Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Emil-Fischer-Str. 42, 97074 Würzburg, Germany.
J Am Chem Soc. 2023 Feb 15;145(6):3283-3288. doi: 10.1021/jacs.2c12266. Epub 2023 Feb 6.
-Stilbene (-St) is a well-known benchmark system for - photoisomerization. -St also produces 4a,4b-dihydrophenanthrene (DHP) in solution with a quantum yield of less than 0.19. The ring closure reaction, however, has never been identified for gaseous -St, and a recent computational simulation predicted the quantum yield of DHP to be only 0.04. In the present study, we identified an ultrafast ring closure reaction of gaseous -St for the first time using extreme ultraviolet time-resolved photoelectron spectroscopy. Surface hopping trajectory calculations at the SA3-XMS-CASPT2(2,2) level of theory reproduce the features of the observed time-resolved photoelectron spectra and predict the -St:DHP:-St branching ratio to be 0.55:0.41:0.04, in contrast with previous estimates. The results indicate that photoexcited -St favors ring closure over - isomerization under the isolated condition.
联苯（-St）是光异构化的知名基准体系。-St 在溶液中也会产生量子产率小于 0.19 的 4a,4b-二氢菲（DHP）。然而，气态 -St 从未发生过环闭合反应，最近的计算模拟预测 DHP 的量子产率仅为 0.04。在本研究中，我们首次使用极紫外时间分辨光电子能谱首次鉴定出气态 -St 的超快环闭合反应。SA3-XMS-CASPT2(2,2)理论水平的表面跳跃轨迹计算再现了观察到的时间分辨光电子能谱的特征，并预测 -St:DHP:-St 分支比为 0.55:0.41:0.04，与之前的估计形成对比。结果表明，在孤立条件下，光激发的 -St 有利于环闭合而不是异构化。
