Synthesis of novel tryptanthrin hydrazide hydrazones for photophysical and biological applications

The synthesis and characterization of novel tryptanthrin hydrazide hydrazones along with their photophysical and biological applications are described. Comprehensive photophysical studies revealed that the chloro derivative of tryptanthrin hydrazide hydrazone (3b) functions as a selective and sensitive fluorescent chemosensor for picric acid (PA) detection with a lowest detection limit of 0.012 μM, maintaining great resistance to interference from other nitro aromatic compounds (NACs). The mechanism of quenching involves (i) inner filter effect (IFE) and (ii) intermolecular hydrogen bond interactions; both mechanisms are supported by density functional theory (DFT) calculations computed at B3LYP/6–311 + G(d,p) level of theory. Analysis of real samples and on-site test strip detection of PA underscore the capability of 3b as a reliable sensor for PA, with promising applications in environmental monitoring and security-related detection. In a separate study, anti-tubercular (anti-TB) activity of the compounds were also evaluated and it was found that 3d-h exhibited very low MIC of 0.125–16 μg mL−1 (against Mtb H37Rv (ATCC 27294)), out of which 3d & 3e showed highest selectivity index (SI) of >200 and 160 respectively.