Conflicting Behavior of a Versatile Host Compound: X-ray Crystal Structures Arising from Solvent-free and Solvent-Containing Crystal Formation

The X-ray crystallographic structures of four new inclusion compounds of the versatile clathrate host 2,2′-bis(9-hydroxy-9-fluorenyl)biphenyl ( 1 ) as well as the crystal structure of the unsolvated host are reported and comparatively discussed with regard to the molecular conformation and the modes of interactions the molecules make use of in the crystal packing. While the inclusion crystals demonstrate full saturation of the hydrogen bond capacity of the host molecule, 1 is only involved in weak intermolecular π-contacts in the solvent-free structure. We draw the conclusion that the well-tried strategy of coordinato-clathration, underlying the present inclusion compounds, should not be regarded as a strict rule with reference to the formation of inclusion crystals but a helpful framework in the search of new efficient clathrate hosts.