ABSTRACT
Since the one-way cis → trans isomerization was discovered in several types of arylethenes, interest in the photochemical cis-trans isomerization has continued to grow in recent years [1-11]. Conventional two-way isomerization and highly selective photochemical cis-trans isomerization can take place on the singlet excited state as well as in the triplet excited state [11-15]. In this chapter, a concept for various types of cis-trans isomerization in the triplet state is described, mainly from the viewpoints of the modes of isomerization and the difference in potential energy surfaces of cis-trans isomerization.
