Sigma-Hole and Lone-Pair-Hole Site-Based Interactions of Seesaw Tetravalent Chalcogen-Bearing Molecules with Lewis Bases

[Image: see text] For the first time, sigma (σ)- and lone-pair (lp)-hole site-based interactions of SF(4) and SeF(4) molecules in seesaw geometry with NH(3) and FH Lewis bases were herein comparatively investigated. The obtained findings from the electrostatic potential analysis outlined the emergence of sundry holes on the molecular entity of the SF(4) and SeF(4) molecules, dubbed the σ- and lp-holes. The energetic viewpoint announced splendid negative binding energy values for σ-hole site-based interactions succeeded by lp-hole analogues, which were found to be −9.21 and −0.50 kcal/mol, respectively, for SeF(4)···NH(3) complex as a case study. Conspicuously, a proper concurrence between the strength of chalcogen σ-hole site-based interactions and the chalcogen’s atomic size was obtained, whereas a reverse pattern was proclaimed for the lp–hole counterparts. Further, a higher preference for the YF(4)···NH(3) complexes with elevated negative binding energy was promulgated over the YF(4)···FH ones, indicating the eminent role of Lewis basicity. The indications of the quantum theory of atoms in molecules generally asserted the closed-shell nature of all the considered interactions. The observation of symmetry-adapted perturbation theory revealed the substantial contributing role of the electrostatic forces beyond the occurrence of σ-hole site-based interactions. In comparison, the dispersion forces were specified to govern the lp–hole counterparts. Such emerging findings would be a gate for the fruitful forthcoming applications of chalcogen bonding interactions in crystal engineering and biological systems.