Mutual influence between halogen bonds and cation-π interactions: a theoretical study.

The interplay between halogen bonds and cation-π interactions is investigated by ab initio calculations at the MP2 level of theory. Different energetic effects are observed in the studied complexes in which halogen bonds and cation-π interactions coexist, which can be ascribed to the direction of charge transfer for the two interactions. These effects are analyzed in detail in terms of the structural, energetic, and charge-transfer properties of the complexes. In addition, the quantum theory of atoms in molecules is employed to characterize the interactions and to examine their enhancement and attenuation in terms of the variations in electron density at the bond and cage critical points. Finally, experimental evidence for a combination of the two interactions is obtained from the Cambridge Structural Database.