Chemiluminescence (CL) in the known 1-3 reaction of fullerenyl radical dimerization was detected for the first time. Chemiluminescence was observed upon irradiation of toluene solutions containing EtC 60 C 60 Et (hereinafter, dimer), С 60 , Et n С 60 H m (n = m = 1-6), and Et n C 60 (n = 2-6) in a ratio of 9.3 : 32.4 : 4 (hereinafter, solution 1) with a W lamp (180 W, λ = 500-600 nm). The compo nent ratio was determined from the surface areas of the corresponding peaks of the HPLC chromatograms of so lution 1 (Et n С 60 H m and Et n C 60 are eluted as one peak). Solution 1 was prepared and analyzed according to a known procedure 4-7 by the oxidation of Et 3 Al by oxygen in toluene in the presence of С 60 followed by hydrolysis of the oxidate with 3% HCl. The residue of О 2 was removed by blowing argon. The irradiation was carried out using two methods under argon. In the first method, solution 1 (0.5 mL) was irradiated for 2 min in an ampule in the cavity of an ESR spectrometer. In the second method, solution 1 (10 mL) was irradiated for 3 min in a Pyrex reactor. The solution from the Pyrex reactor was rapidly (for 7 s) poured into a Pyrex cell to exclude the afterglow of the reactor, and the CL was measured. An ESR signal with g = 2.0023 appears during the irradiation.* This g value coincides with that (2.0022-2.0023) of the EtС 60 • radical generated earlier 8 by photoirradiation of an EtBr solution in the presence of C 60 . After the light was switched off, the intensities of the ESR and CL signals decreased (I max = 5.4•10 7 photon s -1 mL -1 ) (Fig. 1).Of all the components of solution 1, it is the dimer that has the weakest (according to the estimation, 9 53.8 kcal mol -1 ) EtC 60 -C 60 Et bond. Therefore, we at tribute the generation of the ESR and CL signals to the photolytic decomposition of the dimer to two EtC 60 • radi cals (reaction (1)) followed by the recombination of EtC 60 • to form the dimer molecules, some of which are generated in the excited state (reaction (2)).(1) (2) No ESR and CL signals appear upon irradiation of toluene, a solution of С 60 in toluene, and a solution ob tained by another method 10 and containing all compo nents of solution 1, except the dimer. The CL spectrum (λ max = 664 nm) lies in the region (Fig. 2) characteristic of the luminescence of fullerene derivatives. * The authors are grateful to Yu. A. Lebedev (Institute of Physics of Molecules and Crystals, Russian Academy of Sciences, Ufa) for the determination of the g factor of the radical.
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