Finding a mononuclear cobalt(iii)-peroxo complex with 1,4,7,10-tetraazacyclododecane, an intermediate for dioxygen reduction

Abstract

1,4,7,10-Tetraazacyclododecane (L) reacts with CoCl₂ to provide a mononuclear cobalt complex, [Co(L)(Cl)₂]Cl 1, which has been determined by X-ray crystallography. Complex 1 can serve as a new molecular catalyst for the oxygen reduction reaction (ORR). Under −0.4 V, the H₂O₂ yield is almost 100% with 0.20 M KOH. Investigations show that the formation of a cobalt(III)-peroxo species, [L-Co-OO]⁺ in solution is responsible for O₂ reduction. In particular, this cobalt(III)-peroxo species has been isolated from the electrocatalytic system as a binuclear cobalt complex, [Co(L)(μ-OH) (μ-OO)Co(L)](ClO₄)₄2 in the solid state. We hope that these findings can provide a new ideal for the development of electrocatalysts for the ORR.