Optical Memory Systems Based on Transition Metal Photochromism:Photodisproportionation of d sup 1-d sup 1 Dimers with Linear Oxo Bridges

摘要

This project explored the potential as photochromic substrates for optical memorysystems of transition metal complexes in which two d sup 1 transition metal centers are spin paired through a linear oxo bridge. The project was based on the discovery of a dinuclear W(V) tungstenocene derivative in which irradiation into the strong visible region absorbance associated with the d sup 1-d sup 1 oxo bridged chromophore led to marked photochromism following photodisproportionation to a 1:1 mixture of d sup 0 and d sup 2 complexes. Examination of the large class of d sup 1-d sup 1 oxo bridged dimers containing MV2O34+ (M = Mo, W) cores stabilized by bis-chelate dithiocarboxylate-type ligands S2EXn led to the observation that dibenzyldithiocarbamates complexes of these cores undergo an analogous thermally reversible photochromic disproportionation, but dithiophosphate complexes undergo irreversible wavelength dependent photo-bleaching; the complexes are not themselves photoactive but are destroyed through photolysis of d sup 0 products of thermal disproportionation products. Both dithiocarbamate and xanthate complexes of the MoV2O3(4+) core are fluxional, participating in a process in which there is rapid intramolecular exchange of bridging and terminal oxo groups.