Hyper-raman spectroscopy of hydrogen bonding in DMSO-water mixtures

Dimethyl sulfoxide (DMSO) is a biologically important solvent in part due to its dual miscibility with hydrophilic and hydrophobic molecules. Binary solutions of DMSO-water display non-ideal thermodynamics properties such as high viscosity and low freezing point due to hydrogen bonding. The unusual properties of DMSO-water solutions have been exploited to disrupt the formation of secondary structures of proteins during polymerase chain reaction assays and to act as a cryoprotectant for tissues. The exact coordination of the DMSO and water molecules remains unknown. Hyper- Raman scattering was employed for the first time to investigate binary systems of DMSO with water (H2O). As a part of this study, hyper-Raman and Raman spectra of pure solutions were first acquired and compared against existing Raman and IR spectroscopic data. Then the corresponding measurements were taken with deuterated DMSO-d6 and heavy water (D2O) to validate the analysis and to isolate overlapping spectral features. The permissive selection rules of hyper- Raman scattering provide new insight into disruptions of the self-hydrogen bonded networks of DMSO and water and the establishment of hydrogen bonded networks.