Photochemically triggered cheletropic formation of cyclopropenone (c-C 3 H 2 O) from carbon monoxide and electronically excited acetylene
Photochemically triggered cheletropic formation of cyclopropenone (c-C 3 H 2 O) from carbon monoxide and electronically excited acetylene
复制标题
光化学触发一氧化碳和电子激发乙炔形成环丙烯酮 (c-C 3 H 2 O)
DOI：
10.1039/d2cp01978g
复制
发表时间：
2022
影响因子：
3.3
通讯作者：
Kaiser, Ralf I.
中科院分区：
文献类型：
--
作者：
Wang, Jia;Kleimeier, N. Fabian;Johnson, Rebecca N.;Gozem, Samer;Abplanalp, Matthew J.;Turner, Andrew M.;Marks, Joshua H.;Kaiser, Ralf I.
半个多世纪以来，周环反应在增进我们对环加成、σ位移、基团转移反应和电环化反应的基本理解方面发挥了重要作用。然而，光化学激活螯合反应的基本机制仍然存在争议。在这里，我们报告了最简单的螯合反应：基态 18O-一氧化碳 (C18O, X1Σ+) 与 D2-乙炔 (C2D2) 进行 [2+1] 加成，在 5 K 下光化学激发第一激发三重态 (T1)、第二激发三重态 (T2) 和第一激发单重态 (S1)，从而形成 D2-18O-环丙烯酮(c-C3D218O)。在量子化学计算的支持下，我们的研究通过涉及乙炔在 5 K 下的 T2（非绝热）和 S1 态（绝热）的激发态动力学，为环丙烯酮的逐步螯合反应途径提供了有说服力的证据，而 T1 态则大力支持在弛豫到基态后直接解离的中间结构。低温冰实验与激发态计算之间的一致性表明光解实验与理论计算相结合如何能够在分子水平上理清与基本物理有机化学相关的多原子反应，从而提供一种通用策略来解开环状芳香族有机物中奇异的非平衡化学。与在冷分子云和恒星形成区域中冰覆盖的星际纳米颗粒（星际颗粒）上形成有机分子的传统自由基-自由基途径不同，环丙烯酮的光解形成改变了我们如何解释星际介质中复杂有机物的形成的看法，最终导致生物相关分子的分子前体。
For more than half a century, pericyclic reactions have played an important role in advancing our fundamental understanding of cycloadditions, sigmatropic shifts, group transfer reactions, and electrocyclization reactions. However, the fundamental mechanisms of photochemically activated cheletropic reactions have remained contentious. Here we report on the simplest cheletropic reaction: the [2+1] addition of ground state 18O-carbon monoxide (C18O, X1Σ+) to D2-acetylene (C2D2) photochemically excited to the first excited triplet (T1), second excited triplet (T2), and first excited singlet state (S1) at 5 K, leading to the formation of D2-18O-cyclopropenone (c-C3D218O). Supported by quantum-chemical calculations, our investigation provides persuasive testimony on stepwise cheletropic reaction pathways to cyclopropenone via excited state dynamics involving the T2 (non-adiabatic) and S1 state (adiabatic) of acetylene at 5 K, while the T1 state energetically favors an intermediate structure that directly dissociates after relaxing to the ground state. The agreement between experiments in low temperature ices and the excited state calculations signifies how photolysis experiments coupled with theoretical calculations can untangle polyatomic reactions with relevance to fundamental physical organic chemistry at the molecular level, thus affording a versatile strategy to unravel exotic non-equilibrium chemistries in cyclic, aromatic organics. Distinct from traditional radical–radical pathways leading to organic molecules on ice-coated interstellar nanoparticles (interstellar grains) in cold molecular clouds and star-forming regions, the photolytic formation of cyclopropenone as presented changes the perception of how we explain the formation of complex organics in the interstellar medium eventually leading to the molecular precursors of biorelevant molecules.