Hydrogen-bonded systems of water with dimethyl and diethyl sulfoxides. Theoretical study of structures, stability and vibrational spectra

The structural and vibrational characteristics (vibrational frequencies and infrared intensities) of the hydrogenbonded systems dimethylsulfoxide (DMSO)–water (1:1, 1:2) and diethylsulfoxide (DESO)–water (1:1, 1:2) have been investigated employing ab initio and DFT calculations at different basis sets. The calculations show that the optimised structures of the studied systems 1:2 are cyclic while the optimised structures of the hydrogen-bonded systems 1:1 are linear. The corrected values of the dissociation energy for the hydrogen-bonded systems have been calculated by ab initio and DFT calculations at different basis sets in order to estimate their stability. It was established that the hydrogen-bonded systems DESO–water (1:1, 1:2) are more stable than the systems DMSO–water (1:1, 1:2). The influence of the hydrogen bonding on the properties of the monomers (H2O, DMSO and DESO) has been investigated. The hydrogen bonding between H2O and DMSO, and DESO leads to changes in the vibrational characteristics of the monomers. The predicted vibrational characteristics for the studied hydrogen-bonded systems are in very good agreement with the experimentally observed.