PHOTOINDUCED REDUCTION OF W10O324- BY ORGANIC-COMPOUNDS IN AQUEOUS-SOLUTION

The photoreduction of decatungstate anion (W10O324-, DTA), a represent ative polyoxotungstate, was studied in the presence of several types o f organic substrate in aqueous solution. The complete conversion of DT A to DTA(2-) was observed on steady irradiation in the presence of cer tain organic substrates in aqueous solution. Colour-selective irradiat ion showed that the formation of DTA(2-) is due to the photoinduced re duction of excited DTA(-) by organic molecules. Laser flash photolysis with benzyl alcohol, phenol and terephthalaldehyde exhibited differen t time profiles of electron transfer. Prompt formation and second-orde r decay of DTA(-) at the rate of the diffusion limit were observed. Th e quantum yield of reduction changed as a function of the amount of su bstrate, indicating the formation of a complex with organic molecules before photoexcitation. Proton nuclear magnetic resonance (NMR) measur ements supported complex formation. DTA was suggested to play a major role in the photoinduced reactions of aqueous colloidal WO3.