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New Development in Nonradiative Transition by a Thermal Lensing Method at High Pressure

高压热透镜法非辐射跃迁的新进展

基本信息

批准号：
10640495
负责人：
TANAKA Fujio
金额：
$ 2.18万
依托单位：
Osaka Prefecture University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The mechanism for the nonradiative transition from the first excited singlet state was investigated by determining the quantum yield of triplet state formation with a time-resolved thermal lensing. The first group of molecules studied was anthracene carbonyl compounds. The triplet yield for 9-acetylanthracene was approximately unity in solvents besides alcoholic solvents, indicating that the nonradiative deactivation proceeds only through intersystem crossing and the internal conversion process is absent. In contrast, the triplet yield for 9-benzoylanthracene was 0.2 in methylcyclohexane, indicating that the internal conversion is a main nonradiative process, and the triplet yield was strongly dependent on the solvent, showing a tendency that the contribution of internal conversion is smaller in polar solvents. The occurrence of internal conversion was also found out for anthracene carbonyl compounds such as 9-bromo-10-benzoylanthracene, 9-cyano-10-benzoylanthracene and 9-naphthoylanthracene.The instrument for thermal lensing at high pressure was constructed, and thermal lens signals were measured for 9-acetylanthracene and 9-benzoylanthracene in methylcyclohexane at pressures up to 4000 atm. The triplet yield for 9-acetylanthracene increased with pressure, and this result cannot be theoretically explained because the triplet yield is already unity at 1 atm. It must be examined whether the problem inherent to the measurement at high pressures is present. The triplet yield for 9-benzoylanthracene increased remarkably with pressure, indicating that the contribution of internal conversion is decreased by pressure.In measurements at a normal pressure for other carbonyl aromatic molecules such as acetylnaphthalene, benzoylnaphthalene, acetylphenanthrane and acetylpyrene, the contribution of internal conversion was confirmed. Further, the occurrence of internal conversion for 9,10-dimethoxyanthracene in polar solvents was found out.

通过使用时间分辨热透镜确定三重态形成的量子产率，研究了从第一激发单重态的非辐射跃迁的机制。研究的第一组分子是蒽羰基化合物。除醇溶剂外，9-乙酰蒽的三线态产率在溶剂中近似一致，表明非辐射失活仅通过系间交叉进行，并且不存在内部转化过程。相比之下，9-苯甲酰基蒽在甲基环己烷中的三重态产率为0.2，表明内转化是主要的非辐射过程，并且三重态产率强烈依赖于溶剂，显示出在极性溶剂中内转化的贡献较小的趋势。 9-溴-10-苯甲酰蒽、9-氰基-10-苯甲酰蒽、9-萘甲酰蒽等蒽羰基化合物也发现了内转化的发生。搭建了高压热透镜仪，测量了9-乙酰蒽和9-苯甲酰蒽的热透镜信号。甲基环己烷压力高达 4000 atm。 9-乙酰蒽的三重态产率随着压力的增加而增加，并且该结果无法从理论上解释，因为三重态产率在1个大气压下已经是统一的。必须检查是否存在高压测量固有的问题。 9-苯甲酰蒽的三线态收率随着压力的增加而显着增加，这表明内转化的贡献随着压力的增加而减小。在常压下对乙酰萘、苯甲酰萘、乙酰菲和乙酰芘等其他羰基芳香族分子的测量中，证实了内转化的贡献。此外，发现9，10-二甲氧基蒽在极性溶剂中发生内转化。