A.M. Butlerov Institute of Chemistry, Kazan Federal University , Kremlevskaya 18, 420008 Kazan, Russia.
J Phys Chem B. 2013 Nov 21;117(46):14544-56. doi: 10.1021/jp408059b. Epub 2013 Nov 11.
An effective preparation procedure is offered for β-cyclodextrin (bCD) clathrates with volatile guests of moderate hydrophilicity, which otherwise require a finely tuned optimization of the bCD/water/guest ratio. The proposed procedure includes guest exchange in a water-free bCD matrix. As a result, more stable clathrates with a higher inclusion capacity can be prepared than by direct saturation of dried or hydrated bCD. To find an optimal preparation method, the structure-property relationships were studied for four different ways of bCD clathrate formation with guests of varying molecular structure. The study was much simplified by used procedures excluding direct contact of guest and water liquids with bCD. Besides, in clathrate preparation experiments, the thermodynamic activities of water and guest were varied independently, which makes explicit the role of water in this process. Hydration of bCD reduces its inclusion threshold for hydrophobic guests by their activity (relative vapor pressure), giving favorable hydration effect for their inclusion. Besides, water competes with hydrophilic guests for binding sites in bCD at high water activities. Together with bCD dehydration by excess of hydrophilic guests, these observations give a complete thermodynamic picture, which may be fruitful for elaboration of guest encapsulation techniques by cyclodextrins.
提供了一种用于具有中等亲水性挥发性客体的β-环糊精（bCD）包合物的有效制备方法，否则需要对 bCD/水/客体比例进行精细调整优化。所提出的方法包括在无水电-CD 基质中进行客体交换。结果，可以制备出比直接干燥或水合 bCD 饱和更稳定且包合容量更高的包合物。为了找到最佳的制备方法，研究了具有不同分子结构的客体的四种不同 bCD 包合物形成方法的结构-性质关系。通过使用排除客体和水液体与 bCD 直接接触的程序，大大简化了研究。此外，在包合物制备实验中，独立地改变水和客体的热力学活度，这明确了水在该过程中的作用。bCD 的水合作用通过其活性（相对蒸气压）降低了疏水客体的包合阈值，从而有利于它们的包合。此外，在高水活度下，水与亲水客体竞争 bCD 中的结合位点。与过量亲水客体使 bCD 脱水一起，这些观察结果提供了一个完整的热力学图景，这可能有助于通过环糊精阐述客体包封技术。
