Components of the interaction energy of benzene with Na + and methylammonium cations

Abstract

The results of ab initio computations including correlation (MP2) performed on the complexes of Na +, monomethylammonium (MMA) and tetramethylammonium (TMA) with a same ligand, benzene, are compared at the same theoretical level (double-zeta basis set, with polarization functions optimized on molecular polarizabilities). The binding energies, corrected for the basis set superposition error, are in satisfactory agreement with the values of the measured gas-phase enthalpies. The nature of the components of the binding are discussed in light of decomposition of the interaction energies in different adducts. The values of the electrostatic, polarization, charge transfer and correlation (dispersion) components, considered at the equilibrium and upon approach to equilibrium, indicate that the order of the Coulomb attraction of these ions for the same ligand is a good indicator of the order of the total energies, but the weight of the other components is far from negligible, and varies from one ion to another.