Study On The Crystal Structures Of β-Cyclodextrin Inclusion Complexes

Cyclodextrins (CDs) has hydrophile exterior and hydrophobic central cavity, that results in its ability to form inclusion complexes with a variety of hydrophobic molecules with suitable shape and size in aqueous solution. The physicochemical properties of the included guest molecules are different from the pre-included compounds in terms of solubility, spectral and chromatographic properties, et al. Such beneficial property has made it among the most widely used host molecule of supramolecular chemistry and been applied in many fields, including synthesis chemistry, analytical chemistry, pharmaceuticals, and so on. Understanding of the supramolecular structure of its inclusion complexes is the basis of its research and application. X-ray crystallography is the most precise technique to explore the detail intermolecular interaction. Therefore, the study of cyclodextrins and their inclusion complexes can help us understand the weak molecular interactions deeply and reveal the nature of inclusion complexes.The crystals ofβ-CD-o-aminobenzoic acid,β-CD-p-aminobenzoic acid,β-CD-1,10-phenanthroline andβ-CD-adipic acid were successfully obtained and were analyzed by X-ray diffraction method at the same time. With the four crystal datas collected in this paper and crystal datas already reported, detailed analysis and comparison of the four crystal datas were carried out. Through studies we can find out that there are lots of hydrogen bonds formed betweenβ-CDs,β-CD and guest molecules andβ-CD and water molecules in the four crystal structures and these hydrogen bonds form a dense hydrogen-bond network. These hydrogen bonds are the main force to keep the ring conformation ofβ-CD molecules and the guest molecules in position. At the same tinme, we can get the following conclusion that the structure of the guest molecules along with the co-crystallized water molecules play an important role in the formation of the complex and the crystal packing.