MP2 study of cooperative effects between cation-pi, anion-pi and pi-pi interactions

In this manuscript we report high level ab initio calculations (RI-MP2(full)/6-31++G**) and experimental evidence that demonstrate that important non-additivity effects between three noteworthy non-covalent interactions that involve aromatic rings ( benzene and hexafluorobenzene), i.e. cation -pi, anion -pi and pi-pi interactions, occur when the interactions coexist in the same complex. In some cases we have observed very high non-additivity energies (up to - 20.3 kcal mol(-1)) that indicate that the cation -pi and/or the anion - pi have a strong influence on the pi - pi interaction and vice versa.