Formation of oxazine dye by photochemical reaction of N-acyl oxazine derivatives

The synthesis and photochemical reaction mechanism of N-benzoyl oxazine derivatives have been investigated. The synthesized materials were found to be photosensitive and capable of generating oxazine dye upon light irradiation. The initial reactions were found to include homolytic bond cleavage between the oxazine nitrogen and benzoyl carbon atoms proceeding through the excited singlet state and the formation of oxazine and benzoyl radicals. Subsequent reaction steps include direct electron transfer between two oxazine radicals or disproportionation of the oxazine dimer species formed through the recombination of two oxazine radicals. These reactions lead to the formation of the oxazine dye cation and anion pair.