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.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call