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Charge Transfer Interaction and Complex Formation of Free Radicals

电荷转移相互作用和自由基的复杂形成

基本信息

批准号：
11640514
负责人：
OBI Kinichi
金额：
$ 2.3万
依托单位：
Japan Women's University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

In this project, the complex formation of the benzophenone ketyl radical with amines and the decay rates of radical complexes have been studied with the laser flash photolysis technique. The benzophenone ketyl radicals were formed by the hydrogen atom abstraction reaction of triplet benzophenone from solvent molecules, cyclohexane, or amines. The excitation laser used was a 308 nm XeCl excimer laser. When aliphatic amines were added to the cyclohexane solutions of benzophenone, the peak position of transient absorption shifted to red by 5-10 nm and the spectral shapes became broad compared with that of free benzophenone ketyl radical. These facts indicate that the ketyl radical makes complexes with aliphatic amines. On the other hand, one of the aromatic amines, N,N-dimethylaniline, did not show the transient absorption of the ketyl radial, which suggested that the ketyl radical would react with N,N-dimethylaniline.The decays of complexes of the ketyl radical were measured by the trans … More ient absorption at the peak position. The decay rate became slow by the complex formation ; under our experimental conditions, the free ketyl radical almost completely disappeared within about 30μs, but the complexes of amine-ketyl radical survived after 40μs. The kinetic analyses were carried out on triethylamine and tri-n-propylamine complexes. The decays of both radical complexes followed the second order decay law, which indicates that the radical complexes disappeared through the recombination reaction forming benzpinacole like the free ketyl radicals do. The rate constants obtained are 0.5 and 0.45 times smaller than that of the free ketyl radical, respectively. It is revealed that the rate constant decreases about half of the free ketyl radical by the complex formation and that of the tri-n-propylamine complex is smaller than that of triethylamine complex, indicating more bulky amine makes the recombination rate slower. It is concluded that the amines work to hinder the reaction center and supress the recombination reaction. Less

本项目利用激光闪光光解技术研究了二苯甲酮酮自由基与胺类化合物的络合物形成及络合物的衰减速率。三重态二苯甲酮从溶剂分子、环己烷或胺中夺取氢原子形成二苯甲酮基自由基。使用的激发激光器是308 nm XeCl准分子激光器。当二苯甲酮的环己烷溶液中加入脂肪胺时，其瞬态吸收峰位比自由基的吸收峰位红移5-10 nm，光谱形状变宽。这些事实表明，酮基自由基与脂肪胺形成络合物。另一方面，芳香胺N，N-二甲基苯胺没有出现酮自由基的瞬态吸收，这表明酮自由基会与N，N-二甲基苯胺反应。 ...更多信息在峰值位置的吸收。在我们的实验条件下，酮自由基在约30μs内几乎完全消失，而胺-酮自由基复合物在40μs后仍然存在。对三乙胺和三正丙胺络合物进行了动力学分析。两种自由基复合物的衰减均遵循二级衰减规律，表明自由基复合物与自由基一样，通过重组反应生成苯频哪醇而消失。得到的速率常数分别为自由酮基的0.5和0.45倍。结果表明，络合物的形成使酮自由基的速率常数降低了约一半，且三正丙胺络合物的速率常数小于三乙胺络合物的速率常数，表明体积较大的胺使复合速率变慢.结果表明，胺的存在阻碍了反应中心，抑制了复合反应。少