EPR Spectra Of Radical Cations Research Articles

Radical cations in irradiated solid n-alkanes and polyethylene

The method of time-resolved magnetic field effect (TR MFE) in recombination fluorescence of spin-correlated radical ion pairs has been used to detect and identify radical cations generated at early stages after the pulse irradiation of polyethylene and tricosane. From analysis of TR MFE curves, the widths of unresolved EPR spectra of radical cations have been determined, and their g factors have been evaluated. The results have demonstrated that, as distinct from n-alkanes, primary radical cations in polyethylene are localized on chemical defects of the polymer chain in a time of about 1 ns or less.

1,1,1,3,3,3-Hexafluoropropan-2-ol as a solvent for the generation of highly persistent radical cations

1,1,1,3,3,3-Hexafluoropropan-2-ol (HFP) has been found to be a superior solvent for the generation of radical cations, in many cases increasing their half-lives by a factor of 102 compared with those pertaining to trifluoroacetic acid. This study has mainly used 4-tolylthallium(III) bis(trifluoroacetate) and thallium(III) tris(trifluoroacetate) as oxidants, but DDQ could also be employed in the presence of 5% trifluoroacetic acid. Photochemical oxidation by mercury(II) bis(trifluoroacetate) also worked well. Thus room temperature recording of high quality EPR spectra of radical cations previously accessible only by flow or low-temperature procedures has become feasible.

A new experimental approach for obtaining EPR spectra of alkane and alkene radical cations

A new experimental approach for obtaining EPR spectra of alkane and alkene radical cations is described. The method consists in irradiating the hydrocarbon studied (octane and tetramethylethylene in this work) in a pentane matrix at 77 K. A substantial amount of the positive ions formed by irradiation will then be trapped as radical cations of the additive. Fairly pure EPR spectra of these radical cations may subsequently be obtained by taking the difference, by computer, between the EPR spectra before and after selective removal of the radical cation by illumination with light of suitable wavelength.