Noboru Oyama

Spontaneous coating of graphite electrodes by amino ferrocenes

Abstract Conditions are described under which β-ferrocenylethylamine and some other ferrocene derivatives spontaneously bind to the surface of certain types of pyrolytic graphite electrodes. The resulting coatings are long-lived and amount to several monolayers containing electroactive ferrocene centers. The coatings appear to consist of polymeric condensation products resulting from reactions between oxygen-containing groups on the graphite (probably carbonyl) and the amine. The quantity of material attached to the surface as measured electrochemically is larger in acetonitrile as solvent than in water. The possibility that primary aliphatic amines may serve as general linking reagents at oxidized graphite surfaces is discussed.

Spectroelectrochemical observations at transparent graphite electrodes coated with poly(4-vinylpyridine) and RuIII (EDTA)⋆

The coordination and kinetics of dissociation of RuIII(EDTA) from coatings of poly(4-vinylpyridine) (PVP) applied to surfaces of transparent, thin-film graphite electrodes have been monitored spectrally. Comparison between simultaneously measured spectral and electrochemical responses from the bound complexes showed that not all of the Ru(III) within the PVP coating was reduced to Ru(II) during reductive voltammetric scans, but it was totally reduced if the electrode potential was maintained at potentials negative of the peak potential for periods of several minutes. With sufficiently heavy coatings of the PVP-RuIII (EDTA) complex on the tranparent electrode it took on a golden color upon electroreduction of the Ru(III) to Ru(II) and the color was discharged upon reoxidation.

Polarography of a cobalt(III) complex of poly(4-vinylpyridine)

Abstract Polarograms for solutions of a Co(III) complex of poly(4-vinylpyridine) exhibit substantially smaller limiting currents than those for the corresponding complex of monomeric pyridine. The difference reflects more than a simple difference in diffusion coefficients because the ratio of the two limiting currents is a function of the concentration of the complex. It is explained in terms of self-inhibition of the electrode reaction of the polymeric complex by adsorption of its reduction products of the electrode surface. The inhibition can be overcome by addition of small, rapidly reacting metal complexes that serve to catalyze the reduction of the polymeric complex.