The tunability of Y···N chalcogen bond via formation of a cation-π 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-ccpVDZ computational level. Our results indicate that the strength of Y···N and cation-π 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···N and cation-π interactions. For a given aromatic system, the shortening or lengthening of Y···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.
