Disproportionation of Photoexcited C₆₀

Irradiation of C{sub 60}-toluene solution at room temperature affords two ESR bands with g and {Delta}H{sub pp} values of (2.0013, 0.5 G) and (2.0024, 0.75 G), respectively. In the presence of 6% methanol or 12% benzonitrile, the latter band disappears completely. Below 200 K, only the former bank was observed. They were assigned to be {sup 3}C{sub 60} and C{sub 60}{sup .+}, respectively. In the presence of tetraphenylphosphonium tetraphenylborate, the g value of the C{sub 60}{sup .+} cation radical shifts to 2.0006, and an additional broad band of g = 1.9992 and {Delta}H{sub pp}=30 G was observed. Upon cooling, the line width of this new band drops from 30 G at 300 K to 4 G at 77 K. This new band was assigned to be the C{sub 60}{sup .-} anion radical according to its characteristic behavior. At room temperature, photolysis causes the C{sub 60}-toluene solution`s color to turn from purple to brown, and then brown precipitates formed. Desorption chemical ionization (DCI) mass analysis of the brown precipitates indicates the formation of C{sub 60}.H{sub n}(tolyl){sub n} (n = 1-4) adducts. The formation of C{sub 60}{sup .+} and C{sub 60}{sup .-} was rationalized in terms of disproportionation of two {sup 3}C{submore » 60}. The brown precipitates were due to the chemical reaction between the C{sub 60}{sup .+} cation radical and the solvent molecules, which rationalizes the `photodegradation` of fullerene as reported in literature. 38 refs., 5 figs.« less