Anthraquinone triplet state energy

The role of the triplet state in the cis-trans isomerization of stilbenes effected by photosensitizers, such as acetophenone, benzophenone, or anthraquinone, which have large So Ti excitation energies, was first revealed in Ref. [65]. Theoretical considerations and experimental data on intermolecular triplet-triplet energy transfer leading to the sensitized stilbene photoisomerization are described in Section 4.2.2. It was shown that data on positional dependence of the heavy-atom effect on the cis-trans photoisomerization of bromostilbenes were consistent with the fact that, in contrast to the para position, the meta position is near a node in the highest occupied and the lowest unoccupied MO of stilbene [66]. According to [67], internal and external heavy-atom effects induce phosphorescence in frans-stilbene... 

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