Mutual influence between triel bond and cation–π interactions: an ab initio study

Using ab initio calculations, the cooperative and solvent effects on cation–π and B···N interactions are studied in some model ternary complexes, where these interactions coexist. The nature of the interactions and the mechanism of cooperativity are investigated by means of quantum theory of atoms in molecules (QTAIM), noncovalent interaction (NCI) index and natural bond orbital analysis. The results indicate that all cation–π and B···N binding distances in the ternary complexes are shorter than those of corresponding binary systems. The QTAIM analysis reveals that ternary complexes have higher electron density at their bond critical points relative to the corresponding binary complexes. In addition, according to the QTAIM analysis, the formation of cation–π interaction increases covalency of B···N bonds. The NCI analysis indicates that the cooperative effects in the ternary complexes make a shift in the location of the spike associated with each interaction, which can be regarded as an evidence for the reinforcement of both cation–π and B···N interactions in these systems. Solvent effects on the cooperativity of cation–π and B···N interactions are also investigated.