A DSE–ESIPT-active organic luminogen for “turn-on” enantioselective recognition of chiral amino alcohols and selective hydrazine sensing

Abstract

The development of dual-state emissive (DSE) organic luminogens has elevated the ease of recognition of various biological analytes, which demonstrates the multifaceted potential of dual-state emitters. Therefore, in this study, we synthesised a dual-state emissive excited-state intramolecular proton transfer (ESIPT)-based organic luminogen, (E)-4-(5-bromo-2-hydroxybenzylideneamino)-2,3-dimethyl-1-phenyl-1,2-dihydropyrazol-5-one (ANMB), exhibiting excitation-dependent phototunability with large Stokes shifts of 109 nm and 155 nm in both the solution and solid states, respectively, underscoring its potential as a biosensor. The metal-chelating ability of ANMB was investigated, revealing significant fluorescence quenching upon coordination with Cu²⁺ ions, leading to 96% reduction in emission intensity. The introduction of biological analytes, such as amino alcohols, enabled fluorescence recovery, where ANMB demonstrated enantioselective recognition: a single emission peak for the S-enantiomer and dual emission peaks for the R-enantiomer. Furthermore, ANMB demonstrated high selectivity for hydrazine detection in both the solution and solid states, with new emission bands observed at 411 nm and 432 nm, respectively, indicating a fluorescence shift from green to blue. Complementarily, ANMB was successfully applied for real-time imaging of hydrazine in food and plant samples, showcasing its practical adaptability. Additionally, in silico molecular docking studies were performed, revealing the potential therapeutic activity of ANMB against diarrheal targets. Overall, this work highlights the multifunctionality and tunability of DSE–ESIPT-based organic luminogens, positioning ANMB as a promising candidate for the selective recognition of biologically significant analytes in analytical and real-world contexts.