First excited singlet state photophysical properties

The pharmacological activity as well as the side effects of phenothiazine derivatives have been shown to often depend on the nature and position of substituents [4]. Since there is also a correlation between the molecular structure and the photophysical properties of these compounds, it is worthwhile to thoroughly examine their first excited singlet- and triplet-state characteristics. 

Interestingly, imides possess a photochemical behavior that is very similar to that of ketones. Especially, phthalimides behave like phenyl ketones with respect to some of their photophysical properties. Despite many similarities there are at least three important differences. First, phthalimides are more prone to photoelectron transfer (PET) processes than ketones. This property was very successfully applied in the synthesis of a variety of amino acid derivatives (see Section 6.2.3.2). Second, the cyclization of imides often affords 0,7V-acetals as primary products, and this obviously has some consequences for the stability and the follow-up reactions of these products. Third, in contrast to aryl ketones, phthalimides are not quantitatively converted into the triplet state, and thus they may react both from the singlet and the triplet excited state. 

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