The Voltammetric Behavior of Superoxide Dismutase/Catalase Mimics

The voltammetric behavior of the superoxide dismutase/catalase mimics [(NN'-bis(salicylidene)ethylenediamine) Mn(III)]Cl (or salenMn(III) chloride) 1 and [(N, IV'-bis (3 -me thoxysalicylidene) ethylenediamine) Mn (III)] Cl (or 3,3'methoxysalenMn(III) chloride) 2 in acetonitrile is described. Both compounds show quasi-reversible one-electron reductions to the Mn(II) compound. Electroanalytical techniques are used to follow the reaction between superoxide and 1 and 2 and it is shown that it is the reduced Mn(II) compounds which scavenge superoxide. It is also shown that both compounds electrocatalytically generate superoxide in the presence of dissolved dioxygen. The rate constant for this reaction was determined for both compounds using microelectrode steady state voltammetry. A general reaction scheme for interactions between these compounds and both dissolved dioxygen and superoxide is proposed.