Structure and spectroscopic study of a novel complex: Tetrakis(benzimidazole)(perchlorato)copper(II)(perchlorate) hemihydrate

A novel complex tetrakis(benzimidazole)(perchlorato)copper(II)(perchlorate) hemihydrate has been prepared and characterized by single crystal X-ray analysis, FT-IR, Raman and UV–VIS spectroscopy. [Cu(Hbim)4(ClO4)](ClO4)·½H2O crystallizes in the centrosymmetric space group of triclinic system with two molecules in the asymmetric unit cell. The cupric ion of both independent molecules is coordinated by four nitrogen atoms lying in the basal plane and by an oxygen atom located in the axial position. An extensive network of NH···O hydrogen bonds links the oppositely charged [Cu(Hbim)4(ClO4)]+ and ClO4- units into the 2D supramolecular arrangement parallel to (0 1 1) crystallographic plane. The CuN4O chromophore adopts a slightly distorted square-pyramidal geometry (SQP), the degree of trigonality (τ) equals 0.081 and 0.013, for Cu1 and Cu2, respectively. The solid state diffuse-reflectance electronic spectrum shows the principal high-energy band at ca. 19,200 cm−1, which is assigned to the dxy, dxz ≈ dyz → dx2–y2 transitions, whereas the shoulder at ca. 16,030 cm−1 can be assigned to the dz2 → dx2–y2 transition. The FT-IR and Raman spectra have been measured and assigned in the range 4000–50 cm−1. The complicated character of the absorption bands arising from the ClO and NH stretching vibrations confirms the presence of intermolecular hydrogen bonds in crystal. In the far infrared spectrum, the CuN stretching vibration is assigned at 310 cm−1, while the CuO stretching vibration contributes mainly to the band at 160 cm−1, which reflects a weak CuO interaction.