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Quick, M.* ; Berndt, F.* ; Dobryakov, A.L.* ; Ioffe, I.N.* ; Granovsky, A.A.* ; Knie, C.* ; Mahrwald, R.* ; Lenoir, D. ; Ernsting, N.P.* ; Kovalenko, S.A.*

Photoisomerization dynamics of stiff-stilbene in solution.

J. Phys. Chem. B 118, 1389-1402 (2014)
DOI PMC
Open Access Green as soon as Postprint is submitted to ZB.
Photoinduced isomerization of 1,1′-bis-indanyliden (stiff-stilbene) in solution was studied with broadband transient absorption and femtosecond Raman spectroscopies, and by quantum-chemical calculations. Trans-to-cis S 1 isomerization proceeds over a 600 and 400 cm-1 barrier in n-hexane and acetonitrile, respectively. The reaction develops on multiple time scales with fast (0.3-0.4 ps) viscosity-independent and slower (2-26 ps) viscosity-dependent components. In the course of intramolecular torsion (which should be the main reaction coordinate) some excited molecules pass through the perpendicular conformation P and reach the cis geometry, to be temporarily trapped there. Subsequently they relax back to P and further to the ground state S0. The cis-to-trans isomerization reveals ultrafast (0.06 ps) oscillatory relaxation followed by 13 ps decay in n-hexane and 2 ps decay in acetonitrile, corresponding to barriers of 800 and 400 cm-1, respectively. Raman S0 and S1 spectra are reported and discussed. The perpendicular conformation P was not detected, possibly due to its low oscillator strength and short lifetime, or because of strong overlap with hot product spectra. XMCQDPT2 calculations locate a stationary S 1 point on the cis side and two perpendicular-pyramidalized stationary points, to be reached from the former over 300 and 680 cm -1 barrier. Implications for parent stilbene are discussed; in this case we also see evidence for the trans-to-cis adiabatic path, as in stiff-stilbene. Very similar viscosity dependence for the two compounds supports the common isomerization pathway: torsion about the central double bond.
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Publication type Article: Journal article
Document type Scientific Article
Corresponding Author
ISSN (print) / ISBN 1520-6106
e-ISSN 1520-5207
Journal Journal of Physical Chemistry B
Quellenangaben Volume: 118, Issue: 5, Pages: 1389-1402 Article Number: , Supplement: ,
Publisher American Chemical Society (ACS)
Non-patent literature Publications
Reviewing status Peer reviewed
Institute(s) PPM-MEX-Molecular EXposomics (MEX)