Dioxygen reduction in acetonitrile with copper pyridylalkylamine complexes; the influence of acid strength on the catalytic performance

The pyridylalkylamine copper complex [Cu(tmpa)(L)]2+ has previously been proposed to reduce dioxygen via a dinuclear resting state, based on experiments in organic aprotic solvents using chemical reductants. Conversely, mononuclear reaction mechanism was observed under electrochemical conditions neutral aqueous solution. We have investigated the oxygen and hydrogen peroxide reduction catalysed by acetonitrile, several different acids over range of pKa. demonstrate that strong lead loss redox reversibility destabilization non-catalytic conditions. Under milder conditions, (ORR) shown proceed catalytic intermediate, similar what we water. However, acetonitrile rate constants ORR are dramatically lower factor 105, which is caused unfavourable equilibrium formation [CuII(O2•−)(tmpa)]+ acetonitrile. This results higher rates for than ORR.