Structural properties of glucose-dimethylsulfoxide solutions probed by Raman spectroscopy

Raman spectroscopy was employed to achieve a molecular level description of solvation properties in glucose-dimethylsulfoxide (DMSO) solutions. The analysis of Raman spectra confirms the importance of the dipole-dipole interaction in determining structural properties of pure DMSO; the overall intermolecular structure is maintained in the whole 20-75 degrees C temperature range investigated. The blueshift of the CH stretching modes observed at higher temperatures points out that CH(3)...O contacts contribute to the cohesive energy of the DMSO liquid system. The addition of glucose perturbs the intermolecular ordering of DMSO owing to the formation of stable solute-solvent hydrogen bonds. The average number of OH...OS contacts (3.2+/-0.3) and their corresponding energy (approximately 20 kJ/mol) were estimated. Besides, the concentration dependence of the CH stretching bands and the behavior of the noncoincidence effect on the SO band, suggest that the dipole-dipole and CH(3)...O interactions among DMSO molecules are disfavored within the glucose solvation layer. These findings contribute to improve our understanding about the microscopic origin of solvent properties of DMSO toward more complex biomolecular systems.