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

Abstract

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.

An investigation into the Brønsted acidity of the perfluorinated alkoxy silanes {(F3C)3CO}3SiH and {(F6C5)3CO}2Si(Cl)H

“…This extent of F⋯F contacts significantly below the sum of their van der Waals radii is remarkable and to the best of our knowledge unprecedented. In comparison, (C 6 F 5 ) 3 P 19 and 2 (see below) contain fewer and longer F⋯F contacts. The fingerprint plot in Fig.…”

“…NMR spectra ( 1 H, 13 C, 19 F, 29 Si) were recorded at room temperature on a Bruker Avance 600 spectrometer. 1 H, 13 C, 19 F and 29 Si NMR spectra are reported on the δ scale ( ppm) and are referenced against SiMe 4 and CFCl 3 , respectively.…”

“…NMR spectra ( 1 H, 13 C, 19 F, 29 Si) were recorded at room temperature on a Bruker Avance 600 spectrometer. 1 H, 13 C, 19 F and 29 Si NMR spectra are reported on the δ scale ( ppm) and are referenced against SiMe 4 and CFCl 3 , respectively. 1 H and 13 C chemical shifts are reported relative to the residual peak of solvent (7.16 ppm for C 6 D 6 , 7.26 for CDCl 3 ) in the 1 H NMR spectra, and to the peak of the deuterated solvent (128.06 ppm for C 6 D 6 , 77.16 ppm for CDCl 3 ) in the 13 C NMR spectra.…”

“…-NMR (600.2 MHz, C 6 D 6 ): δ = 4.91 (SiH, s, 1 J ( 29 Si-1 H) = 379 Hz) ppm 13. C{ 1 H}-NMR (151.0 MHz, C 6 D 6 ): δ = 119.6 (CF 3 , q, 1 J ( 19 F-13 C) = 290 Hz), 79.0 (m, C(CF 3 ) 3 ) ppm 19. F-NMR (565.0 MHz, C 6 D 6 ): −75.3 ppm.…”

Three for the Price of One: Concomitant I⋯N, I⋯O, and I⋯π Halogen Bonds in the Same Crystal Structure

“…Last but not least, I3 from the third symmetry independent TFDIB moiety, located around the inversion center with Wyckoff position , acts as XB donor towards the pyrazole π-system with a distance of 3.2157(3) Å. As expected by the theoretical electrostatic potential for pyrazoles [ 49 ], the closest contact atom for I3 is the iminic N1 with a distance of 3.241(4) Å. Lewis basic π-systems as XB acceptors are known in literature, e.g., for cyclopentadienyl ligands [ 50 ], imidazoles [ 51 ], or carbazoles [ 52 ], and have been evaluated theoretically [ 53 , 54 , 55 ]; however, to the best of our knowledge, no pyrazole-π⋯I interactions with perfluoronated iodobenzenes have been reported to this date. This is also due to the competition with the more prominent I⋯N XB, as present in interaction A .…”