Photothermal tautomerization of a UV sunscreen (4-tert-butyl-4'-methoxydibenzoylmethane) in acetonitrile studied by steady-state and laser flash photolysis.
Photothermal tautomerization of a UV sunscreen (4-tert-butyl-4'-methoxydibenzoylmethane) in acetonitrile studied by steady-state and laser flash photolysis.
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DOI：
10.1021/jp312774e
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发表时间：
2013-02
期刊：
影响因子：
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通讯作者：
M. Yamaji;Mayumi Kida
中科院分区：
文献类型：
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作者：
M. Yamaji;Mayumi Kida
用稳态光解和激光闪光光解研究了4-叔丁基-4 '-甲氧基二苯甲酰甲烷（商品名Avobenzone）在乙腈中烯醇式和酮式的光热互变异构反应。酮形式是在烯醇仅在乙腈中光解时产生的，量子产率为0.014。测定了酮式的摩尔吸光系数。没有观察到从酮到烯醇形式的光互变异构。酮形式的激光闪光光解确认了三重态的形成。在黑暗中，酮形式经历热互变异构为烯醇，在295 K下的寿命为5.1 h。在乙腈中的烯醇化速率没有加速的醇和/或水的存在下，但随着温度的升高而增加，并遵循Arabius表达。确定了从酮式到烯醇式的烯醇化反应的活化能和频率因子。根据DFT计算得到的异构体和互变异构体的能态，确定了乙腈中光热互变异构反应的能量图。
The photothermal tautomerization processes between enol and keto forms of 4-tert-butyl-4'-methoxydibenzoylmethane (trade name, Avobenzone) in acetonitrile have been studied by steady-state and laser flash photolysis. The keto form is produced upon photolysis of the enol in only acetonitrile with a quantum yield of 0.014. The molar absorptivity of the keto form was determined. Phototautomerization from the keto to the enol form was not seen. Laser flash photolysis of the keto form recognized the formation of the triplet state. In the dark, the keto form underwent thermal tautomerization to the enol with a lifetime of 5.1 h at 295 K. The enolization rate in acetonitrile was not accelerated by the presence of alcohols and/or water but increased with increasing temperature and followed the Arrhenius expression. The activation energy and the frequency factor were determined for the enolization process from the keto to the enol form. On the basis of the energy states of the tautomers and isomers as estimated by DFT calculations, a schematic energy diagram was determined for the photothermal tautomerization processes in acetonitrile.