Photoaddition of water and alcohols to the anthracene moiety of 9-(2′-hydroxyphenyl)anthracene via formal excited state intramolecular proton transfer
Photoaddition of water and alcohols to the anthracene moiety of 9-(2′-hydroxyphenyl)anthracene via formal excited state intramolecular proton transfer
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DOI：
10.1021/ja039078g
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发表时间：
2004-06-30
影响因子：
15
通讯作者：
Wan, P
中科院分区：
文献类型：
--
作者：
Flegel, M;Lukeman, M;Wan, P
标题化合物通过一个羟基溶剂(H(2)O，MeOH，(Me)(2)CHOH)分子在菲的9位和10位上进行有效的光加成，得到可分离的三苯甲醇或三苯基甲醚类型的产物。该反应被认为是通过水介导的形式激发态分子内质子转移(ESIPT)从酚羟基到苯环的10位，生成一种邻苯二酮甲基中间体，该中间体可以通过纳秒激光闪光光解观察到，并且可以被亲核分子捕获。质子转移的“水接力”机制似乎是合理的，但不能直接用现有数据来证明。在氢化溶剂中的辐照导致光加成产物中亚甲基位置上的一个氢原子被掺入，并且回收的起始物质的10位上发生了部分的氢交换，这与所提出的正式激发态质子转移机制是一致的。在类似于5M水(在CH(3)CN或CH(3)OH中)时，氢交换和光加成反应达到最大量子效率，在没有羟基溶剂的情况下没有观察到反应，表明了这类ESIPT对溶剂组成的敏感性。
The title compound undergoes efficient photoaddition of a molecule of a hydroxylic solvent (H(2)O, MeOH, (Me)(2)CHOH) across the 9- and 10-positions of the anthracene moiety to give isolable triphenyl-methanol or triphenylmethyl ether type products. The reaction is believed to proceed via a mechanism involving water-mediated formal excited state intramolecular proton transfer (ESIPT) from the phenolic OH to the 10-position of the anthracene ring, generating an o-quinone methide intermediate that is observable by nanosecond laser flash photolysis, and is trappable with nucleophiles. A "water-relay" mechanism for proton transfer seems plausible but cannot be proven directly with the data available. Irradiation in deuterated solvents led to incorporation of one deuterium atom at the methylene position in the photoaddition product, and partial deuterium exchange of the 10-position of recovered starting material, consistent with the proposed formal excited state proton transfer mechanism. The deuterium exchange and photoaddition reach maximum quantum efficiency at similar to5 M water (in CH(3)CN or CH(3)OH), with no reaction observed in the absence of a hydroxylic solvent, demonstrating the sensitivity of this type of ESIPT to solvent composition.