Density functional study on the molecular structure, infrared and Raman spectra, and vibrational assignment for 4-thiocarbamoylpyridine

4-Thiocarbamoylpyridine is the parent compound of ethionamide. It is an important and efficacious drug in the treatment of multidrug-resistant tuberculosis. The molecular structure, natural atomic charges, vibrational frequencies, infrared and Raman intensities and theoretical vibrational spectra were calculated for 4-thiocarbamoylpyridine monomer and a pair of molecules linked by the intermolecular N-H-... N-py hydrogen bond. The theoretical studies were performed using the B3LYP density functional method with the 6-311G(d,p) basis set. The FT-infrared and FT-Raman spectra of the title compound in the solid state have been measured. The theoretically predicted Raman spectra show good overall agreement with experiment. The detailed interpretation of the vibrational spectra has been made on the basis of the calculated potential energy distribution (PED). The presented vibrational assignment can be used in the further spectroscopic study of thioamides. (c) 2006 Elsevier B.V. All rights reserved.