Magnitude of the CH/π Interaction in the Gas Phase:  Experimental and Theoretical Determination of the Accurate Interaction Energy in Benzene-methane

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 110; no. 13; pp. 4397 - 4404
• Main Authors: Shibasaki, Kenta, Fujii, Asuka, Mikami, Naohiko, Tsuzuki, Seiji
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06.04.2006
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp0605909

The accurate CH/π interaction energy of the benzene−methane model system was experimentally and theoretically determined. In the experiment, mass analyzed threshold ionization spectroscopy was applied to the benzene−methane cluster in the gas phase, prepared in a supersonic molecular beam. The binding energy in the neutral ground state of the cluster, which is regarded as the CH/π interaction energy for this model system, was evaluated from the dissociation threshold measurements of the cluster cation. The experimentally determined binding energy (D 0) was 1.03−1.13 kcal/mol. The interaction energy of the model system was calculated by ab initio molecular orbital methods. The estimated CCSD(T) interaction energy at the basis set limit (D e) was −1.43 kcal/mol. The calculated binding energy (D 0) after the vibrational zero-point energy correction (1.13 kcal/mol) agrees well with the experimental value. The effects of basis set and electron correlation correction procedure on the calculated CH/π interaction energy were evaluated. Accuracy of the calculated interaction energies by DFT methods using BLYP, B3LYP, PW91 and PBE functionals was also discussed.