Copper-dioxygen and copper-oxo species relevant to copper oxygenases and oxidases

Copper proteins mediate both the transport and activation of dioxygen in a number of biological systems. The active sites of these proteins comprise m ononuclear, dinuclear, and trinuclear copper centers, with the copper ions displaying a variety of coordination numbers and stereochemistries. Informa tion regarding the mechanism by which these proteins activate dioxygen has been obtained by studies of the reactions of small molecule model copper co mplexes with dioxygen and its derivatives. Superoxo, peroxo, and bis(mu-oxo ) intermediates in these reactions have recently been characterized by X-ra y crystallography and this article concentrates on the structures of these intermediates, along with several Cu/ O-2 complexes that have been well cha racterized by spectroscopic methods. The oxygenase-type reactivities of a n umber of copper complexes on reaction with dioxygen are also discussed.