Raman spectral studies of ion–molecular interactions of lithium bromide and lithium iodide with dimethyl sulphoxide

Raman spectra in the C−H and S=O stretching and S=O bending regions are reported for solutions of lithium halides and tetrabutylammonium bromide (TBAB) in dimethyl sulphoxide (DMSO) and DMSO-d6. The CD stretching band of DMSO-d6 shows two components in solutions of TBAB with DMSO-d6, whereas the C−H stretching band of DMSO for solutions of LiX (X=Br and I) in DMSO show some broadening and asymmetry in the low-frequency region. The S=O stretching bands show changes in band shapes and band contours in solutions of electrolytes in DMSO. Fourier deconvolution of C−H and S=O stretching bands were carried out to gain more information regarding number of components present under the broad structured bands. All the solutions show a significant decrease in the intensity of the S=O bending bands when compared with the neighbouring C−S bending band. The results are discussed in terms of anion- and cation–molecular interactions with DMSO