Fourier-transform infrared and Raman spectra of cysteine dichloride cadmium(II) anion: DFT: B3LYP/3-21G(d) structural and vibrational calculations

Abstract

The cysteine dichloride cadmium(II) potassium was synthesized and the structural analysis was carried out through the following methods: determination of the C, H, N, S and O contents, thermogravimetry, infrared and Raman spectra. Assuming Cd S, Cd O (O-carboxilate) and Cd N bonds, several hypothetical structures were calculated by means DFT: B3LYP/3-21G(d) quantum mechanical method. The calculations shows that the Cd S and Cd N central bonds are favoured in the anion complex formation [Cd(Cys)Cl 2] −, being the stabilization energy 55.52 kcal mol −1 lower than isotopomers with Cd S and Cd O central bonds. Features of the infrared and Raman spectra confirm the theoretical structural prediction. Full assignment of the vibrational spectra is proposed based on the DFT procedure, and in order to confirm the C H, N H, C C, C N, Cd N, Cd S and Cd Cl stretching and the HNH and HCH bending, a normal coordinate analysis based on local symmetry force field for SC(H 2)C , CdN(H 2)C and SCd(Cl 2)N fragments was carried out.