PHOTOCHEMICAL CIS TO TRANS ONE-WAY ISOMERIZATION OF STYRYLAZULENES ONTHEIR TRIPLET EXCITED-STATE - EXAMINATION OF ETHYLENES WITH NON-BENZENOID SUBSTITUENTS OF LOW TRIPLET ENERGIES
T. Karatsu et al., PHOTOCHEMICAL CIS TO TRANS ONE-WAY ISOMERIZATION OF STYRYLAZULENES ONTHEIR TRIPLET EXCITED-STATE - EXAMINATION OF ETHYLENES WITH NON-BENZENOID SUBSTITUENTS OF LOW TRIPLET ENERGIES, Bulletin of the Chemical Society of Japan, 67(6), 1994, pp. 1674-1679
1-Styrylazulene and 7-isopropyl-1,4-dimethyl-3-styrylazulene (3-styryl
guaiazulene) underwent one-way isomerization from the cis to the trans
isomer on triplet sensitization. Their triplet states as intermediate
s of the isomerization were observed by laser flash photolysis. Howeve
r, their excitation to either the lowest excited singlet state (S1) or
the second excited singlet state (S2) by direct irradiation afforded
photostationary mixtures comprising 98% of the trans and 2% the cis is
omers, which implies the participation of a singlet isomerization path
.