The Structure of the Cyclodextrin Complex. XX. Crystal Structure of Uncomplexed Hydrated γ-Cyclodextrin

Crystal structure of uncomplexed γ-cyclodextrin, C48H80O40·14.1H2O, was determined by the X-ray method. The crystal is monoclinic and the space group is P21 with cell dimensions; a=16.847(2), b=11.098(2), c=20.271(2) Å, and β=104.97(1)°. The structure was solved by the inspection of a Patterson map and the R-map method combined with the rigid-body least-squares technique and refined by the block-diagonal least-squares method to the R-value of 0.061 for 5099 reflections (sinθ⁄λ≥0.57). γ-Cyclodextrin is in a round shape and somewhat distorted from the regular octagonal symmetry. Intramolecular hydrogen bonds are formed between adjacent glucose residues and maintain the round structure of γ-cyclodextrin. γ-Cyclodextrin molecules are arranged in a cage-type packing, and 7.1 water molecules, occupying 14 sites, are located within the host cavity.