Very Long-Range Effects: Cooperativity between Anion-π and Hydrogen-Bonding Interactions

The interplay between two important non-covalent interactions involving aromatic rings (namely anion-pi and hydrogen bonding) is investigated. Very interesting cooperativity effects are present in complexes where anion-pi and hydrogen bonding interactions coexist. These effects are found in systems where the distance between the anion and the hydrogen-bond donor/acceptor molecule is as long as similar to 11 angstrom. These effects are studied theoretically using the energetic and geometric features of the complexes, which were computed using 1 ab initio calculations. We use and discuss several criteria to analyze the mutual influence of the non-covalent interactions studied herein. In addition we use Bader's theory of atoms-in-molecules to characterize the interactions and to analyze the strengthening or weakening of the interactions depending upon the variation of the charge density at the critical points.