Cospatial ?-Hole and Lone Pair Interactions of Square-Pyramidal Pentavalent Halogen Compounds with ?-Systems: A Quantum Mechanical Study.

ABSTRACT: In the spirit of the mounting interest in noncovalent interactions, the present study was conducted to scrutinize a special type that simultaneously involved both ?-hole and lone pair (lp) interactions with aromatic ?-systems. Square-pyramidal pentavalent halogen-containing molecules, including X-Cl-F₄, F-Y-F₄, and F-I-X₄ compounds (where X = F, Cl, Br, and I and Y = Cl, Br, and I) were employed as ?-hole/lp donors. On the other hand, benzene (BZN) and hexafluorobenzene (HFB) were chosen as electron-rich and electron-deficient aromatic ?-systems, respectively. The investigation relied upon a variety of quantum chemical calculations that complement each other. The results showed that (i) the binding energy of the X-Y-F₄···BZN complexes increased (i.e., more negative) as the Y atom had a larger magnitude of ?-hole, contrary to the pattern of X-Y-F₄···HFB complexes; (ii) the interaction energies of X-Y-F₄···BZN complexes were dominated by both dispersion and electrostatic contributions, while dispersive interactions dominated X-Y-F4···HFB complexes; and (iii) the X₄ atoms in F-I-X₄···?-system complexes governed the interaction energy pattern: the larger the X₄ atoms were, the greater the interaction energies were, for the same ?-system. The results had illuminating facets in regard to the rarely addressed cases of the ?-hole/lp contradictory scene.

SUBMITTER: Ibrahim MAA 

PROVIDER: S-EPMC7860235 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature