1. Imaging the Photochemical Ring-Opening of 1,3-Cyclohexadiene by Ultrafast Electron Diffraction
- Author
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Wolf, T. J. A., Sanchez, D. M., Yang, J., Parrish, R. M., Nunes, J. P. F., Centurion, M., Coffee, R., Cryan, J. P., Gühr, M., Hegazy, K., Kirrander, A., Li, R. K., Ruddock, J., Shen, X., Veccione, T., Weathersby, S. P., Weber, P. M., Wilkin, K., Yong, H., Zheng, Q., Wang, X. J., Minitti, M. P., and Martínez, T. J.
- Subjects
Physics - Chemical Physics - Abstract
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-{\AA}ngstr\"om 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. Our work demonstrates the potential of megaelectronvolt ultrafast electron diffraction to elucidate photochemical reaction paths in organic chemistry.
- Published
- 2018
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