In Vitro and Intracellular Sensing of Picric Acid by a Water‐Soluble Aggregation‐Induced Emission Enhancement‐Active Dinuclear Zinc(II) Chemodosimeter Derived from a Bicompartmental Acyclic Schiff Base Ligand

A dinuclear water‐soluble Zn II 2 complex of composition [Zn II 2 L(μ‐Cl)Cl 2 ] ( 1 ) has been synthesized and characterized by elemental analysis, FT‐IR spectroscopy, 1 H and 13 C { 1 H} NMR spectroscopy, and single‐crystal and powder X‐ray diffraction, where HL is the 1 + 2 condensation product of 4‐chloro‐2,6‐diformylphenol and N‐ethylethylenediamine. Steady‐state and time‐resolved photophysical studies, DLS measurements, and UV–vis spectra of 1 in H 2 O─CH 3 CN mixtures reveal aggregation‐induced emission enhancement (AIEE) behavior with formation of H‐type nanoaggregates. Fluorescence sensing experiments demonstrate that 1 functions as a selective turn‐off chemosensor for picric acid (PA) among various aromatic and aliphatic nitro compounds, other organic compounds, and inorganic cations and anions. The final association product formed during sensing has been identified by single‐crystal X‐ray diffraction as [NH 3 (CH 2 CH 2 )NH 2 CH 2 CH 3 ](picrate) 2 ⋅ H 2 O ( 2 ), confirming the chemodosimetric nature of 1 . Based on high‐resolution mass spectrometry and structural data, a sensing mechanism is proposed. The quenching constant, apparent interaction parameter, and detection limit have been determined from fluorescence titration data. Cytocompatibility of 1 has been evaluated in HeLa cells using an MTT assay, confirming substantial biocompatibility. Fluorescence imaging experiments, including control experiments in HeLa cells, demonstrate intracellular detection of PA. The AIEE and sensing behavior are further supported by DFT calculations.