Synthesis and studies of phenothiazine based AIE fluorogens

Phenothiazine based AIE fluorogens linked to phenyl and tetraphenylethylene groups are reported. The N-butylphenothiazine and N-phenylphenothiazine have been substituted at 3,7-positions with phenyl or tetraphenylethylene (TPE) groups. All the target molecules have been characterized by H-1 and C-13 NMR, and mass spectrometry. The UV-Vis absorption, fluorescence and aggregation induced emission (AIE) properties of target molecules have been studied. Typically, the phenyl and TPE substituted phenothiazine molecules exhibit strong absorption band (lambda(abs) = 331 to 358 nm) in THF. Also, weak emission is observed in THF (lambda(em) = 405 to 531 nm) for these compounds; due to AIE phenomenon in water/THF mixture (f(w)>= 70%) the emission intensity is drastically enhanced upon aggregation. Bioimaging studies in A549 cells reveal cytoplasmic distribution of the 3,7-diphenylphenothiazine derivatives with >= 90% cell viability.