Synthesis and study of imidazole-bearing copper(I) complexes and their reversible reaction with dioxygen

Abstract

Magnetochemical and resonance-Raman spectroscopic measurements have been made on oxygenated solutions of {2,6-bis[1-(2-imidazol-4-ylethylimino)ethyl]pyridine}copper(I) cation and related complexes to characterize more fully the nature of the copper–dioxygen interaction. The role, if any, of the imidazole–nitrogen proton in the reversible oxygenation process has been examined. A possible correlation between the redox potential of the Cu^II⇌ Cu^I couple and the reaction of the copper(I) centre towards O₂ has been studied, and for completeness, copper(II) and zinc(II) analogues of all the copper(I) species have also been prepared and fully characterized. Although inconclusive in an absolute sense, the present studies are consistent with the oxygenation products of these copper(I) species being relatively stable Cu–O₂ or Cu–O₂–Cu adducts, at least in the initial stages of oxygenation.