Spin density distributions in some fluorinated radical cations

A theoretical study of π-electron spin density distributions has been made for a series of fluoro-substituted hydrocarbon radical cations using unrestricted Hartree-Fock theory. Although some of the predicted proton splittings are not in very good agreement with experiment, the overall agreement with experiment can be passed as fairly satisfactory considering the approximate nature of the theory used. The experimental fluorine splittings can be well predicted by using a one-parameter relationship between the isotropic fluorine splitting (a_F) and the π-electron spin density (ρ_CC) on the attached carbon. It has been further shown that both ρ_CC and the proportionality constant (Q_eff) in the linear relation, are fairly insensitive to the parameter choice.