Noncovalent Interactions in Complexes Involving the Cyclic C₂H₂X (X=O, S, Se) Molecules and the Lewis Acids YF (Y=F, Cl, Br, H)

Abstract

A computational study of the cyclic Lewis bases C2H2X (X=O, S, Se) interacting with the Lewis acids YF (Y=F, Cl, Br, H) in model C2H2X…YF dyads was undertaken. It was shown that the noncovalent X…Y interaction in these binary complexes increases with increasing YF dipole moment for the C2H2O complexes, but not for the C2H2S and C2H2Se complexes, where instead the X…Y interaction increases with increasing X/Y electronegativity difference. This suggests that electrostatic forces dominate the binding in the former, whereas polarization effects dominate in the latter complexes. These explanations were supported by natural bond orbital (NBO) and atoms in molecules (AIM) analyses of the electron density, as well as interaction energy decomposition analyses. A subsequent study of the cooperative effect of an additional hydrogen bond in the model triads, FH…C2H2X…YF and C2H2X…YF…HF, found that the X…Y interaction in the dyads is weakened in the former and strengthened in the latter, with the trends identified in the dyads persisting in both triads.

Chalcogen Bonding in the Molecular Dimers of WCh2 (Ch = S, Se, Te): On the Basic Understanding of the Local Interfacial and Interlayer Bonding Environment in 2D Layered Tungsten Dichalcogenides

“…Each can be positive or negative depending on the nature of the electron density depletion or accumulation at specific regions on the molecular surface [52,67,68]. When they are positive, the region is electrophilic, and when negative, it is nucleophilic [54,69,70]. These can show up on the same atom in a molecular entity; hence, the charge density on an atom in molecules may be anisotropic.…”

“…These can show up on the same atom in a molecular entity; hence, the charge density on an atom in molecules may be anisotropic. Specifically, the local most maximum of potential, V S,max , on the surface of a bonded atom is commonly observed on the outer extension of a covalent bond, and the local most minimum of potential, V S,min , is commonly observed in a region dominated by π-density and lone-pair electron density [52,69] (i.e., around a covalently bonded atom in a molecule).…”