Cumulative pi-pi interaction triggers unusually high stabilization of linear hydrocarbons inside the single-walled carbon nanotube

摘要

The interactions of linear hydrocarbons C2nH4 and C2nH2 (n = 1-4) with a finite-length armchair (5,5) single-walled carbon nanotube have been investigated using HF and MP2 methods in conjunction with 6-31G(d) basis set, and molecular mechanics (MM) with MM2 force field. In all cases, the results obtained at MP2/631G(d) level show stabilization of these supramolecular systems, contrary to the repulsive interactions obtained with the HF method. The interaction energies computed using MM with MM2 force field are in close agreement with the results obtained using the MP2/6-31G(d) level. They increase gradually as the length of linear hydrocarbon chain increases. The present study indicates that cumulative pi-pi interaction is the origin for the exceptionally high stabilization of the long nanotube-hydrocarbon complexes. Mulliken population analysis reveals a very small charge transfer between the nanotube and the guest. Essentially there is no change in HOMO-LUMO energy gap by the insertion of linear hydrocarbons. (c) 2007 Wiley Periodicals, Inc.