The effect of anions on noncovalent interactions in model clusters of chalcogen-containing (CH3)2X (X = O, S, Se) molecules

Abstract

A computational study of F⁻⋯(CH₃)₂X⋯YF (X = O, S, Se; Y = F, H) triads, with F⁻ bound to the protons of the two methyl groups, found significant enhancement of the X⋯Y interactions relative to the neutral (CH₃)₂X⋯YF dyads, more so for the X⋯F than the X⋯H interaction. A subsequent model study of anionic F⁻⋯(CH₃)₂O⋯YZ (YZ = HF, CH₃F, SiH₃F, GeH₃F, NF₃, OF₂, F₂, ClF) triads revealed a similar enhancement of all O⋯Y noncovalent interactions. The relative stabilities and associated properties of the O⋯Y σ-hole interactions were rationalized using the electronegativity difference between O and Y. Very strongly bound Z⁻⋯(CH₃)₂X–F₂ (Z = F, Cl, Br; X = S, Se) clusters were also predicted and involve interactions between the anion Z⁻, Lewis base (CH₃)₂X and two F atoms sandwiching the central X atom to form a nearly linear F–X–F axis.