Vibrational Properties of Cyclodextrin-Water Solutions Investigated by Low-Frequency Raman Scattering: Temperature and Concentration Effects

Depolarized low-frequency Raman spectra from several cyclodextrin-water solutions have been investigated as a function of both temperature and macrocycle concentration. The differences between the vibrational spectra of solutions and pure water have been discussed, focusing the attention on the modifications of the vibrational bands assigned to the H-bond bending and stretching intermolecular modes of water. These features are in turn related to the structural changes occurring in the H-bonded water molecules allowing us to evince a destructuring effect on the tetrahedral hydrogen bonding arrangements induced in solution by increasing temperature and solute concentration.