北京大学刘运全团队报道了光离环丙烷中Jhhn-Teller畸变的超快成像和相关质子迁移。相关研究成果发表在2024年3月26日出版的《美国化学会杂志》。

Jahn–Teller（JT）畸变是分子和凝聚相物质的基本过程之一。对于具有高度对称性的光离子化有机分子，JT效应导致某些电子构型的几何不稳定性，从而对随后的异构化和质子迁移过程产生重大影响。

利用飞秒泵浦-探针库仑爆炸方法，研究人员探测了单价环丙烷阳离子（C₃H₆⁺）因质子迁移引起的异构化动力学过程，揭示了质子迁移与JT畸变之间的关系。研究发现，C₃H₆⁺阳离子从D³h对称的等边三角形几何结构演变为通过两个细长的C–C键形成的锐角三角形（JT1），或通过单个细长的C-C键（JT2）形成的钝角三角形。

JT1途径不涉及质子迁移，而JT2途径驱动质子迁移，可以映射到库仑爆炸的间接离解通道中。时间分辨实验表明，这两种JT途径之间的延迟时间可以大到～600fs。在JT畸变之后，环丙烷阳离子经历随后的结构演变，这带来了更多种类的离解通道。

附：英文原文

Title: Ultrafast Imaging of Jahn–Teller Distortion and the Correlated Proton Migration in Photoionized Cyclopropane

Author: Jiguo Wang, Bowen Dong, Ming Zhang, Yongkai Deng, Xiaopeng Jian, Zheng Li, Yunquan Liu

Issue&Volume: March 26, 2024

Abstract: The Jahn–Teller (JT) distortion is one of the fundamental processes in molecules and condensed phase matters. For photoionized organic molecules with high symmetry, the JT effect leads to geometric instability in certain electron configurations and thus has a significant effect on the subsequent isomerization and proton migration processes. Utilizing the femtosecond pump–probe Coulomb explosion method, we probe the isomerization dynamics process of a monovalent cyclopropane cation (C3H6+) caused by proton migration and reveal the relationship between proton migration and JT distortion. We found that the C3H6+ cation evolves from the D3h symmetric equilateral triangle geometry either to the acute triangle via two elongated C–C bonds (JT1) or to the obtuse triangle via a single elongated C–C bond (JT2). The JT1 pathway does not involve proton migration, while the JT2 pathway drives proton migration and can be mapped into the indirect dissociation channel of Coulomb explosion. The time-resolved experiment indicates that the delay time between those two JT pathways can be as large as ～600 fs. After the JT distortion, the cyclopropane cation undergoes a subsequent structural evolution, which brings a greater variety of dissociation channels.

DOI: 10.1021/jacs.3c13999

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.3c13999