Monomeric copper(II) superoxide species are proposed as an initial intermediate in the reaction of dioxygen with a variety of copper enzymes. Despite the importance of such species, few monomeric copper(II) superoxide model complexes have been reported, with only two such complexes having been structurally characterized. In addition, there are no reported examples of discrete model complexes containing the intriguing monomeric copper(II) hydroperoxide moiety, proposed as a key intermediate in the chemistry of the copper containing monooxygenases dopamine BETA-monooxygenase and peptidylglycine alpha-amidating enzyme. The research proposed herein is directed at understanding the effect of hydrogen bonding interactions on the stabilization and reactivity of monomeric copper(II) superoxide and copper(II) hydroperoxide moieties in biological systems. Utilizing a novel 1,4,7-triazacyclononane ligand framework bearing differing pendant amide groups capable of hydrogen bonding interactions, a series of copper(I) complexes will be prepared, characterized, and subjected to treatment with dioxygen at low temperature in the hope of generating and observing the reactivity of monomeric copper(II) superoxide complexes. The products of this reaction will be characterized using standard spectroscopic techniques (UV-vis, EPR, EXAFS, resonance Raman) and manometry. In addition, the amide derivatized ligands will be used in an attempt to prepare and study the reactivity of novel monomeric copper(II) complexes bearing aquo, hydroxo, hydroperoxo and acylperoxo ligands. Specifically , this synthetic modeling study is directed at understanding (i) how differences in the availability of hydrogen bonding interactions affects the overall chemistry of mononuclear copper(II) superoxide and hydroperoxide species, and (ii) the influence of hydrogen bonding interactions upon the fundamental stability, structural features, spectroscopy, and reactivity of mononuclear copper(II) centers bearing superoxo, aquo, hydroxo, hydroperoxo, and acylperoxo ligands.
