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Ultrafast Raman observation of the perpendicular intermediate phantom state of stilbene photoisomerization


Transcis photoisomerization is generally described by a model in which the reaction proceeds via a common intermediate having a perpendicular conformation around the rotating bond, irrespective of from which isomer the reaction starts. Nevertheless, such an intermediate has yet to be identified unambiguously, and it is often called the ‘phantom’ state. Here we present the structural identification of the common, perpendicular intermediate of stilbene photoisomerization using ultrafast Raman spectroscopy. Our results reveal ultrafast birth and decay of an identical, short-lived transient that exhibits a vibrational signature characteristic of the perpendicular state upon photoexcitation of the trans and cis forms. In combination with ab initio molecular dynamics simulations, it is shown that the photoexcited trans and cis forms are funnelled off to the ground state through the same, perpendicular intermediate.

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Fig. 1: Ultrafast photoisomerization of stilbenes.
Fig. 2: UV-FSRS of dmSB.
Fig. 3: Isotope effect on femtosecond time-resolved Raman data.
Fig. 4: AIMD simulation of dmSB photoisomerization.

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Data availability

The data supporting the findings of this study are available in the article or Supplementary Information. Source data are provided with this paper. Additional raw data are available from the corresponding author on reasonable request.


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This work was partly supported by JST, PRESTO grant number JPMJPR17P4 to H.K. and CREST grant number JPMJCR1902 to T. Taketsugu, and JSPS KAKENHI grant numbers JP16H04102 to S.T., and JP25104005 and JP21K18943 to T. Tahara.

Author information

Authors and Affiliations



H.K., S.T. and T. Tahara conceived and designed the research. H.K., Z.W., P.K., L.L. and S.T. performed spectroscopic measurements and analysed the data. M.O. synthesized trans- and cis-dimethyl-stilbene and their isotopomers. T. Tsutsumi, K.S. and T. Taketsugu performed theoretical calculations. H.K. and T. Tahara wrote the paper. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Tahei Tahara.

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The authors declare no competing interests.

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Nature Chemistry thanks Christopher Elles and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 Electronic structure of the perpendicular state.

Potential energy curves for the S0, S1, and S2 states, colored by each dipole moment, at the SF-TDDFT(BHHLYP)/6-31 G(d) level of theory. The behavior of the potential energy of the S1 state changes near (S1)twist, where the dipole moment suddenly increases, indicating that the perpendicular state is a zwitterionic state.

Source data

Extended Data Fig. 2 Ultraviolet resonance femtosecond stimulated Raman spectrum of parent cis-stilbene.

UV-FSRS spectrum of parent cis-stilbene in acetonitrile (1 mM) obtained at 1 ps after photoexcitation at 266 nm. The Raman pump wavelength was tuned to 354 nm, which is rigorously resonant with the UV transient absorption band. The UV-FSRS spectrum of cis-dmSB at 1 ps is also shown for comparison. The white-shaded regions are disturbed by the imperfect subtraction of the solvent Raman bands.

Source data

Supplementary information

Supplementary Information

Supplementary Figs. 1–13, Sections 1–9 and discussion.

Source data

Source Data Fig. 1

Time-resolved absorption data.

Source Data Fig. 2

Time-resolved Raman data.

Source Data Fig. 3

Time-resolved Raman data of the isotopomers.

Source Data Fig. 4

AIMD simulation data.

Source Data Extended Data Fig. 1

Analysis of the dipole moment along the reaction pathways.

Source Data Extended Data Fig. 2

Time-resolved Raman data of parent stilbene.

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Kuramochi, H., Tsutsumi, T., Saita, K. et al. Ultrafast Raman observation of the perpendicular intermediate phantom state of stilbene photoisomerization. Nat. Chem. 16, 22–27 (2024).

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