Spectroscopic investigations of vinyl-substituted 10H-phenothiazine

Different 10H-phenothiazine derivatives modified at their 3- and 3,7-positions with conjugated electron-deficient pyridine or pyridinium groups using ethenyl linkers are described. Spectral variations of 3-((E)-2-(Methylpyridium-4-yl)vinyl)-10H-phenothiazine iodide and 3,7-bis((E)-2-(Methylpyridium-4-yl)vinyl)-10H-phenothiazine diiodide, which are attributed to intramolecular charge transfer, electronic rearrangement and contact ion-pair mechanisms, were observed to be either base or ion dependent. Depending on the extent of deprotonation of the nitrogen atom in the 10-position of the phenothiazine core, donor–acceptor or push–pull systems provide fluorophore-switching and potential near infrared sensor application.