ELECTROCHEMICAL PROPERTIES OF C60H2 AND C70H21

The electrochemistry of C60H2 and the 1,9- and 7,8-isomers of C70H2 were investigated in DMF/toluene mixtures and the resulting data compared to that of the parent C-60 and C-70 fullerenes under the same solution conditions. Each dihydrogen derivative is reduced via a series of one-electron transfers. The C60H2 undergoes four reversible reductions which occur at E(1/2) = -1.02, -1.46, -2.07, and -2.58 V vs Fc/Fc(+). The two electroreduced isomers of C70H2 are less soluble than electroreduced C60H2 and only three reductions are seen for these compounds in a toluene/DMF mixture. These occur at E(1/2) = -1.04, -1.48, and -1.96 V vs Fc/Fc(+) for the 7,8-isomer and at E(1/2) = -1.03, -1.52, and -1.93 V vs Fc/Fc(+) for the 1,9-isomer. The electronic effect of these two different structural isomers is not reflected in their electrochemistry since almost identical E(1/2) values are obtained for each reduction process. The stability of the reduced dihydrogen species decreases with an increase of charge, temperature, and/or the DMF content of the toluene/DMF mixture. Singly-reduced C60H2.(-) is the most stable of the reduced compounds, and its EPR spectrum was measured and compared to the spectrum of C60.(-) in neat toluene. The spectrum of C60H2.(-) is centered at g = 2.000 and has a spectral line width of 3 G at 160 K, as compared to a g = 1.997 and a line width of 5.8 G for C-60.(-).