Crystal Structure of a Complex of alpha-Cyclodextrin with 2-Fluoro-4-nitrophenol · 3H₂O

M. Shibakami, and A. Sekiya
[Carbohydrate Research, Vol.260, pp.169-179, 1994]

The crystal structure of a complex of a-cyclodextrin (alpha-CD) with 2-fluoro-4-nitrophenol·3H₂O has been determined by the X-ray diffraction technique. The complex crystallizes in space group P2₁2₁2₁ with cell dimensions: a=13.431(3), b=15.299(4), c=24.780(5) Å. The structure was solved by direct methods and refined to R=6.7% for 4483 reflections. The crystal structure is isomorphous to the alpha-CD-4-nitrophenol·3H₂O complex. The phenyl group is inside the cavity, so that the O-4 hexagon of the alpha-CD is distorted in a systematic manner: the longest diagonal [O-4(G2)...O-4(G5)] is in the direction of the benzene ring. The phenolic OH group protrudes from the secondary OH side of the cavity and the NO₂ group is situated on the primary OH side. The hydrophobic F atom is statistically disordered over two sites and is located in the hydrophilic space, just beyond the rim of the secondary OH side of the cavity.