Tuning of chalcogen bonds by cation-π interactions: cooperative and diminutive effects

The tunability of Y center dot center dot center dot N chalcogen bond via formation of a cation-pi interaction in ternary complexes M+-PhYH-NH3, M+-PhYH-NCH, and M+-PhCCCN-YHF (M=Li, Na; Y=Se, Te) is investigated at MP2/aug-cc-pVDZ computational level. Our results indicate that the strength of Y center dot center dot center dot N and cation-pi interactions in the ternary complexes depends on the role of the aromatic molecule. That is, a cooperative effect is evident if aromatic molecule acts as the Lewis acid and Lewis base, simultaneously, while a diminutive effect is observed when the aromatic molecule acts only as the Lewis base in both Y center dot center dot center dot N and cation-pi interactions. For a given aromatic system, the shortening or lengthening of Y center dot center dot center dot N distances is more important for Li+ complexes than Na+ counterparts. The mechanism of cooperative/diminutive effects in the ternary complexes is studied by molecular electrostatic potential (MEP) and topological analysis of the electron density.