An electronic and vibrational study of the cyclopropenyl ion and its fluoroderivatives

Abstract

This article presents the results of ab initio SCF-MO calculations on both the electronic structure and vibrational spectra of the cyclopropenyl cation (C 3H 3 +) and its fluoroderivatives, C 3H 2F +, C 3HF 2 + and C 3F 3 +. A very simple and unambiguous criterion for choosing the combination of diffuse and polarization functions which, together with the 6311G basis set, best describes the electron distribution in these ions is presented. The electronic structures of the cations are analysed in detail; particular emphasis is given to the analysis of the electronic effects due to successive hydrogen-by-fluorine replacements. The results of vibrational normal mode analysis carried out for all hydrogen-deuterium isotopomers of the studied ions are presented and compared with the available experimental data. The theoretical results are used both to review some band assignments previously proposed for the fluorosubstituted molecules and to give a stronger theoretical foundation to the general interpretation of the vibrational spectra of these compounds.