Vibrational studies of polar aprotic molecule in aromatic chemical and isotropic solvents: experimental and quantum chemical investigations

Raman spectroscopic technique has been used to study the intermolecular interactions and dynamics of SO, C―H and CSC stretching modes of dimethyl sulfoxide (DMSO) in binary mixtures using methyl benzene (MBN) and deuterated methyl benzene (MBNd) aromatic solvents. The Raman band of SO stretching mode has been deconvoluted into four distinct bands for neat DMSO as well as in binary mixtures. Deconvoluted bands in neat DMSO were assigned as monomer, cyclic out‐of‐phase, cyclic in‐phase and chain dimers having peak wavenumbers 1069.10, 1056.60, 1041.50 and 1027.30 cm −1 respectively. Peak wavenumber of SO stretching mode shows red shift, while peak wavenumbers of C―H and CSC stretching modes show blue shift with the increase in solvent concentration. The vibrational relaxation phenomena for all the stretching modes have been studied as a function of solvent concentration. Quantum‐chemical calculations have been carried out to gain more insight into the self‐association of DMSO and in interacting environment with the solvents using ab initio and density functional theory method. The ab initio basis set is HF/6‐31 + G (d, p) for the interacting system. The hydrogen bond complexes of DMSO with MBN and MBNd using IEF‐PCM model have been calculated using B3LYP functional and 6‐31 + G(d,p) basis sets. Theoretical calculations have been compared with the experimental findings and we obtained good coherence of the results. Copyright © 2015 John Wiley & Sons, Ltd.

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