Femtosecond S3-->S1 conversion and structural reorganisation of trans-3-phenylprop-2-enaldehyde and derivatives in solution. |
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Authors: | J L Pérez Lustres Vadim M Farztdinov Sergey A Kovalenko |
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Institution: | Department of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, Berlin, 12489, Germany. lustres@chemie.hu-berlin.de |
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Abstract: | Photoinduced excited-state relaxation of trans-3-phenylprop-2-enaldehyde (cinnamaldehyde) and three derivatives was studied in hexane and acetonitrile with the pump-supercontinuum-probe technique. Transient spectra were measured with 50 fs resolution in the range 260-660 nm after S3<--S0 excitation at 288 nm. The early spectra reveal an ultrafast, 0.1-0.5 ps, interchange of intensity between two excited-state absorption (ESA) bands followed by a approximately 3 ps decay of ESA. This behaviour is interpreted with the help of semiempirical calculations, which indicate that the sub-picosecond evolution is consistent with S3-->S1 excited-state relaxation while the picosecond decay should be due to a structural intramolecular rearrangement. The latter may consist of a twist of the phenyl ring and rotation around the C==C bond to a perpendicular conformation which corresponds to the global energy minimum in the S1 state and serves as source for trans and cis isomers in the ground state. |
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Keywords: | femtochemistry photochemistry semiempirical calculations time‐resolved spectroscopy transition‐state theory |
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