Cavity Closure Dynamics of Peracetylated β-Cyclodextrins in Supercritical Carbon Dioxide
| Autor: | Francesca Ingrosso, Muhannad Altarsha, Manuel F. Ruiz-López |
|---|---|
| Přispěvatelé: | Structure et Réactivité des Systèmes Moléculaires Complexes (SRSMC), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS) |
| Jazyk: | angličtina |
| Rok vydání: | 2012 |
| Předmět: |
Supercritical carbon dioxide
010405 organic chemistry Stereochemistry Chemistry β cyclodextrins 010402 general chemistry 01 natural sciences 0104 chemical sciences Surfaces Coatings and Films [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry Molecular dynamics Chemical engineering 13. Climate action Materials Chemistry Physical and Theoretical Chemistry ComputingMilieux_MISCELLANEOUS |
| Zdroj: | Journal of Physical Chemistry B Journal of Physical Chemistry B, American Chemical Society, 2012, 116 (13), pp.3982-3990. ⟨10.1021/jp3001064⟩ |
| ISSN: | 1520-6106 1520-5207 |
| DOI: | 10.1021/jp3001064⟩ |
| Popis: | Structural properties of peracetylated β-cyclodextrin in supercritical carbon dioxide were investigated by means of molecular dynamics simulations. The study indicated a strong reduction of the cavity accessibility to guest molecules, compared to native β-cyclodextrin in water. Indeed, the cavity is self-closed during the largest part of the simulation, which agrees well with suggestions made on the basis on high-pressure NMR experiments. Self-closure happens because one glucose unit undergoes a main conformational change (from chair to skew) that brings one of the acetyl groups in the wide rim of the cyclodextrin to the cavity interior. This arrangement turns out to be quite favorable, persisting for several nanoseconds. In addition to the wide rim self-closure, a narrow rim self-closure may also occur, though it is less likely and exhibits short duration (1 ns). Therefore, the number of solvent molecules reaching the cavity interior is much smaller than that found in the case of native β-cyclodextrin in water after correction to account for different molar densities. These findings support the weak tendency of the macromolecule to form host-guest complexes in this nonconventional medium, as reported by some experiments. Finally, Lewis acid/base interactions between the acetyl carbonyl groups and the solvent CO(2) molecules were analyzed through ab initio calculations that revealed the existence of a quite favorable four-member ring structure not yet reported. The ensemble of these results can contribute to establish general thermodynamic principles controlling the formation of inclusion complexes in supercritical CO(2), where the hydrophilicity/hydrophobicity balance is not applicable. |
| Databáze: | OpenAIRE |
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