While the four-electron, four-proton reduction of dioxygen to two equivalents of water is well-known in aqueous solution, the effect of metal ions (and organic solvent) is less understood, including knowledge of O2-derived species’ reduction potentials when metal ion bound and in non-aqueous media. These factors are important to consider due to the significance of metal-oxygen species in many oxidative transformations, both in biological and synthetic systems. In this presentation, the interconversion of reduced dioxygen species (i.e., superoxide, peroxide, and hydroperoxide) bound to a binuclear copper complex will be discussed. A novel dicopper(II) superoxide complex, [CuII2(XYL-O–)(O2–)]2+ (XYL-O– is a m-xylene derivative with two bis[(2-(2-pyridyl)ethyl)amine] arms and a bridging phenolate), characterized by UV-vis, EPR, and resonance Raman spectroscopies, has been synthesized at cryogenic temperatures via two different methods. This complex can be generated from oxygenation of the Robin-Day Class I mixed-valent complex [CuICuII(XYL-O–)(L)]2+ or from oxidation of the previously described peroxide complex [CuII2(XYL-O–)(O22–)]+. When decamethylferrocenium ion is used as the oxidant, an equilibrium between the superoxide and peroxide complexes is observed; a redox potential of the CuII2(O2–)/CuII2(O22–) couple has been calculated and compared to a recently published dicopper complex bearing a similar binucleating ligand. The superoxide complex can also react with phenolic substrates to give a phenoxyl radical and the dicopper hydroperoxide complex [CuII2(XYL-O–)(–OOH)]2+ (also previously known) verified by EPR and UV-vis spectroscopies, respectively.

Interconversion of reduced dioxygen species bound to binuclear copper complexes

254th National Meeting (2017)

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