Hemilabile Thio– and Selenoethers in Bis(benzimidazolyl)Amine Copper Complexes Relevant to the Active Sites of Copper-Dependent Monooxygenases

Abstract

Copper complexes supported by benzimidazole-based tetradentate neutral ligands featuring thio- and selenoether donors, resemble the coordination environment of the active site in copper dependent monooxygenases Dopamine-β-monooxygenase (DβM) and peptidylglycine-α-hydroxylating monooxygenase (PHM). The cuprous complexes react with O2 at low temperature generating a reactive copper-oxygen species assigned to a side-on cupric–superoxo complex, which activates the C─H bond of dihydroanthracene. Based on structural, 1H and 77Se NMR, and EPR spectroscopic characterization, together with DFT computations, the selenoether moiety likely acts as a hemilabile ligand in these scaffolds, which results in an electrophilic cupric–superoxide intermediate poised for H-atom transfer, as has been proposed for related bis(benzimidazole)-thioether analogues and selenoether-modified enzymatic systems.