AN ELECTRONIC AND VIBRATIONAL STUDY OF THE CYCLOPROPENYL ION AND ITS FLUORODERIVATIVES

This article presents the results of ab initio SCF-MO calculations on both the electronic structure and vibrational spectra of the cycloprop enyl cation (C3H3+) and its fluoroderivatives, C3H2F+, C3HF2+ and C3F3 +. A very simple and unambiguous criterion for choosing the combinatio n of diffuse and polarization functions which, together with the 6-311 G basis set, best describes the electron distribution in these ions is presented. The electronic structures of the cations are analysed in d etail; particular emphasis is given to the analysis of the electronic effects due to successive hydrogen-by-fluorine replacements. The resul ts of vibrational normal mode analysis carried out for all hydrogen-de uterium isotopomers of the studied ions are presented and compared wit h the available experimental data. The theoretical results are used bo th to review some band assignments previously proposed for the fluoros ubstituted molecules and to give a stronger theoretical foundation to the general interpretation of the vibrational spectra of these compoun ds.