02-15T11:30:32Z
2024-02-15T11:30:32Z
2020-12-01
Thesis
https://hdl.handle.net/10023/29255
https://doi.org/10.17630/sta/764
en
https://hdl.handle.net/10023/21652
https://doi.org/10.17630/b9e6219f-8976-4ad7-830e-8e11bf2079aa
Sood, D. E., Champion, S., Dawson, D. M., Chabbra, S., Bode, B. E., Sutherland, A. C., & Watson, A. J. B. (2020). Deoxyfluorination using CuF2: enabled by a Lewis base activating group strategy. Angewandte Chemie International Edition, 55(22), 8460-8463. https://doi.org/10.1002/anie.202001015 [https://hdl.handle.net/10023/21652 : Open Access version]
Design and Development of a Deoxyfluorination Method Using Transition Metal Fluorides (thesis data)
Sood, D. E., University of St Andrews, 17 Jul 2020.
DOI: https://doi.org/10.17630/b9e6219f-8976-4ad7-830e-8e11bf2079aa
250
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/151242019-03-29T11:19:20Zcom_10023_51com_10023_18col_10023_53
2018-07-09T11:52:22Z
urn:hdl:10023/15124
New variations of the 1, 6, 6aλ⁴-triheterapentalene structure
Mitchell, James Alexander
Reid, D. H.
Science Research Council (Great Britain)
The reaction between 3-substituted-5-phenyl-1, 2-dithiolium salts and various aminoheterocycles was investigated. Substituted 2-aminopyridines gave, in most cases, a mixture of two isomeric products, formulated as dithiadiazacyclopent [a] indenes. Similarly, 2-amino-2-thiazoline and 2-aminothiazole gave a mixture of products. The effect of using different solvents and leaving groups in these reactions was studied. 4-Aminopyridine, 2-aminopyrimidine and 2-aminobenzimidazole each gave only one product, whereas 2,6-diaminopyridine produced a mixture of two disubstitution products- N-Phenylbenzamidine gave a small quantity of 5-phenyl-3-phenylimino- 3H-1, 2-dithiole, while 2-methylpyridine produced no useful material. Two byproducts, 5-phenyl-1, 2-dithiole-3-thione and 5-phenyl-1, 2- dithiole-3-one were formed in each reaction which was investigated. 2-Amino-4-methylpyridine reacted with perchloromethyl mercaptan to give a sulphenamide. Reaction of this compound with benzoylacetic acid, followed by thionation, provided an alternative route to one of the dithiadiazacyclopent [a] indene isomers. The sulphenamides of 2-amino-2-thiazoline and 2-aminothiazole failed to react with benzoylacetic acid. 1, 2, 4-Thiadiazoles were used to synthesise compounds formulated as 1H- and 6H-triheterapentalenes. 4, 5-Dihydro-5-imino-1, 2, 4-thiadiazoles reacted with arenediazonium fluoroborates to give 6H-3aλ⁴ -thia-1, 2, 3, 4 , 6-pentaazapentalehes. 4, 5-Dihydro-5-imino - 1,2,4-thiadiazoles formed Vilsmeier salts which reacted with aqueous methylamine or sodium hydrogen sulphide solution, producing 1H-3aλ⁴ thia-1,3,4,6-tetraazapentalenes and 6H-3, 3aλ⁴ -dithia-1, 4 , 6-triazapentalenes respectively. Sodium hydroxide and sodium hydrogen selenide solutions failed to react with these Vilsmeier salts. 6H-3-oxa-3aλ⁴ -thia-1, 4, 6-triazapentalenes were prepared from 5-acetamino-3-methyl-1, 2, 4 -thiadiazole, 5-formamino- 3-methyl- 1, 2, 4 - thiadiazole,3,6-dimethyl-5-methyl- thio-6H-3aλ⁴ -thia-1, 3, 4, 6-tetraazapentalene and from 4, 5-dihydro- 5-imino- 3, 4 - dimethyl-1, 2, 4 - thiadiazole. 6H-3, 3aλ⁴ -Dithia-1,4,6-triazapentalenes were prepared by thionating oxathiaazapentalenes, and by allowing carbon disulphide to react with 1, 2, 4-thiadiazolium salts. An attempted synthesis of 5,6-dimethyl-6H-3, 3aλ⁴ -dithia- 1, 2, 4 , 6-tetraazapentalene from 5-amino-3, 4-dimethyl-4H-1, 2, 4- thiadiazolium iodide proved unsuccessful. 4, 5-Dihydro-5-imino-3,4-dimethyl- 1, 2, 4-thiadiazole reacted with phenylisocyanate giving 2-aminophenyl-5, 6-dimethyl- 6H-3-oxa-3aλ4-thia-1, 4 , 6-triazapentalene. Phenylisothiocyanate gave 2-aminophenyl-5, 6-dimethyl-6H-3, 3aλ4-dithia-1, 4 , 6-triaza- pentalene. Thiophosgene gave 1, 3-bis(3, 4-dimethyl-1, 2, 4- thiadiazol-5-ylidene)acetone.
2018-07-09T11:52:22Z
2018-07-09T11:52:22Z
1979
Thesis
http://hdl.handle.net/10023/15124
en
xiv, 157 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/5732019-03-29T11:19:21Zcom_10023_51com_10023_18col_10023_53
2008-12-02T16:40:22Z
urn:hdl:10023/573
Enzyme immobilisation and catalysis in ordered mesoporous silica
Smith, Graham Michael
Botting, Nigel P.
Avecia Biotechnology
Enzyme
Mesoporous
CALB
Immobilisation
Hydrolysis
Transesterification
SBA-15
A range of mesoporous materials based on SBA-15 have been prepared and characterised. The materials were templated by neutral block copolymer P123, and typically have a hexagonal (p6mm) pore structure, with high surface areas and narrow pore size distributions. The removal of the surfactant template by calcination and solvent extraction has been investigated. The aqueous stability of this material, and the hydrolysis of the surface was studied.
Organic functional groups were incorporated into the silica surface by co-condensation, or by post synthesis grafting. A range of functional groups were incorporated, including amine, carboxy, allyl and thiol groups. The pore size of the materials was controlled by the addition of trimethoxybenzene during synthesis, which significantly increased the pore size and uptake capacity of the materials.
The adsorption of CALB by SBA-15 was investigated, with support materials extracted by calcination or solvent extraction. Rapid uptake at high loading was observed, with a maximum loading of 450 mg g-1 measured. The leaching of the enzyme from the support was investigated, and found to be high with unfunctionalised supports. The leaching from functionalised supports incorporating sulfur groups was significantly reduced.
The activity of the immobilised CALB was measured by tributyrin hydrolysis in aqueous media, and by enantioselective transesterification of (R)-1-phenylethanol in organic media. The effect of surface functionalisation for reusability and thermal stability in aqueous systems was investigated.
Preliminary studies of supported CALB for dynamic kinetic resolution were carried out, with an investigation of acidic zeolites and a mesoporous supported catalyst for 1-phenylethanol racemisation. The encapsulation of immobilised CALB was investigated, and the activity and reusability of these systems studied.
2008-12-02T16:40:22Z
2008-12-02T16:40:22Z
2008-06-25
Thesis
http://hdl.handle.net/10023/573
en
x, 188 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/119482019-03-29T11:19:22Zcom_10023_51com_10023_18col_10023_53
2017-10-30T14:26:00Z
urn:hdl:10023/11948
A possible low-intermediate temperature proton conductor based on silicon oxide phosphate
Saxin, Stefan
Irvine, John T. S.
Engineering and Physical Sciences Research Council (EPSRC)
The main material studied in this project is silicon oxide phosphate, often referred to in the literature as Si₅O(PO₄)₆. This material has highly unusual coordination of the silicon (octahedral, as well as the more common tetrahedral). The structure is hexagonal, it has been assigned to space group R -3 and lattice parameters a ≈ 7.85 Å, c ≈ 24.14 Å. This work’s main focus is on understanding the interplay between structure and properties in order to enhance protonic conductivity for a fuel cell electrolyte. Silicon oxide phosphate was synthesised with the solid-state method, using a gel precursor made from H₃PO₄, water and SiO₂. Various compositions were made with different P/Si starting ratios, ranging between 0.57 - 1.5. There were small but significant differences in the a,b axes for the different compositions that corresponded to conductivity behaviour of hydrothermally treated P-Si compositions. This correlation was also found to appear in ³¹P NMR for the chemical shift at - 44 ppm for untreated P-Si compositions as well as in the temperatures of the DTA peaks for the hydrothermally treated compositions. This all implies that this particular P-Si system with the addition of water becomes a ternary system that enables protonic conductivity. A proposed mechanism for the protonic conductivity is given where it is suggested that protons flow along the internal channels of the structure using two waters that provide dual pathways for protons. This is possible through utilization of a proton thought to be in the structure (a P_OH bond of 1.57 Å).
Protonic conductivity could further be increased in the system by incorporating 85%
H₃PO₄ in the P-Si materials, thus these materials act as matrices for the phosphoric acid. Another composition, Ge₅O(PO₄)₆ with 5% extra germanium, was hydrothermally treated and found to have protonic conductivity at higher temperatures than the silicon oxide phosphate analogues.
2017-10-30T14:26:00Z
2017-10-30T14:26:00Z
2015-05
Thesis
http://hdl.handle.net/10023/11948
en
182 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/276152023-06-21T11:11:57Zcom_10023_51com_10023_18col_10023_53
2023-05-15T14:01:53Z
urn:hdl:10023/27615
To bind or not to bind - dissociation equilibria studied by pulse dipolar EPR
Wort, Joshua
Bode, Bela Ernest
Biotechnology and Biological Sciences Research Council (BBSRC)
University of St Andrews. School of Chemistry
Pulse dipolar EPR is an appealing strategy for structural characterisation of complex systems in solution that complements other biophysical techniques. Significantly, the emergence of genetically encoded self-assembling spin labels exploiting exogenously introduced double-histidine motifs in conjunction with Cull chelates offers high precision distance determination in systems non-permissive to thiol- directed spin labelling. However, the non‐covalent CuII coordination approach is vulnerable to low binding‐affinity. Here, an approach is outlined where dissociation constants (KD) are investigated directly from the modulation depths of relaxation‐induced dipolar modulation enhancement (RIDME) EPR experiments applied to the model protein Streptococcus sp. group G. protein G, B1 domain (GB1). This reveals low‐ to sub‐μM CuII-chelate KDS under RIDME conditions at cryogenic temperatures. We show the feasibility of exploiting the double‐histidine motif for EPR applications even at sub‐μM protein concentrations in orthogonally labelled CuII–nitroxide systems.
Additionally, modulation depth quantitation in CuII–CuII RIDME to simultaneously estimate a pair of non- identical independent KDS is addressed. Furthermore, we develop a general speciation model to optimise CuII labelling efficiency, depending upon pairs of identical or disparate KDS and total label concentration. We find the KD estimates are in excellent agreement with previously determined values. We also investigated the vulnerability of binding to both competition from adventitious divalent metal ions, and pH sensitivity. A combination of room-temperature isothermal titration calorimetry (ITC) and CuII-nitroxide RIDME measurements are applied to GB1. Results demonstrate double-histidine spin labelling using CuII-nitrilotriacetic acid (CuII-NTA) is robust against the competitor ligand ZnII-NTA at >1000-fold excess, and high nM binding affinity is retained at acidic and basic pH, despite room-
temperature behaviour suggesting a stronger dependence.
.
2023-05-15T14:01:53Z
2023-05-15T14:01:53Z
2022-06-15
Thesis
http://hdl.handle.net/10023/27615
https://doi.org/10.17630/sta/466
en
https://doi.org/10.17630/ec8eef86-099d-4a1b-8a0d-814a997f352d
To Bind or Not to Bind - Dissociation Equilibria Studied by Pulse Dipolar EPR (thesis data) Wort, J., University of St Andrews, 11 May 2023. DOI: https://doi.org/10.17630/ec8eef86-099d-4a1b-8a0d-814a997f352d
286
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/292732024-02-22T14:45:47Zcom_10023_51com_10023_18col_10023_53
2024-02-16T11:57:20Z
urn:hdl:10023/29273
Studies of hydride ion conductors using combined spectroscopy techniques
Irvine, Gavin John
Irvine, John T. S.
Jones, Martin Owen
UK Research and Innovation (Agency). ISIS Neutron and Muon Source
James E. Crockett Educational & Charitable Trust
Hydride
Superionic conductor
Neutron scattering
Crystallography
QENS
Total scattering
PDF
Ionic conductivity
Concerted migration
Vacancy mediated conductivity
Liquid-like sublattice
RMCProfile
This thesis presents research into two superionic conductors: BaH₂ and β-Ca₂NH. The research presented herein explores the diffusion pathway of hydride ions (H⁻) in the solid-state of these materials.
Using novel combined spectroscopic techniques, we show that BaH₂ has a diffusion pathway that involves the partial melting of its crystal lattice. This "liquid-like" sublattice is analysed in detail in order to elucidate the origins of such behaviour as well as provide a physical description of a sublattice manifesting as "liquid-like."
The second material explored in this thesis is a novel superionic conductor not previously published, β-Ca2NH. The analysis shows that Ca₂NH (nitride- hydride) materials come in at least two distinct polymorphs, with dramatically different ionic conductivities. Using in situ neutron powder diffraction along with several other techniques, we explore the unique configurations of the different Ca₂NH polymorphs and identify what gives rise to ionic conductivity in one form and not the other. Furthermore, Ca₂NH is contrasted to the closely related imide (NH₂⁻) and amide (NH₂⁻).
Barium hydride is shown to have an ionic conductivity of 0.32 S/cm at 600 ◦C and its conduction due to the presence of a liquid-like sublattice. Calcium nitride-hydride, on the other hand, is shown to have an ionic conductivity of 0.08 S/cm at 600 ◦C and its conduction defined by an intrinsic vacancy concentration created by anti-Frenkel defects. Thus, the thesis explores two excellent solid-state ionic conductors with dramatically different ionic conduction mechanisms.
The synthesis route for the following compounds are detailed in this thesis: BaH₂, BaD₂, Ca₂NH - both polymorphs, CaNH, and Ca(NH₂)₂.
2024-02-16T11:57:20Z
2024-02-16T11:57:20Z
2022-06-15
Thesis
https://hdl.handle.net/10023/29273
https://doi.org/10.17630/sta/775
en
http://creativecommons.org/licenses/by-nd/4.0/
Embargo period has ended, thesis made available in accordance with University regulations
Creative Commons Attribution-NoDerivatives 4.0 International
184
University of St Andrews
The University of St Andrews
Rutherford Appleton Laboratory, STFC
oai:research-repository.st-andrews.ac.uk:10023/154622019-03-29T11:19:23Zcom_10023_51com_10023_18col_10023_53
2018-07-17T09:28:04Z
urn:hdl:10023/15462
A study of some free radicals by electron spin resonance
Rorke, David
2018-07-17T09:28:04Z
2018-07-17T09:28:04Z
1965
Thesis
http://hdl.handle.net/10023/15462
en
162 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/292912024-02-25T03:01:15Zcom_10023_51com_10023_18col_10023_53
2024-02-19T15:18:43Z
urn:hdl:10023/29291
Title redacted
Reid, Ellie
Kay, Euan Robert
Lusby, Paul
Engineering and Physical Sciences Research Council (EPSRC). Centre for Doctoral Training in Critical Resource Catalysis (CRITICAT)
Abstract redacted
2024-02-19T15:18:43Z
2024-02-19T15:18:43Z
2024-06-13
Thesis
https://hdl.handle.net/10023/29291
https://doi.org/10.17630/sta/781
EP/L016419/1
en
https://doi.org/10.17630/e6337edf-bbc6-46b9-9b96-28c81082108b
Data underpinning Ellie Reid's thesis Reid, E., University of St Andrews, 16 Feb 2029. DOI: https://doi.org/
10.17630/e6337edf-bbc6-46b9-9b96-28c81082108b
2029-02-16
Thesis restricted in accordance with University regulations. Restricted until 16 February 2029
401
The University of St Andrews
University of Edinburgh
oai:research-repository.st-andrews.ac.uk:10023/21252019-03-29T11:19:23Zcom_10023_51com_10023_18col_10023_53
2011-12-21T14:38:17Z
urn:hdl:10023/2125
Solvothermal chemistry of luminescent lanthanide fluorides
Jayasundera, Anil
Lightfoot, Philip
Exploration of novel lanthanide fluoride framework materials in inorganic-organic hybrid
systems under solvothermal conditions towards development of new luminescent
materials is discussed. X-ray single crystal and powder diffraction methods have been
used as crystallographic characterisation techniques. Determination and study of
luminescence properties for selected hybrid materials has also been carried out.
The first organically templated luminescent lanthanide fluoride framework, [C₂N₂H₁₀]₀.₅
[Ln₂F₇] (Ln= Nd, Tb, Dy, Ho, Er, Yb and Lu), has been synthesised and characterised.
This structure type consists of a three-dimensional yttrium fluoride framework
incorporating two similar, but crystallographically distinct, yttrium sites.
Photoluminescence studies of [C₂N₂H₁₀]₀.₅ [Y₂F₇]: Ln³⁺ (Ln³⁺ = Gd³⁺, Eu³⁺ and Tb³⁺)
have been explored and characteristic luminescence emissions are reported.
An inorganic-organic hybrid indium fluoride and its scandium fluoride analogue,
[C₄H₁₄N₂][MF₅](M=In and Sc) is reported. The structure consists of infinite trans vertex
sharing (InF₅)[subscript(∞)] chains, which are linked via H-bonded organic moieties. The scandium
and fluorine local environments of [C₄H₁₄N₂][ScF₅] are characterised by ¹⁹F, and
⁴⁵Sc
solid-state MAS NMR spectroscopies. A single scandium site has been confirmed by
⁴⁵Sc
MAS NMR. ¹⁹F MAS NMR clearly differentiates between bridging and terminal
fluorine. The photoluminescence properties of these complexes, [C₄H₁₄N₂][In[subscript(1-x)] Ln[subscript(x)]F₅]
(Ln=Tb and/or Eu), have been explored. The optimum composition for Eu³⁺ doped
samples occurs at x = 0.05 Eu³⁺ and the “asymmetry ratio” of R = I₅₉₀/I₆₁₅ (
⁵D₀ →
⁷F₂ and
⁵D₀ →
⁷F₁) gives a clear picture of the sensitivity for crystal field of the compound.
For x = 0.08 Tb³⁺, a strong down-conversion fluorescence corresponding to
⁵D₄ →
⁷F₅ (green at 543.5 nm) occurs. In addition, a Tb³⁺/Eu³⁺ co-doped sample exhibits a
combination of green (Tb³⁺) and orange (Eu³⁺) luminescence, with Tb³⁺ enhancing the
emission of Eu³⁺ in this host.
Exploration of novel indium, aluminium, and zirconium fluoride crystal structures with
potential luminescent properties has also been undertaken. A chiolite-like phase K₅In₃F₁₄
(space group P4/mnc) has been synthesised. No phase transition occurs over the
temperature range 113K< T< 293 K, as has been seen in other chiolite-like structures. An
organically templated indium fluoride, [NH₄]₃[C₆H₂₁N₄]₂[In₄F₂₁] has been prepared; this
features the trimeric unit [In₃F₁₅]³⁻ which appears to be the first of its type in a metal fluoride. A new hybrid fluoride, Sr[N₂C₂H₁₀]₂[Al₂F₁₂].H₂O has been synthesised.
Because the ionic radius of Eu²⁺ is similar to that of Sr
²⁺ this may be a potential host for
blue luminescent Eu²⁺. The new material KZrF₅.H₂O shows pentagonal-bipyramidal
geometry of Zr⁴⁺ with a polar space group, Pb2₁m, which may potentially have
ferroelectric properties.
2011-12-21T14:38:17Z
2011-12-21T14:38:17Z
2009
Thesis
http://hdl.handle.net/10023/2125
en
vii, 195
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/217972021-09-27T15:58:53Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:37:34Z
urn:hdl:10023/21797
Production of alkyl lactate esters by the alkoxycarbonylation of vinyl acetate
Rucklidge, Adam J
Cole-Hamilton, D. J. (David John)
Chemistry Theses
The methoxycarbonylation of vinyl acetate to methyl 2 and 3- (acetoxy)methylpropanoate has been studied using a variety of bidentate phosphine ligands in the presence of a palladium precursor and acid. In some cases (Bu ᵗ₂P(CH₂)ₙPBuᵗ₂ and 1,2-bis(di-tert-butyIphosphinomethyl)benzene (DTBPMB) the ligands were already known, but new syntheses were established for a variety of other ligands, mostly with xylene backbones. The compounds of general formula 1,2- (RR'PCH₂)C₆H₄ were synthesised either from the reaction of o-xylene with a mixture of KOᵗBu and n-BuLi, followed by R₂PCl (R = ᵗBu, R = ⁱPr, R = Ph, R = Et) or by the reaction of LiPRR'(BH₃) with l,2-bis(dichloromethyl)benzene (R = ᵗBu R' = ⁱPr). LiPRR'(BH₃) was in turn prepared from the reaction of PRR'Cl with NaBH₄ to form PRR'H, and the subsequent reaction with n-BuLi. Similar reactions were used to prepare l,2-bis(di-tert-butylphosphinomethyl)naphthalene (borane protected route) and 2,3-bis(di-tert-butylphosphinomethyl)naphthalene (dianion route). The synthesis of unsymmetrical ligands such as ᵗBuₙPr₂₋ₙPCH₂C₆H₄PCH₂ᵗBu₂ (n = 0 or 1) proved much more problematic. Eventually, they were successfully prepared from the sequential reaction of the cyclic sulphates with Li PRⁱPr(BH₃) (R = ⁱPr or ᵗBu) and Li PᵗBu₂ (BH₃). During the methoxycarbonylation of vinyl acetate, the competing transesterification with methanol to give methyl acetate and dimethoxyethane via ethanal, usually drastically reduces the yield. The addition of tertiary phosphines such as PEt₃, but not DTBPMB, catalyses the degradation reaction, as does methanesulphonic acid. However, provided that the ligand is present in excess over the acid, so that all the acid is present as the phosphonium salt, the degradation reaction does not occur even at 80 °C. The phosphonium salt is sufficiently acidic to allow protonation of the palladium catalyst and DTBPMB promotes good activity for the methoxycarbonylation of vinyl acetate even under very mild conditions (1 bar CO, 25 °C). Optimisation studies have allowed the branched:dinear (b:l) to be improved from 1.2 at 30 bar and 80 °C to 3.6:1 at 1 bar and 25 °C. l,2-bis(di-tert-butylphosphinomethyl)naphthalene and 2,3-bis(di-tert-butylphosphinomethyl)naphthalene both give very similar results, but the other ligands are all inferior. The relative importance of steric and electronic effects on the reaction selectivity are discussed.
2021-04-08T08:37:34Z
2021-04-08T08:37:34Z
2005
Thesis
http://hdl.handle.net/10023/21797
en
231 p : ill., charts 30 cm. + 1 computer laser optical disc (4 3/4 in.)
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/151872019-03-29T11:19:24Zcom_10023_51com_10023_18col_10023_53
2018-07-10T13:25:52Z
urn:hdl:10023/15187
Nitrosothiols as no-donor drugs: Synthesis, mechanistic studies, chemical stability, pharmacological and physiological activity
Al-Sa'doni, Haitham H.
Butler, Anthony (Anthony R.)
S-Nitrosothiols (RSNO) are an important class of NO-donor drugs. They have been used clinically and occur naturally where they may have a role in several biological and physiological processes in the human body. The medical importance of S-nitrosothiols has been highlighted recently by several reports which describe the clinical use of GSNO (13) to inhibit platelet aggregation during coronary angioplasty and also to treat a form of preeclampsia, a high blood pressure condition suffered by some pregnant women. We set out to extend the range of compounds of this type by synthesising a novel series of biologically active S-nitrosothiols (1-13) and to look for a correlation between structure, chemical stability, and physiological activity. The situation has been complicated by the recent discovery that the main route for the release of NO from S-nitrosothiols is a copper- catalysed process. A detailed kinetic study of copper ions, and thiols on the stability of the compounds we synthesised has shown that the dominant pathway for the decomposition of S-nitrosothiols in most circumstances is one catalysed by Cu⁺ ions. We suggest that Cu⁺ ions are formed by the reaction of Cu²⁺ ions with thiol, present in the S-nitrosothiols as an impurity. The implications of this discovery for an understanding of the biological action of S-nitrosothiols is suggested. All the new S-nitrosated dipeptides (2-12) examined show less susceptibility to copper (I)- catalysed release of NO than SNAP (1) but are more reactive than GSNO (13). We found that S-nitrosated dipeptides are potent vasodilators and suitable inhibitors of platelet aggregation but are chemically very stable in the absence of copper ions. All thirteen compounds combine the favoured property of chemical stability with a high level of biological activity. We found that copper(I)-chelation induced reduction of the biological activity of S- nitrosothiols in smooth muscle relaxation. The results show that responses to both SNAP and GSNO are reversibly inhibited by neocuproine. We conclude that relaxation of vasodilator smooth muscle by SNAP and GSNO is caused in part by NO released into solution via a Cu⁺-dependent catalytic reaction, and provide evidence that endogenous Cu⁺ ions may also contribute to the maintenance of vasodilator 'store' in vivo by catalysing the decomposition of naturally-occurring S-nitrosothiols. A particularly interesting finding recently by Gordge et al. (1995) shows that the inhibition of platelet aggregation activity shown by GSNO is much reduced in the presence of neocuproine and the closely related bathocuproine, both specific Cu⁺-chelating agent. However, it was shown very recently (Schrammel et al, 1996) that copper ions inhibit basal and NO-stimulated recombinant soluble guanylate cyclase activity and that Cu⁺ is more effective than Cu²⁺ in this regard. L-Ascorbic acid (vitamin C) could play a role in the in vivo release of NO from naturally occurring and exogenous S-nitrosothiols and so play a part in smooth muscle relaxation and in inhibition of platelet aggregation. All thirteen compounds examined show the ability to release NO in vitro. The inhibitory effect of Hb, a recognised NO scavenger, was investigated. In smooth muscle, responses to intermediate doses of S-nitrosothiols were significantly inhibited by Hb, though not abolished entirely. In platelet, we found that the inhibitory activity of these S-nitrosothiols was reversed by haemoglobin, indicating the involvement of NO in the process. We found that the solution stability of the S-nitrosothiols did not correlate with relaxation of vascular smooth muscle or inhibition of platelet aggregation, again suggesting that the tissue specificity is a function of the R- group. We conclude that the biological activity of S-nitrosothiols depends upon the release of NO in a process catalysed by Cu(I), and that the decomposition may occur inside or outside the cell, depending upon the structure of RSNO.
2018-07-10T13:25:52Z
2018-07-10T13:25:52Z
1996
Thesis
http://hdl.handle.net/10023/15187
en
247 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/218282021-10-25T10:10:15Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:57:04Z
urn:hdl:10023/21828
The chemistry of simple alcohols, amino acids and nucleic acid bases on silicon substrates
Gómez, Alberto López
Richardson, N. V. (Neville V.)
The interaction between organic molecules and silicon substrates has been investigated using several surface sensitive techniques. The studies of the competitive reactions between simple alcohols and water show that only isopropanol is able to passivate the surface and inhibit further adsorption of H2O. The reaction occurs through cleavage of OH bonds and the formation of Si-O linkages. At room temperature, the cleaved H atoms are kept at the surface through the formation of Si-H bonds. Unsaturated heterocyclic molecules like maleic anhydride react with the silicon surface through a 2+2-cycloaddition reaction and provide a well defined ordered template to achieve further film growth. Bifunctional molecules like glycine and 4-aminobenzoic acid react with the surface through the carboxylate group, leaving the amino group available for further film growth. Similarly to the alcohols, the reaction occurs through cleavage of OH bonds and formation of Si-O-C linkages. The presence of a surface modifier like Na, modifies the interaction of the carboxylate groups with the surface from unidentate to bidentate. This leads to the formation of an ordered layer with well-defined bonding sites. The study of the adsorption of uracil on Si(100)-2x1 showed that this molecule is able to form well ordered structures on the surface. The vibrational spectroscopy study indicated that only the enol tautomer of uracil is able to react with the surface.
2021-04-08T08:57:04Z
2021-04-08T08:57:04Z
2002
Thesis
http://hdl.handle.net/10023/21828
en
141p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/112392019-03-29T11:19:25Zcom_10023_51com_10023_18col_10023_53
2017-07-18T13:20:15Z
urn:hdl:10023/11239
Research into the structure of the alkaloid aspidospermine
Smith, G. F. (George Fouet)
Openshaw, H. T.
Great Britain. Department of Scientific and Industrial Research
2017-07-18T13:20:15Z
2017-07-18T13:20:15Z
1949-10
Thesis
http://hdl.handle.net/10023/11239
en
153 leaves
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/275982023-06-28T21:03:08Zcom_10023_51com_10023_18col_10023_53
2023-05-12T13:03:06Z
urn:hdl:10023/27598
Title redacted
Irvine, Matthew
Irvine, John T. S.
Gover, Richard Keith Branson
AWE
Abstract redacted
2023-05-12T13:03:06Z
2023-05-12T13:03:06Z
2023-06-14
Thesis
http://hdl.handle.net/10023/27598
https://doi.org/10.17630/sta/459
en
https://doi.org/10.17630/c0d6d626-a8b2-4a96-a9a0-fdf024b5af9d
Data underpinning Matthew Irvine's PhD (thesis data) Irvine, M., University of St Andrews, 6 May 2025. DOI: https://doi.org/10.17630/c0d6d626-a8b2-4a96-a9a0-fdf024b5af9d
2025-05-06
Thesis restricted in accordance with University regulations. Restricted until 6th May 2025
244
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/108182023-03-31T11:18:51Zcom_10023_51com_10023_18col_10023_53
2017-05-23T14:57:23Z
urn:hdl:10023/10818
A synthetic and structural investigation of pnictogen and chalcogen peri-substituted naphthalenes
Nejman, Phillip S.
Kilian, Petr
Woollins, J. D. (J. Derek)
Engineering and Physical Sciences Research Council (EPSRC)
Donor–acceptor complexes have been known for over a century and enjoy a long list of applications in chemistry. The work presented in this thesis explores the dative interaction between phosphorus and its heavier congener bismuth. Utilising peri-substitution, atoms can be forced in close proximity to one another resulting in a repulsive (non-bonding) interaction or an attractive (bonding) interaction. Hence, peri-substitution can be used to support traditionally ephemeral species. A range of phosphorus and bismuth containing peri-substituted compounds were synthesised and characterised using multi-nuclear NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction with the data for several structures collected and solved personally. Where the bismuth moiety contained two aryl groups, no bonding interaction between the phosphorus and bismuth was observed owing to the poor Lewis acidity of the bismuth. Upon increasing the Lewis acidity, by exchanging one of the aryl groups with a halogen, the formation of a donor‒acceptor complex was observed. This series of compounds represents rare examples of structurally characterised phosphine‒bismuthine donor‒acceptor complexes. The formation of bismuth(V) derivatives proved to be incredibly challenging with only one compound obtained. The compound was identified as a phosphino‒bismuthonium salt.
The coordination of S,S bidentate ligands remains an important area of chemistry. Complexes bearing this type of ligand have a number of industrial applications including catalysts in vulcanisation and lubricant additives. These complexes can also show a range of electrochemical properties and can support unusual magnetic properties. Two series of rhodium and iridium complexes were prepared using aromatic dithiolates of varying flexibility and size. These were characterised using multinuclear NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction with the data for most of the structures collected and solved personally. Bimetallic complexes were shown to form via bridging sulfur and/or chlorine atoms when the metal centre was coordinatively unsaturated. A large variation in the type of structure was observed depending on the flexibility of the aromatic backbone with an interesting tetrameric structure obtained when the biphenyl backbone was utilised. Monomeric forms of the complexes were obtained using a phosphorus donor to occupy the vacant site. The change in flexibility of the backbone was shown to have little effect on the structure formed. Altering the size and electronics of the phosphorus ligand was investigated with the electronic properties shown to overcome any steric restrictions imposed by an increased size as determined by the Tolman cone angle.
2017-05-23T14:57:23Z
2017-05-23T14:57:23Z
2017-06-21
Thesis
http://hdl.handle.net/10023/10818
https://doi.org/10.17630/10023-10818
en
xiv, 235 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/132702020-09-03T16:01:44Zcom_10023_51com_10023_18col_10023_53
2018-05-01T14:15:05Z
urn:hdl:10023/13270
A multi-diverse approach to catalysis : ruthenium, gold and FLP catalysis
Piola, Lorenzo
Kamer, Paul (Paul C. J.)
Smith, Andrew David
Engineering and Physical Sciences Research Council (EPSRC)
Ruthenium
Gold
FLP
Metathesis
C-H activation
Hydrogenation
Formic acid
Ruthenium-based homogenous catalysis is a broad and extremely useful branch of transition metal catalysis. Surely, the most famous example is olefin metathesis, for which Yves Chauvin, Robert Grubbs and Richard Schrock were awarded the 2005 Chemistry Nobel Prize. Although some of the most well-known catalysts are widely used and considered benchmark catalysts, the research around this topic has not stopped. The modification of known systems to achieve better performance and better understanding of the catalytic mechanism is very important and an example of such modification is reported in this thesis. The newly synthesised catalysts were compared to the parent commercially available catalyst showing better reactivity.
Ruthenium catalysis, though, is not limited to olefin metathesis and C-H activation, for example, it has become a useful approach to the functionalisation of organic molecules. In this field, the deuteration of C-H bonds is an interesting transformation, which has many applications. The synthesis of new hydridosilylruthenium complexes and their application in the deuteration of a variety of substrates is reported in this manuscript. The unprecedented synthesis of tetradeuterated Ketoprofene is also reported.
Recently, ruthenium-based catalysts have found application in the dehydrogenation of suitable compounds, such as formic acid, ammonia-borane and other hydrogen-rich substances. The driving force behind these discoveries is the use of H₂ as an energy vector in place of fossil fuels. A hydrido-ruthenium catalyst was shown to catalyse the decomposition of formic acid in CO₂ and H₂ and to catalyse the reduction of olefinic substrates.
The released CO₂ from the reaction did not interfere with the fuel cell due to its inertness. This property makes its employment as C1 source very challenging, although its use would also be extremely attractive because of the abundance of this gas. In these regards, both frustrated Lewis pairs (FLPs) and gold catalysts have shown interesting reactivity in the activation of CO₂. A new FLP and a silica supported gold catalyst were synthesised to test them in CO₂ activation and the results are reported in this manuscript.
2018-05-01T14:15:05Z
2018-05-01T14:15:05Z
2018-06-27
Thesis
http://hdl.handle.net/10023/13270
en
http://creativecommons.org/licenses/by-nc-nd/4.0/
2022-04-17
Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 17th April 2022
Attribution-NonCommercial-NoDerivatives 4.0 International
xviii, 215 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/34072019-09-30T11:36:07Zcom_10023_51com_10023_18col_10023_53
2013-03-20T16:16:50Z
urn:hdl:10023/3407
Chemical biology studies on 5-nitrofurans and sirtuin inhibitors
Zhou, Linna
Westwood, Nicholas James
Cancer Research UK
Overseas Research Students Awards Scheme (ORSAS)
ALDH2
Nitrofuran
Zebrafish
Trypanosome
Target identification
Part I: Target identification studies are one of the most difficult but rewarding challenges in
chemical biology. Part I of this thesis describes target identification studies for 5-nitrofuran
containing hits. The 5-nitrofurans used in this study were identified in a phenotypic screen for
compounds that induced melanocyte cells death in zebrafish.
Chapter 1 provides brief overviews on three related areas of the project: 1) the use of
zebrafish as a model organism in drug discovery; 2) phenotypic screening using zebrafish and
3) the strategies used in target identification studies.
Chapter 2 describes the synthesis of and SAR studies on two series of 5-nitrofuran
containing analogues. The design and preparation of biotinylated chemical probes based on
the SAR data is also described. These chemical tools are then used in affinity
chromatography studies and genetic validation of a potential target (zebrafish Aldh2) of the
5-nitrofuran compounds is reported.
Chapter 3 provides a review of the biological and chemical processes that human ALDHs
are known to mediate. In addition, small molecules that modulate ALDH2 activity are
reviewed. A detailed study of the interaction between 5-nitrofurans and human ALDH2
including in vitro enzymatic assays is described leading to the conclusion that the 5-
nitrofurans under study are substrates of human ALDH2. Further mechanism of action
investigations using model reactions are also presented.
Chapter 4 introduces the use of 5-nitrofuran containing drugs in the clinic and highlights the
reported side-effects. Further investigation of the interaction between ALDH2 and 5-
nitrofurans in zebrafish and yeast using ALDH2 inhibitors is described. Based on these
results, a combination therapy strategy is proposed. Finally, the trypanocidal activity of the
newly synthesised 5-nitrofurans is discussed.
Experimental details and future work for Part I are presented in Chapters 5 and 6
respectively.
Part II: Human sirtuins are associated with various biological functions and diseases,
including cancer and neurodegeneration. Previous work from the Westwood Lab has led to
the discovery of the tenovins that act as inhibitors of SIRT1 and SIRT2. Part II of the thesis
reports the development of potent fixed ring tenovin analogues with high SIRT2 selectivity.
Chapter 7 provides a brief review of the biology of human SIRT2 and the reported SIRT2
inhibitors available to date. This is followed by a short summary of the previous work on the
tenovins in the Westwood Lab and the design of the fixed ring tenovin analogues.
Chapter 8 describes the synthesis of three series of fixed ring tenovin analogues. SAR data is
generated based on in vitro enzymatic assays against both SIRT1 and SIRT2 and the prepared
analogues showed relatively high potency and selectivity against SIRT2. Further cell-based
deacetylation assay are also discussed. All the experimental details are reported in Chapter 9
and Chapter 10 provides with conclusions and proposed future work.
2013-03-20T16:16:50Z
2013-03-20T16:16:50Z
2012-12
Thesis
http://hdl.handle.net/10023/3407
en
2020-04-25
Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 25th April 2020
294
University of St Andrews
The University of St Andrews
Chemistry
oai:research-repository.st-andrews.ac.uk:10023/291212024-02-01T03:01:09Zcom_10023_51com_10023_18col_10023_53
2024-01-31T15:49:51Z
urn:hdl:10023/29121
Chiral phosphoric acid-catalyzed asymmetric protonation reactions of vinylheteroaryls
Ashford, Matthew
Watson, Allan John Bell
University of St Andrews
This thesis describes investigations into the chiral phosphoric acid-catalyzed aza-Michael addition-asymmetric protonation between arylamines and various α-substituted vinylheterocycles.
Initially, research focused on the development of optimal reaction conditions for the aza-Michael addition-asymmetric protonation reaction of arylamines and fluorovinylheterocycles, furnishing heterocyclic phenethylamine products containing benzylic stereocentres with a carbon-fluorine bond in good yields (up to 95%) and enantioselectivity (up to >99:1 e.r.). Investigation into the asymmetric protonation step was carried out through DFT calculations and kinetic experiments, this provided evidence for a stereocontrolled proton transfer from catalyst to substrate. Additionally, the conformation of the heterocyclic phenethylamine products was explored through DFT calculations and XRD.
Chlorovinylheterocycles were also investigated within the aza-Michael addition- asymmetric protonation reaction, furnishing heterocyclic phenethylamine products containing benzylic stereocentres with a carbon-chlorine bond in good yields (up to 99%) and enantioselectivity (up to 99:1 e.r.). Development of a one-pot aza-Michael addition- asymmetric protonation-ring closure reaction was also carried out to furnish chiral heterocyclic aziridines in good yields (up to 81%) and enantioselectivity (up to 97:3 e.r.). Product derivatization of the chiral heterocyclic aziridines furnished chiral vicinal diamines in good yields (up to 84% yield) and enantioselectivity (up to 96:4 e.r.). Catalyst variation experiments showed the importance of steric interactions from the catalyst
alkyl groups in enforcing high enantioselectivity.
2024-01-31T15:49:51Z
2024-01-31T15:49:51Z
2022-06-15
Thesis
http://hdl.handle.net/10023/29121
https://doi.org/10.17630/sta/718
en
http://hdl.handle.net/10023/20485
Ashford, M., Xu, C., Molloy, J. J., Carpenter-Warren, C. L., Slawin, A. M. Z., Leach, A. G., & Watson, A. J. B. (2020). Catalytic enantioselective synthesis of heterocyclic vicinal fluoroamines using asymmetric protonation: a method development and mechanistic study. Chemistry - A European Journal, 26(53), 12249-12255. Advance online publication. https://doi.org/10.1002/chem.202002543 [http://hdl.handle.net/10023/20485 : Open Access version]
269
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/168152019-10-15T09:27:47Zcom_10023_51com_10023_18col_10023_53
2019-01-09T12:03:47Z
urn:hdl:10023/16815
Title redacted
Smith, Duncan Robert Miller
Goss, Rebecca J.
2019-01-09T12:03:47Z
2019-01-09T12:03:47Z
2017-12-07
Thesis
http://hdl.handle.net/10023/16815
en
2020-09-20
Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 20th September 2020
xxvi, 283 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/218562021-10-28T09:08:58Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:57:14Z
urn:hdl:10023/21856
A study of halogen adducts of some arsines
Mahomedy, Amina Y.
Harris, G. S.
2021-04-08T08:57:14Z
2021-04-08T08:57:14Z
1978
Thesis
http://hdl.handle.net/10023/21856
en
vii, 194 p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/9322019-07-01T10:03:09Zcom_10023_51com_10023_18col_10023_53
2010-06-22T13:29:58Z
urn:hdl:10023/932
New nitric oxide releasing materials
McKinlay, Alistair C.
Morris, Russell Edward
Nitric oxide
Metal organic framework
MOF
Release
Wound healing
Controlled release
M-CPO-27
Applications
The aim of this thesis was to examine the ability of metal organic frameworks (MOFs) to store and controllably release biologically significant amounts of nitric oxide (NO). Initial work involved the synthesis of a series of isostructural MOFs, known as M-CPO-27, which display coordinatively unsaturated metal sites (CUSs) when fully activated (guest solvent molecules both coordinated and uncoordinated to the metal atom are removed). Two of these frameworks (Ni and Co CPO-27) displayed exceptional performance over the entire cycle of activation, storage and delivery showing the largest storage and release of NO of any known porous material (up to 7 mmolg⁻¹). These frameworks would therefore be considered for initial research into the formulation of MOFs, for possible use in medical applications. It was shown that they still release large amounts of NO even when placed inside porous paper bags, creams or hydrocolloids. The other versions of M-CPO-27 also displayed significant adsorption of NO however they show poor total NO release. It was also shown that it is possible to synthesise both Ni and Co CPO-27 using microwave synthesis without any detrimental effect to the porous structure.
Several iron-based MOFs were also investigated for NO storage and release. The results showed that Fe MIL-88 based structures adsorb good amounts of NO but only release a small amount of the irreversibly adsorbed NO. Two successfully amine grafted giant pore MOFs were then investigated to attempt to improve the NO adsorption and release. This result was not observed however, due to the poor total amine grafting coverage and pore blockage resulting from the amines. In-situ IR studies reveal that when exposed to NO, activated Fe MIL-100 forms a chemical bond with the NO. The studies also displayed that when water is then allowed to attempt to replace the NO that only a small amount of NO is actually released, the majority of the NO either remains chemically bonded to the Fe atom or forms N₂O in conjunction with a Fe-OH group.
Other MOFs were also successfully synthesised and characterised for NO storage and release. Both Ni succinate and Ni STA-12 display good adsorption and excellent release of NO. This indicates that Ni based MOFs show the best results for NO adsorption and release.
In the conclusion of the thesis I am able to categorise the NO release ability of MOFs based on composition and formulate a theory as to why this happens.
2010-06-22T13:29:58Z
2010-06-22T13:29:58Z
2010-06-23
Thesis
http://hdl.handle.net/10023/932
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
259
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/156942019-03-29T11:19:28Zcom_10023_51com_10023_18col_10023_53
2018-07-24T14:26:44Z
urn:hdl:10023/15694
Synthesis and battery application of nanomaterials and the mechanism of O₂ reduction in aprotic Li-O₂ batteries
Liu, Zheng
Bruce, Peter G.
Engineering and Physical Sciences Research Council (EPSRC)
SORS
Lithium ion batteries
Lithium oxygen batteries
Electrochemistry
Nanomaterials
TiO₂
Hunting for improved energy storage devices based on rechargeable Li-ion batteries and
other advanced rechargeable batteries is one of the hottest topics in today’s society. Both Li-
ion batteries and Li-O₂ batteries have been studied within the thesis. The research work of
this thesis contains two different parts. Part 1. The controlled synthesis of the extreme small
sized nanoparticles and their application for Li-ion batteries; Part 2. The study of the O₂
reduction mechanism in Li-O₂ batteries with aprotic electrolytes.
In the first part, two different types of extremely small-sized TiO₂ nanoparticles with at lease
on dimension less than 3 nm was synthesised via solvothermal/hydrothermal reaction, i.e.,
anatase nanosheets and TiO₂(B). These nanoparticles were obtained without any
contamination of long chain organic surfactants. A series of systematic characterisation
methods were employed to analyse the size, phase purity, and surface condition. These
extremely small-sized nanoparticles exhibit improved capacity, rate performance as anode
materials for Li-ion batteries. The shapes of load curves of charge and discharge are
significantly modified due to the reduced size of TiO₂ nanoparticles.
In chapter 3, we will see the variation of the capacity and the load curve shape of the anatase
nanosheets according to their thickness and surface conditions. The origin of the excessive
capacity is analysed based on the electrochemical data. It has been identified that both
pseudocapacitive (interfacial) Li+ storage and the excessive Li+ -storage from the bulk
contribute to the increased capacity.
In chapter 4, the shape and size of the sub-3 nm TiO₂(B) nanoparticles are studied, a method
based the PXRD data is established. These nanoparticles demonstrate a reversible capacity of
221 mAh/g at a rate of 600 mA/g and remain 135 mAh/g at 18000 mA/g without significant
capacity fading during cycling.
In the last part, a systematic study of O₂ reduction mechanism for aprotic Li-O₂ batteries
based on the combination of a series of electrochemical and spectroscopic data is presented.
The novel mechanism unifies two previous models for the growth of Li₂O₂ during discharge,
i.e., Li₂O₂ particle formation in the solution phase and Li₂O₂ film formation on the electrode
surface. The new mechanism provides fundamental conceptions for the improvement of
Li₂O₂ batteries and shed light on the future research of Li₂O₂ batteries.
2018-07-24T14:26:44Z
2018-07-24T14:26:44Z
2016-03
Thesis
http://hdl.handle.net/10023/15694
en
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/155182020-11-13T17:07:46Zcom_10023_51com_10023_18col_10023_53
2018-07-18T09:12:30Z
urn:hdl:10023/15518
Studies of mass transport in some poly(ethyleneoxide)-based polymer electrolytes
Hardgrave, Martin Thomas
Vincent, Colin Angus
Science and Engineering Research Council (SERC)
The work in this thesis relates to the transport of salt species in polymer electrolytes, which are solid ionic conductors in which mass transport is similar to that in liquids, rather than in ion-conducting glasses. A brief examination of some of the experimental techniques which have been used to study polymer electrolytes is given before examining in more detail the processes involved when these materials are polarised between non-blocking electrodes. A theoretical treatment is given for various models of polymer electrolytes, in particular polymer electrolytes containing free ions and polymer electrolytes containing free ions and ion-pairs. Non-ideality has been considered for the free ion model. Computer simulations of the free ion and ion-pair model predict that the steady-state current that these materials pass may be proportional to the applied potential difference for many tens of volts, in contrast with the free ion model, where the potential difference limit is of the order of millivolts. The use of the terms "transference number" and "transport number" is discouraged, because of the effect of the motion of uncharged species in practical systems. A new parameter, the current fraction, is defined for steady-state polarisation experiments. An experimental study of amorphous polymer electrolytes is described, in which electrolytes were polarised to steady-state using non-blocking electrodes. The application of the Hittorf technique to these materials has been demonstrated, with true transference numbers determined for some electrolytes. Conductivity and neutron scattering experiments suggest that the reported unusual conductivity behaviour of lithium triflate-based electrolytes does not exist or is not generally displayed.
2018-07-18T09:12:30Z
2018-07-18T09:12:30Z
1991
Thesis
http://hdl.handle.net/10023/15518
en
244 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/35552019-07-01T10:08:42Zcom_10023_51com_10023_18col_10023_53
2013-05-27T11:11:54Z
urn:hdl:10023/3555
Synthesis and structure-property relationships in rare earth doped bismuth ferrite
Kavanagh, Christopher M.
Morrison, Finlay D.
Lightfoot, Philip
BiFeO₃
Perovskite
Octahedral tilting
Magnetostriction
Invar effect
Negative thermal expansion
Multiferroic
Superexchange
La
Nd
There has been significant interest in BiFeO₃ over the past decade. This interest has focused on the magnetic and electrical properties, which in the long term may prove useful in device applications.
This thesis focuses on the synthesis, electrical characterisation, and structural origin of the electrical properties of rare earth doped bismuth ferrite. Two systems have been studied: BiFeO₃ doped with lanthanum and neodymium (Bi₁₋ₓREₓFeO₃ RE= La, Nd). Specific examples have been highlighted focusing on a detailed structural analysis of a lanthanum doped bismuth ferrite, Bi₀.₅La₀.₅FeO₃, and a neodymium analogue, Bi₀.₇Nd₀.₃FeO₃. Both adopt an orthorhombic GdFeO₃-type structure (space group: Pnma) with G-type antiferromagnetism.
Structural variations were investigated by Rietveld refinement of temperature dependent powder neutron diffraction using a combination of both conventional “bond angle/bond length” and symmetry-mode analysis. The latter was particularly useful as it allowed the effects of A-site displacements and octahedral tilts/distortions to be considered separately. This in-depth structural analysis was complemented with ac-immittance spectroscopy using the multi-formulism approach of combined impedance and modulus data to correlate structural changes with the bulk electrical properties. This approach was essential due to the complex nature of the electrical response with contributions from different electroactive regions.
The structural variations occur due to a changing balance between magnetic properties and other bonding contributions in the respective systems. This results in changes in the magnitude of the octahedral tilts, and A-site displacements giving rise to phenomena such as negative thermal expansion and invariant lattice parameters i.e., the invar effect.
More specifically, analysis of Bi₀.₅La₀.₅FeO₃ highlights a structural link between changes in the relative dielectric permittivity and changes in the FeO₆ octahedral tilt magnitudes, accompanied by a structural distortion of the octahedra with corresponding A-site displacement along the c-axis; this behaviour is unusual due to an increasing in-phase tilt mode with increasing temperature. The anomalous orthorhombic distortion is driven by magnetostriction at the onset of antiferromagnetic ordering resulting in an Invar effect along the magnetic c-axis and anisotropic displacement of the A-site Bi³⁺ and La³⁺ along the a-axis. This contrasts with the neodymium analogue Bi₀.₇Nd₀.₃FeO₃ in which a combination of increasing A-site displacements in the ac-plane and decrease in both in-phase and anti-phase tilts combine with superexchange giving rise to negative thermal expansion at low temperature. The A-site displacements correlate with the orthorhombic strain.
By carefully changing the synthesis conditions, a significant change in bulk conductivity was observed for a number for Bi₁₋ₓLaₓFeO₃ compositions. A series of Bi₀.₆La0.₄FeO₃ samples are discussed, where changes in the second step of the synthesis result in significantly different bulk conductivities. This behaviour is also observed in other compositions e.g. Bi₀.₇₅La₀.₂₅FeO₃. Changes in the electrical behaviour as a function of temperature are discussed in terms of phase composition and concentration gradients of defects. Activation energies associated with the conduction process(es) in Bi₁₋ₓLaₓFeO₃ samples, regardless of composition, fall within one of two broad regimes, circa. 0.5 eV or 1.0 eV, associated with polaron hopping or migration of charge via oxygen vacancies, respectively.
The use of symmetry-mode analysis, in combination with conventional crystallographic analysis and electrical analysis using multi-formulism approach, presents a new paradigm for investigation of structure-property relationships in rare earth doped BiFeO₃.
2013-05-27T11:11:54Z
2013-05-27T11:11:54Z
2013-06-26
Thesis
http://hdl.handle.net/10023/3555
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
180
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/4822019-07-01T10:16:05Zcom_10023_51com_10023_18col_10023_53
2008-05-15T09:33:02Z
urn:hdl:10023/482
New reactions under homogeneous conditions
Núñez Magro, Ángel Alberto
Cole-Hamilton, D. J. (David John)
BDTBPMB has been proven to be an essential ligand in carbonylation chemistry.
Its two tert-butyl groups and wide bite angle give it the ideal characteristics for this kind
of chemistry, and leads to high activity and selectivity with use of its complexes. During
this work the group of reactions where this ligand has been proven to be active has been
extended with two new protocols for hydroxycarbonylation and aminocarbonylation. In
the hydroxycarbonylation process, a large variety of unsaturated compounds were studied.
Dioxane was found to be the ideal solvent, due to its properties in terms of coordinability,
and miscibility with water. Using this solvent as the medium, a BDTBPMB complex of
palladium was found to be highly active and selective under mild conditions.
Initial attempts to address the aminocarbonylation of alkenes catalysed by the
Pd/BDTBPMB system did not give high activity. This problem was overcome by the
addition of an arylalcohol. Under those conditions, high selectivity and conversion was
obtained in a wide variety of amides. However, attempts to address the
aminocarbonylation of alkenes with ammonia gas to generate primary amides did not
result in any conversion. The generation of these primary amides was obtained with
transamidation of N-phenylnonamides which can be prepared by aminocarbonylation.
Amides have been successfully hydrogenated to amines catalysed by a
Ru/Triphos system. This system has been proven to be highly active in this reaction.
High selectivities have been obtained in the generation of secondary amine. However,
initial results of the hydrogenation of primary amides resulted in no formation of primary
amines. A careful analysis of the mechanism of the formation of various products from
the hydrogenation of primary amides allows the selective formation of primary amines by
the ruthenium/Triphos system in the presence of ammonia. The possibility of the
generation of primary amides in situ from acids under hydrogenation conditions, giving
primary amines was explored with high conversion and moderate selectivities.To complete this work, a system based on a palladium complex for the
decarboxylation of benzoic acids was developed. Usually, the decarboxylation reactions
catalysed by copper require high temperatures. However, palladium complexes of highly
electron donating ligands such as BDTBPMB or P(ᵗBu)₃ were found to be highly active
under milder conditions. This catalytic system was proven to be active in desulfonation
reactions giving high conversion.
2008-05-15T09:33:02Z
2008-05-15T09:33:02Z
2007
Thesis
http://hdl.handle.net/10023/482
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
263
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/153152019-03-29T11:19:30Zcom_10023_51com_10023_18col_10023_53
2018-07-12T13:39:41Z
urn:hdl:10023/15315
Preparation and reactions of 2-alkyltetrahydrofurans from fatty alcohols
Dawes, Margaret
Gunstone, F. D.
2-Alkyltetrahydroftirans have been prepared from C₁₀-C₁₈ primary alcohols. Complete characterisation of these compounds by mass spectral and NMR studies has been achieved. Ring-opening reactions of the 2-alkyltetrahydrofurans have been studied and have provided an insight into the chemistry of these compounds, highlighting differences in reactivities and reaction products compared with the parent molecule, tetrahydrofuran. The C₁₀-C₁₈ 2-alkyltetrahydrofurans have been subjected to a variety of ring cleavage reactions involving reaction with Lewis acids and/or acyl halides to produce compounds of the type;
RCH(X)CH₂CH₂CH₂-Y and RCH(Y)CH₂CH₂CH₂-X
R = C₆H₂₉ - C₁₄H₂₉, X = halogen atom, Y = acyl group
This work has demonstrated the ease with which these compounds may be ring opened. In some cases the reaction with the 2-alkyltetrahydrofiirans was observed to be more rapid and vigorous than with tetrahydrofuran itself. This was not always the case: The acid catalysed reaction of tetrahydrofiaran with dodecanol resulted in formation of the diether shown below, and a diester was similarly formed by the acid catalysed reaction of tetrahydrofliran with lauric acid.
R0(CH₂)₄OR diether (R = C12H25) RCOO(CH₂)₄OCOR diester (R= C₁H₂₃)
The analogous reactions with substituted tetrahydrofurans were slow and diether/diester yield was extremely low. Introduction of the alkyl group at position two of the tetrahydrofuran ring severely impeded the reaction. Instead the hydroxy ethers shown below were the major cyclic ether derived products.
C₁₂H₂₅-O-CH(R)(CH₂)₃-OH and C₁₂H₂₅-O-(CH₂)₃CH(R)-0H.
(R = C₆H₁₃)
Oxidation of the 2-alkyltetrahydrofurans was readily achieved by treatment with ruthenium tetroxide and resulted in formation of the corresponding alpha-alkyl-gamma-lactones and gamma-keto acids in almost quantitative yields and
RCO(CH₂)₂COOH
(R=C₆H₁₃-C₁₄H₂₉)
2018-07-12T13:39:41Z
2018-07-12T13:39:41Z
1996
Thesis
http://hdl.handle.net/10023/15315
en
201 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/173522021-02-19T14:46:38Zcom_10023_51com_10023_18col_10023_53
2019-03-22T16:39:36Z
urn:hdl:10023/17352
Structure-property relationships in ferroelectric tungsten bronze oxides
McNulty, Jason Allan
Morrison, Finlay
Engineering and Physical Sciences Research Council (EPSRC)
2019-03-22T16:39:36Z
2019-03-22T16:39:36Z
2019-06-26
Thesis
http://hdl.handle.net/10023/17352
https://doi.org/10.17630/10023-17352
en
https://doi.org/10.17630/dde8f5e2-3c91-4449-b6c6-c56d07c2cd3e
Structure-property relationships in ferroelectric tungsten bronze oxides (Thesis data) McNulty, J.A., University of St Andrews. DOI: https://doi.org/10.17630/dde8f5e2-3c91-4449-b6c6-c56d07c2cd3e
http://creativecommons.org/licenses/by-nc-nd/4.0/
2021-03-07
Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 7th March 2021
Attribution-NonCommercial-NoDerivatives 4.0 International
xii, 219 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/36702019-03-29T11:19:31Zcom_10023_51com_10023_18col_10023_53
2013-06-12T10:14:26Z
urn:hdl:10023/3670
Novel chiral wide bite angle ligands for asymmetric catalysis
Czauderna, Christine F.
Kamer, Paul (Paul C. J.)
Homogeneous catalysis
Wide bite angle
Asymmetric catalysis
Chiral diphosphorus ligands
Hydrogenation
Hydroformylation
Organometallic chemistry
Achiral wide bite angle ligands have been shown to be highly active and to induce excellent chemo- and regioselectivities in many homogeneously catalyzed reactions. However, only a few examples of chiral wide bite angle ligands are known so far. A diphenyl ether backbone was selected to allow maximum synthetic versatility and potential for a modular approach to design and synthesize such chiral diphosphorus ligands. Three synthetic strategies have been explored in this thesis: i) introduction of chiral substituents in the ligand backbone, ii) the use of P-stereogenic donor atoms and iii) the synthesis of chiral mixed-donor ligands bearing chiral auxiliary groups on the phosphorus atoms.
Functionalization of the 3,3’-positions of 2,2’-bis(diphenylphosphino)diphenyl ether by carboxylic acid or ether auxiliaries was achieved via straightforward four-step routes to generate a library of ligands that were tested in various catalytic reactions. In the Pd-catalyzed asymmetric allylic alkylation of l,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate with dimethyl malonate the enantioselectivity was found to depend on the size of the chiral auxiliary introduced within the diphenyl ether backbone and its proximity to the phosphorus donor groups and hence to the active metal centre.
Two types of mixed donor bidentate diphosphorus ligands based on the diphenylether backbone have been established, i.e. phosphine-phosphite and phosphine-phosphonite derivatives. A small ligand library bearing different chiral auxiliaries was accomplished via straightforward syntheses that enable derivatization of the respective phosphite and phosphonite moieties in the final step. In the Rh-catalysed hydrogenation of several benchmark substrates high conversion and moderate to high enantioselectivities (up to 97% for dimethyl itaconate) were obtained. The enantioselectivity was influenced by the size of the ortho-substituent on the chiral auxiliary group of the phosphite or phosphonite fragment.
Two modular synthetic approaches for the preparation of novel wide bite angle diphosphine ligands containing stereogenic P-atoms have been developed. Both protocols involved diphenylether as backbone and the chiral ephedrine based precursor (2R[subscript(P)],4S[subscript(C)],5R[subscript(C)])-oxazaphospholidine borane as initial auxiliary to induce chirality at phosphorus. Various novel diphosphines were isolated as highly enantioenriched compounds with dr-ratios up to 95:5.
2013-06-12T10:14:26Z
2013-06-12T10:14:26Z
2013-03-01
Thesis
http://hdl.handle.net/10023/3670
en
Print and electronic copy restricted util 11th April 2015
Thesis restricted in accordance with University regulations
268
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/152892019-03-29T11:19:32Zcom_10023_51com_10023_18col_10023_53
2018-07-12T09:24:30Z
urn:hdl:10023/15289
Some aspects of the molecular structure of heterocyclic and organometallic compounds
Cutherbertson, Alastair Fraser
Glidewell, Christopher
Various rules which have been used to rationalise molecular geometries are discussed. After this the results from MNDO calculations on simple carbenes, ethers and amines are presented, and these were designed to test the hypothesis that in the presence of ligands of low electronegativity lone pairs would not fulfil their stereochemical role assigned to them in the VSEPR model. Following on are MNDO calculations on cyclic molecules: the cyclopentadiene ring is planar in silylcyclopentadiene and non-planar in trimethylsilylcyclopentadiene. The calculations attempt to resolve this and in addition the nature of the fluxional exchange. The intermediates which are formed by diazepinium salts when they are protodebrominated are then discussed in the light of MNDO calculations. Single crystal x-ray work was carried out for four heterocyclic molecules. The compounds reported are: 4-phenyl-3-phenylamino-1,2,4-thiadiazolin-5-one; 5-(N-methylthiocarbamoylimino)-4-phenyl-3-phenylamino-4H-l,2,4-thiadiazoline; N,N-bis[2-(5-t-butyl-3H-1,2-dithiol-3-ylidene)ethylidene]hydrazine and N,N-dimethyl-N-[2-(5-t-butyl-3H-1,2-dithiol-3-ylidene)ethylidene]hydrazine. Details of MNDO calculations which were undertaken on molecules related to the x-ray work are then presented, and in the final chapter a discussion of the heterocyclic crystal structures appears. The first appendix reports the structure of a macrocyclic ligand, the second provides a list of publications and the third appendix is a list of the structure factors, least-squares planes and anisotropic temperature parameters for the crystal structure determinations.
2018-07-12T09:24:30Z
2018-07-12T09:24:30Z
1983
Thesis
http://hdl.handle.net/10023/15289
en
viii, 157 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/165652023-11-13T13:35:32Zcom_10023_51com_10023_18col_10023_53
2018-11-28T10:30:00Z
urn:hdl:10023/16565
Title redacted
Orsi, Angelica Fortunata
Wright, Paul Anthony
Seventh Framework Programme (European Commission)
2018-11-28T10:30:00Z
2018-11-28T10:30:00Z
2018-06-27
Thesis
http://hdl.handle.net/10023/16565
en
https://doi.org/10.17630/685771e2-ff51-443f-a8f0-3afb10bd667a
Data underpinning Angelica Orsi's thesis. Orsi, A.M.A.F., University of St Andrews, DOI: https://doi.org/10.17630/685771e2-ff51-443f-a8f0-3afb10bd667a
http://creativecommons.org/licenses/by-nc-nd/4.0/
2024-06-03
Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 3rd June 2024
Attribution-NonCommercial-NoDerivatives 4.0 International
x, 281 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/219642022-03-01T12:03:55Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:59:40Z
urn:hdl:10023/21964
Synthetic studies on some fatty acids
Baker, Charles Derek
Gunstone, F. D.
Part 1 – Synthesis of some Monoethenoid Acids with Potential Essential Fatty Acid Activity.
The cis-isomers of the four acids, teradec-8-enoic, hexadeco-10-enoic, octadic-12-enoic and cicos-14-enoic have been synthesised via the corresponding acetylenic acids.
Part II – Configuration of Natural 9-hydroxyoctadecanoic Acid.
9D-Hydroxyoctadecanoic acid has been synthesised and found to possess no measurable optical activity. It is suggested, on the evidence of a mixed melting point, that the natural acid has the d-configuration.
Part III – Synthetic studies on 6,8-Dihydroxyoctanoic Acid.
Two synthetic routes to 6,8-dihydroxyoctanoic acid have been examined. Both were eventually abandoned.
2021-04-08T08:59:40Z
2021-04-08T08:59:40Z
1961
Thesis
http://hdl.handle.net/10023/21964
en
105 p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/26322019-07-01T10:14:24Zcom_10023_51com_10023_18col_10023_53
2012-06-04T15:35:53Z
urn:hdl:10023/2632
The vicinal difluoro motif in organic chemistry : the synthesis and behaviour of compounds derived from 2,3-diflurosuccinic acids
Schueler, Martin
O'Hagan, David
The following work describes the synthesis of compounds carrying a vicinal difluoro
motif and the evaluation of this structural element to influence the conformation of
organic molecules. The synthesis of erythro and threo 1,2-difluoro-1,2-diphenylethane
was achieved by bromofluorination and subsequent halogen exchange from stilbene.
Oxidative degradation of the phenyl rings allowed to access erythro and threo 2,3-
difluorosuccinic acids and a variety of derivatives thereof. The conformations of these
compounds were investigated by means of X-ray analysis and NMR spectroscopy.
Conformational analysis of derivatives of 2,3-difluorosuccinic acid was carried out
using JHFandJHHNMR coupling constants. A clear preference for the conformations in
which the two vicinal C-F bonds are gauche emerged from these calculations, which
was confirmed by temperature and solvent dependent NMR analyses.
The vicinal difluoro motif was incorporated into small peptide structures. In the solid
state, a strong preference to align the vicinal C-F bonds gauche to each other was
observed and when adjacent to an amide moiety, the C-F bond was found to prefer an
anti periplanar orientation with respect to the carbonyl bond. These effects appeared to
override steric and electrostatic interactions. The conformation of these fluorinecontaining
peptides showed a clear dependence on the stereochemicaol rientation of the
C-F bonds, and this appears to be an effective tool for influencing the secondary and
consequently tertiary structure in a predictable manner. In order to access single
enantiomerso f peptides having the vicinal difluoro, motif, a stereoselectiver oute to R,R
and SS 2,3-difluorosuccinic was developed. This involved nucleophilic fluorination of
the cyclic sulfates generated from (R, R)- and (SS)- diethyl tartrates and subsequent
deoxofluorination of the intermediate fluorohydrins.
2012-06-04T15:35:53Z
2012-06-04T15:35:53Z
2006
Thesis
http://hdl.handle.net/10023/2632
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
288
University of St Andrews
The University of St Andrews
Edinburgh and St Andrews Research School of Chemistry
oai:research-repository.st-andrews.ac.uk:10023/292712024-02-16T23:03:39Zcom_10023_51com_10023_18col_10023_53
2024-02-16T11:25:26Z
urn:hdl:10023/29271
Fluorite type oxide-ion conductors : new approaches
Zhang, Shuoshuo
Irvine, John T. S.
Savaniu, Cristian Daniel
China Scholarship Council (CSC)
Doped zirconia
Oxide ion conduction
Short-range ordering
Defect
The development of electrolyte materials for the high temperature (800-1000 ∘C) solid oxide fuel cell (SOFC) is mostly based on anion-deficient fluorite oxides, especially cubic stabilised zirconia and ceria. The 8 mol % yttria stabilised zirconia (8YSZ) is so far the most commonly used one owing to its fairly high ionic conductivity and good stability at high temperature cell operation. However, new materials with higher ionic conductivities are demanded to reduce the cell ohmic loss at high temperatures. Although doped ceria provides a higher ionic conductivity than doped zirconia, the reduction of Ce⁴⁺ in the fuel cell reducing atmosphere introduces electronic conduction and lattice expansion which can be detrimental to cell performance. The perovskite structured strontium-magnesium doped lanthanum gallate (LSGM) has high ionic conductivity that is comparable to doped ceria. The limitation for this material comes from its interaction with the traditional Ni-YSZ anode. This means developments of new anode materials, or interlayer designs are required. The scandia stabilised zirconia (SSZ) in the doped zirconia family is a very attractive candidate as it offers the highest ionic conductivity amount the doped zirconia systems. However, 11SSZ, which offers the highest ionic conductivity in the Sc₂O₃ − ZrO₂ system that is comparable to doped ceria and LSGM in the high temperature operating range, undergoes a
rhombohedral-cubic phase transition at about 600 ∘C, with the cubic phase existing only at T > 600 ∘C. Apart from this phase stability issue, most SSZ compositions show a significant conductivity degradation behaviour over time.
Accordingly, this thesis is to investigate new electrolyte materials, with a particular focus on the co-doped 11SSZ systems, that may offer higher ionic conductivities, and improved phase and conductivity stabilities for the high temperature fuel cell application. The material's properties are all related to its underlying chemistry. As a matter of fact, this thesis provides new approaches in evaluating the observed properties and conductivity behaviours in the fluorite materials, links the experimental evidence to its underlying chemistry. This thesis aims to provide a deep level understanding on the fundamental of zirconia and stabilised zirconia: its chemistry and defect structure, in order to uncover the fundamental of phase stabilisation, factors that limit the maximum ionic conductivity and driving forces for the conductivity degradation, etc., in doped zirconia systems. This is extended to all the fluorite-based and related systems. It follows that the electrolyte performance is closely related to its microdomain structural changes. In particular, the problem of conductivity degradation is tackled by the elimination of short-range ordering of oxygen vacancies. Apart from the microdomain structure, the total ionic conductivity is also closely related to the crystal phase assembly and microstructures.
The elimination of conductivity degradation in one of the Mg, In co-doped zirconia composition (IMSSZ) significantly improves the long-term conductivity stability, together with a stable, simple crystal structure and a high ionic conductivity (0.14 S cm⁻¹ at 850 ∘C and the ionic conductivity can reach 0.4 S cm⁻¹ at 1000 ∘C). This will contribute to an overall improved cell performance when integrating into the SOFC. The theory, concepts and characterisation methods developed in this study for fluorite and fluorite-related materials, especially those related to microdomain structural studies and characterisations, can be applied further to any energy material with a certain adaptation. This is hoped to provide some insights into new material design, in particular the electrolyte.
2024-02-16T11:25:26Z
2024-02-16T11:25:26Z
2021-06-30
Thesis
https://hdl.handle.net/10023/29271
https://doi.org/10.17630/sta/774
en
2022-05-10
Thesis restricted in accordance with University regulations. Restricted until 10 May 2022
362
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/273132024-01-22T10:54:41Zcom_10023_51com_10023_18col_10023_53
2023-03-31T11:39:01Z
urn:hdl:10023/27313
Probing the structure and reactivity of zeolites in their interactions with water
Rice, Cameron Mark
Morris, Russell Edward
Ashbrook, Sharon E.
Engineering and Physical Sciences Research Council (EPSRC)
Chemistry
Zeolites
NMR
Nuclear magnetic resonance
Water
Materials
Porous materials
Isotope
Isotopic enrichment
Synthesis
Publication
The work presented in this thesis has been performed to increase the understanding of the interactions of zeolites with water, under a range of reaction conditions. The systems studied have been selected on the basis of their known hydrolytic instability or as model systems for which new avenues for hydrolytic instability can more easily be followed. The focus of research detailed in this thesis is split into three main sections. The mechanism of the ADOR (Assembly, Disassembly, Organisation, Reassembly) process for the synthesis of new zeolites from germanosilicate UTL is probed to deepen the understanding of the intermediate species formed and how the local structure and long-range order of the products are affected by reaction variables. Subsequently, the CHA framework has been selected as a model system for the study of a newly-identified bond lability exhibited by some non-‘ADORable’ aluminosilicate zeolite materials. To further aid characterisation and understanding of this lability, a series of inter-zeolite transformations from the FAU to CHA framework have been adapted to allow ¹⁷O enrichment and ¹⁷O NMR spectroscopic investigation, to characterise and identify key intermediate and framework species. The complexity and high structural disorder of the materials studied in this work mean that a multivariate approach to characterisation and analysis is required. Pri- marily, solid-state NMR spectroscopy and powder X-ray diffraction have been used to characterise the materials, elucidating differences between their local structure and long-range order. In addition, energy-dispersive X-ray spectroscopy, scanning electron microscopy, thermogravimetric analysis and density functional theory calculations have also been used to further aid characterisation and understanding of these complex systems. Results presented demonstrate that both zeolites and water interact strongly with one another when combined. Zeolites and water are found to be reactive even under mild conditions, e.g. room temperatures, where ¹⁷O NMR spectroscopy has shown the rapid exchange of H₂¹⁷O oxygen into the frameworks of UTL, CHA and FAU zeolites, by resolving signals attributed to framework zeolite linkages. Whilst favourable under ambient conditions, these bond lability processes are also found to be selective, with observed enrichment found to differ between frameworks with different topologies, com- positions and extraframework cations. In some cases, observed exchange of framework oxygen species has been attributed in part to the defective nature of zeolite frameworks. A further mechanistic explanation for the enrichment of zeolites for which the structure is not thought to be defective has also been predicted by collaborators using molecular dynamics. Whilst this mechanism may explain the facile bond lability seen for CHA frameworks, its widespread applicability to other zeolite frameworks that show rapid exchange of framework oxygen with that in water is not known. Water is also found to interact strongly with zeolite frameworks undergoing structural transformations, such as during the ADOR process or during post-synthetic transformations. Here, under the elevated temperatures of reaction conditions, ¹⁷O supplied from H₂¹⁷O reagent has been shown to be incorporated into the structure of zeolite frameworks, especially in regions considered non-reactive within the reaction. These results demonstrate that both zeolites and water interact and react when combined and provide further evidence to the contrary that zeolites are perceived as static, inert scaffolds. The findings have potential implications for the commercial uses of zeolites, where a balance between framework stability and flexibility is important.
2023-03-31T11:39:01Z
2023-03-31T11:39:01Z
2022-11-29
Thesis
http://hdl.handle.net/10023/27313
https://doi.org/10.17630/sta/382
EP/N509759/1
en
https://doi.org/10.17630/f835c79c-efc5-4580-a0c7-0a3cee869eac
Probing the Structure and Reactivity of Zeolites in their Interactions with Water (thesis data) Rice, C. M., University of St Andrews, 1 Nov 2024. DOI: https://doi.org/10.17630/f835c79c-efc5-4580-a0c7-0a3cee869eac
2024-11-01
Thesis restricted in accordance with University regulations. Restricted until 1st November 2024
295
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/32792019-07-01T10:10:53Zcom_10023_51com_10023_18col_10023_53
2012-12-05T17:01:38Z
urn:hdl:10023/3279
Environmental effects in quantum chemistry : QM/MM studies of structures, NMR properties and reactivities in extended systems
Bjornsson, Ragnar
Bühl, Michael
Quantum chemistry
QM/MM
NMR
Environmental effects
Computational modelling of chemical systems is most easily carried out in the vacuum for single molecules. Accounting for environmental effects accurately in quantum chemical calculations, however, is often necessary for computational predictions of chemical systems to have any relevance to experiment.
This PhD thesis focuses on accounting for environmental effects in quantum chemical calculations by quantum mechanics/ molecular mechanics (QM/MM) approaches, taking on diverse examples from the solid state, the liquid phase and the protein environment. The methods are applied to compute a variety of properties from transition metal NMR properties of molecular crystals and enzymes, via conformational properties of zwitterions in aqueous solution, to an intramolecular amidation reaction in peptides.
Chapter 3 concerns QM/MM calculations of molecular properties in the solid state, both molecular crystals and metalloenzymes, with a focus on transition metal chemical shift and EFG properties. We demonstrate that solid-state effects on such properties in molecular crystals can be accounted for by a simple general black-box QM/MM approach. We also describe preliminary QM/MM calculations of 51V anisotropic NMR properties for a vanadium-dependent enzyme.
In Chapter 4 the focus is on solvent effects on the conformational preference of a small zwitterionic molecule, 3F-γ-aminobutyric acid (3F-GABA), calculated using QM/MM molecular dynamics simulations. NMR spin-spin coupling constants in solution are also calculated. Our simulations highlight the difficulty of accounting for solvation effects well enough to achieve agreement with experimental observations.
Chapter 5 concerns the reaction mechanism of an intramolecular amidation reaction in a bacterial peptide, predicted by QM/MM calculations. We predict a reaction mechanism that accounts well for the experimental observations both for the wild-type and mutants.
We demonstrate that environmental effects can often be satisfactorily accounted for by QM/MM approaches, thus helping to bridge the gap between theory and experiment.
2012-12-05T17:01:38Z
2012-12-05T17:01:38Z
2012-11-30
Thesis
http://hdl.handle.net/10023/3279
en
http://creativecommons.org/licenses/by/3.0/
Creative Commons Attribution 3.0 Unported
181 p.
University of St Andrews
The University of St Andrews
School of Chemistry
oai:research-repository.st-andrews.ac.uk:10023/154652019-03-29T11:19:35Zcom_10023_51com_10023_18col_10023_53
2018-07-17T09:59:45Z
urn:hdl:10023/15465
The thermal decomposition of benzyl iodide
Gow, John Stobie
Horrex, Charles
Carnegie Trust for the Universities of Scotland
The results of the work, described in this thesis, may be summarized as follows:- 1) The gas phase pyrolysis of benzyl iodide, either alone or in the presence of added free iodine, proceeds via the following mechanism
BzI ⟷Ke Bz + I
I + I ⟷ I ₂
Bz + Bz ⟶ k2 Bz-Bz
An analysis of the data has been carried out where reactions (a) and (b) are presumed to reach equilibrium and reaction (c) is rate determining. Over a temperature range of 516°K, carried out using both static (516-557°K) and flow (611-702°K) systems with benzyl iodide partial pressures from. 03 mm. to 9.0 mm., the logarithm of 2 k₂Ke² plotted against 1/(T°K) gave a straight line. The slope of this Line on the above mechanism is equal to (2 △h+E)/2.3R (where △ = change in heat content associated with the equilibrium BzI ⟷Bz + I and E = the activation energy of the reaction Bz + Bz ⟶ Bz-Bz) and (2 △H + E) was found to be 84 K cal./mol. On the assumption that E = O, this is equivalent to a benzyl iodide bond strength of 42 K cal./mol. This experimentally derived bond strength must be reduced by 1 K cal./mol. for every 2 K cal./mol. Of energy of activation required by the recombination of tow benzyl radicals. A review of the literature, on free radical recombination energies, suggests that for benzyl radicals it is not likely to exceed 4-5 L cal./mol. And therefore the present investigation leads to a value of 40-42 K cal./mol. for the strength of the carbon-iodine bond in benzyl iodide.
2) It has been shown that, in the presence of excess hydrogen iodide as a radical acceptor, benzyl iodide decomposes according to the following mechanism –
(a) BzI ⟶ Bz + I
(b) I + I ⟷I₂
(d) Bz + HI ⟶ Bz-H + I
(e) I + BzI ⟶ Bz + I₂
In this scheme, the rate determining process is the dissociation process in (a) since, with sufficient HI present, reaction (d) prevents an equilibrium concentration of benzyl radicals being built up. It has been shown to be possible to obtain conditions where the rate of iodine formation is independent of HI concentrations. Using such conditions, reaction epsilon was shown to be a very significant contributor to the total rate. Moreover, the elimination of the back reaction in (a) produced a large increase in decomposition rate, so much so that the range of temperature used in this section of the work was over 100oC below that for the previous section. The energy of activation of the reaction (e); has been determined as 4.1 K cal./mol. (This value was calculated from results covering the temperature range 505 to 585°K). Using Perlman and Rollefson's(78) data on the dissociation of molecular iodine, this activation energy of 4.1 K cal./mol. is equivalent to a benzyl iodide bond strength of 40.6 K cal./mol. This value is in good agreement with that obtained from the pyrolysis work in the absence of a radical acceptor. The initial dissociation reaction (Bzl ⟶ Bz + I) has been found to be between first and second order at the partial pressures of benzyl iodide used (0.02 mm. - 0.13 mm.) and this is attributed to the normal Hinshelwood-Lindemann effect for unimolecular reactions. An approximate value of 0.35 sec.⁻¹ for the high pressure limiting rate constant at 585°K has been deduced. This corresponds to an Arrhenius factor for the decomposition of 1014.6 sec.⁻¹, if the benzyl iodide bond strength is assumed to be 40.6 K cal./mol. 3) At the very lowest partial pressures used (~0.02 mm.), the initial dissociation reaction approaches second order behaviour and the temperature dependence of assumed second order rate constants leads to an activation energy of 40 K cal./mol. for the decomposition. The corresponding pre-exponential factor is 10 ²⁰.⁴, which is of the order of magnitude to be expected for a reaction of this type. The data, in this low pressure region, are, however, insufficient to establish that the reaction in accurately second order at these pressure. 4) If the bond strength of benzyl iodide is taken as 41 K cal./mol., as determined in this present investigation, a value may be calculated for the heat of formation of the benzyl radical. Using 27.2 K cal./mol. for the heat of benzyl iodide, as suggested by skinner(63), a value of 43 K cal./mol. is obtained for △Hf (benzyl). This is in close agreement with the values of 45.3 K cal./mol. and 44.8 cal./mol., obtained in this department by Alexander(58) and Davidson(59) respectively - their values were derived their determinations of the bond strength of the central carbon-carbon bond in dibenzyl. The present value of 43 L cal./mol. is also in accord with the 44.9 K cal./mol., deduced from Benson and buss(47) determination of the toluene bond strength as 84 K cal./mol. The more commonly quoted toluene bond strength of 77.5 K cal./mol., obtained by Szwarc(48) leads to a △Hf (Benzyl) of only 37.4 K cal./mol. and would, therefore, seem to be too low.
2018-07-17T09:59:45Z
2018-07-17T09:59:45Z
1961
Thesis
http://hdl.handle.net/10023/15465
en
137 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/26082019-07-01T10:18:04Zcom_10023_51com_10023_18col_10023_53
2012-05-23T09:14:43Z
urn:hdl:10023/2608
SA-CASSCF and R-matrix calculations of low-energy electron collisions with DNA bases and phosphoric acid
Bryjko, Lilianna
van Mourik, Tanja
Engineering and Physical Sciences Research Council (EPSRC)
R-matrix
The research presented in this thesis was carried out as part of a collaboration between the groups of Dr Tanja van Mourik at the School of Chemistry, University of St Andrews and Professor Jonathan Tennyson at the Department of Physics and Astronomy at University College London.
This thesis presents State-Averaged Complete Active Space Self Consistent Field (SA-CASSCF) calculations on nucleic acid bases, deoxyribose and phosphoric acid H₃PO₄). In the case of uracil, for comparison, Multireference Configuration Interaction calculations were also performed. The SA-CASSCF orbitals were subsequently used in R-matrix electron scattering calculations using the close-coupling model.
Of major importance for obtaining accurate SA-CASSCF results is the choice of the active space and the number of calculated states. Properties such as the electronic energy, number of configurations, excitation energy and dipole moment were considered in the choice of active space.
Electron-collision calculations were performed on two of the most stable isomers of phosphoric acid, a weakly dipolar form with all OH groups pointing up and a strongly dipolar form where one OH group points down. A broad shape resonance at about 7 eV was found for both isomers. Ten-state close-coupling calculations suggest the presence of narrow, Feshbach resonances in a similar energy region. Elastic and electronically inelastic cross sections were calculated for both isomers.
The R-matrix calculations on uracil were done by the group from UCL.
R-matrix calculations are currently being done on guanine.
Scattering calculations on the other DNA bases will be performed in the near future.
2012-05-23T09:14:43Z
2012-05-23T09:14:43Z
2011-06-22
Thesis
http://hdl.handle.net/10023/2608
en
http://creativecommons.org/licenses/by/3.0/
Creative Commons Attribution 3.0 Unported
162
University of St Andrews
The University of St Andrews
UCL
oai:research-repository.st-andrews.ac.uk:10023/26112019-03-29T11:19:36Zcom_10023_51com_10023_18col_10023_53
2012-05-23T09:35:51Z
urn:hdl:10023/2611
Enantioselective homogeneous catalysts for the synthesis of fluorinated organic compounds
Jones, Charlotte E. S.
Clarke, Matt
Asymmetric catalysis
Organocatalysis
Ene reaction
Fluorination
Hydrogenation
Thiourea
This thesis is divided into three main results chapters that reflect the path my research took. In the first results chapter, the first organocatalyst for the carbonyl-ene reaction was discovered and found to give high conversion using 1,3-bis(3,5-bis(trifluoromethyl)phenyl)thiourea. Various carbonyl and alkene precursors were examined in the ene reaction in both catalysed and uncatalysed reactions. It was found that ene reactions using fluoral and ethyl trifluoropyruvate give higher rates of reaction when compared to other carbonyl compounds. A novel enantiopure thiourea was synthesised and the ene reaction was catalysed enantioselectively to 33% e.e. In an attempt to catalyse the reaction to a further extent a new thiourea bonded to a P(=S)R2 group was developed. However, the intramolecular hydrogen bonding of this catalyst was thought to be so strong that this it did not catalyse the reaction. The synthesis of a chiral phosphoric acid was achieved but this was an unsuccessful catalyst in the ene reaction. Two component achiral thiourea and chiral acids were also examined in the ene and Mannich-type reaction. The new easily synthesised thiourea for this reaction has an interesting intermolecular hydrogen bonding coordination in the solid state.
Asymmetric fluorination of ketoesters using palladium is a dynamic kinetic resolution. In the 2nd chapter cationic palladium complexes were synthesised and used to determine the optimum parameters for bidentate ligands in this reaction. Four carbon chain phosphines were found to give the highest conversion for this reaction among those ligands tested such as 1,4-bisdiphenylphosphinobutane (bite angle 99º). A new bis-phosphinous amide chiral ligand was developed with a bite angle of 96.7º. The dichloropalladium complex of this phosphine was isolated and structurally characterised. The use of the palladium complex in asymmetric fluorination was attempted however this was found to be unsuccessful. Mechanistic studies reveal that the formation of the desired cationic catalyst did not occur under conditions shown to work well for other palladium phosphine complexes. The ligand was investigated further in hydrogenation reactions.
The phosphinous amide was protected as its borane and was used in the rhodium catalysed hydrogenation of alkenes to give high conversion and up to 93% e.e. The borane protected phosphinous amide was also found to catalyse the hydrogenation of acetophenone using copper complexes with up to 84% e.e for the hydrogenation of acetophenone, although conversion was quite low.
2012-05-23T09:35:51Z
2012-05-23T09:35:51Z
2011-06
Thesis
http://hdl.handle.net/10023/2611
en
229
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/217692021-04-06T02:01:30Zcom_10023_51com_10023_18col_10023_53
2021-04-05T09:53:11Z
urn:hdl:10023/21769
Optimisation of performance of tin oxide based anodes for high energy density lithium batteries
Attidekou, Pierrot S.
Irvine, John T. S.
Kabushiki-gaisha GS Yuasa Kōporēshon (Firm)
The goal of this work was to synthesise and investigate a tin based oxide compound, SnP₂O₇ and its doped analogues, as a potential negative electrode for lithium battery. SnP₂O₇ has two polymorphs: the cubic and the layered forms. It has been proven that the cubic form has a better performance on cycling compared to the layered. This work has focused on the cubic form in order to understand the mechanisms occurring upon charge and discharge in order to improve the capacity and the cycling ability. The achievement of this task requires several steps.
SnP₂O₇ was synthesised and fully characterised structurally and electrochemically. The structural characterisation has elucidated the complexity of the material that crystallises in a 3x3x3 superstructure with the presence of nanodomains. Electrochemical characterisation has shown that on insertion of lithium into the material, finely dispersed tin nanoparticles are formed in an amorphous lithiated pyrophosphate matrix before the tin particles alloy with lithium providing the useful capacity of the battery. This material displays an irreversible capacity of 965mAh/g and a reversible capacity of 365 mAh/g. The overall reaction of lithium toward SnP₂O₇ was divided into 3 different zones and the kinetic and thermodynamic features evaluated. The thermodynamic study made on a cell with SnP₂O₇ electrode has provided a very high value of entropy upon the conversion of SnP₂O₇ to metallic tin plus lithiated pyrophosphate matrix. The lithiated phosphate matrix form is then reduced to another lithiated phosphate matrix, which is stable with an unusual oxidation state of phosphorus that we believe to be Pᴵⱽ. The lithium diffusion was estimated as 8x10⁻¹⁵cm²/s and matches those obtained for other lithium battery materials.
The addition of borate to the tin pyrophosphate system such as (SnO₂:B₂O₃)[sub](y/2)/(SnP₂O₇)[sub](1-y/2) was studied in order to lighten the matrix and increase the specific capacity and to evaluate the role of the matrix toward capacity retention. As it has been shown that amorphous materials often cycle better than the crystalline tin composite oxides, the addition of borate should be beneficial due to the decrease in crystallinity. This study has revealed upon substitution 3 different phase domains that were characterised to be crystalline up to y = 0.19, a mix of crystalline and amorphous (0.25 < y < 1.75) and a fully amorphous region for high borate content (y > 1.75). At all levels of substitution there was a decrease in both irreversible and reversible capacity. The best capacity of borate doped samples was found in the low borate crystalline region. Therefore borate appears not to be a suitable matrix for lithium batteries.
Titanium was added to SnP₂O₇ to see the effect of a smaller cation in the system. Titanium substitution has shown a co-existence of different chemistry types such as both alloying and non-alloying processes for Sn₁₋ₓTiₓP₂O₇ system. Pure titanium pyrophosphate has shown complex electrochemistry and seems to form a transition metal oxide in a phosphate matrix, with additional formation of SEI that was depicted by HRTEM. The electrochemistry has shown formation of several different linephases, biphasic regions and solid solution transformations. The best capacity found was for composition with y = 0.15, which has shown an increase of the reversible capacity of 10% over pure SnP₂O₇.
2021-04-05T09:53:11Z
2021-04-05T09:53:11Z
2005-06-22
Thesis
http://hdl.handle.net/10023/21769
https://doi.org/10.17630/sta/54
en
[16], 260 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/154612019-03-29T11:19:37Zcom_10023_51com_10023_18col_10023_53
2018-07-17T09:15:37Z
urn:hdl:10023/15461
Synthesis and anti-tumour activity of some new derivatives of flavone-8-acetic acid
Wilson, David William Joseph
Association of International Cancer Research
A robust six-step synthesis of substituted flavone-8-acetic acid sodium salts has been developed and optimised to allow preparation of a wide variety of products for testing as anti-tumour agents. The condensation and cyclisation steps have been combined in an efficient one-pot procedure and efficient procedures for subsequent oxidative cleavage of an allyl group and salt formation have been developed. Using this method a total of 18 derivatives bearing substituents on the 2-phenyl ring have been prepared. Based on encouraging activity from methoxy substituted compounds, attention has been concentrated on these and various mono-, di-, tri- and tetramethoxy compounds have been prepared, most for the first time. Activity of these against MAC15A, both in vitro and in vivo has been determined by collaborators at Bradford and several compounds have comparable or greater activity than the unsubstituted prototype. The presence of a 2'-methoxyl substituent appears to be particularly favourable to activity. Five different heterocyclic analogues with furyl, thienyl and benzothienyl groups at the 2-position have been obtained and these also show good activity with the 3-methyl-2-thienyl compound showing the highest in vivo activity of any compound examined. Attempts to prepare pyridyl and quinolyl derivatives were unsuccessful. The 2-benzyl and 2-diphenylmethyl compounds have also been prepared and while the former shows good activity in vitro, it is inactive in vivo probably due to metabolic breakdown. The latter compound is completely inactive probably due to a requirement for planarity in the 2- substituent. An extended derivative has been obtained by an unexpected mode of reaction encountered in an attempt to prepare the 2-phenylethynyl compound. Both this and a dimeric ether analogue show significant activity, thereby adding to our understanding of the structural requirements for activity. Variation in the 8-acetic acid substituted has been examined by synthesis of three compounds with CH₂C(O)CH₂OH at this position and, by a separate multi-stage synthesis, the compound with tetrazolylmethyl. The former compounds are too insoluble for activity to be measured, while the latter is inactive. A comparison of electron density, as reflected by ¹H and ¹³C NMR shifts, against activity in vitro has been made for all the compounds prepared, and while some trends may be discerned, the correlation is generally poor. A suitable single crystal of flavone acetic acid was prepared and its X-ray structure was obtained by the SERC Crystallography Unit, Cardiff. The structure, which proved to be of the monohydrate showed the preferred orientation of the 2- and 8-substituents and provided accurate dimensions for future theoretical work.
2018-07-17T09:15:37Z
2018-07-17T09:15:37Z
1995
Thesis
http://hdl.handle.net/10023/15461
en
187 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/44232019-03-29T11:19:40Zcom_10023_51com_10023_18col_10023_53
2014-01-28T09:44:21Z
urn:hdl:10023/4423
Structure and properties of some triangular lattice materials
Downie, Lewis James
Lightfoot, Philip
Solid state chemistry
Fluorides
Oxides
Crystallography
Magnetism
Ferroelectrics
Neutron diffraction
Synchrotron X-ray diffraction
This thesis is concerned with the study of two families of materials which contain magnetically frustrated triangular lattices. Each material is concerned with a different use; the first, analogues of YMnO₃, is from a family of materials called multiferroics, the second, A₂MCu₃F₁₂ (where A = Rb¹⁺, Cs¹⁺, M = Zr⁴⁺, Sn⁴⁺, Ti⁴⁺, Hf⁴⁺), are materials which are of interest due to their potentially unusual magnetic properties deriving from a highly frustrated Cu²⁺-based kagome lattice.
YFeO₃, YbFeO₃ and InFeO₃ have been synthesised as their hexagonal polymorphs. YFeO₃ and YbFeO₃ have been studied in depth by neutron powder diffraction, A.C. impedance spectroscopy, Mössbauer spectroscopy and magnetometry. It was found that YFeO₃ and YbFeO₃ are structurally similar to hexagonal YMnO₃ but there is evidence for a subtle phase separation in each case. Low temperature magnetic properties are also reported, and subtle correlations between the structural, electrical and magnetic properties of these materials have been found. InFeO₃ was found to adopt a higher symmetry and is structurally similar to the high temperature phase of YMnO₃. TbInO₃ and DyInO₃ have also been synthesised and studied at various temperatures. The phase behaviour of TbInO₃ was analysed in detail using neutron powder diffraction and internal structural changes versus temperature were mapped out – there is also evidence for a subtle isosymmetric phase transition. Neither DyInO₃ nor TbInO₃ show long-range magnetic order between 2 and 300 K, or any signs of ferroelectricity at room temperature.
The new compounds Cs₂TiCu₃F₁₂ and Rb₂TiCu₃F₁₂ have both been synthesised and shown to be novel kagome lattice based materials. The former shows a transition from rhombohedral to monoclinic symmetry in the powder form and from rhombohedral to a larger rhombohedral unit cell in the single crystal – a particle size based transition pathway is suggested. For Rb₂TiCu₃F₁₂ a complex triclinic unit cell is found, which distorts with lowering temperature. Both materials show magnetic transitions with lowering temperature. The solid solution Cs₂₋ₓRbₓSnCu₃F₁₂ (x = 0, 0.5, 1.0, 1.5, 2.0) was synthesised and investigated crystallographically, demonstrating a range of behaviours. Rb₂SnCu₃F₁₂ displays a rare re-entrant structural phase transition. In contrast, Cs₀.₅Rb₁.₅SnCu₃F₁₂ shows only the first transition found in the Rb⁺ end member. CsRbSnCu₃F₁₂ adopts a lower symmetry at both room temperature and below. Cs₁.₅Rb₀.₅SnCu₃F₁₂ and Cs₂SnCu₃F₁₂ show a rhombohedral - monoclinic transition, which is similar to that found in Cs₂TiCu₃F₁₂.
2014-01-28T09:44:21Z
2014-01-28T09:44:21Z
2014-06-25
Thesis
http://hdl.handle.net/10023/4423
en
200
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/93172019-03-29T11:19:40Zcom_10023_51com_10023_18col_10023_53
2016-08-16T15:50:39Z
urn:hdl:10023/9317
Dynamic molecular control of nanoparticle building block assembly
Borsley, Stefan
Kay, Euan Robert
Nanoparticles have generated much excitement as a result of their often unique
properties, inherently dependent on nanoparticle material, shape and size.
Virtually all conceivable nanoparticle applications will require excellent control
over how nanoparticles are assembled and linked to other components. When
several nanoparticles are brought together, the assembly structure is crucial in
determining their newly emergent properties. However, the synthetic chemistry
techniques required to control nanoparticle functionalisation and assembly are
still under-developed, with complex biological or supramolecular systems being
the current best approaches. There remains a need for simple, generalisable
strategies for molecular-level control over nanoparticle functionalisation and
assembly. This thesis presents the development of a toolkit of nanoparticle
building blocks, which may be assembled in a predictable and controlled way,
governed by simple and easily optimised abiotic molecular systems.
Efficient, size-controlled, direct synthesis of functionalised gold nanoparticle
building blocks with control over size and dispersity is developed.
¹⁹F NMR spectroscopy studies provide a fundamental understanding of the implications
of confinement at the nanoparticle surface for molecular reactivity. Two self-assembly strategies, each resulting in structures of high order and predictability,
are presented. First, the reversible nature of dynamic covalent boronic ester
formation is exploited to induce reversible nanoparticle self-assembly. Links
between molecular details and resulting morphology are demonstrated and
rationalised. A second strategy exploits multivalent non-covalent interactions,
resulting in ‘planet–satellite’ structures displaying high order, stability and
predictability.
This thesis demonstrates that relatively simple molecular systems present a
viable, and ultimately more flexible, alternative to existing methods of directing
precise, predictable control of nanoparticle functionalisation and assembly.
Advancing a molecular-level understanding of the underlying processes enables a high level of control. Future application of this molecular approach to dynamic nanomaterial control will lead to more complex and sophisticated
nanostructures, helping nanotechnology progress towards its undoubtedly
revolutionary full potential.
2016-08-16T15:50:39Z
2016-08-16T15:50:39Z
2016-06
Thesis
http://hdl.handle.net/10023/9317
en
xi, 228 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/63712019-07-01T10:09:59Zcom_10023_51com_10023_18col_10023_53
2015-03-27T09:39:59Z
urn:hdl:10023/6371
Synthesis and characterization of crystalline microporous materials : investigation of new synthetic routes
Tian, Yuyang
Morris, Russell Edward
China Scholarship Council (CSC)
Microporous materials
Synthesis
Zeolites
Metal organic frameworks
Ionothermal synthesis
Post-synthetic route
Aluminophosphates
Conventionally, crystalline microporous materials such as zeolites and metal-organic frameworks (MOFs) are synthesized through the hydrothermal route or the trial-and-error approach. Other synthetic strategies may lead to the synthesis of microporous materials with new architectures or interesting properties. The general aim of this thesis is to investigate some new synthetic routes towards crystalline microporous materials.
A top-down and post-synthesis method is reported in Chapter 4. Some zeolites are built up by layers and double-4-ring pillars. Germanium is preferentially located in the double-4-ring sites of a zeolite framework and is hydrolytically unstable. The idea of the top-down method is to disassemble these zeolites to the layer structures by dissolving the Ge-containing pillars and reassemble them to a new framework. This method is applied to the germanosilicate IWW and ITH zeolites for the first time. The effects of framework chemical compositions, Ge distributions and disassembling conditions on the top-down treatment process are investigated. The products obtained from the top-down treatment are characterised.
An ionic liquid assisted strategy for the synthesis of zeolites is described in Chapter 5. The ionic liquid assisted strategy is a solvent free reaction. The raw materials are transformed to zeolites through a solid state reaction. The ionic liquids are first used as structure-directing agents (SDAs) in this solvent free reaction to replace the expensive quaternary ammonium hydroxide. A TON zeolite is synthesized using 1-ethyl-3-methylimidazolium bromide as the SDA. Moreover, the ionic liquid assisted strategy is considered as a “green chemistry” synthetic route due to the high yield of the zeolites and the minor production of waste water.
Many aluminophosphates have been successfully synthesized through ionothermal routes. Most of them are synthesized using 1-alkyl-3-methylimidazolium based ionic liquids. A new ionic liquid, 1-(2-hydroxyl-ethyl)-3-methylimidazolium chloride ([HOEmim]Cl), is prepared and used for the ionothermal synthesis of aluminophosphate materials. A zeolite analogue with the CHA framework has been synthesized. At high synthetic temperatures, the products are large single crystals. The structures of the framework and the SDA are investigated by single crystal diffraction and other characterisation methods.
Flexible MOF materials are usually synthesized by a trial-and-error approach. Recently a flexible MOF compound was synthesized using 5-sulfoisophthalic acid (SIP) as the ligand. It was proposed the sulfonate is weakly coordinated to the metal, which brings flexibility to the compound, and the carboxylate groups keep the framework intact. 2-sulfoterephthalic acid (STP) which also contains one sulfonate group and two carboxylate groups is believed to be an alternative ligand for the targeted synthesis of flexible MOFs. In Chapter 7, a MOF compound is synthesized using STP and 4, 4’-bipyridine (Bpy) as ligands to validate the proposed strategy can be generalized. Variable temperature single crystal diffraction analysis solves the structure and reveals a reversible structure transformation upon dehydration and rehydration.
2015-03-27T09:39:59Z
2015-03-27T09:39:59Z
2014-12-01
Thesis
http://hdl.handle.net/10023/6371
en
http://creativecommons.org/licenses/by-nc-nd/4.0/
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
183
University of St Andrews
The University of St Andrews
School of Chemistry
oai:research-repository.st-andrews.ac.uk:10023/152912019-03-29T11:19:42Zcom_10023_51com_10023_18col_10023_53
2018-07-12T09:40:48Z
urn:hdl:10023/15291
Novel derivatives of DPP and related heterocycles
Morton, Colin J. H.
Smith, D. M.
This thesis discusses the synthesis of new organic, heterocyclic materials for potential application as pigments. Chapter 1 comprises an introduction to the field of pigment and dye chemistry, discussing the rudimentary elements of colour theory, before advancing to a review of the pertinent literature regarding high performance organic pigments. In particular, the development of 1,4-diketopyrrolo[3,4-c]pyrrole (DPP) pigments is described and the central objective of synthesising alkenyl-DPPs is outlined. Chapters 2 and 3 describe synthetic efforts towards alkenyl-DPPs, employing retro Diels-Alder methodology. The reactions involving the furan-acrylonitrile adduct as the nitrile component in the standard DPP synthesis led mainly to aromatisation of the bicyclic system and the cyclopentadiene-acrylonitrile adduct failed to react altogether. The explanation for this failure has been investigated. In the course of this these studies, several DPPs incorporating a secondary alkyl substituent were prepared, not least a novel cyclohexenyl-DPP. Chapter 4 describes the use of α β-unsaturated nitriles in the standard DPP synthesis. These behaved as Michael acceptors and in the case of cinnamonitriles led to a new family of coloured materials, namely substituted 4-hydroxy-2/7- cyclopenta[c]pyrrol-1-one-5-carbonitriles. Chapter 5 describes the corresponding reaction of cinnamate esters, but in these cases bicyclic systems were not formed. The reactions are analogous to Claisen acylations and the stereochemistry of the products varied according to the substituents. Chapter 6 contains the detailed experimental work for these investigations and concludes with a portfolio of X-ray structural data.
2018-07-12T09:40:48Z
2018-07-12T09:40:48Z
1999
Thesis
http://hdl.handle.net/10023/15291
en
212 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/151152019-03-29T11:19:43Zcom_10023_51com_10023_18col_10023_53
2018-07-09T10:58:55Z
urn:hdl:10023/15115
The nature, origin and mechanism of development off-flavour in frozen cod (Gadus morhus)
McGill, Alister Smith
Gunstone, F. D.
Fish is a highly perishable foodstuff best preserved by low temperature storage but even under these conditions deterioration still occurs and off-flavours are produced. This thesis describes an investigation into the nature, origin and mechanism of development of the components responsible for this off-flavour in cod (Gadus morhua). An understanding of these matters may make it possible to prevent the development of this flavour or at least minimise the effect. In Chapter I the current theories of the perception and mechanism of taste and alfaction are described, as are the complexities of the chemical nature of flavour in food and especially fish. The causes of off-flavour development in fish are discussed and the background to the cold storage phenomenon introduced. The characterisation of the compounds responsible for the off-flavour is described in Chapter II. By using dinitrophenylhydrasone derivatisation it was found that carbonyls are largely responsible but these derivatives could not be used for a complete analysis. The technique that was finally used to fractionate the mixture was that of gas liquid chromatography supported by organoleptic assessment. In this chapter, the experimental procedures adopted in the investigation are described. In Chapter III the major component responsible for the cold storage flavour is shown to be present at extremely low concentrations in the fish and is identified as hept-cis-4-enal. Details of other volatile components present in cod flesh are also presented including two other aldehydes, hept-trans-2-enal and hepta-trans-2-cis-4-dienal which possess some of the off-flavour character. Chapter IV presents the evidence for the production of those compounds by an autoxidative pathway and gives information on their rate of production with temperature. Taste panel assessments carried out during the latter work showed that there was a positive correlation between increase in hept-cis-4-enal concentration and cold storage flavour. A more detailed study indicated that hept-cis-4-enal is produced by to 3 polyenoic fatty acid oxidation but it was not possible to resolve whether a specific fraction or the total lipid was involved in this production. The results show that in white fish the rate of oxidation in cold storage is slow despite the unsaturated nature of the lipids and an explanation for this is advanced in Chapter V where the general mechanism of autoxidation is discussed. Some consideration is also given to the method of formation of hept-cis-4-enal from the w 3 polyenoic acids. A number of possible routes have been identified but the most probable pathway is via one of the major peroxide Intermediates in the autoxidation
2018-07-09T10:58:55Z
2018-07-09T10:58:55Z
1976
Thesis
http://hdl.handle.net/10023/15115
en
xi, 195 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/112322019-03-29T11:19:43Zcom_10023_51com_10023_18col_10023_53
2017-07-18T08:40:00Z
urn:hdl:10023/11232
The molecular structure of inulin
Stevenson, John Whiteford
Irvine, James Colquhoun
2017-07-18T08:40:00Z
2017-07-18T08:40:00Z
1928-04
Thesis
http://hdl.handle.net/10023/11232
en
83 leaves
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/169252019-06-29T02:06:13Zcom_10023_51com_10023_18col_10023_53
2019-01-23T12:01:41Z
urn:hdl:10023/16925
Applications of isothioureas in surface chemistry : modification of self-assembled monolayers and immobilisation on polymer supports
Chisholm, Ross
Smith, Andrew David
The research outlined in this thesis describes the development of organocatalytic methodology
for the modification of self-assembled monolayers on silicon dioxide surfaces and its extension
towards an asymmetric protocol and immobilisation of isothiourea organocatalysts to polystyrene
supports.
Chapter 1 aims to describe the fundamental aspects of self-assembled monolayers and their place
within the wider area of surface chemistry. A recent overview of catalytic surface
functionalisation is discussed as well as the historical context of this project, with respect to
research within the Smith group, is also presented. A statement of the initial aims and objectives
of the research is presented.
Chapter 2 describes the proof-of-concept study undertaken to develop methodology towards the
functionalisation of silicon oxide surfaces using an isothiourea-catalysed organocatalytic Michael
addition-lactonisation process. Subsequent characterisation of the resulting surfaces and a
reaction scope is also carried out in this system.
Chapter 3 describes an extension of the methodology carried out in the previous chapter to allow
for an asymmetric protocol. The sense of enantioenduction of the resulting surfaces was then
examined using chemical force microscopy using a novel AFM probe with the results show that
chiral discrimination can be achieved using this methodology. Control experiments were also
undertaken by depositing enantiopure starting materials on a surface and measuring the adhesion
forces confirming the presence of a chiral surface.
Chapter 4 describes the immobilisation (R)-BTM and (2R,3S)-HyperBTM analogues onto
polystyrene supports and their evaluation in several different reaction classes previously
investigated within the Smith group. Results show that the polymer-supported catalyst (2R,3S)-
HyperBTM can be recycled up to 8 times without any major loss in yield or selectivity.
Chapter 5 offers a brief summary of the work undertaken in this PhD and some of the conclusions
that can be drawn from it as well as an insight into the potential future developments of this
research and areas where it could possibly expand and develop.
2019-01-23T12:01:41Z
2019-01-23T12:01:41Z
2017-05-11
Thesis
http://hdl.handle.net/10023/16925
en
xiv, 199 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/274202024-02-15T16:55:57Zcom_10023_51com_10023_18col_10023_53
2023-04-18T14:54:13Z
urn:hdl:10023/27420
Peri-substituted phosphorus-selenium and -tin acenaphthenes : syntheses, reactivities and radical species
Zhang, Lu-Tao
Kilian, Petr
Woollins, J.D. (J. Derek)
China Scholarship Council (CSC)
University of St Andrews. St Leonard's College
University of St Andrews. School of Chemistry
The investigation of 𝘱𝘦𝘳𝘪-substitution has yielded fascinating approaches to unusual chemical bonds and interactions involving two or more atoms forced to close proximity. In this thesis, we discuss the syntheses and reactivities of a series of 𝘱𝘦𝘳𝘪-substituted P-Se and P-Sn species. Several dialkylphosphino-arylselanyl acenaphthenes Acenap (P𝘪Pr₂)(SeAr) (Ar = Mes, TRIP, Mes*), along with their transition metal complexes [M(Acenap(P𝘪Pr₂)(SeAr))ₙ] (M = Mo, Pd, Hg, Ag), have been prepared. Crystal structures and NMR properties (e.g. 𝘑MP and 𝘑MSe couplings) of these compounds have also been examined. We aimed to develop stable 𝘱𝘦𝘳𝘪-substituted systems that contain a captodative P-Se hemibond (2c-3e bond). We used P-Se acenaphthenes as radical candidates, investigating potential single-electron oxidation reactions with nitrosonium and silver (I) salts, expecting the formation of respective radical cations. The -P𝘪Pr₂ substituent is strongly electron-donating, and the bulky -SeAr groups are relatively electron-withdrawing. Therefore, the two captodative motifs were expected to form a stable P-Se hemibond. The stability of the radical centre was expected to be increased by steric shielding from the vicinal bulky arylselanyl groups and the presence of a large AI(ORꟳ)₄ weakly coordinated anion. The redox properties of the phosphine-selanes have been tested via electrochemical methods (e.g., cyclic voltammetry). The products of the potential single-electron oxidation reactions have been characterised by EPR spectroscopy. Despite all our efforts, the isolation of the desired cation radicals was not successful. In a separate project, we have investigated P-Sn acenaphthenes Acenap (P𝘪Pr₂)(SnHR₂) (R=Me, Ph) to get insight into their potential use as C-H coupling precursors. We have shown that the thermally induced reaction of these generates a phosphine-stabilised stannylene via elimination of benzene. Our observations have been supported by NMR spectroscopy; also, a gas trapping experiment indicates that benzene is formed as one of the products from fermal decomposition.
2023-04-18T14:54:13Z
2023-04-18T14:54:13Z
2021-06-30
Thesis
https://hdl.handle.net/10023/27420
https://doi.org/10.17630/sta/406
en
2026-01-15
Thesis restricted in accordance with University regulations. Restricted until 15 January 2026
203
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/149332019-03-29T11:19:44Zcom_10023_51com_10023_18col_10023_53
2018-07-04T15:29:10Z
urn:hdl:10023/14933
Diffusion controlled oxidation and stabilisation of polyolefins
Fairgrieve, Stuart Paterson
MacCallum, J. R.
A mathematical model was derived for the oxidation behaviour of a polymer film, taking into account both diffusion free and diffusion controlled kinetics. Comparison with experimental results showed excellent agreement. Expressions were derived from this model for the reaction induction time, and the limiting thickness of film at which diffusion effects become important. Investigation of the photostabilisation mechanism of Hindered Amine Light Stabilisers was undertaken. After experimental investigation of numerous proposed stabilisation processes, and their rejection, a reaction scheme was proposed involving the scavenging of trace transition metal ions in the polymer matrix.
2018-07-04T15:29:10Z
2018-07-04T15:29:10Z
1984
Thesis
http://hdl.handle.net/10023/14933
en
150 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/113652019-09-30T11:29:59Zcom_10023_51com_10023_18col_10023_53
2017-08-03T14:04:09Z
urn:hdl:10023/11365
Title redacted
Kasten, Kevin
Smith, Andrew David
2017-08-03T14:04:09Z
2017-08-03T14:04:09Z
2017
Thesis
http://hdl.handle.net/10023/11365
en
2021-03-07
Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 7th March 2021
301 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/217982021-10-20T12:14:09Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:37:35Z
urn:hdl:10023/21798
Synthetic applications of flash vacuum pyrolysis over magnesium
Oyewale, Adebayo Ojo
Aitkin, R. A.
The thermal reaction over activated magnesium of some 120 organic
substrates has been investigated under flash vacuum pyrolysis(FVP)
conditions. The activation was achieved by freshly resublimed Grignard
grade magnesium onto glass wool at 700°C under vacuum. Magnesium
prepared in this form showed an effective dehalogenating activity on a
wide range of organic halides. FVP of simple aliphatic halides like
2-chloro-2,3-dimethylbutane and 2,3-dichloro-2,3-dimethylbutane,
resulted in dehydrohalogenation to give the corresponding monoenes and
dienes. The dehydrobromination of neopentyl bromide over magnesium
gave a mixture of 2-methyl-2-butene and 2-methyl-l-butene, a product
mixture that cannot be accounted for by either radical or carbene
chemistry. A similar process was observed with terminal dihalides to give
dienes, however with increased chain length a dehalogenation process
involving hydrogen transfer predominates to give monoenes. The
debromination of 1,3-dibromopropane over magnesium led to
cyclopropane. Dehydrohalogenation was similarly observed with cyclic
dihalides, haloalkenes and haloalkynes and for substrates of adequate
chain length, dehalogenation of the haloalkenes or haloalkynes was
followed by cyclisation on to the unsaturated end of the molecule to give
cyclic products. Germinal dihalides underwent dehalogenative
homocoupling to give symmetrical dienes except for 1,1-dichloropropane
and 2,2-dichloropropane where simple dehydrochlorination was observed
to give the chloroalkenes. FVP of benzylic- and benzylidene- halides over magnesium led to
dehalogenative homocoupling to give bibenzyls and stilbenes respectively. Various substituted
bibenzyls and stilbenes were prepared in moderate to
high yields. The amount of magnesium surface available for reaction and a comparative study of the thermal reaction of zinc, calcium and magnesium with benzyl chloride was carried out. On pyrolysis of
o-halobenzyl halides and o-halobenzylidene halides in the presence of
excess magnesium, the loss of both side chain and ring halogens led to
coupling and cyclisation to 9,10-dihydrophenanthrene and phenanthrene
respectively. The ease of ring dehalogenation decreases from iodine to
bromine and chlorine, with fluorine virtually unreactive. Attempts to
prepare symmetrical disubstituted phenanthrenes from substituted
o-halobenzylidene chlorides met with only limited success. Under the
pyrolytic conditions, benzotrichloride was converted to
α, α'-dichlorostilbene, α, α, α', α'-tetrachlorobibenzyl and diphenylacetylene,
the yield of the last two products being dependent on the reaction conditions.
The thermal dehalogenation of α, α'-dihalo-o-xylenes over
magnesium gave benzocyclobutene. The same process afforded fluorinated
benzocyclobutenes and benzodicyclobutene in good yields.
The debromination of α, α, α', α'-tetrabromo-m-xylene over magnesium led to pyrene.
For haloalkylbenzenes, the basic reaction on pyrolysis over
magnesium was dehydrohalogenation to arylalkenes, but this was
sometimes accompanied by bond isomerisation and rearrangement. In the
case of 1-chloro-4-phenylbutane, an additional process of cyclisation on to
the phenyl ring to give tetrahydronaphthalene was observed. The thermal
reaction of 3-chloropropiophenone and 2-bromoacetophenone over
magnesium led not only to dehalogenation products but also to
deoxygenated products. 2-Bromoethyl phenyl ether mainly underwent
dehalogenation and fragmentation to phenol. The
dehalogenation of chlorobenzene and 1,2-dihalobenzenes was also achieved on
pyrolysis over magnesium. Although the main product obtained from the latter was
triphenylene, the involvement of benzyne as an intermediate is in doubt.
The dehalogenation of long chain acid chloride over magnesium,
Was accompanied by fragmentation to give a mixture of alkenes and alkanes.
The magnesium-induced 1,6-dehalogenation of α, α'-halogenated
p -xylenes in the gas phase led to p-xylylenes, which
polymerised. α, α'-Dichloro-p-xylene gave poly(p-xylylene) and
poly(a-chloro-p-xylyene); while α, α, α', α'-tetrachloro-p-xylene and
α, α, α', α'-tetrabromo-p-xylene gave poly(α, α'-dichloro-p-xylylene) and
poly(α, α'-dibromo-p-xylyene) respectively. Also prepared were
poly(α, α,α',a'-tetrachloro-p-xylylene) and poly(α, α, α', α'-tetrafluoro-p-
xylylene) from the corresponding hexahalo-p-xylene. Thermal stability
measurements and the solid state 13C NMR, including molecular weight
estimation were carried out on the polymers.
Some of the processes observed with aryl compounds on pyrolysis
Over magnesium were extented to halogenated thiophene compounds,
especially for the preparation of 1,2-dithienylethenes and derivatives.
Attempts to prepare benzodithiophenes from halo-dichloromethyl-
thiophenes gave halogenated products and isomeric benzodithiophenes.
The isomeric benzodithiophenes obtained and the likely route to them was
investigated. Attempts to generated 2,3-thiophyne by dehalogenation of
mono- and di-halothiophe.nes were inconclusive. The thermal reaction of
a series of epoxides in the presence or absence of magnesium was
investigated. The main process in the absence of magnesium, was
rearrangement to carbonyl compounds, while in the presence of
magnesium, deoxygenation and dehydration reactions were observed in
addition to the thermal rearrangement.
2021-04-08T08:37:35Z
2021-04-08T08:37:35Z
1991
Thesis
http://hdl.handle.net/10023/21798
en
248p
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/104042019-07-01T10:08:14Zcom_10023_51com_10023_18col_10023_53
2017-03-06T11:26:53Z
urn:hdl:10023/10404
Structural and biochemical studies on the biosynthetic pathways of cyanobactins
Bent, Andrew F.
Naismith, Jim
Biotechnology and Biological Sciences Research Council (BBSRC)
Cyanobactins
Cyclic peptides
X-ray crystallography
Cyclic peptides have potential as scaffolds for novel pharmaceuticals, however their chemical synthesis can be challenging and as such natural sources are often explored. Several species of cyanobacteria produce a family of cyclic peptides, the cyanobactins, through the ribosomal synthesis of precursor peptides and post-translational tailoring. The patellamides, a member of the cyanobactin family, are cyclic octapeptides containing D-stereo centres and heterocyclised amino acids. A single gene cluster, patA - patG, contains the genes for the expression of the precursor peptide and the enzymes responsible for post-translational modifications including a heterocyclase, protease, macrocyclase and oxidase. Biochemical and structural analysis on the patellamide and related cyanobactin pathways has been carried out.
The crystal structure of PatF, a proposed prenyl transferase, has been determined, highlighting that it is likely evolutionary inactive due to changes to key residues when compared to active homologues. This is in agreement with the knowledge that no naturally prenylated patellamides have been discovered to date.
The crystal structure of the macrocyclase domain of PatG has been determined in complex with a substrate analogue peptide. The structure, together with biochemical analysis has allowed a mechanism of macrocyclisation to be proposed, confirming the requirement of a specific substrate conformation to enable macrocyclisation.
Using isolated enzymes from the patellamide and related pathways, a small scale library of macrocycles made up of diverse sequences has been created in vitro and characterised by mass spectrometry and in certain cases NMR. In order to further enhance diversity, macrocycles containing unnatural amino acids have been created using three approaches; SeCys derived precursor peptides, intein-mediated peptide ligation and pEVOL amber codon technology.
Finally, two oxidase enzymes from cyanobactin pathways have been purified, characterised and confirmed active for thiazoline oxidation. Native X-ray datasets on crystals of the oxidase CyaGox have been collected and phasing trials are on-going.
2017-03-06T11:26:53Z
2017-03-06T11:26:53Z
2016-06-22
Thesis
http://hdl.handle.net/10023/10404
en
http://creativecommons.org/licenses/by-nc-nd/4.0/
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
xxv, 236 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/80802024-02-12T12:12:59Zcom_10023_51com_10023_18col_10023_53
2016-01-25T17:07:51Z
urn:hdl:10023/8080
Multivicinal fluorine substitution of the cyclohexane ring
Durie, Alastair J.
Engineering and Physical Sciences Research Council (EPSRC)
Highly polar organic fluorinated motifs are of interest in materials chemistry, for
example, in liquid crystal applications. Cyclohexane is an important and widely used
structural motif within organic chemistry. Work has been carried out to prepare
single stereoisomers of multivicinal fluorinated cyclohexanes, a class of compounds
that has not been previously produced. A synthesis of the all-syn-1,2,3,4-tetrafluorocyclohexane, in 9 steps from cyclohexa-1,3-diene will be presented. The
¹⁹F NMR spectra of the all-syn-1,2,3,4-tetrafluorocyclohexane shows interesting
dynamic conformational effects. This is a small polar organic molecule, which was
crystalline at room temperature. The structure of the compound was confirmed by
single crystal X-ray diffraction studies.
The synthesis of the all-syn-1,2,4,5-tetrafluorocyclohexane from cyclohexa-1,4-diene is also presented. The synthesis of a single diastereoisomer of 1,2,3,4,5,6-hexafluorocyclohexane, derived from benzene in 5 steps, is presented. As with the tetrafluoro compounds, the ¹⁹F NMR spectra of this compound shows dynamic conformational effects. The
structure of the compound was confirmed by single crystal X-ray diffraction
studies. The 1,2,4,5-tetrafluorocyclohexane motif was elaborated to contain a phenyl
group, producing “rod-like” molecules. This motif was synthesised in view of
potential applications for liquid crystalline materials.
2016-01-25T17:07:51Z
2016-01-25T17:07:51Z
2014
Thesis
http://hdl.handle.net/10023/8080
en
Electronic copy restricted until 15 April 2016
Electronic thesis unavailable: permission not provided to allow public access
217
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/122992019-03-29T11:19:45Zcom_10023_51com_10023_18col_10023_53
2017-12-08T14:36:43Z
urn:hdl:10023/12299
Part I. Some methyl ethers of mannitol ; Part II. The structure of rubremetine
Wood, Hamish Christopher Swan
Openshaw, H. T.
2017-12-08T14:36:43Z
2017-12-08T14:36:43Z
1950
Thesis
http://hdl.handle.net/10023/12299
en
141 leaves
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/39652019-03-29T11:19:48Zcom_10023_175com_10023_39com_10023_51com_10023_18col_10023_177col_10023_53
2013-08-16T11:22:42Z
urn:hdl:10023/3965
Structural studies of CRISPR-associated proteins
Reeks, Judith
Naismith, Jim
X-ray crystallography
CRISPR/Cas
S. solfataricus
FaNaC
ASIC
Clustered regularly interspaced short palindromic repeats (CRISPRs) act to prevent viral infection and horizontal gene transfer in prokaryotes. The genomic CRISPR array contains short sequences (“spacers”) that are derived from foreign genetic elements. The CRISPR array is transcribed and processed into CRISPR RNAs (crRNAs) used in the sequence-specific degradation of foreign nucleic acids. This process is called interference and is mediated by CRISPR-associated (Cas) proteins.
This thesis has focused on the structural and functional characterisation of four Cas proteins from the CRISPR/Cas system of Sulfolobus solfataricus. The crystal structure of Cmr7 (Sso1725), a Sulfolobales-specific subunit of the ssRNA-degrading CMR complex, allowed for the identification of a putative protein-binding site, though no specific function could be ascribed to the protein. Cas6 (Sso1437) is the enzyme responsible for crRNA maturation and the characterisation of this protein allowed for the molecular rationalisation of its atypical RNA cleavage mechanism. Csa5 and Cas8a2 are subunits of the aCascade complex that targets dsDNA. Csa5 (Sso1398) was shown to have a putative role in R-loop stabilisation during interference while the role of Cas8a2 (Sso1401) was not determined. The structures of these two proteins were used to define relationships between the subunits of interference complexes from various CRISPR/Cas systems.
A second aspect of this work has been the expression and purification of eukaryotic ion channels for structural studies. The acid sensing ion channel (ASIC) and FMRFamide-gated sodium channel (FaNaC) are gated ion channels with unknown mechanisms of channel activation. These ion channels must be expressed in eukaryotic systems and so human embryonic kidney (HEK) cells and baculovirus-insect cell expression systems were developed to express ASIC and FaNaC constructs. The expression and purification protocols have been optimised to allow for the preparation of soluble protein that will in future be used for crystallography and electron paramagnetic resonance (EPR) studies.
2013-08-16T11:22:42Z
2013-08-16T11:22:42Z
2013-11-29
Thesis
http://hdl.handle.net/10023/3965
http://hdl.handle.net/10023/3954
http://hdl.handle.net/10023/3863
http://hdl.handle.net/10023/3550
http://hdl.handle.net/10023/5991
en
Reeks , J , Sokolowski , R D , Graham , S , Liu , H , Naismith , J H & White , M F 2013 , ' Structure of a dimeric crenarchaeal Cas6 enzyme with an atypical active site for CRISPR RNA processing ' Biochemical Journal , vol 452 , no. 2 , pp. 223-230
Reeks , J A , Naismith , J & White , M F 2013 , ' CRISPR interference : a structural perspective ' Biochemical Journal , vol 453 , no. 2 , pp. 155-166
Reeks , J A , Graham , S , Anderson , L , Liu , H , White , M F & Naismith , J 2013 , ' Structure of the archaeal Cascade subunit Csa5 : Relating the small subunits of CRISPR effector complexes ' RNA Biology , vol 10 , no. 5 , pp. 762-769
Zhang , J , Rouillon , C , Kerou , M , Reeks , J , Brugger , K , Graham , S , Reimann , J , Cannone , G , Liu , H , Albers , S-V , Naismith , J H , Spagnolo , L & White , M F 2012 , ' Structure and mechanism of the CMR complex for CRISPR-Mediated antiviral immunity ' Molecular Cell , vol 45 , no. 3 , pp. 303-313
330
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/9312019-03-29T11:19:48Zcom_10023_51com_10023_18col_10023_53
2010-06-22T13:11:48Z
urn:hdl:10023/931
Characterisation of the ceria and yttria co-doped scandia zirconia; produced by an innovative sol-gel and combustion process
de Carvalho Tomás, Eduarda M. S.
Irvine, John T. S.
SUPERGEN UK
Scandia zirconia
Electrolytes
In the last decade new materials appeared that are candidates to be used as an electrolyte in a Solid Oxide Fuel Cell, SOFC. Some materials show high ionic conductivity but lack in important properties, such as mechanical stability or chemical compatibility with other materials in the fuel cell.
Scandia Stabilised Zirconia, SSZ, became a possibility when the scandia price dropped with the opening of the Chinese and Russian markets. In the starting system Ce[subscript(x)]Y[subscript(0.2-x)]Sc₀.₆Zr₃.₂O[subscript(8-δ)], (0≤x≤0.2), scandia is introduced to improve conductivity and stabilise the cubic phase; yttria is introduced to fully stabilise the cubic phase and ceria to enhance conductivity lost with the introduction of yttria.
The aim of this project is to develop a reliable new method to produce quality ceramics that are not strongly composition dependent, then to prepare a range of compositions and compare intrinsic properties without having to be concerned that poor sintering dominates conduction properties.
This project can be divided in two sections, the first section the powder production method, the characteristics of the powders and its final products are in focus. In the second section the relation between electric characteristics and microstructure of the material is reported.
In the first section, the effect of different compositions of the system Ce[subscript(x)]Y[subscript(0.2-x)]Sc₀.₆Zr₃.₂O[subscript(8-δ)], (0≤x≤0.2) is studied, in terms of structure, phase and microstructure. The nature, size and shape of the powders are discussed, and their effect on the final product. The sol-gel and combustion method gives the formation of hard agglomerates (shells), during the combustion, a wide range of grain sizes, between less than 1µm and 200 µm, and the formation of grains with non spherical shape. In this project, the sol-gel and combustion process and solid state method are also compared.
In the second section of this project, AC Impedance measurements, as a function of temperature, oxygen partial pressure and time are discussed. The Arrhenius plot for all compositions shows two regions (high and low temperature) and the change of region occurs at 580 °C. At low temperatures there is a slight difference between compositions but this difference is less at high temperatures. The obtained ionic conductivity, at 350 °C, varies from 3.84×10⁻⁶ to 5.53×10⁻⁵ S/cm; at 700 °C, ionic conductivity from 0.013 to 0.044 S/cm.
At low temperatures, the activation energy associated with bulk process is generally lower than grain boundary process; for example, the composition Ce₀.₁Y₀.₁Sc₀.₆Zr₃.₂O₇.₆₅ has an activation energy, for the bulk process, of 1.05 eV and an activation energy, for the grain boundary process, of 1.17 eV. For compositions with higher ceria content, activation energy, for bulk and grain boundary, have similar values.
The AC impedance as function of oxygen partial pressure show that the amount of ceria introduced as an effect on the conductivity at low oxygen partial pressure. For the sample with no ceria in its composition, Y₀.₂Sc₀.₆Zr₃.₂O₇.₆₀, the conductivity does not vary significantly as the oxygen partial pressure is decreased; for oxygen partial of 0.21 atm, conductivity is 0.018 S/cm and when oxygen partial pressure is approximately 10⁻²⁴ atm conductivity is 0.018 S/cm. For the sample with a higher content of ceria, Ce₀.₁₂Y₀.₀₈Sc₀.₆Zr₃.₂O₇.₆₆, there is a decrease in conductivity while oxygen partial pressure decreases; and there is also the appearance of a semi-circle for lower oxygen partial pressures. For oxygen partial pressure approximately 0.21 atm, conductivity is 0.019 S/cm, but when oxygen partial pressure is decreased to 10⁻²⁴ atm conductivity decreases to 0.011 S/cm.
AC impedance measurements as a function of annealing time at 600 °C were performed. Total conductivity is fairly stable, for all compositions, until 1800 hours but after this time, conductivity slowly decreases. Some compositions show a second semi-circle in the AC impedance spectra, either from the beginning, time equals 0 hours, or after some working hours. Here, the changes in conduction and conduction processes with time are discussed.
2010-06-22T13:11:48Z
2010-06-22T13:11:48Z
2010-06-23
Thesis
http://hdl.handle.net/10023/931
en
227
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/155152019-03-29T11:19:49Zcom_10023_51com_10023_18col_10023_53
2018-07-18T08:40:14Z
urn:hdl:10023/15515
Investigations of some energy transfer processes associated with acetylacetonate complexes of the lanthanoid and groups I and II metal ions
Neilson, John Duncan
Shepherd, T. M.
Science Research Council (Great Britain)
Intermolecular energy transfer occurs between Tb(aa)₃.3H₂0 and Ln(aa)₃.3H₂O complexes (Ln = Pr, Nd, Sm, Eu, Dy, Ho or Er; aa = acetylacetonate) in n-butanol solution at 293K. Measurement of the decay time of the Tb³⁺ ⁵D₄level indicates that transfer occurs from this level to excited levels of the Ln³⁺ ions with bimolecular rate constants within the range 0.5 - 4.9 x 10⁵ dm³ mol s ⁻¹. Data from similar measurements on a mixed crystal EuxTb(1-x)(aa)₃.3H₂O and other considerations indicate that this is a very short range electron-exchange transfer. Similar measurements of the Tb³⁺ ion phosphorescence yield indicate the presence of a further intermolecular transfer process between a higher excited state of the Tb³⁺ complex and the added Ln³⁺ complexes. The Stern-Volmer Quenching constants vary from 11 dm³ mol⁻¹ for Ho and Sm to 110 dm³ mol⁻¹ for Pr. It is concluded that this transfer is unlikely to occur from either the ligand singlet or triplet levels and it is proposed that a higher Tb³⁺ level such as the ⁵D₃ may be involved in both inter- and intramolecular energy transfer. Intermolecular energy transfer between excited state Tb³⁺ ions in Tb(aa)₃.3H₂O and Ln³⁺ ions in Ln(aa)₃.3H₂O, where Ln = Eu and Sm, is shown to be markedly solvent dependent. It is proposed that the Tb³⁺ → Ln³⁺ energy transfer occurs in mixed metal dimers where the Tb-Ln distance is likely to be ca. 0.4 nm. The solvent dependent behaviour is related to the relative concentrations of monomeric and dimeric species in the various solvents. The rate controlling step in the intermolecular energy transfer is probably that, of monomer-dimer reaction which at 273K is of the order of 10⁵ dm³ mol⁻¹ s⁻¹. The activation energy of this reaction between Tb, Eu and Sm acetylacetonates is estimated to be ca. 23 kJ mol⁻¹. ¹H NMR spectra of Lu(aa)3.2H2O in several solvents are reported. The spectral profiles are temperature dependent in benzene and toluene solutions and the multiplicity of ligand methyl resonances is attributed to slow exchange between non-equivalent methyl groups in a dimeric structure. The temperature dependence in acetone solution is consistent with the presence of a monomer-dimer equilibrium with △H° = -28.2 ± 1.5 kJ mol⁻¹ and △S° = -74.5 ± 4.5 J K ⁻¹ mol⁻¹. The single ligand-methyland 3-H resonances in the' strongly coordinating solvents dimethyl sulphoxide and pyridine indicate the sole presence of solvated monomers. Previous proposals about the anomalous spectrum of Mg(aa)₂ in CDCl₃ are also discussed. The extremely low efficiency of the intermolecular enrgy transfer process in europium acetylacetonate compared with the corresponding terbium acetylacetonate is attributed to the presence of a charge-transfer excited state lying below the ligand singlet states. This is supported by the anomalous absorption spectrum of the Eu³⁺complex and the effects of added anions in other ligand systems. The phosphorescence spectra of the Group I and Group II metal acetylacetonates (Metal = Li, Na, K, Rb, Gs, Mg, Ca, Sr and Ba) have all been measured in solid Ethanol glass solutions at 77K and found to have profiles similar to that of Al(aa)₃. The phosphorescence decays are non-exponential and this behaviour is attributed to the presence of both coordinated and free acetylacetonate anion. Time resolved spectroscopy and other considerations indicate that the energies of the lowest excited ligand singlet and triplet states of the aa⁻ ion are, unlike the triplet state lifetime, little affected by coordination. Solvolysis is reported in ethanol solution which invalidates some previously-reported spectral parameters.
2018-07-18T08:40:14Z
2018-07-18T08:40:14Z
1979
Thesis
http://hdl.handle.net/10023/15515
en
viii, 87 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/281032023-08-05T02:01:29Zcom_10023_51com_10023_18col_10023_53
2023-08-04T11:06:53Z
urn:hdl:10023/28103
Synthesis of peri-substituted acenaphthenes for carbon-heteroatom coupling
Kerr, Hannah
Kilian, Petr
University of St Andrews. School of Chemistry
Peri-substitution
Acenaphthenes
Carbon-heteroatom bonding
Synthesis
The work presented in this thesis is an extension to the work started around peri¬-substituted acenaphthenes for carbon-heteroatom coupling, an expansion to dehydrocoupling and dealkacoupling (H–H and C–H bond formation). This thesis explores the synthesis of several classes of peri-substituted heteroatom species and investigates how the internal strain within the acenaphthene molecule is the catalyst for intermolecular coupling reaction tested under various conditions.
The main focus of this thesis is the synthesis of peri-substituted acenaphthenes of phosphinous thioesters, using a range of alkyl, cyclic and dialkyl thiols. These underwent the coupling reaction under various reaction conditions; thermal, radical initiator with AIBN and under UV irradiation. Addition of a radical initiator indicates that the mechanism of the coupling reaction is indeed radical. This completed the sulfur series, allowing for comparison not only structurally but also with regards to the coupling reaction. These compounds demonstrate that C–S coupling is viable, although these compounds are sensitive to both air and moisture.
This concept was extended to C–N heteroatom coupling, where a series of novel peri-substituted species were synthesised and where possible, structurally authenticated using single crystal X-ray diffraction. These were also subjected to the coupling reaction under both thermal and radical initiator conditions. However, unlike the sulfur series the nitrogen compounds do not couple under radical initiator conditions but do under thermal, indicating a higher activation barrier confirmed by computational calculations. Using one of the nitrogen compounds, the use of acenaphthene amines as a ligand for metal complexes was studied, allowing us to investigate the change in coupling constants between the two peri-atoms.
Finally, additional bis(phosphino) monoxides were synthesised to extended the current class of compounds. These species were subjected to the coupling reaction under thermal, radial initiator and UV irradiation, with thermal conditions showing the most promise.
2023-08-04T11:06:53Z
2023-08-04T11:06:53Z
2023-11-29
Thesis
http://hdl.handle.net/10023/28103
https://doi.org/10.17630/sta/563
en
2026-08-01
Thesis restricted in accordance with University regulations. Restricted until 1st August 2026
343
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/8662019-07-01T10:08:52Zcom_10023_51com_10023_18col_10023_53
2010-04-09T09:44:22Z
urn:hdl:10023/866
Molecular probes for the evaluation of three isomerase enzyme mechanisms in secondary metabolism
Nasomjai, Pitak
O'Hagan, David
Royal Thai Government
Isomerisation
Alkaloid
Cytochrome P450
Fluorometabolite
5-fluoro-5-deoxyribulose-1-phosphate
Phostone
2-C-methylerythitol-phophate-2-phosphate
This thesis is focused on an investigation of the mechanisms of three enzymatically mediated carbon skeleton isomerisation reactions.
Chapter 1 provides an overview of some representative examples of the carbon skeleton rearrangement reactions in enzymology.
Chapter 2 describes the preparation and use of fluorolittorines to explore the mechanism of the rearrangement of the tropane alkaloid littorine to hyoscyamine which is a reaction mediated by the cytochrome P450 enzyme.
Chapter 3 describes the synthesis of D-ribose-1-phosphonates and the cyclic phosphonates (phostone) that are candidate inhibitors of the enzymatic isomerisation of 5-fluoro-5-deoxy-ribose-1-phosphate (5-FDRP) to 5-fluoro-5-deoxy-ribulose-1-phosphate (5-FDRulP), an important step in fluorometabolite biosynthesis pathway in Streptomyces cattleya.
Chapter 4 describes the synthesis of 5-hydroxy-3,4-dioxohexylphosphonate and [5-13C]-5-hydroxy-3,4-dioxohexylphosphonate. These compounds are proposed as candidates for the transition state of the retro-aldol/aldol mechanism of the enzymatic isomerisation of 1-deoxy-D-xylulose-5-phosphate (DXP) to 2-C-methylerythitol-phophate-2-phosphate (MEP) in the biosynthesis of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP). The influence of pH on tautomerisation of [5-13C]-5-hydroxy-3,4-dioxohexylphosphonate is also described.
Chapter 5 describes the general chemical and biochemical methodologies utilised in this research project.
2010-04-09T09:44:22Z
2010-04-09T09:44:22Z
2010
Thesis
http://hdl.handle.net/10023/866
en
http://creativecommons.org/licenses/by-nc-nd/3.0/
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
267
University of St Andrews
The University of St Andrews
School of Chemistry
oai:research-repository.st-andrews.ac.uk:10023/25882019-03-29T11:19:50Zcom_10023_51com_10023_18col_10023_53
2012-05-08T14:54:25Z
urn:hdl:10023/2588
Nanomaterials for solid oxide fuel cell electrolytes and reforming catalysts
Kosiński, Marcin Robert
Baker, Richard
University of St Andrews. School of Chemistry
MEL
Engineering and Physical Sciences Research Council (EPSRC)
Solid oxide fuel cells
YSZ
SDC
Electrolyte
Nanopowder
In this work, a broad range of analytical methods was applied to the study of the following three materials systems: yttria-stabilised zirconia (YSZ), samarium-doped ceria (SDC) and SDC-supported metal catalysts. YSZ and SDC were studied in the light of their application as solid electrolytes in Solid Oxide Fuel Cells. The SDC-supported metal catalysts were evaluated for application in the reforming of methanol.
The conductive properties of YSZ pellets derived from powders of different Y contents and particle size ranges were investigated using Impedance Spectroscopy (IS). Comparative studies of the crystallography (by X-ray Powder Diffraction (XRD)), morphology (by Scanning and Transmission Electron Microscopy (SEM, TEM)), chemical composition (by Energy Dispersive X-ray Spectroscopy (EDX) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS)) and sintering behaviour (dilatometry) were employed in the overall assessment of the conductivity results collected.
Detailed studies of three SDC compositions were performed on nanopowders prepared by a low temperature method developed in the Baker group. Modifications led to a simple and reliable method for producing high quality materials with crystallites of ~10 nm diameter. The products were confirmed by XRD and TEM to be single-phase materials. Thermogravimetric analysis, dilatometry, specific surface area determination, elemental analysis and IS were carried out on these SDC powders. The relationships between particle size, chemical composition, sintering conditions and conductivity were studied in detail allowing optimum sintering conditions to be identified and ionic migration and defect association enthalpies to be calculated.
Finally, the interesting results obtained for the SDC nanopowders were a driving force for the preparation of SDC-supported metal catalysts. These were prepared by three different methods and characterised in terms of crystallographic phase, specific surface area and bulk and surface chemical composition. Isothermal catalytic tests showed that all catalysts had some activity for the reforming of methanol and that some compositions showed both very high conversions and high selectivities to hydrogen. These catalysts are of interest for further study and possibly for commercial application.
2012-05-08T14:54:25Z
2012-05-08T14:54:25Z
2011-11-28
Thesis
http://hdl.handle.net/10023/2588
en
219
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/225712021-10-05T11:40:16Zcom_10023_51com_10023_18col_10023_53
2021-04-08T09:15:41Z
urn:hdl:10023/22571
1, 2, 4 - triazines and 1, 2, 4, 5 - tetrazines as monomers for Diels-Alder polymerisations
Bruce, Michael John
Smith, D. M.
Chemistry Theses
Chapter 1 (Introduction) comprises a brief overview of the origins,
mechanism and scope of the Diels-Alder reaction. It deals with the three different Diels Alder reaction types and highlights the utilisation of the reaction in general terms for the
synthesis of aromatic and heteroaromatic ring systems. Particular attention has been
paid to the inverse electron-demand Diels-Alder reactions of nitrogen-containing
heterocycles, where aromatisation is brought about by the thermodynamically-driven
loss of molecular nitrogen, leading to both carbocyclic and heterocyclic ring systems.
Chapter 2 (Results and Discussion) develops the ideas formed in Chapter
1 to seek possible bis-dienes and bis-dienophiles for utilisation in polymer synthesis.
Attention has been concentrated on possible routes to bis-l,2,4-triazines and 1,2,4,5-
tetrazines, which are novel compounds, and on their possible use in both inter- and
intra-molecular Diels-Alder reactions.
A new method for the synthesis of bis-glyoxals involving the oxidation of the
corresponding diacetyl-aromatics using HBr/DMSO is the most reliable and is capable
of being scaled up without safety/environmental problems. The bis-glyoxals are then
readily convertible into 5,5'-linked bis-l,2,4-triazines which are potential bis-dienes for
Diels-Alder reactions. The attempted intermolecular reactions of the bis-triazines with a
range of diethynyl-aromatics have, however, proved unsuccessful so far. Attempts to
form bis-(o-ethynylphenols) for intramolecular Diels-Alder reactions after coupling to
bis-triazines have also been unsuccessful.
Several 5-(substituted phenyl)-1,2,4-triazines have also been formed, with the
intention of coupling these through the phenyl substituent to a central difunctional core.
Several 1,2,4,5-tetrazines have been formed with similar intent.
Chapter 3 (Experimental) details the synthetic procedures and the
Bibliography follows.
2021-04-08T09:15:41Z
2021-04-08T09:15:41Z
1995
Thesis
http://hdl.handle.net/10023/22571
en
92 p.
University of St Andrews
The University of St Andrews
oai:research-repository.st-andrews.ac.uk:10023/218302021-10-26T02:01:34Zcom_10023_51com_10023_18col_10023_53
2021-04-08T08:57:05Z
urn:hdl:10023/21830
Studies of 2-AZA analogues of 1, 6, 6a λ⁴-trithiapentalenes : introduction of the =N-S unit into four-electron three-centre bonded structures and reactions of 1, 6, 6a λ⁴-trithiapentalenes with arenediazonium tetrafluoroborates
Briggs, Alexander Gibson
Reid, D. H.
There is only one report in the literature of a structure of the trithiapentalene type containing the =N—S unit. We have 4 thionated 3,4-dimethyl - 1 - oxa - 6, 6aλ⁴. -di selena- 2 -azapentalene with phosphorus pentasulphide and obtained two products, 3,4- 4 dimethyl-1-thia-6, 6a λ⁴ -diselena-2-azapentalene and 3, 4-dimethyl-4 1, 6-dithia-6a λ⁴ - selena-2-azapentane, both new systems which contain this moiety. A third product from the same reaction was 3,4- dimethyl-1-oxa-6—thia-6a λ⁴ - selena-2-azapentalene, the first trithiapentalene analogue containing four different heteroatoms. An attempt to introduce the =N—S unit into 4, 5-dihydro-3H-benzo [cd ]-l-oxa-6, 6a λ⁴ -dithia-2-azapentalene by treatment with phosphorus pentasulphide was unsuccessful.
We have demonstrated that the very large increase in acidity of isothiazole-5-carboxaldoxime on methylation at N-2, which had been reported in the literature, is due to the formation of a stabilised bicyclic three-centre bonded structure on deprotonation of the resulting salt in solution. This investigation thus led to the isolation of 6-methyl- 1 -oxa- λ⁴ -thia-2, 6-diazapentalene, the first member of a new heterocyclic system. An attempt to introduce the =N—S unit into this product by thionation with phosphorus pentasulphide was precluded by the low yield in which this compound was obtained. Several other related compounds were also studied.
It has been suggested that the products from reactions of 4 l,6,6a λ⁴ -trithiapentalenes with arenediazonium electrophiles arise from two distinct mechanisms, one involving attack at C-3(4) and the other involving attack at S-1(6). We have provided further verification of the latter mechanism by obtaining S-arylation products from the reaction of 5-methyl(ene)- 1, 2-dithiole-3-thiones with arenediazonium tetrafluoroborates. We have also trapped a dithiolium salt intermediate from this type of reaction as 3-p-nitrophenylthio-5-t-butyl- 1, 2-dithiolium tetrafluoroborate.
2021-04-08T08:57:05Z
2021-04-08T08:57:05Z
1977
Thesis
http://hdl.handle.net/10023/21830
en
xii, 109 p
University of St Andrews
The University of St Andrews
didl///col_10023_53/100