Acta Crystallographica Section B

Structural Science

Volume 54, Part 4 (August 1998)

research papers

Acta Cryst. (1998). B54, 450-455 [ doi:10.1107/S0108768197014547 ]

Channel-Type Crystal Packing in the Very Rare Space Group P42₁2 with Z' = 3/4: Crystal Structure of the Complex -Cyclodextrin-Methanol-n-Hydrate

T. Steiner and W. Saenger

Abstract: The crystal structure of the title compound is discussed with focus on its unusual crystal packing mode. The [gamma] -cyclodextrin molecules stack in columns which have internal channels and additional large channels are formed between the columns. Both types of channels are so wide that more or less free diffusion of water and small guest molecules is possible, preventing characterization of the solvent and guest arrangements. Although the space group P42₁2 (no. 90) and the unit-cell content Z' = $3\over 4$ are extremely rare in general, this is the favorite crystal packing arrangement of [gamma] -cyclodextrin inclusion complexes. This space group has not been observed as yet for other purely organic compounds.