Chemically modified SnO2 electrodes were prepared, using zeolite Y which had been ion-exchanged with a metal tris(bipyridyl) complex, M(bpy)3 2+ (M = Ru, Os), and a metallocene cation, M(CpR)2 + or M(Cp)(CpR)+ (M = Co, Fe; Cp = η5-cyclopentadienyl; R = -H, -CH3, -NH2, -COOCH3, -CH2N(CH3)3). The rate of charge transfer between the electrode and the metallocene contained within the zeolite is enhanced at least tenfold by adsorbing M(bpy)3 2+ onto the zeolite surface. Both oxidation and reduction of the metallocene are facile if the potentials of the M(bpy)3 2+ and M(CpR)2 + couples are matched, but only one of these processes occurs if the potentials are dissimilar. This behavior is attributed to a rapid electron-transfer cross reaction between the two complexes. The equilibrium potentials of the zeolite-bound M(CpR)2 +/0 couples were found to be 300-600-mV positive of the corresponding potentials in polar organic solvents. The charge transport diffusion coefficient for Co(CpCH3)2 +/0 in zeolite Y, from linear sweep voltammetry, was found to be ca. 2 × 10-10 cm2/s.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry