Vibrational spectroscopic studies of metal(II) halide benzimidazole

Infrared spectra (4000–200 cm⁻¹) are reported for metal halide(II) benzimidazole complexes of the following stoichiometries: M(benz)X₂ M=Cd, Cu; X=Cl, Br; BENZ=benzimidazole], Co(benz)₂, and Co(benz)₂X₂ X=Cl, Br, I]. Vibrational assignments are given for all the observed bands. The analysis of the vibrational spectra indicates that there are some structure–spectra correlations. For a given series of isomorphous complexes the sum of the difference between the values of the vibrational modes of uncoordinated benzimidazole and coordinated to metal ion benzimidazole was found to increase in the order of the second ionization potentials of metals.