Dielectric behaviour of α-cyclodextrin, heptakis (2,3,6-tri-Omethyl)-β-cyclodextrin, randomly methylated β-cyclodextrin and low frequency Raman spectra of α- and β-cyclodextrins

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

“…[20][21][22][23][24] On the contrary, less literature has regarded till now the properties of water molecules surrounding CD in aqueous solution [25][26][27] due to the difficulties to reveal separate solute and solvent dynamics, especially in case of diluted solutions. In this context, recently, depolarized light scattering has been used by some of us as a powerful tool to distinguish spectral features coming from solute rotational dynamics, hydrogen bonding solvent dynamics, and vibrational intermolecular modes of saccharides and proteins aqueous solutions (Rossi et al, submitted for publication).…”

Solute–Solvent Interactions in Aqueous Solutions of Sulfobutyl Ether-β-cyclodextrin As Probed by UV-Raman and FTIR-ATR Analysis

“…The understanding of the interactions that give origin to the peculiar properties of CDs in aqueous solutions is still an open interesting question. Many papers have been published dealing with the study of hydration/dehydration properties of CDs in crystalline and amorphous phases, − but there are only few reports addressing the complex behavior of water molecules surrounding CDs in aqueous solution. , Low wavenumber depolarized Raman spectra from aqueous solutions of α-CD, β-CD, and methyl-β-CD (Me-β-CD) have been recently analyzed in order to investigate the effect of temperature and concentration on the H-bond bending and stretching intermolecular modes of water. A characteristic “structure-breaker” effect on the tetrahedral H-bond arrangements of water solvent has been observed because of increasing of both temperature and solute CD concentration.…”

Dipole relaxation and proton transport in polycrystalline γ-cyclodextrin hydrate: A dielectric spectroscopy study

“…This is because the respective dielectric data apart from vindicating the origin and reversibility of the already detected dynamic phenomena during the cooling process also address the influence of the progressive dehydration on the underlying charge transport mechanisms; this particular issue has been neglected so far in the dielectric studies of α-and β-CD hydrates [22][23][24]. From 109.0 to 254.3 K, the real part ε′ increases in an extended sigmoid fashion with inflection point ε′ = 6.43 at T = 194.5 K (Fig.…”

“…The dielectric measurements of β-CD hydrate by other researchers [22] as well as of α-CD and β-CD hydrates by our group [23,24] have detected all the phase transitions that are associated with changes in the dynamic properties of the water molecules and the CD hydroxyl groups. More thoroughly, the isothermal (fixed temperature) and isochronal (fixed frequency) experimental data of α-CD and β-CD hydrates have revealed the following issues: (i) at temperatures lower than~230.0 K, the former system displays no order-disorder transition of the existing hydrogen bonds and consequently no important variation of its dielectric permittivity (ε′) and loss (ε″); (ii) on the contrary, the latter system exhibits considerable order-disorder phenomena below~230.0 K being consistent with concerted proton reorientations that make a great contribution to the relevant dielectric properties; (iii) both the dielectric permittivity (ε′) and loss (ε″) of these two systems increase rapidly above~230.0 K due to the rise of the dc-conductivity which involves extensive proton transfer.…”