Photoinduced Isomerism of Stilbenes: Picosecond Timescale Results

摘要: It is well known that substituted ethylene can undergo cis-trans isomerism following optical excitation. A large literature already exists on this topic and the particular case of stilbenes (1,2-diphenylethylenes) was recently reviewed by Saltiel coworkers [1]. Phenyl ethylenes have received considerable attention from photochemists because their spectra are in near ultraviolet, readily accessible to traditional light sources. Although ground work for understanding photoisomerism process solutions laid basis conventional (pre-laser) experiments [1,2] Intrinsic molecular steps Involved now vapor phase studies be subnanosecond [3,4]. The basic model a twisted, less conjugated form stilbene formed excitation [5]. This twisted may then relaxation processes result both cis trans structures [6]. effect solvent slow down isomerization at sufficiently low temperature or high viscosity rate found even slower than radiative [7]. fluorescent properties system therefore used monitor isomerization. [8,9] shown principal photochemistry arises singlet excited surface although triplet state involved when sensitizers present [9,10]. There also evidence not exclusive photoprocess since small yields rearranged species been reported [11], but such will considered further article.