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.
Lustres
J L Pérez
JL
Department of Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, Berlin, 12489, Germany. lustres@chemie.hu-berlin.de
Farztdinov
Vadim M
VM
Kovalenko
Sergey A
SA
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