Preparation and Detection Performance of Metal Complex Probes With Multicarboxylic Acid and Hydrazine Auxiliary Ligands Exhibiting Multi‐Substrate Fluorescence Responses Toward Selected Ions

ABSTRACT A new high‐performance fluorescent material, namely, [Zn(L)(p‐HPA)(H 2 O) 2 ] n ( 1 ) (L = 1,4‐bis(4‐pyridyl)‐2,3‐diaza‐1,3‐butadiene, H 2 HPA = 4‐carboxyphenylacetic acid), was designed and synthesized under solvothermal conditions for the fluorescent detection of toxic pollutants in water. The coordination polymer was characterized and investigated by Hirshfeld surface analysis, powder x‐ray diffraction (PXRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), luminescence spectroscopy, and so forth. X‐ray single‐crystal diffraction analysis revealed that complex 1 exhibits a mononuclear coordination geometry, wherein the structural units are interconnected via extensive hydrogen‐bonding interactions to form a 3D supramolecular architecture. Fluorescence studies demonstrated that 1 serves as a highly sensitive and selective probe for the detection of Fe 3+ , CrO 4 2− , and Cr 2 O 7 2− in aqueous media, with low detection limits (on the order of 10 −8 M) and strong anti‑interference ability. The quenching mechanisms were systematically investigated and attributed to competitive absorption and energy transfer processes.