EFFECT OF SUPPORTING ELECTROLYTE ON THE MEDIATED REDUCTION OF [FE(H2O)6]3+ BY AN OSMIUM-CONTAINING POLY(4-VINYLPYRIDINE) FILM

The ability to control the mediation kinetics of [Fe(H2O)6]3+ reduction by [Os(bipy)2(PVP)10CI]CI films through electrode potential, film thickness and supporting electrolyte is demonstrated; bipy = 2,2'-bipyridyl, PVP = poly(4-vinylpyridine). In H2SO4, the mediated reduction is controlled by film thickness for surface coverages between 7 x 10(-10) and 1 x 10(-8) mol cm-2 (Lk mechanism). For surface coverages > 10(-7) mol cm-2 total catalysis is obtained where substrate diffusion in solution limits the reduction rate (LSK mechanism). In HCIO4 the mediated reaction is of the surface type and occurs between [Fe(H2O)6]3+ still in solution and the film within a region of molecular dimensions (Sk" mechanism). These observations are considered in relation to film structure and with regard to potential applications.