TY  - JOUR
A1  - Wolf, Thomas J. A.
A1  - Sanchez, David M.
A1  - Yang, J.
A1  - Parrish, R. M.
A1  - Nunes, J. P. F.
A1  - Centurion, M.
A1  - Coffee, R.
A1  - Cryan, J. P.
A1  - Gühr, Markus
A1  - Hegazy, Kareem
A1  - Kirrander, Adam
A1  - Li, R. K.
A1  - Ruddock, J.
A1  - Shen, Xiaozhe
A1  - Vecchione, T.
A1  - Weathersby, S. P.
A1  - Weber, Peter M.
A1  - Wilkin, K.
A1  - Yong, Haiwang
A1  - Zheng, Q.
A1  - Wang, X. J.
A1  - Minitti, Michael P.
A1  - Martinez, Todd J.
T1  - The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction
JF  - Nature chemistry
N2  - 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. Although the relaxation from the photoexcited electronic state during the ring-opening has been investigated in numerous studies, the accompanying changes in atomic distance have not been resolved. Here we present a direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and subangstrom length scale using megaelectronvolt ultrafast electron diffraction. We followed the carbon-carbon bond dissociation and the structural opening of the 1,3-cyclohexadiene ring by the direct measurement of time-dependent changes in the distribution of interatomic distances. We observed a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to a 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 subpicosecond timescale.
KW  - Organic chemistry
KW  - Photochemistry
KW  - Physical chemistry
KW  - Theoretical chemistry
Y1  - 2019
U6  - https://doi.org/10.1038/s41557-019-0252-7
SN  - 1755-4330
SN  - 1755-4349
VL  - 11
IS  - 6
SP  - 504
EP  - 509
PB  - Nature Publ. Group
CY  - London
ER  -