Barrierless photoisomerisation of the "simplest cyanine": joining computational and femtosecond optical spectroscopies to trace the full reaction path.
Phys Chem Chem Phys
; 14(38): 13350-64, 2012 Oct 14.
Article
em En
| MEDLINE
| ID: mdl-22933313
ABSTRACT
The photoisomerisation of 1,1'-diethyl-2,2'-pyridocyanine, regarded by Brooker as the simplest cyanine, is examined in methanol by time-resolved experiments and PCM/TD-CAM-B3LYP calculations. Femtosecond transient absorption, fluorescence upconversion, and stimulated Raman scattering, all with broadband coverage, provide a panoramic view of the photoreaction. On the computational side, evolving distributions on an S(1) minimum-energy path are obtained by solving the Smoluchowski equation for drift and diffusion of torsional motion. Absorption and fluorescence bandshapes are calculated and compared to the observations; near-quantitative agreement implies that the entire S(1) path has been observed. Most importantly the global S(1) minimum, i.e. the perpendicular "phantom state" P*, can be identified and characterized in this way. Internal conversion of P* (3.7 ps), assisted by solvent equilibration, leads to the hot ground state. Within 5 ps, vibrational bands of cis and trans isomers are recognized with the help of calculated Raman spectra. The differences between observed and simulated spectra are discussed.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Quinolinas
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Phys Chem Chem Phys
Assunto da revista:
BIOFISICA
/
QUIMICA
Ano de publicação:
2012
Tipo de documento:
Article
País de afiliação:
Alemanha