Synthesis and crystal structure of a one-dimensional Hg(II) coordination polymer with two distinct metal centers and its selective fluorescent sensing of Ni²⁺

A new Hg(II) coordination polymer {(2-ApzH) 2 [Hg 2 (pydc)Cl 4 ]} n (HgCP) [where pydc = pyridine-2,6-dicarboxylate (dipicolinate), 2-ApzH = 2-aminopyrazinium] with two crystallographically independent metal centers was synthesized and characterized by elemental analysis, spectral (IR, UV–Vis, FL), thermal (TG/DTG/DTA) analysis as well as single crystal X-ray diffraction. Structural analysis reveals a 1D polymeric chain of Hg(II) ions bridged by chloride ligands, which extends into a 3D supramolecular network through hydrogen-bonding and π stacking interactions. Fluorescence studies show a pronounced blue-shift and enhanced emission compared to the free ligands, attributed to ligand immobilization and structural rigidity. Remarkably, HgCP exhibits selective and sensitive luminescence response toward Ni2⁺ ( K sv = 1.72 × 10 5 M −1 , LOD = 1.8 μM), highlighting its potential as an efficient probe for nickel detection.