ABSTRACT: Quantum chemistry study was performed on interaction between tetramethylammonium (TMA) and
aromatic cages by means of the MP2 method to show how TMA sits in an aromatic cage that is composed of benzenes.
The MP2 calculations on TMA每(benzene)n complexes demonstrate that the more the benzene molecules in
the aromatic cage, the stronger the binding strength between the cage and TMA. In details, the structure of
TMA每(benzene)n (n?1每4) complexes can be easily constructed by superimposing n TMA-benzene complexes
via TMA, and the binding energies of the TMA每(benzene)n complexes are the sum of the n corresponding
TMA-benzene systems. For instance, the distances between the N of TMA and the plane of the benzene ring are
4.238, 4.252, 4.264 ,and 4.276 A ∼ , respectively, for TMA每(benzene)n (n?1每4) complexes, and the BSSE corrected
binding energies at MP2/6-311ttG level are 8.8, 17.3, 25.8 and 34.3 kcal/mol, respectively, for TMA每
(benzene)n (n?1每4) complexes. Thus, this study provides us useful information on how a cation interacts with an
aromatic cage in terms of complex geometry and binding strength.