Enes Roger F, Tomé Augusto C, Cavaleiro José A S, Amorati Riccardo, Fumo Maria Grazia, Pedulli Gian Franco, Valgimigli Luca
Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
Chemistry. 2006 Jun 2;12(17):4646-53. doi: 10.1002/chem.200501495.
Fullerene derivatives incorporating one or two 3,5-di-tert-butyl-4-hydroxyphenyl groups were synthesized by 1,3-dipolar cycloaddition of azomethine ylides to C(60). The O-H bond dissociation enthalpies (BDEs) of these compounds were estimated by studying, by means of EPR spectroscopy, the equilibration of each of these phenols and 2,6-di-tert-butyl-4-methylphenol (BHT) with the corresponding phenoxyl radicals. The antioxidant activity of the investigated phenols was also determined by measuring the rate constants for their reaction with peroxyl radicals in controlled autoxidation experiments and compared to that recorded under identical experimental settings for [60]fullerene itself and unlinked BHT. The results indicate that linking of the BHT structure to C(60) does not substantially alter the thermochemistry and kinetics of its reaction with peroxyl radicals, but such adducts may behave as interesting bimodal radical scavengers. The inherent rate constant for trapping of peroxyl radicals by C(60) per se (k(inh)=3.1+/-1.1 x 10(2) m(-1) s(-1)) indicates that, contrary to previous reports, [60]fullerene is an extremely weak chain-breaking antioxidant.
通过甲亚胺叶立德与C(60)的1,3 - 偶极环加成反应，合成了含有一个或两个3,5 - 二叔丁基 - 4 - 羟基苯基的富勒烯衍生物。通过电子顺磁共振光谱研究这些酚类化合物以及2,6 - 二叔丁基 - 4 - 甲基苯酚（BHT）与相应苯氧自由基的平衡，估算了这些化合物的O - H键解离焓（BDEs）。在可控的自氧化实验中，通过测量所研究酚类与过氧自由基反应的速率常数，确定了它们的抗氧化活性，并与在相同实验条件下[60]富勒烯本身和未连接的BHT的记录结果进行比较。结果表明，将BHT结构连接到C(60)上并不会显著改变其与过氧自由基反应的热化学和动力学，但这些加合物可能表现为有趣的双模式自由基清除剂。C(60)本身捕获过氧自由基的固有速率常数（k(inh)=3.1±1.1×10(2) m(-1) s(-1)）表明，与之前的报道相反，[60]富勒烯是一种极其弱的链断裂抗氧化剂。
