Design of Reactivity of Organic Cation Radicals Generated by Photoinduced Electron Transfer

本文研究了溶液中光敏电子转移产生的有机阳离子自由基的反应性设计。敏化剂包括2，4，6-三苯基吡喃盐(TPP)、2，4，6-三苯基硫代吡喃盐(STPP)和9，10-二氰基菲(DCA)1。首先，用TPP、STPP和/或DCA生成二芳基乙醇的阳离子自由基，并对产物进行比较。还进行了激光闪光光解，以阐明所涉及的反应中间体。结果表明，DCA和TPP敏化反应中含4，4-二甲氧基的二芳醛在有氧条件下的反应性有很大不同。其次，以DCA和TPP为增敏剂考察了四(4-甲基苯基)乙酮，发现两种反应均发生C-C键断裂，生成同类产物的机理不同。第三，研究了DCA和TPP敏化9，10-二氢菲在氧气存在下的去质子化反应。我们发现，TPP敏化氧化生成的是蒽，而DCA敏化生成的主要产物是蒽酮。结果用超氧阴离子(O_2^-)的酸性来解释。参与DCA敏化氧合，这在TPP敏化氧合中是不存在的。4.对二苯乙烯(St)、三苯乙烯(TPE)和四苯乙烯(Tepe)进行了TPP和DCA敏化氧化反应，产物比较表明，Tepe不与分子氧反应，而ST和TPE反应。所研究的所有烯烃均与O_2^-反应。从中间过氧基阳离子和二氧杂环己烷阳离子的稳定性方面讨论了观察到的烯烃阳离子自由基反应活性的差异。

The present study deals with the design of reactivity of organic cation radicals generated by photosensitized electron transfer in solution. The sensitizers employed are 2, 4, 6-triphenylpyrylium salt (TPP), 2, 4, 6-triphenylthiapyrylium salt (STPP), and 9, 10-dicyanoanthracene (DCA) 1. Firstly, cation radicals of diarylethanals were generated by TPP, STPP and/or DCA, and the products were compared. Laser flash photolysis has also been carried out to elucidate the reactive intermediates involved. The results suggest that the reacivity of diarylethanal having 4, 4-dimethoxy groups in the presence of oxygen is quite different between DCA and TPP sensitized reactions.2. Secondary, tetrakis (4-methylphenyl) ethanone was investigated with DCA and TPP as sensitizers, and it was found that the C-C bond cleavage occurred in both reactions with different mechanisms for the product formation of same kinds.3. Thirdly, Deprotonation of 9, 10-dihydroanthracene was studied in the presence of oxygen with DCA and TPP sensitization. We have found that TPP sensitized oxygenation gave anthracene whereas DCA sensitization gave anthrone as a primary, major product. The results were interpreted in terms of the acidity of superoxide radical anion (O_2^-.) involved in DCA sensitized oxygenation, which is absent in the TPP sensitized oxygenation. 4. Lastly, TPP and DCA sensitized oxygenation were carried out for stilbene (ST), triphenylethylene (TPE), and tetraphenylethylene (TEPE), and comparison of products revealed that TEPE does not react with molecular oxygen while ST and TPE react. All olefins studied were found to react with O_2^-. The observed difference of reactivity of olefin cation radicals were discussed in terms of stability of intermediate peroxy radical cations and dioxetane cation radicals.