Substitution dependent multi-color AIE behavior and ESIPT active A-D-A type triphenylamine supported bis unsymmetrical azine derivatives and their antibacterial activity

A facile synthetic approach afforded a new family of AIE active and ESIPT featured A-D-A (Acceptor-DonorAcceptor) type symmetrical triphenylamine centered bis unsymmetrical azine derivatives TPSA, TPHY, TPDS and TPOV. Depending upon the substituent in the periphery, all compounds displayed frail fluorescence in the solution state and exhibited strong multi-color luminescence character in aggregated/solid state. The results achieved from UV-visible absorption, emission and theoretical studies confirmed the existence of the intramolecular proton transfer phenomenon in the excited state (ESIPT). The experimental results affirmed AIE behavior present in the compounds and it might be due to the restriction of the intramolecular rotation (RIR) mechanism. The in vitro antibacterial activity of the compounds was also scrutinized against elected bacterial strains (B. subtilis, S. aureus, E. coli, and P. aeruginosa) in different concentrations (0.5 mM, 1 mM, 1.5 mM). The results revealed that all four compounds have excellent antibacterial activity at 1.5 mM than other concentrations tested in the present study. Further, the fluorescence feature of the compounds was explored via fluorescence microscopy to probe the microbes (Pseudomonas aeruginosa).

Automated summary

A new family of AIE active and ESIPT featured compounds were synthesized using a facile approach. These compounds displayed weak fluorescence in solution state and strong multi-color luminescence in aggregated/solid state. The experimental results confirmed the existence of AIE behavior in the compounds, possibly due to the restriction of intramolecular rotation. Additionally, the compounds showed excellent antibacterial activity against selected bacterial strains.