ELECTROCHEMISTRY OF POLYOXOMETALATES IMMOBILIZED IN ION-EXCHANGE POLYMER-FILMS

The polyoxometalate ions PMo12O403-, PW12O403-, and SiW12O404- are inc orporated in polymeric ruthenium(II)(vinyl)bipyridine (poly-Ru(vbpy)(3 )(2+)) films from aqueous and dioxane-water electrolytes. Despite thei r large mass the ions exist as freely diffusing species that compensat e for up to 30% of the charge in poly-Ru(vbpy)(3)(2+). An investigatio n of the effect of environmental conditions on electrochemical behavio r reveals that the first two one-electron reduction waves of SiW12O404 - coalesce into a single two-electron reaction and those of PW12O403- shift significantly in potential upon a change from pure aqueous to 50 (v/v)% dioxane/water solvent. The observation is attributed to destabi lization of the one-electron reaction products as the solvent is enric hed is dioxane. Incorporation of polyoxometalates in protonated poly(v inyl)pyridine and poly-Ru(vbpy)(3)(2+) films from dioxane-water solven t results in differences in electrochemical behavior. Polyoxometalate anions incorporated in poly-Ru(vbpy)(3)(2+) films catalyze the electro chemical reduction of hydrogen ion.