Electron-transfer properties of C₆₀ and tert-butyl-C₆₀ radical

The rate constants of electron transfer from C₆₀·^- and C₆₀^2- to electron acceptors such as allyl halides and manganese(III) dodecaphenylporphyrin are correlated with those from semiquinone radical anions and their derivatives; linear correlations are obtained between the logarithms of the rate constants and the oxidation potentials of C₆₀·^-, C₆₀^2-, and semiquinone radical anions for different electron acceptors. Such correlations indicate that reorganization energies for the electron- transfer reactions of C₆₀·^- and C₆₀^2- are essentially the same as those of semiquinone radical anions. The self-exchange rate constants between p-benzoquinone and the semiquinone radical anion as well as between tetramethyl-p-benzoquinone and the semiquinone radical anion in benzonitrile are determined at various temperatures by analyzing line width variations of the ESR spectra. The fast-exchange rate constants and small activation enthalpies demonstrate the efficient electron-transfer properties of the p- benzoquinone/semiquinone radical anion, C₆₀/C₆₀·^-, and C₆₀·^- /C₆₀^2- systems. The self-exchange rate constant between t-BuC₆₀· and t-BuC₆₀^- is also determined by analyzing line width variations of the ESR spectra.