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

Two new dinucleating phenol-based ligands ( m-HL_SMe and p-HL_SMe) 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 K_M values determined for the complexes in presence of 3, 5-dtbc and are not correlated directly with the redox properties of the dicopper center. [ABSTRACT FROM AUTHOR]