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

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.