Aromatic systems as charge insulators: Their simultaneous interaction with anions and cations

A theoretical approach, using ab initio MP2(full)/6-31++G** and MP2(full)/6-311++G** levels, has been used to characterize the interaction of the pi-cloud of C6F6 with cations (Y+ = Li+, Na+, and K+). In addition, the situation where C6H6 and C6F6 simultaneously interact with an anion (X- = F-, Cl-, and Br-) and a cation in opposite faces of the aromatic ring has been studied. For comparative purposes, other dispositions, such as those of the isolated cations and the anions and the complexes between neutral XY salts and the aromatic systems, have been considered. Complexes where the T-cloud of the aromatic ring interacts with a cation or, simultaneously, with a cation and an anion have been found to be mimima structures. However, these complexes show high relative energies when compared to other minima of the potential hypersurface. The interaction energy has been decomposed into MEP, polarization and charge-charge interaction terms.