Abstract

The new copper(I) complexes [Cu(L 1) 2](BF 4), L 1 = 2-pyridyl-N-(2?-methylthiophenyl) methyleneimine, and [Cu(L 2) 2]-(ClO 4), L 2 = 2-pyridyl-N-(2?-benzylthiophenyl)methyleneimine, have been prepared and structurally characterized. In contrast to the known [Cu(L 1) 2](ClO 4) 2, which exhibits partial thioether S binding to effect five-coordinate Cu 2+, the copper(I) compounds reported here contain four-coordinate metal ions with exclusively N-donor binding. Cyclic voltammetry reveals a fully reversible oxidation of the Cu I species, which suggests a small barrier for reorganization. The reduction at negative potentials is irreversible for compounds [Cu(L) 2](X) and for the structurally characterized new compound [Cu(L 1)(PPh 3) 2](ClO 4). UV/Vis spectroelectrochemistry shows the typical low-energy absorption bands of copper(I) (MLCT transition) and copper(II) (ligand-field transition) in the visible region; the Cu II form develops an intense band at 350 nm attributed to a S-to-Cu ligand-to-metal charge transfer (LMCT). © 2011 Wiley-VCH Verlag GmbH & Co. KGaA.