A computational examination of helical perfluoroalkane conformations and implications for the adsorption of perfluoroalkanes on platinum(111) surfaces

Abstract The two lowest-energy conformers of perfluorohexane and perfluoroheptane were investigated at the Hartree–Fock RHF/6-31G* level and the structures, properties, and vibrational frequencies determined. The lowest-energy conformers of perfluorohexane were found to differ by 8.600 kJ mol -1 (2.055 kcal mol –1 ) at this level of theory, while the lowest-energy conformers of perfluoroheptane differed by 8.662 kJ mol –1 (2.070 kcal mol –1 ). In addition, a transition state for the interconversion between the two lowest-energy conformers of perfluorohexane was investigated at the RHF/6-31G* level, and was found to lie 13.247 kJ mol –1 (3.166 kcal mol –1 ) above the energy of the lowest-energy conformer, while a transition state for the equivalent interconversion between the perfluoroheptane conformers was 15.279 kJ mol –1 (3.652 kcal mol –1 ) above the energy of the lowest-energy conformer. These results have been used to interpret previously published thermal desorption and infrared reflection–absorption spectroscopic data for the monolayer and sub-monolayer adsorption of perfluorocarbon molecules on a single-crystal Pt(111) surface under ultra-high vacuum conditions. To cite this article: W.G. Golden et al., C.R. Chimie 7 (2004) .