Crystal structures and Hirshfeld surface analysis of a series of 4-O-arylperfluoropyridines

In each crystal of the title compounds the packing is driven by C—H⋯F intertactions, along with a variety of C—F⋯π, C—H⋯π, C—Br⋯N, C—H⋯N, and C—Br⋯π contacts. Hirshfeld surface analysis was conducted to aid in the visualization of these various influences on the packing.


Chemical context
Pentafluoropyridine, or perfluoropyridine (C 5 F 5 N) is one of the most important perfluoroheteroaromatic compounds. It is commercially available and its chemistry is well understood. As a result of the presence of five fluorine atoms, in addition to the nitrogen atom of the pyridine ring, these systems are highly electrophilic and undergo substitution reactions readily in a predictable pattern (Baker & Muir, 2010;Chambers et al., 1988). This chemistry has already been used in the design of several drugs (Bhambra et al., 2016) and in peptide modification (Gimenez et al., 2017). In an effort to further understand the intermolecular interactions in the solid state of these fluorinated compounds, five new crystal structures of pentafluoropyridine derivatives are herein reported as well as their syntheses.
Owing to the presence of nitrogen, oxygen and bromine atoms in the various structures, several other contact types are confirmed by the Hirshfeld surface maps. In II, the C9-Br1Á Á ÁN1 (symmetry code: 1 2 À x, 1 2 À y, À 1 2 + z) halogen bond is clearly visible. The analogous halogen bond is not observed in IV. Only in III does a C-HÁ Á ÁN interaction significantly contribute to the packing, with the C15-H15Á Á ÁN1 (symmetry code: Àx, y + 1 2 , Àz + 1 2 ] visible in the d norm surface plot.

Database survey
A search of the November 2019 release of the Cambridge Structure Database (Groom et al., 2016), with updates through May 2019, was performed using the program ConQuest (Bruno et al., 2002). The search was limited to organic structures with R 0.  Table 5 Contact geometry (Å , ) for V.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

2,3,5,6-Tetrafluoro-4-[(naphthalen-2-yl)oxy]pyridine (III)
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq    (7) 0.0234 (7) 0.0264 (7) 0.0018 (6) −0.0010 (6) 0.0003 (6) C15 0.0237 (7) 0.0259 (7) 0.0231 (7 (12) Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Br1 1.11387 (6) 0.12723 (7)  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.54 e Å −3 Δρ min = −0.24 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.