Quantitative insights into noncovalent interactions involving halogen and tetrel bonds in 2,4,6-trimethylpyrylium...

The crystal and molecular structure of an organic salt, in which a 2,4,6-trimethylpyrylium cation forms a salt with a tetrafluoroborate anion, namely, 2,4,6-trimethylpyrylium tetrafluoroborate, C₈H₁₁O⁺·BF₄^-, has been experimentally realized. The compound crystallizes in the orthorhombic centrosymmetric space group Pnma. The crystal packing is stabilized via a subtle interplay of [F₃-B-F]^-...O⁺-C fluorine/oxygen-centred halogen/chalcogen bonds and C^δ+...F^δ- tetrel-bonded contacts. Although the O centre has a formal charge of +1, the estimation of the partial negative charges on O is in accordance with electronegativity considerations. Hirshfeld surface analysis, which also includes an analysis of the three-dimensional deformation density, along with molecular electrostatic potential (MESP) calculations, provides quantitative insights into the nature of the intermolecular interactions. The topological analysis of the electron-density distribution has been performed using AIMAll and TOPOND, and unequivocally establishes the bonding character associated with the different noncovalent interactions. In addition, NBO analysis and polarizability calculations using PolaBer render deeper physical insights into the electronic characteristics of these noncovalent interactions.