ELECTRON-SPIN-RESONANCE STUDY AND THEORETICAL CALCULATIONS OF SOME METHOXYBENZENE RADICAL CATIONS

Reaction of methoxybenzene derivatives with phenyliodine(III) bis(trif luoro-acetate), PIFA, yielded the corresponding radical cations, which were observed and characterized by ESR and visible spectroscopies, Th e application of this methodology to this kind of compound has allowed well-resolved ESR spectra to be obtained of the one-electron oxidized compounds, thus determining the hyperfine coupling constants of the c ation radical when the solvent was 1.1,1.3,3,3-hexafluoroprapanol (HFP ). The requirements of the substitution pattern of the aromatic ring h ave been studied, In contrast, it was not possible to obtain the ESR s pectra of N,N-dialkylaniline radical cations in the same reaction cond itions. The ESR spectra obtained corresponded to non-identified second ary reaction products. The spectral resolution obtained by application of this method has been compared with that obtained when the radical cations were generated by in situ electrochemical oxidation. Semiempir ical calculations have allowed the coupling constants to be assigned t o the magnetic centers in the radical cation. The spin densities obtai ned from these calculations have been correlated with bibliographic da ta on the reactivity of radical cations under nucleophilic attack. (C) 1998 Elsevier Science B.V. All rights reserved.