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

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 O-2 reduction. In particular, this cobalt(iii)-peroxo species has been isolated from the electrocatalytic system as a binuclear cobalt complex, [Co(L)(mu-OH) (mu-OO)Co(L)](ClO4)(4)2 in the solid state. We hope that these findings can provide a new ideal for the development of electrocatalysts for the ORR.