Rare 'head-to-tail' arrangement of guest molecules in the inclusion complexes of (+)- and (-)-menthol with β-cyclodextrin

The inclusion of (+)- and (-)-menthols in beta-cyclodextrin has been studied by X- ray crystallography. The obtained [2:2] complexes show typical for beta-cyclodextrin form of head- to- head dimer. In both (+)- and (-)- cases, the menthol molecule in one of cyclodextrins forming dimer exhibits disorder and occupies two major sites. Also both of the diastereoisomeric complexes show unusual ` head to tail' arrangement of guest molecules - two guest molecules are differently oriented inside b- cyclodextrin cavity. Stability constants for both complexes in solution were measured. (c) 2012 Elsevier B. V. All rights reserved.