Copper (II)-thiolate complexes with novel tripodal- and tetrapodal-like benzimidazoles

Abstract

The tripodal copper(II) thiolate complexes Cu(L1)(Cl)-2H2O and Cu(L1)(mim)(Cl) [H(L1) = N-(2-mercaptoethyl)-N,N-bis (pyrid-2′-ylmethyl)amine and mim = N-methylimidazole] have been isolated. Both contain monomeric copper(II) and display two ligand field bands and axial cryogenic e.p.r. spectra, suggesting a squarebased geometry. A copper(II) thiolate complex Cu(L2)(Cl)-H2O [H(L2) = N-(2-mercaptoethyl)-N,N′,N′-tris(benzimidazol-2′-ylmethyl)-1,2-ethanediamine] with a CuN5S chromophore has been also isolated. It exhibits only one ligand field band and an axial cryogenic e.p.r. spectrum, consistent with a distorted tetragonal coordination geometry. All the thiolates display intense S− → CuII charge transfer bands in the u.v. region, suggesting equatorial thiolate coordination. All of the complexes exhibit irreversible electrochemical behaviour.