Mechanism of radiation-induced reactions in aqueous solution of coumarin-3-carboxylic acid: Effects of concentration, gas and additive on fluorescent product yield
Mechanism of radiation-induced reactions in aqueous solution of coumarin-3-carboxylic acid: Effects of concentration, gas and additive on fluorescent product yield
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DOI：
10.3109/10715762.2012.684879
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发表时间：
2012-04
影响因子：
3.3
通讯作者：
S. Yamashita;G. Baldacchino;T. Maeyama;M. Taguchi;Y. Muroya;Mingzhang Lin;Atsushi Kimura;T. Murakami;Y. Katsumura
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文献类型：
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作者：
S. Yamashita;G. Baldacchino;T. Maeyama;M. Taguchi;Y. Muroya;Mingzhang Lin;Atsushi Kimura;T. Murakami;Y. Katsumura
摘要采用35 MeV电子束脉冲辐解、60 Co γ辐照后的最终产物分析和确定性模型模拟，研究了水溶性香豆素衍生物香豆素-3-羧酸（C3 CA）在水溶液中的辐射诱导反应。脉冲辐解表明，C3 CA与羟基自由基（·OH）和水合电子（e− aq）的反应速率常数分别为6.8 × 109和2.1 × 1010 M−1 s−1。C3 CA对O2· −的反应性未通过脉冲辐解得到证实。荧光分子7-羟基-香豆素-3-羧酸（7 OH-C3 CA）的产生通过使用与高效液相色谱（HPLC）系统耦合的荧光光谱仪进行最终产物分析来确认。在60 Co γ射线照射后，7 OH-C3 CA的产率取决于照射条件，范围为0.025至0.18（100 eV）−1。产率随饱和气体、添加剂和C3 CA浓度的变化而变化，这意味着C3 CA与·OH的清除反应后至少存在两种能够提供7 OH-C3 CA作为稳定产物的途径，包括过氧化/消除序列和反硝化途径。提出了两种途径的反应机理，并将其纳入确定性模拟，表明该机理可以解释实验测量的7 OH-C3 CA产率，从·OH清除到7 OH-C3 CA生产的恒定转换因子为4.7%，除非加入t-BuOH。
Abstract The radiation-induced reactions of a water-soluble coumarin derivative, coumarin-3-carboxyl acid (C3CA), have been investigated in aqueous solutions by pulse radiolysis with a 35 MeV electron beam, final product analysis following 60Co γ-irradiations and deterministic model simulations. Pulse radiolysis revealed that C3CA reacted with both hydroxyl radicals (•OH) and hydrated electrons (e− aq) with near diffusion-controlled rate constants of 6.8 × 109 and 2.1 × 1010 M−1 s−1, respectively. The reactivity of C3CA towards O2• − was not confirmed by pulse radiolysis. Production of the fluorescent molecule, 7-hydroxy-coumarin-3-carboxylic acid (7OH-C3CA), was confirmed by final product analysis with a fluorescence spectrometer coupled to a high performance liquid chromatography (HPLC) system. Production yields of 7OH-C3CA following 60Co γ-irradiations depended on the irradiation conditions and ranged from 0.025 to 0.18 (100 eV) −1. Yield varied with saturating gas, additive and C3CA concentration, implying the presence of at least two pathways capable of providing 7OH-C3CA as a stable product following the scavenging reaction of C3CA with •OH, including a peroxidation/elimination sequence and a disproportionation pathway. A reaction mechanism for the two pathways was proposed and incorporated into a deterministic simulation, showing that the mechanism can explain experimentally measured 7OH-C3CA yields with a constant conversion factor of 4.7% from •OH scavenging to 7OH-C3CA production, unless t-BuOH was added.