Synthetic Copper-(Di)oxygen Complex Generation and Reactivity Relevant to Copper Protein O₂-Processing

Abstract

Synthetic copper-dioxygen complex design, generation and characterization, play a crucial role in elucidating the structure/function of copper-based metalloenzymes, including dopamine β-monooxygenase, lytic polysaccharide monooxygenases, particulate methane monooxygenase, tyrosinase, hemocyanin, and catechol oxidase. Designing suitable ligands to closely mimic the variable active sites found in these enzymes poses a challenging task for synthetic bioinorganic chemists. In this review, we have highlighted a few representative ligand systems capable of stabilizing various copper-dioxygen species such as Cu^II-(O₂^•-)(superoxide), Cu₂^II-(μ-η¹:η¹-O₂^2-) (trans/cis-peroxide), Cu₂^II-(μ-η²:η²-O₂^2-) (side-on peroxide) and Cu_n^II-^–OOH (hydroperoxide)species. Here, we discuss the ligand type utilized, syntheses, and spectroscopic characterization of these species. We also delineate reactivity patterns, particularly electrophilic arene hydroxylation by a side-on peroxo species which occurs via a “NIH shift” mechanism and thermodynamic-kinetic relationships among Cu₂-(O₂^•-)/O₂^2-/ ^-OOH moieties.