Theoretical study on cooperativity effects between anion-π and halogen-bonding interactions.

This article analyzes the interplay between lone pair-π (lp-π) or anion-π interactions and halogen-bonding interactions. Interesting cooperativity effects are observed when lp/anion-π and halogen-bonding interactions coexist in the same complex, and they are found even in systems in which the distance between the anion and halogen-bond donor molecule is longer than 9 Å. These effects are studied theoretically in terms of energetic and geometric features of the complexes, which are computed by ab initio methods. Bader's theory of "atoms in molecules" is used to characterize the interactions and to analyze their strengthening or weakening depending upon the variation of charge density at critical points. The physical nature of the interactions and cooperativity effects are studied by means of molecular interaction potential with polarization partition scheme. By taking advantage of all aforementioned computational methods, the present study examines how these interactions mutually influence each other. Additionally, experimental evidence for such interactions is obtained from the Cambridge Structural Database (CSD).