Geometrical Effects on Intramolecular Quenching of Aromatic Ketone (π,π*) Triplets by Remote Phenolic Hydrogen Abstraction
Geometrical Effects on Intramolecular Quenching of Aromatic Ketone (π,π*) Triplets by Remote Phenolic Hydrogen Abstraction
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DOI：
10.1021/ja991207z
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发表时间：
1999-12
影响因子：
15
通讯作者：
E. C. Lathioor;and William J. Leigh;M. S. Pierre
中科院分区：
文献类型：
--
作者：
E. C. Lathioor;and William J. Leigh;M. S. Pierre
利用激光闪光光解技术研究了一系列带有远程酚基的烷氧基苯乙酮衍生物的光化学。所述化合物具有经由间-或对-氧乙基键连接至羰基发色团的对-或间-酚部分的结构，并且各自具有π，π* 构型的最低三重态。相应的甲氧基取代的化合物也进行了检查。的三重态寿命的酚酮的氧乙基间隔基的羰基和酚部分的连接（Meta或帕拉）的位置而变化，表明一个非常强的依赖性的几何因素的分子内H-抽象率。例如，在室温下，由于快速的分子内H-提取，帕拉，对位'-连接的酚酮在干燥的MeCN溶液中的寿命为τT ≥ 12 ns，而Meta，间位'-衍生物在无限稀释时的寿命为τT ≥ 11.5 μs，并且没有可检测到的分子内反应性。只有0.03 M的水存在于...
The photochemistry of a series of alkoxyacetophenone derivatives bearing remote phenolic groups has been studied using laser flash photolysis techniques. The compounds are structured with a p- or m-phenolic moiety attached via a m- or p-oxyethyl linkage to the carbonyl chromophore, and each have a lowest triplet state of π,π* configuration. The corresponding methoxy-substituted compounds have also been examined. The triplet lifetimes of the phenolic ketones vary with the positions of attachment (meta or para) of the oxyethyl spacer to the carbonyl and phenolic moieties, indicating a very strong dependence of the rate of intramolecular H-abstraction on geometric factors. For example, the para,para‘-linked phenolic ketone has a lifetime τT ≈ 12 ns in dry MeCN solution at room temperature due to rapid intramolecular H-abstraction, while the meta,meta‘-derivative exhibits a lifetime τT ≥ 11.5 μs at infinite dilution and no detectable intramolecular reactivity. The presence of as little as 0.03 M water in the ...