Femtosecond S3-->S1 conversion and structural reorganisation of trans-3-phenylprop-2-enaldehyde and derivatives in solution.
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.
Department of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, Berlin, 12489, Germany. lustres@chemie.hu-berlin.de
J L Pérez
JL
Lustres
Vadim M
VM
Farztdinov
Sergey A
SA
Kovalenko
D000097:Acetonitriles / Q000737:chemistry*; D000171:Acrolein / Q000031:analogs & derivatives* / Q000737:chemistry; D006586:Hexanes / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D011789:Quantum Theory; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis; D013237:Stereoisomerism; D013997:Time Factors
D000097:Acetonitriles; D006586:Hexanes; D000171:Acrolein; C012843:cinnamaldehyde; C032159:acetonitrile