Preparation of solvent-free clathrand structures by the exclusion of an unwelcome guest

Crystallisation of clathrate host molecules, using an appropriate dual-nature solvent, can encourage both the growth of crystals and its exclusion as a guest. To achieve this end, the solvent should contain a part-structure that interacts favourably with the host molecules, thereby encouraging host association and crystal nucleation. It should also contain a part-structure that interacts unfavourably with the hosts, so that the solvent ultimately is excluded as the material crystallises. We report that trifluoromethylbenzene is an excellent solvent for obtaining crystalline solvent-free clathrands belonging to the diquinoline inclusion family. The X-ray crystal structures of one of these and its corresponding toluene inclusion compound are described and compared.