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Studies on Energy Transfer with Spin Polarization Conservation in organic Photochemical Reactions

有机光化学反应中自旋极化守恒能量转移的研究

基本信息

批准号：
02453002
负责人：
IKEGAMI Yusaku
金额：
$ 3.97万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

The studies have been carried out to clarify the spin polarization conservation during triplet-triplet energy transfer in fluid solution. This phenomenon first demonstrated by us in 1984 for the photochemical cleavage of the dimers of neutral pyridinyl radicals is important to interpret molecular energy transfer mechanism. The following results have been obtained.1. Monomer-dimer equilibrium of pyridinyl radicals and its photochemistry. Neutral pyridinyl radicals are substantially in equilibrium with their dimers and the dimers show photochemical cleavage producing the radicals. Time-resolved EPR studies on the initial process disclosed the precursor of photolysis to be the singlet excited state. On the other hand, in the presence of an appropriate triplet sensitizer, triplet-triplet energy transfer with spin polarization conservation occurred leading to the generation of the radical through excited triplet state. Detailed studies on many pyridinyl dimers established a characteristic chemistry of pyridinyl radicals.2. Spin polarization conservation during the intramolecular triplet-triplet energy transfer. This phenomenon was successfully demonstrated by the measurements of transient triplet EPR spectra for two types of spiran compounds containing energy-donor and acceptor moieties. Spin alignment is conserved in the molecular frame and high field approximation can not explain the spin polarization pattern of the specatra.3. Other photochemical processes. The photochemical initial processes have been clarified for the following titles : (1) CIDEP studies on radicals produced from photochemical reactions of some aromatic carbonyl compounds ; (2) Time-resolved EPR studies on photochemical hydrogen abstraction reactions of 4-substituted pyridines ; (3) Time-resolved EPR study on the excited triplet state of non-phosphorescent tropone.

本文研究了流体溶液中三重态-三重态能量传递过程中的自旋极化守恒。我们在1984年首次在中性吡啶基自由基二聚体的光化学裂解中证明了这一现象，这对解释分子能量传递机制具有重要意义。得到了以下结果：1。吡啶基自由基的单体-二聚体平衡及其光化学。中性吡啶基自由基与其二聚体基本处于平衡状态，二聚体发生光化学裂解产生自由基。初始过程的时间分辨EPR研究揭示了光解的前体是单线态激发态。另一方面，在适当的三重态敏化剂存在下，发生了具有自旋极化守恒的三重态-三重态能量转移，导致自由基通过激发态产生。对许多吡啶基二聚体的详细研究建立了吡啶基自由基的特征化学。分子内三重态-三重态能量传递过程中的自旋极化守恒。这一现象通过测量两类含能量供体和受体的螺旋化合物的瞬态三重态EPR谱成功地证明了。自旋排列在分子框架内是保守的，高场近似不能解释光谱的自旋极化模式。其他光化学过程。阐明了光化学初始过程的几个题目：(1)一些芳香羰基化合物光化学反应产生自由基的CIDEP研究；(2) 4-取代吡啶光化学吸氢反应的时间分辨EPR研究；(3)非磷光tropone激发态的时间分辨EPR研究。