Copper(II) complexes of new unsymmetrical NSN thioether ligands

The reactions of 2-(mercaptoethyl)benzimidazole with 2-vinylpyridine and 2-picolyl chloride (in basic medium) yield the new unsymmetrical ligands 1-(2-benzimidazolyl)-5-(2′-pyridyl)-3-thiapentane (Biptp) and 1-(2-benzimidazolyl)-4-(2′-pyridyl)-3-thiabutane (Biptb), respectively. Copper(II) complexes of these ligands with differing anions were prepared. Crystal structures are reported for [Cu(Biptp)](CF3SO3)2·2H2O and [Cu(Biptb)](CF3SO3)2·0.5(C7H8)·H2O, in which the Cu(II) ions exhibit distorted square-pyramidal geometries. Powder ESR spectra of the copper compounds are rhombic and the degree of rhombicity is related to the identity of the anions. Charge-transfer bands and intense absorption in the visible region are observed in the electronic spectra. Electrochemical studies indicate that one-electron reductions are involved, the reductions occurring at relatively high potentials.