Photostability of Phenoxazine Derivatives

Abstract Phenoxazine is a commonly used molecular building block, for example in optoelectronic applications and pharmaceuticals. However, it is highly susceptible to rapid photodegradation, especially in halogenated solvents. In the present study, we identify the degradation products in both halogenated and non‐halogenated solvents by UV/Vis absorption, NMR spectroscopy and mass spectrometry. We also propose a substitution strategy aimed at effectively suppressing the high photoreactivity. Kinetic studies show that the quantum yield of photodegradation φ differs by a factor of more than 1000 between trisubstituted derivatives and N‐substituted phenoxazine.