Photosensitized [2+2] cycloreversion reactions of arylated cage compounds in nonpolar solvents. Highly efficient adiabatic exciplex isomerization
Photosensitized [2+2] cycloreversion reactions of arylated cage compounds in nonpolar solvents. Highly efficient adiabatic exciplex isomerization
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芳基化笼状化合物在非极性溶剂中的光敏[2 2]环化回复反应。
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
T. Mukai
中科院分区：
文献类型：
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作者：
E. Hasegawa;K. Okada;H. Ikeda;Y. Yamashita;T. Mukai
报道了几种氰基芳烃为增敏剂的芳基化笼型化合物1与二烯2的光敏[2+2]环还原反应。在乙腈中，1a通过有效的阳离子-自由基链过程异构化为2a。相反，1a到2a的异构化是通过苯中的外络合物进行的。有趣的是，在1a猝灭的荧光中观察到的激复合体发射最大值与2a相同。在不同溶剂中的一系列芳基化笼形化合物1a-d和二烯2a-d中也观察到这种巧合。这些观察结果与反应和异构体发射猝灭实验的结果一起清楚地证明了1到2的绝热异构体异构化的发生。通过比较观察到的异构体发射强度与二烯异构体发射强度得到绝热过程的效率（ea）相当高，在某些情况下几乎可以量化。随着笼形化合物1a-d的氧化电位（e 1/2 ox）的降低，敏化剂的还原电位（e 1/2 red）的增加，溶剂极性（e 1/2 red）的增加，ea值也随之增加
Photosensitized [2+2] cycloreversion reactions of arylated cage compounds 1 to dienes 2 using several cyanoaromatics as sensitizers are reported. In acetonitrile, 1a, isomerized to 2a via an efficient cation-radical chain process. In contrast, the isomerization of 1a to 2a proceeded via an exciplex in benzene. Interestingly, the exciplex emission maximum observed in the fluorescence quenching by 1a was the same as that by 2a. Such a coincidence was also observed in a series of arylated cage compounds 1a-d and dienes 2a-d in various solvents. These observations together with the results obtained from reaction and exciplex emission quenching experiments clearly demonstrated the occurrence of adiabatic exciplex isomerization of 1 to 2. Efficiencies (A e ) of the adiabatic process obtained by comparing the intensities of the observed exciplex emissions with those of diene exciplex emissions were quite high and became almost quantitative in some cases. A e values were found to increase as (1) the oxidation potentials (E 1/2 ox ) of cage compounds 1a-d decreased, (2) the reduction potentials (E 1/2 red ) of sensitizers increased, and (3) the solvent polarity (E T ) increased