Distortion Isomerism of Cu(II) Chloride Adducts with Bis(2-benzimidazolyl)ethane. Synthesis, Characterization, X-ray Structures and Spectroscopy of Four Different Isomers

Abstract

3D structures and spectroscopic properties are reported of four compounds with the ligand bis(2-benzimidazolyl)ethane (hereafter abbreviated as dbz) attached to CuCl2, all having the general formula [Cu(dbz)Cl2](Hb) x . (in which Hb = EtOH or MeOH and x = 1/2 or 1). The X-ray crystal structure has been solved from these four slightly different compounds, namely: green α-[CuCl2dbz](C2H5OH)1/2 (1), the red compound β-[CuCl2dbz](C2H5OH)1/2 (2), which both have two slightly different units in the unit cell, the red α-[CuCl2dbz](CH3OH) (3) and a blue–green compound β-[CuCl2dbz](CH3OH) (4). The geometry around the Cu(II) anion is distorted tetrahedral for all four compounds, with chromophores consisting of two nitrogen atoms of the bidentate chelating dbz molecule and two chloride anions. The unit cells of compound 1 and 2 consist of two chemically identical, but crystallographically different units, while compounds 3 and 4 each have only one independent CuCl2-(dbz) unit. The major differences are observed in the dihedral angles NCuN–ClCuCl, which vary from 29.3 to 77.1° for the four compounds. The differences are related to different packing effects, ring–ring stacking and H-bond interaction, due to the two different alcohols used. In fact these four compounds represent a new range of examples of distortion isomerism in pseudo-tetrahedrally coordinated species. Characterisation of the four compounds has been completed by IR, EPR and LF spectroscopy.