A tetrahedral zinc(II) coordination polymer: Synthesis, characterisation, and application in ascorbic Acid fluorescence sensing

A new coordination polymer (CP), {[Zn(HL)₂(bib)]ₙ.0·25H₂O} (1), was synthesized and characterized for its structural, thermal, and luminescence properties. The compound was obtained by reacting H₃L= 3-(4-carboxyphenoxy)-5-methylbenzoic acid, bib = 1,4-bis(1-imidazoly)benzene, and Zn(ClO₄)₂·6H₂O in aqueous solution, followed by hydrothermal treatment at 120 °C for 72 h. Single-crystal X-ray diffraction revealed a 1D polymeric chain with zinc centres in a distorted tetrahedral geometry, coordinated by carboxylate and imidazole-based ligands. Infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) confirmed the bonding environment and thermal stability. CP 1 exhibited strong luminescence, peaking at 205 nm upon excitation at 285 nm, and demonstrated selective sensing of ascorbic acid (AA) with a high quenching efficiency (K_sv = 4.35 × 10² M⁻¹) and a detection limit of 3.15 × 10^⁻4 M The luminescence was pH-dependent, with optimal fluorescence near neutral pH. These findings highlight the potential of CP 1 as a sensitive probe for AA detection, offering applications in environmental monitoring and chemical sensing.