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

The rate constants of electron transfer from C-60(.-) and C-60(2-) to electron accepters 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 C-60(.-), C-60(2-), and semiquinone radical anions for different electron accepters. Such correlations indicate that reorganization energies for the electron-transfer reactions of C-60(.-) and C-60(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, C-60/C-60(.-), and C-60(.-)/C-60(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.