Pseudopolymorphic clathrate structures formed by an alicyclic dialcohol inclusion host

Dialcohol host 2,7-dimethyltricyclo[4.3.1.0(3,8)]undecane-syn-2,syn-7-diol 1 can form either ellipsoidal clathrate or helical tubulate inclusion compo unds where only dispersion forces operate between the hosts and guests. The former (tetragonal space group I4(l)/acd), built from two interpenetrating sublattices containing both diol enantiomers, encloses the guests in rugby ball-shaped cavities. The latter (trigonal space group P3(1)21 or P3(2)21) , containing only one diol enantiomer, traps the guests within parallel tub es. Which inclusion type is produced is determined by the guest size and sh ape and, hence, control is possible over these structures. At room temperat ure, cyclohexane gives the tetragonal structure, but fluorocyclohexane yiel ds the trigonal structure. Chloroform produces both pseudopolymorphs: the t etragonal form at higher and the trigonal form at lower temperatures. Powde r and single-crystal structural X-ray data are reported for these clathrate compounds.