Theoretical and experimental study of dimethyl sulfoxide and N-substituted DMSO

Infrared spectrum of dimethylsulfoxide (DMSO) has been studied using quantum chemical calculations and FTIR spectroscopy. Theoretical infrared and electronic absorption spectra for the ions of DMSO, DMSO in water solvent and nitrogen substituted DMSO (N-DMSO) have also been obtained using second order Moller-Plesset and 6-311++g(d,p) basis set. The IEFPCM model has been used to study the solvation effect for DMSO. The geometrical parameters and dipole moments for the neutral DMSO have been compared with the available experimental determinations. Calculated vibrational frequencies have been compared with the experimental frequencies for the DMSO obtained using FTIR spectrometer. Rotational and centrifugal distortional constants for these molecules have been reported. The electronic absorption spectra of DMSO, its ions, and N-DMSO have been obtained using time dependent density functional theory (TDDFT) approach. Almost all the vibrational modes in the vibrational spectrum of DMSO anion are intense whereas fewer intense modes have been observed in the vibrational spectra of DMSO, its cation, DMSO in water solvent and N-DMSO. The most intense mode is different for DMSO, its ions and N-DMSO. The S=O stretching mode is the most intense mode for DMSO as well as DMSO in water solvent and it is red shifted by 62 cm(-1) in latter than the former.