Strong halogen bonds between halo-perfluorobenzenes (C6F5X) and pyridine molecules: A combined theoretical and crystallographic data study

Abstract X⋯N interactions between halo-perfluorobenzenes and pyridine derivatives play a crucial role in halogen-bond-based crystal engineering and supramolecular architecture. In this work, a series of complexes of C 6 F 5 X (X = Br and I) with several pyridine molecules, which were extracted from crystal structures, have been calculated at the M05-2x level of theory. It was found that X⋯N interactions in the studied complexes are comparable in strength to medium strong hydrogen bonds. The introduction of electron-withdrawing substituents in pyridine attenuates X⋯N interactions, while the presence of electron-donating substituents enhances these halogen bonds. The quantum theory of atoms in molecules (QTAIM) and electrostatic potential (ESP) analyses were also employed to characterize these interactions. The results showed that electrostatic terms contribute significantly to the formation of X⋯N halogen bonds. Finally, some X-ray crystal structures retrieved from the Cambridge Structural Database (CSD) were selected to provide experimental evidence of present halogen bonds.