Revised crystal and molecular structure, FT-IR spectra and DFT studies of chlorotetrakis(imidazole)copper(II) chloride

Copper(II) complex with imidazole, [Cu(ImH)4Cl]Cl, was prepared and characterized by a single crystal X-ray analysis and infrared spectroscopy. This complex is one of the two polymorphic forms of the title compound. The crystal and molecular structures, and the patterns of intermolecular hydrogen bonding in two polymorphs have been compared and discussed. The two forms crystallize in the same monoclinic space group (P21/n) with different unit cell parameters. The detailed assignments of the FT-IR spectra of the title complex have been made on the basis of theoretical studies of the [Cu(ImH)4Cl]+ cation using the unrestricted B3LYP method and the combined basis set: 6-311++G(3df,3pd) for non-metal atoms and LanL2DZ for Cu. The bands at 285, 259 and 229 cm−1 in the IR spectrum are assigned to the CuN(imidazole) stretching vibrations.