Spectral characterization, photophysics, and photochemistry of the four stereoisomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene

Using a synthetic strategy, based on retention of stereochemistry in the re agent cinnamaldehyde, the four geometrical isomers of 1-(2-anthryl)-4-pheny l-1,3-butadiene were obtained and chromatographically purified. Their struc tures were established by optical and nuclear magnetic spectrometry and con firmed by their photochemical behavior. Their excited state properties were investigated by stationary and pulsed fluorimetric techniques and by laser Bash photolysis. This paper reports the spectral characterization of the f our isomers and the photophysical and photochemical parameters obtained by irradiation in a nonpolar solvent at different temperatures. The important contribution of adiabatic pathways in the photoisomerization mechanism and the role of an upper excited singlet state in the relaxation properties are discussed. Indication of the presence of at least two conformers was obtai ned only when exciting at the extreme red onset region of the absorption sp ectrum.