Ab initio study of the complexation of benzene with ammonium cations

Complexes of benzene with ammonium cations (MenH(4−n)N+ for n=0−4) were studied using ab initio calculations with electron correlation included. The most stable structure and binding energies of the complexes are reported. The calculated binding energies are in good agreement with experiment. Two types of NH-aromatic π and CH-aromatic π interactions, which are important in biological systems, are responsible for the binding. From analysis of the structures and energies, the π-σ∗ through-space interactions are seen to be significant in both types of NH-π and CH-π interactions.