Rehybridization dynamics into the pericyclic minimum of an electrcyclic reaction imaged in real-time

• Published in: arXiv.org
• Main Authors: Liu, Yusong, Sanchez, David M, Ware, Matthew R, Champenois, Elio G, Yang, Jie, Nunes, J Pedro F, Attar, Andrew, Centurion, Martin, Cryan, James P, bes, Ruaridh G, Hegazy, Kareem, Hoffmann, Matthias C, Ji, Fuhao, Ming-Fu, Lin, Luo, Duan, Saha, Sajib K, Shen, Xiaozhe, Wang, Xijie, Martínez, Todd J, Wolf, Thomas J A
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 27.09.2022
• Subjects: Electron diffraction; Excitation; Internal conversion; Photochemical reactions; Physics - Chemical Physics; Ring opening; Wave packets
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2209.13691

Electrocyclic reactions are characterized by the concerted formation and cleavage of both {\sigma} and {\pi} bonds through a cyclic structure. This structure is known as a pericyclic transition state for thermal reactions and a pericyclic minimum in the excited state for photochemical reactions. However, the structure of the pericyclic geometry has yet to be observed experimentally. We use a combination of ultrafast electron diffraction and excited state wavepacket simulations to image structural dynamics through the pericyclic minimum of a photochemical electrocyclic ring-opening reaction in the molecule {\alpha}-terpinene. The structural motion into the pericyclic minimum is dominated by rehybridization of two carbon atoms, which is required for the transformation from two to three conjugated {\pi} bonds. The {\sigma} bond dissociation largely happens after internal conversion from the pericyclic minimum to the electronic ground state. These findings may be transferrable to electrocyclic reactions in general.