Photoresponsive inorganic polymers obtained by metal alkoxides

The polymerization of metal alkoxides was carried out in organic solvents and light responsive polymers were obtained. As starting materials for polymerization, Ti(OBu)₄, Zr(OBu)₄, Nb(OEt)₅, and Ta(OEt)₅ were used. The polymerization yield roughly corresponds to the formation of TiO₂, ZrO₂, NbO₂(OEt), and TaO₂(OEt), respectively. The polymers obtained are paramagnetic and all give similar (dark) ESR spectra. When illuminated by visible light, a new ESR absorption is detected in the vicinity of g = 2.00, or 330–340 mT (for 9.450 GHz) region. The formation and decay rates of this ESR absorption was measured. The decay rate constants obtained from the formation curves were larger than those obtained from the decay curves, indicating relatively short lived species are formed during light illumination. The polymers thus prepared have photocatalytic activity and can photolyze 1 : 1 methanol/water system with visible light. Other possible uses of these polymers as paramagnetic or photochromic materials are discussed.