J. Phys. Chem. 1993,97, 192&1923
1920
Cis-Trans Photoisomerization of Bis-stilbenes with Ethylene Bridges Ingjald Anger? KjeU !hndros,* Mikael Sundahl,’J and Olof Wennerstrtimt Departments of Organic and Physical Chemistry, Chalmers University of Technology, S-412 96 Gbteborg, Sweden Received: October 20, 1992; In Final Form: December 17, 1992
The mechanisms for Z-E photoisomerization of two bisstilbenes, 4,4’-bis(3,5-di-tert-butylstyryl)bibenzyl, 1, and [2.2]-4,4’-stilbenophane,2, have been studied. The isomerizations of ZZ1 and EE1 are similar to those of Z-and E-stilbene, respectively. On excitation of ZEl there is a competition between an energy transfer process from the E- to the 2-chromophore and isomerization. This results in a small quantum yield (
