“Useless Channels” in a Molecular Crystal Formed via F···F and F···π Halogen Bonds

Tris­(pentafluorophenyl)­phosphine molecules in a new phase pack to form hourglass-shaped one-dimensional channels, whose inner surface is occupied by only fluorine. The channels show an effective diameter of 3.80 Å at the belly and only 2.68 Å at the neck, neither being possible for the encapsulation of any solvent molecules or for the permeability of air (N₂ and O₂), thus demonstrating an absolute vacuum. Such “vacuum” channels in the crystals have never been reported and would be of great significance in photo- and electrophysics. In addition, the structural analysis indicated that F···F contacts and F···π interactions are mainly responsible for the specific packing in the new phase, and a σ-hole-type attraction is found in both F···F and F···π forces according to the DFT computations.