Electron transfer to [60]fullerene and its o-quinodimethane adducts in dimethyl sulfoxide (EPR, visible/near-IR, and electrochemical study)

The o-quinodimethane adducts 2-4 of [60]fullerene dissolved in dimethyl sulfoxide (DMSO) form the corresponding monoanion radicals with a yield of up to 20% if W-irradiated under argon at 295 K. The radicals are presented in EPR by a single Lorentzian line with g(2-4) = 2.0000 and a peak-to-peak width of pp = 0.105 mT. Simultaneously, a characteristic monoanion band in the near-LR spectrum al 1006 nm appears to be accompanied by a decrease in original fullerene absorption in the UV region at 265 nm. Given alternating saturation with oxygen and argon followed by irradiation, the decay and regeneration process for the monoanion can be repeated many times. The reoxidation of monoanion is coupled with the formation of superoxide anion. Lowering the temperature from 380 to 260 K narrows the line from pp(380 K) = 0.2026 mT to pp(260 K) = 0.089 mT, then widens it abruptly at 240 K to a Lorentzian with pp congruent to 0.3 mT, and then leaves it constant down to 100 K. This temperature behavior is reversible and no wide-line component is evident. [60]Fullerene 1 also forms a monoanion with the same g value as its derivatives 2-4, but with slightly smaller pp = 0.09 mT and in considerably lower concentration due to its limited solubility in DMSO.