Probing cooperative effects in hydrogen- and halogen-bonded supramolecular assemblies
Abstract
This Thesis describes the fundamental features and applications of the
supramolecular assemblies generated by molecular systems incorporating two
different sets of self-complementary molecular recognition units based on either
hydrogen or halogen bonds.
In Chapter 1, an overview of the noncovalent interactions exploited in
supramolecular chemistry to date is provided through illustrative examples. The
concept of cooperativity is introduced and analysed: with particular emphasis on
the concept of chelate cooperativity. The different definitions and analyses of this
phenomenon, as described by different authors, are discussed.
Chapter 2 provides an introduction to synthetic self-replicating systems. Starting
from the description of the minimal model of self-replication and its kinetic
analyses, a brief review of the relevant literature is proposed from the first
synthetic deoxyribonucleotide-based self-replicating system to small molecule
replicators. The self-replicating abilities of isoxazolidine-based replicators are
described in depth through examples showing their efficiency in isolation and
within different scenarios in which they are in competition with each other.
Chapter 3 describes the design, synthesis and applications of a new
isoxazolidine-based self-replicator that benefits from recognition elements that
have significantly increased association constants. The efficiency of this
self-replicator is tested in isolation and in a simple competition scenario in
presence of a competitor isoxazolidine-based replicator. The limitations of this
system are identified and analysed and, in order to overcome these, a modified
system is synthesised and its performance is compared with other replicators.
In Chapter 4, the concept of halogen bonding is introduced through its early
historical developments up to its recent definition and rationalisation. The solid
state and solution state applications of this noncovalent interaction in the current
literature are reviewed. The designs and syntheses of two molecular scaffolds
incorporating a variously substituted iodophenyl-based halogen bond donors and
a pyridine-based halogen bond acceptors are discussed and analysed by means of
DFT calculations and their solid state structures. The limitations of these early
designs are evaluated.
Chapter 5 reports the design and syntheses of a novel class of halogen bond
donors, namely 5-iodo-1-(perfluorophenyl)-4-phenyl-1,2,3-triazoles. The halogen
bond properties of this Lewis acidic species are examined computationally as well
as in the solid and solution states. The ability of these halogen bond donors to be
easily combined with nitrogen- and oxygen-based halogen bond acceptors leading
to self-complementary molecules able to dimerise in solution through the
formation of halogen bonds is described.
Chapter 6 describes the implementation of strong oxygen-based halogen bond
acceptors to iodotriazole-based halogen bond donors. The ability of these systems
to associate in solution and in thin films to form stable and functional halogen
bonded assemblies is demonstrated.
Chapter 7 provides a summary of the research presented within this Thesis and
highlights some possible future directions.
Experimental details of the synthetic procedures described in this thesis are given
in Chapter 8.
Chapter 9 lists the references cited within this Thesis.
Type
Thesis, PhD Doctor of Philosophy
Rights
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