Unraveling the ability of electronically diverse 9H-carbazoles as potential fluorophores in cellular imaging applications with BSA binding affinities

Abstract

In the present study, fluorophores based on 9H-carbazole have been synthesized from readily accessible 2-nitrochalcones in a single-step reductive cyclization reaction with methyl acetoacetate. The molecular geometry was confirmed based on IR, NMR and mass analysis. The ground state geometry for all the synthesized compounds was optimized using DFT-based methods to explore the localization of frontier molecular orbitals in electronically diverse carbazoles. The photophysical studies revealed a higher Stokes shift for PPM 17 due to the presence of the naphthyl group at C-1 of carbazole. The high stability of PPM14, as evidenced by high chemical hardness, prompted us to explore its BSA binding affinity using fluorescence titration, synchronous,3-D fluorescence and energy transfer analysis. The probe (PPM 14) displayed a “turn-off” response in the presence of Fe3+ ions. The less cytotoxic behavior of PPM 14, its “turn-off” fluorescence response with Fe3+, and its utility in cell imaging application establish it as a potential small organic framework-based bio-sensor.