The structure of the Cyclodextrin Complex. XIV. Crystal Structure of Hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin–Benzaldehyde (1 : 1) Complex

The crystal structure of the hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin (abbreviated to methyl-α-CDx)–benzaldehyde (1:1) complex, C54H96O30·C7H6O, was investigated by the X-ray method. The crystal is monoclinic with the space group P21 and Z=2; the cell dimensions are a=11.604(1), b=23.832(3), c=13.539(1) Å, and β=106.11(1)°. The structure was determined by inspection of a Patterson map and a trial-and-error method combined with the rigid-body least-squares technique, and refined by the block-diagonal least-squares method to the final R-value of 0.10 for 3597 reflections (sinθ⁄λ≤0.49). The methyl-α-CDx molecule is in the shape of a distorted and truncated hexagonal cone. The guest benzaldehyde molecule is fully included within the host cavity. The carbonyl group is located at the center of the cavity, while the phenyl group is located at the baseside of the host cone. Methyl-α-CDx molecules, of which pseudo hexagonal axis is inclined by an angle of 17.0° against the crystallographic a axis, are stacked along the a axis to form a head-to-tail channel-type structure.