Stilbene analogs in Hula-twist photoisomerization.
Photoisomerization of several cis- or Z-stilbene analogs and two E-analogs in low temperature organic glasses was examined. From a mechanistic view-point, the compounds can be divided into three types: (i) those giving identical Hula-twist (HT) and one-bond-flip (OBF) products, (ii) those giving a single HT product that is different (hence distinguishable) from the OBF product and (iii) those showing two distinct HT processes but only one OBF process. Examples for all three types of analogs are provided emphasizing the most informative Type-II (stilbene analogs with identical but unsymmetrically substituted phenyl rings), including linear as well as conformationally constrained compounds. Conditions necessary for establishing HT and OBF processes are defined. Proper choice and design of model systems are essential for establishing or eliminating HT mechanism(s) of isomerization.
Yang
Lan-Ying
LY
Department of Chemistry, University of Hawaii, 2545 The Mall, Honolulu, HI 96822, USA.
Harigai
Miki
M
Imamoto
Yasushi
Y
Kataoka
Mikio
M
Ho
Tong-Ing
TI
Andrioukhina
Elena
E
Federova
Olga
O
Shevyakov
Sergei
S
Liu
Robert S H
RS