Andrea Baschieri, Zongxin Jin, Riccardo Amorati, Kristian Vasa, Allegra Baroncelli, Stefano Menichetti and Caterina Viglianisi
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引用次数: 0
摘要
研究人员对三种新的α-生育酚噻吩衍生物进行了高效合成、表征,并首次将其用作链断裂抗氧化剂,以抑制参考可氧化底物的自氧化作用。通过使用压差传感器测量苯乙烯或异丙苯自氧化过程中的耗氧量,确定了噻吩-生育酚化合物与烷基过氧自由基(ROO˙)反应的速率常数和自由基捕获量(n)。在 30 °C 的无极性溶剂中与 ROO˙自由基反应的测量结果显示,抑制率常数(kinh)在 104 M-1 s-1 的数量级。为了合理解释动力学结果,我们通过理论计算研究了噻吩环对官能化生育酚的 O-H 基团捐献 H 原子的影响。非共价相互作用(包括不寻常的 O˙⋯S键)对构象稳定性的重要性已经得到证明,这些衍生物的 O-H 键解离焓(BDE(OH))也已确定。最后,研究了这些新化合物的光物理特性,以了解噻吩基团的加入是否会改变生育酚骨架的吸收或发射光谱,从而了解它们作为发光分子探针的应用可能性。
Kinetic study of the reaction of thiophene-tocopherols with peroxyl radicals enlightenings the role of O˙⋯S noncovalent interactions in H-atom transfer†
Three new α-tocopherol thiophene derivatives were efficiently synthesized, characterized and used for the first time as chain-breaking antioxidants for the inhibition of the autoxidation of reference oxidizable substrates. The rate constant of the reaction with alkylperoxyl (ROO˙) radicals and the stoichiometry of radical trapping (n) for the thiophene-tocopherol compounds were determined by measuring the oxygen consumption during the autoxidation of styrene or isopropylbenzene, using a differential pressure transducer. The measurement of the reaction with ROO˙ radicals in an apolar solvent at 30 °C showed inhibition rate constants (kinh) in the order of 104 M−1 s−1. To rationalise the kinetic results, the effect of the thiophene ring on the H-atom donation by O–H groups of the functionalized tocopherols was investigated by theoretical calculations. The importance of noncovalent interactions (including an unusual O˙⋯S bond) for the stability of the conformers has been shown, and the O–H bond dissociation enthalpy (BDE(OH)) of these derivatives was determined. Finally, the photophysical properties of these new compounds were investigated to understand if the addition of thiophene groups changes the absorption or emission spectra of the tocopherol skeleton for their possible application as luminescent molecular probes.