Supramolecular networks as templates for hierarchical assembly on the sub-5 nm scale
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In this study, the templating role of bimolecular triple hydrogen bonded honeycomb network consisting perylene-3,4,9,10-tetracarboxydi-imide and melamine is investigated, using scanning tunneling microscopy. Although the stability of the network upon modification is a major obstacle toward higher complexity, three different approaches in this work highlight formation of successful architectures in a sequential way. 1. Insertion of pore modifier star shaped molecules based on tri(phenylene ethynylene)benzene core in the pores to construct a new template. 2. Insertion of iodinated molecules in the pores to study the network as a nanoreactor. 3. Electrochemical deposition of metals in the pores. Self-assembly monolayer of four different molecules based on tri(phenylene ethynylene)benzene core on uniform gold surface revealed different structures. The degree of the order within the structures depends highly on the symmetry of the molecules, and hence asymmetric molecule formed disordered structure. Upon insertion into the pores of the network, one of molecules did not match the pores size, while others fitted and illustrated rotation depending on the strength of their interaction with the network components and the substrate. The rotation is significantly reduced by modifying the molecules. These new architectures are used as templets hosting C₆₀ molecules which resulted in isolated single C₆₀ molecules. Self-assembly of iodinated molecule under different conditions on uniform gold surface leads to formation of different structures including monomers and dimers. Upon thermal treatment on the uniform surface oligomers are formed, whereas for the molecules confined in the pores of the network, the covalent bond formation was limited to dimerisation. Electrochemical copper deposition into the pores of the network under acidic condition (pH = 1 - 2) is not possible because of the stability of the network. However, by increasing pH of the electrolyte (pH = 5 – 7), a bilayer of Cu and anion is formed in the pores of the network, confirmed by scanning tunneling microscopy and X-ray photoelectron spectroscopy.
Thesis, PhD Doctor of Philosophy
Embargo Date: 2019-04-01
Embargo Reason: Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 1st April 2019, pending formal approval