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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photochemistry of the Stilbenes in Methanol. Trapping the Common Phantom Singlet State
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Photochemistry of the Stilbenes in Methanol. Trapping the Common Phantom Singlet State

机译：甲醇中斯蒂芬的光化学。 捕获常见的幻影单线状态

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A comparative study of the photochemistry of cis- and trans-stilbene in methanol shows that both isomers undergo methanol photoaddition giving similar yields of a-methoxybibenzyl in competition with cis-trans photoisomerization. Methanol addition occurs primarily following torsional relaxation of the lowest excited singlet states of each isomer, (l)c* and (1)t*, to a common twisted singlet excited state intermediate, (1)p*, initially called the phantom singlet state. The addition is consistent with the zwitterionic character of (1)p. Ether forms by direct 1,2-addition of CH 3 OH to the central carbon atoms and by 1,1-addition following rearrangement to 1-benzyl-1-phenylcarbene. Use of CD3OD and GC/MS (gas chromatographic/mass spectroscopic) analysis of the ether products revealed that the ratio of carbene/direct addition pathways is higher starting from cis-stilbene. We conclude that (1)p* formed from (1)c* is hotter than (1)p* formed from (1)t*. Surprisingly, except for favoring the carbene pathway, the use of higher energy photons (254 vs 313 nm) does not affect the overall ether quantum yield starting from cis-stilbene but significantly enhances both pathways starting from trans-stilbene. It appears that carbene formation and direct methanol addition to higher trans-stilbene excited state(s) compete with relaxation to S-1. Substitution of D for the vinyl Hs of stilbene enhances the direct addition pathway more than 2-fold and strongly suppresses the carbene insertion pathway, revealing a large, k(pc)(d0)/k(pe)(d2) : = 6.3, primary deuterium isotope effect in the carbene rearrangement. The 2-fold increase in the ether quantum yield is due primarily to a 2.75-fold increase in the lifetime of (1)p* on deuterium substitution of the vinyl hydrogens.
机译：甲醇中CIS-和反式芪的光化学的比较研究表明，两种异构体都经历了甲醇光学制剂，其在与CIS-TRASS光硅白化竞争中具有相似的A-甲氧基苄基的产率。甲醇添加主要发生在每个异构体，（1）C *和（1）T *的最低激发态态的扭转弛豫之后，常见的扭曲单次激发态中间体，（1）P *，最初被称为Phantom单线状态。添加与（1）p的两性离子特征一致。通过直接1,2-加入CH 3 OH至中央碳原子的醚形式，并在重排到1-苄基-1-苯基氨基之后1,1-1。使用CD3OD和GC / MS（气相色谱/质谱）分析醚产品的分析显示，从CIS-斯蒂烯开始，卡宾/直接添加途径的比例较高。我们得出结论（1）P *由（1）C *形成的p *比（1）P *由（1）T *形成。令人惊讶的是，除了有利于卡宾途径，使用较高能量的光子（254 Vs 313nm）不会影响从顺式 - 斯蒂烯开始的总醚量产率，但显着增强了从反式芪开始的两种途径。似乎卡贝蛋白形成和直接甲醇添加到更高的反式斯蒂烯激发态（S）与S-1放松竞争。芪的乙烯基HS的取代增强了2倍以上的直接加成途径，强烈抑制卡宾插入途径，露出大K（PC）（D0）/ K（PE）（D2）：= 6.3，初级氘同位素在卡宾重排中的作用。醚量子产率的2倍增加主要是由于乙烯基氢氘取代的寿命增加2.75倍。

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