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CONTROL OF PHOTOCHEMICAL REACTIONS BY HYDROGEN BONDING

通过氢键控制光化学反应

基本信息

批准号：
08640666
负责人：
ARAI Tatsuo
金额：
$ 1.22万
依托单位：
UNIVERSITY OF TSUKUBA
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

We have investigated the effect of hydrogen bonding to control the efficiency and the mode of photochemical isomerization. Furthermore, novel photoinduced hydrogen atom transfer to give the tautomer have been studied.We found a co-operative effect of intramolecular hydrogen bonding and solvent to control the efficiency and the selectivity of photoisomerization in an olefin with a pyrrole ring and a quinoxaline ring (I). In benzene, I underwent one-way trans*cis photoisomerization due to the intramolecular hydrogen bonding. Thus, cis-I did not undergo cis-to-trans isomerization, but undergo intramolecular hydrogen atom transfer to give the tautomer as revealed by the observation of the fluorescence emission with considerably large Stokes-shift. One the other hand, the cis-to-trans isomerization prevails over trans-to-cis isomerization in methanol by making an intermolecular hydrogen bonding.In 2'-hydroxychalcone (II), we found a novel one-way cis*trans isomerization induced by the intramolecular hydrogen atom transfer in the triplet state based on the results by laser transient spectroscopy.We also found an novel effect of formyl group on the behavior of intramolecularly hydrogen bonded compound ; the introduction of the formyl group increased the efficiency of hydrogen atom transfer to give the tautomer. Thus, 2 [2- (2-pyridy) ethenyl] pyrrole-5-carboxaldehyde III with formyl group at the pyrrole ring exhibited considerably high quantum efficiency of fluorescence emission from the tautomer produced by intramolecular hydrogen atom transfer, although the intersystem crossing to the triplet state is also accelerated as revealed from the observation of the quantum chain process.

我们研究了氢键对光化学异构化效率和模式的控制作用。此外，我们还研究了光诱导氢原子转移反应生成互变异构体的新方法，发现分子内氢键和溶剂的协同作用控制了含吡咯环和喹喔啉环的烯烃的光异构化效率和选择性（I）。在苯中，由于分子内氢键的作用，我发生了单向的反 * 顺光异构化。因此，顺式-I没有经历顺式-反式异构化，但经历分子内氢原子转移，得到互变异构体，如通过观察具有相当大的斯托克斯位移的荧光发射所揭示的。另一方面，在甲醇中通过形成分子间氢键，顺式至反式异构化优于反式至顺式异构化。我们发现了一种新颖的单向顺式基于激光瞬态光谱的结果，我们讨论了分子内氢原子三重态转移引起的反式异构化，并发现了甲酰基对分子内氢行为的一种新的影响键合化合物甲酰基的引入增加了氢原子转移的效率，得到互变异构体。因此，在吡咯环上具有甲酰基的2-[2-（2-吡啶基）乙烯基]吡咯-5-甲醛III显示出相当高的荧光发射的量子效率，该荧光发射来自通过分子内氢原子转移产生的互变异构体，尽管如从量子链过程的观察所揭示的，到三重态的系统间交叉也被加速。