关键词: 光化学反应, 微波辐射, 富勒烯吡咯烷衍生物, 临界聚集浓度, 静态光散射, 超氧阴离子自由基

Photochemical reaction of C60 with iminodiacetic methyl ester [NH(CH₂COOMe)₂] produced 2,5-bis(methoxycarbonyl)fulleropyrrolidine (1) in a 52% yield (based on consumed C60). N-Alkylation of fulleropyrrolidine derivative 1 with methyl chloroacetate (ClCH₂COOCH₃) by phase transfer catalysis without solvent under microwave irradiation afforded 2,5-bis(methoxycarbonyl)-N-(methoxycarbonyl)-methylfulleropyrrolidine (2) in a 47% yield (relative to the methyl derivative 1). Fulleropyrrolidine derivatives 1 and 2 were hydrolyzed with NaH and methanol in toluene, and then acidified with HCl to result in the corresponding fulleropyrrolidine dicarboxylic acid (3) and fulleropyrrolidine tricarboxylic acid (4), respec- tively, in 65% and 53% yields (relative to fulleropyrrolidine derivatives 1 and 2). Fulleropyrrolidine derivatives 1～4 were structurally characterized by ¹H NMR, ¹³C NMR, IR, FAB-MS methods and elementary analysis. Critical aggregation concentrations (CAC) of sodium salts of dicarboxylic acid derivative 3 and tricarboxylic acid derivative 4 were determined by conductivity measurements, which were 3.58×10^－4 mol/L (3) and 3.33×10^－4 mol/L (4), respectively. The results were supported by characteristic change of UV-Vis absorption spectra of the derivatives 3 and 4 at the neighborhoods of CAC. The aggregation behavior of 3 and 4 was also examined using static light scattering (SLS) and transmission electron microscopic (TEM) techniques, and the aggregate sizes of derivative 3 (radius R_g ～21 nm) in a buffer solution (0.001 mol/L Na₂CO₃-NaHCO₃) were found to be different from derivative 4 (radius R_g ～21 nm). Critical aggregation concentrations (CAC) of sodium salts of the derivative 3 is bigger than that of sodium salts of derivative 4, and their aggregate sizes were different from each other, indicating that the formation of aggregate is effected by the number of carboxyl connected to fulleropyrrolidine mono-adduct derivatives. Scavenging effects of derivatives 3 and 4 on superoxide radicals (O₂^－·) in a buffer solution (0.05 mol/L Na₂CO₃-NaHCO₃) were studied by chemiluminescence technique. They were found to show an obvious quantity effect, that the eliminating efficiencies was increased with the increase of concentration. However, when exceeding certain concentration (CAC) , the eliminating efficiency showed the turn (3: ～3.50×10^－4 mol•L^－1, 4: ～3.25×10^－4 mol•L^－1), and decline. This phenomenon was in accordance with that of CAC detected by conductance method, further confirming that derivatives 3 and 4 had tendency of aggregation in aqueous solution of higher concentration, and the formation of aggregate had a great influence on their scavenging activity for superoxide radicals (O₂^－·).

Key words: photochemical reaction, microwave irradiation, fulleropyrrolidine derivative, critic aggregation concentration, static light scattering, superoxide radical