Mechanisms of the Dismutation of Superoxide Catalyzed by the Copper(II) Phenanthroline Complex and of the Oxidation of the Copper(I) Phenanthroline Complex by Oxygen in Aqueous Solution

By using the technique of pulse radiolysis to generate 0₂-, it is demonstrated that copper 1,10-phenanthroline ((op)₂Cu²⁺) is capable of catalytically dismutating 0₂- with a “turnover” rate constant k_cat = (5.1 ± 0.9) X 10⁸ M^-1 s^-1. The rate constants of the reduction of (op)₂Cu²⁺ and of the oxidation of (op)₂CU+ by O₂- have been determined to be (1.93 ± 0.07) X 10⁹ and (2.95 ± 0.3) X 10⁸ M^-1 s^-1, respectively. The kinetic results of the oxidation of (op)₂CU+ by molecular oxygen in aqueous solution are interpreted by a mechanism that proceeds via a superoxide intermediate, and the rate constant k-₁₀ = (5.0 ± 0.3) X 10⁴ M^-1 s^-1 has been determined. The rate constant of the oxidation of (op)₂CU+ by H₂O₂ was measured to be k₂₂ = (937 ± 20) M^-1 s^-1.