Theoretical insights into two types of Se···N Chalcogen Bonds between phenylselenium halides (PhSeX, X = F, Cl, Br, I) and pyridine: perpendicular versus linear binding modes via tunable σ-holes.

CONTEXT: In this work, the Se···N chalcogen-bonding interactions in pyridine-phenylselenium halides (C5H5N-PhSeX, X = F, Cl, Br, and I) complexes were systematically investigated at the ωB97XD/def2-TZVPD theoretical level. Two typical structural configurations, namely perpendicular and linear orientations, were identified for all studied complexes. The calculated binding energies suggest that the linear-oriented systems exhibit remarkably stronger intermolecular interactions (- 6 to - 12 kcal/mol) than their perpendicular counterparts (- 2 to - 4 kcal/mol). For the perpendicular-oriented structures dominated by chalcogen-bonding with secondary hydrogen-bonding interactions, the intermolecular interaction strength increases in the order F > I > Br > Cl. In contrast, the interaction strength of linear-oriented chalcogen-bonding complexes follows the sequence of F > Cl > Br > I. Energy component analysis indicates that both electrostatic and dispersion contributions dominate the attractive forces in perpendicular chalcogen-bonded systems. By comparison, the stabilization of linear complexes is predominantly governed by electrostatic interactions.

METHODS: Geometry optimizations of all complexes and the corresponding monomers were carried out at the ωB97XD/def2-TZVPD level. The nature of the intermolecular interactions was then characterized by NBO population analysis, QTAIM (AIM), and IRI analyses.In addition,the interaction energies of the two types of chalcogen-bonded complexes were further decomposed by means of symmetry-adapted perturbation theory (SAPT).