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

摘要

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