Investigations on the Reactivity of Copper(I) Complexes with a N3S Thioether Ligand System

Abstract

In the active site of several copper monooxygenases, thioether residues are coordinated through the sulfur atom, e. g. dopamine-β-monooxygenase (DβM). The reaction of dioxygen with a series of copper(I) complexes with thioether groups in tripodal ligands based on either derivatives of tris(2-pyridylmethyl)amine (TMPA) or a guanidine system were investigated by low-temperature stopped-flow measurements. The formation of labile intermediates, an end-on superoxido complex, and μ-1,2-trans-peroxido copper(II) complexes were spectroscopically detected and a kinetic analysis allowed the calculation of activation parameters for these reactions supporting the postulated mechanism. Most interesting was the finding that replacing the ethyl group in the tren-guanidine derivative (TMGEt)2(SEtEt)N with a methyl group allowed a dramatic increase in the stability of the formed superoxido copper complex. Measurements with ozone were performed in order to find an alternative way to obtain and stabilize the labile intermediates.