How important is the dispersion interaction for cyclobis(paraquat-p-phenylene)-based molecular "shuttles"?: A theoretical study

Inclusion complexes of cyclobis(paraquat-p-phenylene) and various aromatic molecules in their neutral and oxidized form were studied at the LMP2/6-311+G**//BHandHLYP/6-31G* level of theory, which represents the highest level theoretical study to date for these complexes. The results show that it is dispersion interaction that contributes most to the binding energy. One electron oxidation of a guest molecule leads to complete dissociation of inclusion complex generating strong repulsion potential between guest and host molecules. Electrostatic interactions also can play an important role, provided the guest molecule has a dipole moment; however, dispersion interactions always dominate in binding energy. (C) 2004 Wiley Periodicals, Inc.