1.1- diary lethylene

This chapter deals with the properties of the excited states of 1,2-diary lethylenes in general, with the effects caused by specific variation of reaction conditions on photochemical cis trans isomerization in condensed phase, and with the reaction mechanisms. In particular, the influence of substitution on the properties of excited states involved in cis trans isomerization in solution is examined. Besides various substituted stilbenes (which have been most extensively studied), styrylpyridines (StPs, azastilbenes) including some of their positively charged derivatives (quaternary stilbazolium salts), dipyridylethylenes (DPEs), styrylnaphthalenes (StNs), their pyridine analogues (NPEs), and some related compounds, such as dinaphthylethylenes (DNEs), are surveyed. Results on photochemical cis ttrans isomerization of stilbenes and other 1,2-diarylethylenes under direct (Section II) and sensitized (Section III) irradiation conditions are summarized, as well as their photophysical excited singlet and triplet state properties (Section IV) and some selected side reactions (Section V). The mechanistic section (Section VI) describes several photochemical isomerization routes. Characteristic photophysical and photochemical aspects of specific classes of substituted stilbenes are discussed and mechanistic schemes are critically examined with reference to their experimental basis. 

TABLE 16d Absorption Maxima and Lifetime of the Triplet of trans-l, 2-Diary lethylenes"... 

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