Reactivity of a heterobinuclear heme-peroxo-Cu complex with -substituted catechols shows a p -dependent change in mechanism.

In biological systems, heme-copper oxidase (HCO) enzymes play a crucial role in the oxygen reduction reaction (ORR), where the pivotal O-O bond cleavage of the (heme)Fe-peroxo-Cu intermediate is facilitated by active-site (peroxo core) hydrogen bonding followed by proton-coupled electron transfer (PCET) from a nearby (phenolic) tyrosine residue. A useful approach to comprehend the fundamental relationships among H-bonding/proton/H-atom donors and their abilities to induce O-O bond homolysis involves the investigation of synthetic, bioinspired model systems where the exogenous substrate properties (such as p and bond dissociation energy (BDE)) can be systematically altered. This report details the reactivity of a heme-peroxo-copper HCO model complex (LS-4DCHIm) toward a series of substituted catechol substrates that span a range of p and O-H bond BDE values, exhibiting different reaction mechanisms.