A coordination polymer based on mixed ligand strategy: Synthesis, structural investigation, and fluorescence performance

A coordination polymer, [Mn(SCND²⁻)(4,4′-Dm-2,2′-bpy)(H₂O)₂]_n (Mn-CP), based on 4-sulfo-N-(4-carboxyphenyl) naphthalene-1,8-dicarboximide (H₂SCND) and 4,4′-Dimethyl-2,2′-bipyridine (4,4′-Dm-2,2′-bpy) ligands has been successfully synthesized. The single-crystal X-ray diffraction (SCXRD) reveals that Mn-CP crystallizes in the P1 space group of the triclinic crystal system. In this structure, 1D chain structures are formed by SCND²⁻ ligands and metal centers, in which 4,4′-Dm-2,2′-bpy act as a capping ligand. These chains are further connected through hydrogen bonds and π···π interactions, forming a three-dimensional (3D) supramolecular structure. Mn-CP exhibits excellent photoluminescence with high stability. Notably, it can selectively detect Cr₂O₇²⁻ / o-NA (o-nitroaniline) / p-NP (p-nitrophenol) / Norfloxacin (NFX) / Nitrofurazone (NFZ) in solution, with excellent selectivity and recyclability. The sensing mechanism likely involves fluorescence resonance energy transfer and competitive absorption, as indicated by experimental results. This work provides a new method for detecting hazardous substances in solution.