Intramolecular Phenolic H-Atom Abstraction by a N 3 ArOH Ligand-Supported (μ-η 2 :η 2 -Peroxo)dicopper(II) Species Relevant to the Active Site Function of oxy-Tyrosinase.

Synthetic side-on peroxide-bound dicopper(II) ( S P ) complexes are important for understanding the active site structure/function of many copper-containing enzymes. This work highlights the formation of new {Cu II (μ-η 2 :η 2 -O 2 2- )Cu II } complexes (with electronic absorption and resonance Raman (rR) spectroscopic characterization) using tripodal N 3 ArOH ligands at -135 °C, which spontaneously participate in intramolecular phenolic H-atom abstraction (HAA). This results in the generation of bis(phenoxyl radical)bis(μ-OH)dicopper(II) intermediates, substantiated by their EPR/UV-vis/rR spectroscopic signatures and crystal structural determination of a diphenoquinone dicopper(I) complex derived from ligand para -C═C coupling. The newly observed chemistry in these ligand-Cu systems is discussed with respect to (a) our Cu-MeAN (tridentate N , N , N ', N ', N ″-pentamethyldipropylenetriamine)-derived model S P species, which was unreactive toward exogenous monophenol addition ( J . Am . Chem . Soc . 2012 , 134, 8513-8524), emphasizing the impact of intramolecularly tethered ArOH groups, and (b) recent advances in understanding the mechanism of action of the tyrosinase (Ty) enzyme.