Ibrahim MAA, Ahmed OAM, El-Taher S, Al-Fahemi JH, Moussa NAM, Moustafa H. Cospatial σ-Hole and Lone Pair Interactions of Square-Pyramidal Pentavalent Halogen Compounds with π-Systems: A Quantum Mechanical Study.
ACS OMEGA 2021;
6:3319-3329. [PMID:
33553949 PMCID:
PMC7860235 DOI:
10.1021/acsomega.0c05795]
[Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 01/13/2021] [Indexed: 05/08/2023]
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 σ-hole and lone pair (lp) interactions with aromatic π-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 σ-hole/lp donors. On the other hand, benzene (BZN) and hexafluorobenzene (HFB) were chosen as electron-rich and electron-deficient aromatic π-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 σ-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···π-system complexes governed the interaction energy pattern: the larger the X4 atoms were, the greater the interaction energies were, for the same π-system. The results had illuminating facets in regard to the rarely addressed cases of the σ-hole/lp contradictory scene.
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