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

Y Liu; D M Sanchez; M R Ware; E G Champenois; J Yang; J P F Nunes; A Attar; M Centurion; J P Cryan; R Forbes; K Hegazy; M C Hoffmann; F Ji; M-F Lin; D Luo; S K Saha; X Shen; X J Wang; T J Martínez; T J A Wolf

doi:10.1038/s41467-023-38513-6

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

Nat Commun. 2023 May 18;14(1):2795. doi: 10.1038/s41467-023-38513-6.

Authors

Y Liu^#^{1

2}, D M Sanchez^#^{1

3

4}, M R Ware¹, E G Champenois¹, J Yang^{1

5

6}, J P F Nunes^{7

8}, A Attar⁵, M Centurion⁷, J P Cryan¹, R Forbes⁵, K Hegazy¹, M C Hoffmann⁵, F Ji⁵, M-F Lin⁵, D Luo⁵, S K Saha⁷, X Shen⁵, X J Wang⁵, T J Martínez^{9

10}, T J A Wolf¹¹

Affiliations

¹ Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.
² Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11790, USA.
³ Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA, 94305, USA.
⁴ Design Physics Division, Lawrence Livermore National Laboratory, Livermore, CA, USA.
⁵ SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.
⁶ Center of Basic Molecular Science, Department of Chemistry, Mong Man Wai Building of Science and Technology, S-1027 Tsinghua University, Beijing, China.
⁷ Department of Physics and Astronomy, University of Nebraska-Lincoln, Theodore Jorgensen Hall 208, 855 N 16th Street, Lincoln, NE, 68588, USA.
⁸ Diamond Light Source, Harwell Science Campus, Fermi Ave, Didcot, OX11 0DE, UK.
⁹ Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA. toddjmartinez@gmail.com.
¹⁰ Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA, 94305, USA. toddjmartinez@gmail.com.
¹¹ Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA. thomas.wolf@slac.stanford.edu.

^# Contributed equally.

Abstract

Electrocyclic reactions are characterized by the concerted formation and cleavage of both σ and π 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 α-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 π bonds. The σ 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.

Abstract

Grants and funding