Structural characterization of two solvates of a luminescent copper(II) bis(pyridine)-substituted benzimidazole complex

Abstract

Copper(II) complexes of benzimidazole are known to exhibit biological activity that makes them of interest for chemotherapeutic and other pharmaceutical uses. The complex bis(acetato-κO){5,6-dimethyl-2-(pyridin-2-yl)-1-[(pyridin-2-yl)methyl]-1H-benzimidazole-κ²N²,N³}copper(II), has been prepared. The absorption spectrum has features attributed to intraligand and ligand-field transitions and the complex exhibits ligand-centered room-temperature luminescence in solution. The acetonitrile monosolvate, [Cu(C₂H₃O₂)₂(C₂₀H₁₈N₄)]·C₂H₃N (1), and the ethanol hemisolvate, [Cu(C₂H₃O₂)₂(C₂₀H₁₈N₄)]·0.5C₂H₆O (2), have been structurally characterized. Compound2has two copper(II) complexes in the asymmetric unit. In both1and2, distorted square-planar N₂O₂coordination geometries are observed and the Cu—N(Im) bond distance is slightly shorter than the Cu—N(py) bond distance. Intermolecular π–π interactions are found in1and2. A weak C—H...π interaction is observed in1.