Spectroscopic, kinetic and mechanistic studies of the influence of ligand and substrate concentration on the activation by peroxides of CuI–thiolate and other CuI complexes

Abstract

Both free-radical and non-radical routes for peroxide oxidation of Cu^I can be identified for copper complexes obtained by the reduction of Cu^II by thiols, including glutathione. Copper(I)–thiolate complexes are obtained, except in the presence of e.g. 1,10-phenanthroline, and these undergo ready reaction with H₂O₂ and ^tBuOOH. EPR spin-trapping studies establish a free-radical reaction mechanism (to give ^tBuO˙) with the latter, and the formation of HO˙ from the former occurs only at low concentrations of copper. Kinetic studies (using UV-vis and EPR spectroscopies), together with NMR analysis, lead to the proposal that Cu^I aggregates react via non-radical pathways in contrast to monomeric Cu^I.