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

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.