Single copper ion containing copper(I)-dioxygen adducts possessing nitrogen-containing chelating ligands can be best described as cupric-superoxide complexes. Such initial complexes are also found in copper enzymes where they either attack a substrate or are protonated-reduced. Thus, the structures, physical properties and reactivity toward protons-electrons and/or substrates are of fundamental interest in biological and chemical systems where dioxygen-reduction occurs (e.g., also in fuel cells), and where organic substrates are oxidized or oxygenated. Our primary research approach in copper-dioxygen chemistry focuses on ligand design and variation and the use of cryogenic solution handling for the study of new complexes. In these contexts, a description of new (ligand)CuIIn-superoxo complexes (n = 1, 2) will be presented, Tripodal tetradentate ligands with built-in hydrogen-bonding modalities enhance both the stability (i.e., solution lifetime) and reactivity toward O-H (i.e., phenols) and C-H containing substrates. With a binucleating ligand framework, mixed-valent Cu(I)Cu(II) precursors reacts to form superoxo-dicopper(II) products which can be reversibly reduced to a peroxo-dicopper(II) analogue. For some cases, dicopper(II) superoxo/peroxo reduction potentials have been obtained. Also, superoxo-dicopper(II) complexes can undergo hydrogen-atom abstraction reactions with O-H or C-H substrates; aspects of reaction mechanism thermodynamics have been sought and will be discussed.

Copper(I)-dioxygen adduct stabilization and substrate oxidative reactivity

2019 Fall National Meeting

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