Assessing the Significance of Hexafluorobenzene as a Unique Guest Agent through Stacking Interactions in Substituted Ethynylphenyl Benzamides

A series of differently substituted host molecules have been employed to systematically investigate the nature and strength of the stacking interactions with hexafluorobenzene in the solid state. The hexafluorobenzene guest binds to the crystal lattice of the parent compound, the <i>N</i>-ethynylphenyl benzamide host and its nine other halogenated (-F/-CF3/-Cl/-Br at ortho/meta/para positions individually) analogues via stacking of aromatic rings. The geometrical and energetic features of intermolecular interactions in host–guest molecules have been investigated, and the results elucidate the dominancy of dispersion in the stabilization of the aryl-hexafluorobenzene stacking, while the electrostatic component also plays an important role. The plots of the molecular electrostatic potential provide a fundamental basis of the electrostatic complementarity that exists in between the host and the guest. The topological characterization reveals unambiguous evidence for the direct participation of the substituents in closed-shell bonding interactions with the aromatic rings at the local geometry, which remarkably controls the nature and energetics of such motifs. Additionally, the observed upfield 19F NMR chemical shifts for perfluorinated guest upon complexation with the host compounds provide evidence for the existence of the host–guest stacking interaction also in the solution state