Towards models for the oxygen evolving centre of photosystem II and analysis of Lewis acidic metals within novel salen derivatives

The synthesis and characterisation of a range of ligands capable of binding four or five transition metals has been explored in an attempt to synthesise a model for the oxygen evolving centre of photosystem II. Difficulty was encountered in isolating the pure, deprotected ligands. A ligand based on 1,4,7-triazacyclononane containing three alcohol donors was isolated, investigated and compared against similar ligands. A series of copper N-oxide Bis(N,N'-Disalicylalethylenediamine) derivatives were synthesised and fully characterised. The electron paramagnetic resonance spectra (EPR) of these complexes were measured and compared in order to determine the relative Lewis acidity of the central metal. Electron nuclear double resonance (ENDOR) spectra were recorded of the complexes they revealed the catalytic activity of these complexes towards cyclopropanation was tested with a variety of styrene derivatives. A zinc N-oxide Bis(N,N'-Disalicylalethylenediamine) derivative was extensively studied for enantiomeric discrimination of a small amine, methylbenzyl amine (MBA). This was monitored via lH NMR titrations in three different solvents, CDCI3, CD3CN and CD3OD. The ability of MBA to displace a solvent molecule from the coordination sites was investigated and the data inserted into a kinetic model. Chloroform was found to have the weakest interaction while methanol had the strongest. The difference in affinity of ii-complex for i-MBA over S-MBA was also investigated and a preference for the heterochiral mixture was revealed