Cobalt Octaethyltetrapyrazinoporphyrazine: Spectroscopy, and Electrocatalytic and Kinetic Study of Dioxygen Reduction at a Glassy Carbon Electrode

Abstract

Cobalt octaethyltetrapyrazinoporphyrazine was synthesized and characterized by electronic absorption and magnetic circular dichroism spectroscopy. These spectroscopies and molecular orbital calculations within the framework of the Pariser–Parr–Pople approximation revealed that the effective π-conjugation system of octaethyltetrapyrazinoporphyrazine is smaller than phthalocyanines. For the first time, the electrochemical behaviour of cobalt octaethyltetrapyrazinoporphyrazine irreversibly adsorbed onto a glassy carbon electrode as a surface modifier is reported. The cobalt derivative/glassy carbon electrode showed catalytic activity for oxygen reduction. Surprisingly, the peak potentials for oxygen reduction at this electrode coincide well with those where Co II is reduced to Co I over the whole pH range, indicating that the active species for dioxygen reduction is Co I rather than the Co II species. A possible mechanism for the electrocatalysis of oxygen is discussed.