Photochemistry of heteropoly electrolytes: the 1:12 tungstates

1:12 tungstates are photosensitive in near visible and ultra-violet areas at the oxygen to metal charge transfer bands, in the presence of a great variety of organic reagents. Photosensitivity results in multi- electoral reduction of tungstates with concomitant oxidation of oganic compounds. Photosensitivity follows the order PW₁₂O_4o^3? > SiW₁₂O_4o^4? > FeW₁₂O_4o^5? > H₂W₁₂O_4o^6?, which is the same order with the increasing negative redox potentials. Maximum quantum yield ～ 15% is obtained with high concentrations of organic reagents (1–10 M). The reduced heteropoly compounds (HPC) are eacily re-oxidized by atmospheirc oxygen. They are also capable of reducing hydrogen ions and this limits the extent of photoreduction.