FULLERENE ANION FORMATION BY ELECTRON-TRANSFER FROM AMINO DONOR TO PHOTOEXCITED C-60 - ELECTRON-PARAMAGNETIC-RESONANCE STUDY

Upon UV irradiation of C-60 fullerene in 1:1 toluene/(methanol, aceton itrile, or toluene) solutions the photoexcited state of C-60 was quenc hed in the presence of Et(3)N, and single lines of anion radicals A an d B were observed in in situ EPR measurements. The formation of A is a ccompanied by the appearance of a band at 1077 nm in vis/near-IR spect rum characteristic of C-60 monoanion. Radical B is a consecutive produ ct of A (probably associate of C60(.-) or C-60 dianion). Monoanion A w ith g = 2.0000 and peak-to-peak width, pp = 0.09 mT converts to radica l B with g = 2.0006 and pp = 0.035 mT increasingly after prolonged irr adiation and at higher ratios of Et(3)N:C-60. The shortest lifetime of C-60 monoanion was found in the presence of methanol (t(1/2) = 28 s), and it increased considerably upon the addition of tetrabutylammonium perchlorate (TBAP) salt (t(1/2) = 210 s in 0.38 M TBAP) or if methano l was replaced by acetonitrile (tin = 260 s). Lowering the temperature from 300 to 200 K, the linewidth of A decreases from pp(300 K) = 0.09 mT to pp(200 K) = 0.038 mT. At 100 K a broadened line spread over 3 m T was found with a narrow line superimposed on it. The ratio of the br oadened to the narrow line increases with the increased time intervals and is more pronounced following prior prolonged irradiation at 300 K or upon the addition of TBAP.