Electron Transfer and Axial Coordination Reactions of Cobalt Tetra(Aminophenyl)Porphyrins Covalently Bonded to Carbon Electrodes

Electrochemistry of tetra(aminophenyl)porphyrin covalently attached to glassy carbon and then cobalt‐metallated, was investigated in DMSO and solvents in the presence of pyridine. Shifts in formal potential were used to measure complex stability constants and coordination number for the pyridine complexes of the immobilized metalloporphyrin. Unusually slow electrochemistry of the Co(III/II) reaction was also studied by cyclic voltammetry and by reflectance spectroelectrochemistry. It is proposed that coordination of cobalt by surface carboxylate groups causes extraordinarily slow electron transfer for the Co (III/II) step.