INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
Confinement of polar solvents within beta-cyclodextrins
JAVIER RODRIGUEZ, DANIEL HERNÁN RICO, LUIS DOMENIANNI Y D. LARIA
JOURNAL OF PHYSICAL CHEMISTRY B
AMERICAL CHEMICAL SOCIETY
Año: 2008 vol. 112 p. 7522 - 7522
Using Molecular Dynamics techniques, we examined equilibrium and dynamicalcharacteristics pertaining to the solvation of a single beta-cyclodextrin (CD)in water (W) and in dimethylsulfoxide (DMSO). Compared to its global minimum structure,the overall shape of the solute in solution is reasonably well preserved.While in aqueous solutions, the average number of solvent molecules retained withinthe central cavity of the oligosaccharide is close to 5, for DMSO, thatnumber reduces to approximately 1. No evidence of significant orientational correlations ofthe trapped molecules were found in either solvent.The main contributions to the hydrogen-bond (HB) connectivity between the solute andthe bulk phases are due to the more distal HO6-O6 hydroxyl groups, acting asHB donors and acceptors.The average residence time for retained DMSO was found to bein the nanosecond range and it is, at least, one order of magnitude longer thatthe one observed for W.We also analyzed the characteristics of the solvation of the beta-CD in anequimolar W-DMSO mixture.In this environment, we found a preferential localization of a single DMSO moleculein the interior of the CD, and a much minor retention of W.In the mixture, the characteristic time of residence of the trapped DMSO molecule increasesby a factor of approximately 2. The observed difference was rationalized in terms of thefluctuations of the local concentrations of the two species in the vicinity of theCD top and bottom rims.