Acta Crystallographica Section B

Structural Science, Crystal Engineering and Materials

Volume 70, Part 1 (February 2014)

crystal engineering

Acta Cryst. (2014). B70, 126-131    [ doi:10.1107/S2052520613031727 ]

Solvent-guest control of two extremely similar tetrahydrofuran inclusion structures

J. Gao, M. M. Bhadbhade and R. Bishop

Abstract: Racemic 2,4,6,8-tetracarbomethoxybicyclo[3.3.0]octa-2,6-diene-3,7-diol, C16H18O10 (1), was known previously to yield two solvent-free polymorphs and also a clathrate inclusion crystal form. Crystallization of (1) yields two inclusion compounds containing tetrahydrofuran (THF): (1)4·THF is obtained from a mixture of THF and methanol, whereas (1)2·THF is obtained from pure THF. The X-ray crystal structures reveal that the two compounds are extremely similar and that their host arrangements are essentially identical. They differ, however, in the proportion, orientation and host-guest interaction of the included THF molecules. The disordered guest molecules in (1)4·THF are oriented along the guest channel direction, whereas in (1)2·THF they lie across the channel. This unusual solvent-guest control of inclusion structures has implications relating to the formation of polymorphic structures and other competing crystal forms.

CCDC references: 958231 and 958232

Keywords: solvent-guest; inclusion compounds; clathrate crystal; polymorphism.

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[ doi:10.1107/S2052520613031727/bi5023sup4.pdf ]
Details of the refinement of the disordered THF molecules, and of the SQUEEZE procedure


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