1Modeling and Optimization Research Center in Science and Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran, P.O. Box 11365-4435
2Department of Chemistry, Faculty of Sciences, Arak University, Arak 38156-8-8349, Iran
Density functional (DFT) calculations at M05-2x/aug-cc-pVDZ level were used to analyze the interactions between dimethyl sulfoxide (DMSO) dimers. The structures obtained have been analyzed with the Atoms in Molecules (AIMs) and Natural Bond Orbital (NBO) methodologies. Four minima were located on the potential energy surface of the dimers. Three types of interactions are observed, CH•••O, CH•••S hydrogen bonds and orthogonal interaction between the lone pair of the oxygen with the electron-deficient region of the sulfur atom. Stabilization energies of dimers including BSSE and ZPE are in the range 27–40 kJ mol-1. The most stable conformers of dimers at DFT level is cyclic structure with antiparallel orientation of S=O groups that pairing with three C–H…O and a S…O interactions.