Abstract
Irradiation of C 60 -toluene solution at room temperature affords two ESR bands with g and ΔH 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 band was observed. They were assigned to be 3 C 60 and C 60 °+ , respectively. In the presence of tetraphenylphosphonium tetraphenylborate, the g value of the C 60 °+ cation radical shifts to 2.0006, and an additional broad band of g = 1.9992 and ΔH 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 60 °- anion radical according to its characteristic behavior. At room temperature, photolysis causes the C 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 60 °H n (tolyl) n (n = 1-4) adducts. The formation of C 60 °+ and C 60 °+ was rationalized in terms of disproportionation of two 3 C 60 . The brown precipitates were due to the chemical reaction between the C 60 °+ cation radical and the solvent molecules, which rationalizes the "photodegradation" of fullerene as reported in literature. The important role of the C 60 °+ and C 60 °- to the peculiar photochemical behavior of fullerene solutions or films, such as nonlinear optical property, photoinduced polymerization in solid film, nonlinear photoconductivity, etc, will be discussed.