The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction

T. J. A. Wolf, D. M. Sanchez, J. Yang, R. M. Parrish, J.P.F. Nunes, M. Centurion, R. Coffee, J. P. Cryan, M. Gühr, K. Hegazy, A. Kirrander, R. K. Li, J. Ruddock, X. Shen, T. Vecchione, S. P. Weathersby, P. M. Weber, K. Wilkin, H. Yong, Q. ZhengX. J. Wang, M. P. Minitti, T. J. Martínez

Research output: Contribution to journalArticlepeer-review


The ultrafast photoinduced ring-opening of 1,3-cyclohexadiene constitutes a textbook example of electrocyclic reactions in organic chemistry and a model for photobiological reactions in vitamin D synthesis. Here, we present direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and sub-Ångström length scale by megaelectronvolt ultrafast electron diffraction. We follow the carbon-carbon bond dissociation and the structural opening of the 1,3 cyclohexadiene ring by direct measurement of time-dependent changes in the distribution of interatomic distances. We observe a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to steepening of the electronic potential gradient towards the product minima. The ring-opening motion transforms into rotation of the terminal ethylene groups in the photoproduct 1,3,5-hexatriene on the sub-picosecond timescale.
Original languageEnglish
Pages (from-to)504–509
Number of pages6
JournalNature Chemistry
Early online date15 Apr 2019
Publication statusPublished - Jun 2019


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