Spectroscopic Tracking of Structural Evolution in Ultrafast Stilbene Photoisomerization
Satoshi Takeuchi,1
Sanford Ruhman,2
Takao Tsuneda,3
Mahito Chiba,4
Tetsuya Taketsugu,5
Tahei Tahara1*
Understanding a chemical reaction ultimately requires the knowledge
of how each atom in the reactants moves during product formation.
Such knowledge is seldom complete and is often limited to an
oversimplified reaction coordinate that neglects global motions
across the molecular framework. To overcome this limit, we recorded
transient impulsive Raman spectra during ultrafast photoisomerization
of
cis-stilbene in solution. The results demonstrate a gradual
frequency shift of a low-frequency spectator vibration, reflecting
changes in the restoring force along this coordinate throughout
the isomerization. A high-level quantum-chemical calculation
reproduces this feature and associates it with a continuous
structural change leading to the twisted configuration. This
combined spectroscopic and computational approach should be
amenable to detailed reaction visualization in other photoisomerizing
systems as well.
2 Institute of Chemistry, Hebrew University, Jerusalem 91904, Israel.
3 School of Engineering, University of Tokyo, Tokyo 113-8656, Japan.
4 National Institute of Advanced Industrial Science and Technology, Tsukuba 305-6568, Japan.
5 Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
* To whom correspondence should be addressed. E-mail: tahei{at}riken.jp
