ANION-RADICALS OF [60]FULLERENES - AN EPR STUDY

Photochemically induced electron transfer in homogeneous systems (usin g triethylamine donor) and heterogeneous systems (using photoexcited T iO2 suspension) was applied in in situ reduction of [60]fullerene. The anion radicals generated were characterized by means of EPR and VIS/n ear-IR spectroscopy. Narrow EPR lines were found. Radical A with g(A) = 2.0000 and peak-to-peak width, pp(A) = 0.09 mT was observed as the p rimary product; followed by its consecutive product B with g(B) = 2.00 06, pp(B) = 0.04 mT, and in some cases product C with g(C) = 2.0009 an d pp(C) < 0.1 mT. Radical A was assigned to [60]fullerene mono-anion, also characterized by a near-IR band at 1077 nm. B is presumably di-an ion or a dimeric form of mono-anion. Identical results were also obtai ned using cathodic in situ reduction. Applying these generation techni ques to [60]fullerene derivatives produced narrow EPR lines analogous to those described for pristine [60]fullerene. This was the case not o nly in organic solvents, but also in aqueous solutions. The results ob tained present a contrast with the original ex situ EPR investigations describing [60]fullerene mono-anion with wide lines. According to the results presented here, the narrow and wide EPR lines do not represen t contradictory phenomena, but are an integral part of the relatively complicated manifestations of various fullerene states and both will h ave to be seriously considered in the future.