Interplay between Aryl•••Perfluoroaryl and Hydrogen Bonding Interactions in Cocrystals of Pentafluorophenol with Molecules of Trigonal Symmetry

Cocrystals of seven star-shaped triaryl compounds with pentafluorophenol (pfp) were prepared and structurally characterized by the single-crystal X-ray diffraction method. Cocrystallization of pfp with planar (or almost planar) compounds gave six 3:1 molecular complexes with well-defined layered structures. The layers are composed of alternating pfp(3) trimers, linked by hydrogen bonding, and triaryl molecules held together in planes by the weak C-H center dot center dot center dot F interactions. Stacking interactions of the triaryl-substituted molecules with the perfluorinated rings of pfp are responsible for the overall crystal packing, but most likely also stabilize the trimers in the solid state, as the assembly of the pfp into trimers provide an optimal geometry for the pi center dot center dot center dot pi interaction. The layers are flat for the cases of components with almost planar geometry and corrugated for those with more twisted geometry. In the case of nonplanar triphenyl isocyanurate, the pfp cocrystal does not contain pfp(3) trimers, the stoichiometry changes from 3:1 to 3:2 (3 refers to pfp), and the packing is mainly controlled by intermolecular O-H center dot center dot center dot O = C hydrogen bonding.