Experimental determination of the relationship between S=O bond length and its stretching frequency of the DMSO molecule

Time-of-flight neutron diffraction, x-ray diffraction, and attenuated total reflection infrared spectroscopic measurements have been carried out for pure deuterated dimethylsulfoxide (DMSO-d6), concentrated 20 mol% lithium bis(trifluorosulfonyl)amide–DMSO-d6, 14 mol% LiCl–DMSO, and 3 mol% NiCl2–DMSO solutions in order to obtain the relationship between the intramolecular S=O bond length (rSO) and its stretching vibrational frequency (νSO) in the liquid state. The S=O bond length of the DMSO molecule has been determined from the least-squares fitting analysis of neutron and x-ray total interference terms observed in the high Q-region. The νSO–rSO plot that involved the present results and experimental data reported for gaseous and crystalline DMSO as well as DMSO complexes with metal ions has indicated that the νSO–rSO relationship is well approximated by a linear function. The value dνSO/drSO = −3,600 ± 400 cm−1Å−1 was obtained from the slope of the fitted function. It has been revealed that the S=O bond length of the DMSO molecule sensitively reflects the intermolecular interactions that it is receiving from its environment.