Four Zn(ii)-5-(2-carboxy-phenoxy)-1,3-benzenedicarboxylate coordination polymers induced by different N-ligands: synthesis, structure, and fluorescence detection for BPA and IMH

Abstract

Four Zn(II) metal–organic coordination polymers (Zn-MCPs), [Zn₂(O-cpia)(2,2′-bpy)·OH] (1), Zn₂(O-cpia)(4,4′-bpy)_0.5·OH (2), Zn₃(O-cpia)₂(bpp)₂·H₂O (3) and [Zn₄(O-cpia)₂(phen)₂·(OH)₂] (4), were synthesized by using the mixed ligand approach, namely 5-(2-carboxyl-phenoxy)-1,3-benzenedicarboxylic acid (O-cpiaH₃) and different auxiliary N-donor ligands 2,2′-bipyridine (2,2′-bpy), 4,4′-bipyridine (4,4′-bpy), 1,3-di(4-pyridyl)propane (bpp), and 1,10-phenanthroline (phen). The four Zn-MCPs exhibited different architectures based on different secondary building units (SBUs) and different ligand bridging modes. Four adjacent Zn²⁺ ions and two μ₃-OH groups formed [Zn₄(μ₃-OH)₂] tetranuclear SBUs in 1, 2, and 4, further linking together to build different frameworks by different ligand bridging modes. Moreover, the [Zn₄(μ₃-OH)₂] units are composed of Zn(II) ions in different coordination environments. 3D (1) is composed of [Zn₄(μ₃-OH)₂] containing [Zn1O₅] and [Zn2O₄N₂] units by an O-cpia linker. 3D (2) consists of [Zn₄(μ₃-OH)₂] with [Zn1O₄N₁] and [Zn2O₄] units via O-cpia/4,4′-bpy mixed ligands. 3D (3) comes from [Zn₂(COO)₄] ([Zn2O₄N₁]) and [Zn1O₂N₂] by O-cpia/bpp mixed ligands. 2D network (4) is composed of [Zn₄(μ₃-OH)₂] with [Zn1O₄N₂], [Zn2O₅], [Zn3O₅], and [Zn4O₄N₂] units by O-cpia ligands. Luminescence sensing studies revealed that 1 detected 2,2-bis(4,4′-hydroxyphenyl)-propane (BPA) and imipramine hydrochloride (IMH) with detection limits of 1.495 × 10⁻⁶ M and 9.92 × 10⁻⁵ M, respectively. The sensing mechanism is attributed to the absorption of BPA/IMH under excitation.