Functionalisation of polyoxometalates: towards advanced applications in catalysis and materials

Abstract

This thesis focuses on reactions involving the assembly of polyoxometalate building blocks, specifically the Wells-Dawson trilacunary species [P2W15O56]12-. This reactive fragment can have the vacant sites filled with a variety of transition metals and can form extended architectures. The variables of a reaction intended to substitute various transition metals into the lacunary Dawson species were systematically tested. This resulted in the formation of numerous structures, some of which were recurring with different transition metals and some of which were found to have interesting magnetic properties. The magnetic properties of a Ni-W cubane were studied and it was shown to display ferromagnetic coupling behaviour. A nine Co atom containing trimer and fourteen Co atom containing tetrameric compound were synthesised and their magnetic properties studied. The tetrameric compound was found to display single molecule magnet behaviour. A Mn trimer analogous to the Co atom trimer was also synthesised as were two ‘banana-shaped’ sandwich clusters with either Mn or Co. The V substituted {P2W15} fragment has been widely used for hybrid applications and it was discovered that this compound can form a sandwich cluster with a V oxide double cubane in the centre of the two POMs. This cluster was studied by mass spectrometry, x-ray diffractometry and electrochemical methods and was found to have interesting electronic properties. New analogues of previously known {P2W15V3} dumbbell structures were synthesised with a view to studying vesicle formation. The compounds presented here have functional groups that have not been incorporated into these structures before