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Importance of Packing Coefficients of Host Cavities in the Isomerization of Open Host Frameworks: Guest‐Size‐Dependent Isomerization in Cholic Acid Inclusion Crystals with Monosubstituted Benzenes
Author(s) -
Nakano Kazunori,
Sada Kazuki,
Kurozumi Yukio,
Miyata Mikiji
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010105)7:1<209::aid-chem209>3.0.co;2-y
Subject(s) - isomerization , chemistry , steric effects , van der waals force , stacking , crystallography , cholic acid , crystal engineering , crystal structure , supramolecular chemistry , stereochemistry , molecule , organic chemistry , catalysis , bile acid , biochemistry
The crystal structures of inclusion compounds of cholic acid ( CA ) with 28 monosubstituted benzenes have been systematically investigated. All of the crystals belong to the monoclinic space group P 2 1 and have bilayer structures with one‐dimensional molecular channels that can include guest compounds. They are classified into four types of host frameworks that depend on the conformations and stacking modes of the host compound. The host frameworks and the host–guest ratios depend primarily on the molecular volumes of the guest compounds. The packing coefficient of the host cavity ( PC cavity ), which is the volume ratio of the guest compound to the host cavity, is used to clarify the relationship between the guest volume and isomerization of the host frameworks. The value of PC cavity for stable inclusion compounds lies in the range of 55–70 %. Compounds out of this range induce isomerization of the host frameworks. The packing coefficients of other host–guest compounds, in which the guest components are included in the host cavities through steric dimensions and van der Waals forces, are also in this range. These results indicate that PC cavity is a useful parameter correlation for guest recognition and isomerization of the host frameworks.