Covalently Linked Scaffold of Cobalt Corrins on Graphite for Electrochemical Catalysis in Microemulsions

• Published in: Journal of the American Chemical Society 1999-03, Vol.121 (12), p.2909-2914
• Main Authors: Zhou, De-Ling, Njue, Christopher K, Rusling, James F
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja984178l

Catalytic films were constructed by covalently binding poly-l-lysine (PLL) onto oxidized carbon electrodes and then forming covalent amide linkages from PLL to the cobalt corrin vitamin B12 hexacarboxylic acid [B12(COOH)6]. Covalent bonds from electrode to PLL and PLL to B12(COOH)6 provided good stability in microemulsions. PLL−B12(COOH)6 films gave reversible electron transfer for the Co(II)/Co(I) redox couple and exhibited characteristic voltammetric features of surface-confined electrochemistry. Formal potentials of the Co(II)/Co(I) couple in the films were controlled by the concentration of electrolyte in the fluid and by Coulombic interactions with surfactant. PLL−B12(COOH)6 films demonstrated excellent catalytic activity in microemulsions for the reduction of vicinal dihalides to olefins, for dechlorination of trichloroacetic acid, and for alkylation of an activated olefin. Turnover numbers for conversion of dibromocyclohexane to cyclohexene in microemulsions were 3-fold larger for PLL−B12(COOH)6 on carbon cloth cathodes than those for the same cobalt catalyst chemisorbed onto nanocrystalline TiO2 cathodes.