Syntheses, structures, and luminescence properties of five new coordination polymers based on 3-carboxy-1-(3′-carboxybenzyl)-2-oxidopyridinium and neutral ligands

Abstract

A series of coordination polymers, namely [Zn(μ₃-L)(H₂O)₂] (1), [Zn(μ₂-L)(2,2′-bpy)(H₂O)] (2), [Zn(μ₃-L)(μ₂-4,4′-bpy)_0.5] (3), [Cd(μ₃-L)(2,2′-bpy)] (4), and [Cd(μ₂-L)(phen)(H₂O)] (5) (H₂L = 3-carboxy-1-(3′-carboxybenzyl)-2-oxidopyridinium, 2,2′-bpy = 2,2′-bipyridine, 4,4′-bpy = 4,4′-bipyridine, phen = 1,10-phenanthroline), have been synthesized under hydrothermal conditions. These coordination polymers have been characterized by single-crystal X-ray diffraction, elemental analyses, infrared spectroscopy, thermogravimetric analyses and powder X-ray diffraction. The structure analysis by single crystal X-ray diffraction reveals that compound 1 shows a 1D double chain which can be expanded to a 2D supramolecular architecture through intermolecular π–π stacking interactions. In compound 2, the 1D wave-like chains are extended to a 3D supramolecular framework by intermolecular hydrogen bonds and π–π stacking interactions. In compound 3, the infinite rod-like metal ion chains are linked with L²⁻ anions and 4,4′-bpy to form a 3D framework. In compound 4, the adjacent 1D loop-like chains are interconnected to a 3D supramolecular framework by intermolecular hydrogen bonds and π–π stacking interactions. Compound 5 displays a 3D supramolecular architecture extended from the 1D zigzag chains by intermolecular hydrogen bonds and π–π stacking interactions. The result reveals that the organic ligand plays a key role in the self-assembly of coordination polymers. The luminescence sensing experiments reveal that compounds 1–5 can effectively detect Fe³⁺, Cr₂O₇²⁻, and NB. In particular, compound 1 shows a high quenching constant and a low limit of detection for Fe³⁺.