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

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-η ¹:η ¹-O₂ ^2-) (trans/cis-peroxide), Cu₂ ^II-(μ-η ²:η ²-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.