Key Laboratory of Theoretical Chemistry of Environment, School of Environment, South China Normal University, Guangzhou 510006, P. R. China.
Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
Phys Chem Chem Phys. 2023 Mar 8;25(10):7417-7422. doi: 10.1039/d2cp05143e.
Donor-acceptor Stenhouse adducts (DASA) have recently emerged as a class of visible-light-induced photochromic molecular switches, but their photocyclization mechanism remains puzzling and incomplete. In this work, we carried out MS-CASPT2//SA-CASSCF calculations to reveal the complete mechanism of the dominant channels and possible side reactions. We found that a new thermal-then-photo isomerization channel, , EEZ → EZZ → EZE, other than the commonly accepted EEZ → EEE → EZE channel, is dominant in the initial step. Besides, our calculations rationalized why the expected byproducts ZEZ and ZEE are unobserved and proposed a competitive stepwise channel for the final ring-closure step. The findings here redraw the mechanistic picture of the DASA reaction by better accounting for experimental observations, and more importantly, provide critical physical insight in understanding the interplay between thermal- and photo-induced processes widely present in photochemical synthesis and reactions.
供体-受体 Sten豪斯加合物（DASA）最近成为一类可见光诱导的光致变色分子开关，但它们的光环化机制仍然令人费解且不完整。在这项工作中，我们进行了 MS-CASPT2//SA-CASSCF 计算，以揭示主要反应通道和可能的副反应的完整机制。我们发现，除了常见的 EEZ→EEE→EZE 通道外，一个新的热然后光异构化通道，即 EEZ→EZZ→EZE，在初始步骤中占主导地位。此外，我们的计算还解释了为什么预期的副产物 ZEZ 和 ZEE 未被观察到，并提出了最终闭环步骤的竞争性分步通道。这里的发现通过更好地解释实验观察结果重新绘制了 DASA 反应的机理图，更重要的是，为理解广泛存在于光化学合成和反应中的热诱导和光诱导过程之间的相互作用提供了关键的物理见解。
