Thiomethyl Substituted Dicopper Complexes: Attempts to Reproduce the Asymmetry of the Active Site from Type 3 Copper Enzymes

Abstract

AbstractTwo new dinucleating phenol‐based ligands (m‐HLSMe and p‐HLSMe) bearing pyridine‐containing pendant arms with a SMe group on one pyridine (meta or para position relative to the pyridine nitrogen atom) have been synthesized. After coordination by two copper(II) ions, the corresponding μ‐phenoxido, μ‐hydroxido dicopper(II) complexes were isolated and characterized by UV/Vis, EPR spectroscopy, single‐crystal X‐ray analysis (for the complex with the SMe substituent at the meta position) and electrochemistry. The presented compounds mimic the active site of type 3 copper enzymes and in particular the distinct environments of the copper ions.Both complexes are active as catalysts for the oxidation of 3, 5‐di‐tert‐butylcatechol to the respective quinone. The catalytic properties of the complexes depend on substrate binding, as reflected by the KM values determined for the complexes in presence of 3, 5‐dtbc and are not correlated directly with the redox properties of the dicopper center.