A self-penetrated three-dimensional zinc(II) coordination framework based on 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tribenzoic acid and 1,3-bis[(imidazol-1-yl)methyl]benzene ligands: synthesis, structure and properties

Abstract

With the rapid development of metal–organic frameworks (MOFs), a variety of MOFs and their derivatives have been synthesized and reported in recent years. Commonly, multifunctional aromatic polycarboxylic acids and nitrogen-containing ligands are employed to construct MOFs with fascinating structures. 4,4′,4′′-(1,3,5-Triazine-2,4,6-triyl)tribenzoic acid (H3TATB) and the bidentate nitrogen-containing ligand 1,3-bis[(imidazol-1-yl)methyl]benzene (bib) were selected to prepare a novel ZnII-MOF under solvothermal conditions, namely poly[[tris{μ-1,3-bis[(imidazol-1-yl)methyl]benzene}bis[μ3-4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tribenzoato]trizinc(II)] dimethylformamide disolvate trihydrate], {[Zn3(C24H12N3O6)2(C14H14N4)3]·2C3H7NO·3H2O} n (1). The structure of 1 was characterized by single-crystal X-ray diffraction, IR spectroscopy and powder X-ray diffraction. The properties of 1 were investigated by thermogravimetric and fluorescence analysis. Single-crystal X-ray diffraction shows that 1 belongs to the monoclinic space group Pc. The asymmetric unit contains three crystallographically independent ZnII centres, two 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tribenzoate (TATB3−) anions, three complete bib ligands, one and a half free dimethylformamide molecules and three guest water molecules. Each ZnII centre is four-coordinated and displays a distorted tetrahedral coordination geometry. The ZnII centres are connected by TATB3− anions to form an angled ladder chain with large windows. Simultaneously, the bib ligands link ZnII centres to give a helical Zn–bib–Zn chain. Furthermore, adjacent ladders are bridged by Zn–bib–Zn chains to form a fascinating three-dimensional self-penetrated framework with the short Schläfli symbol 65·7·813·9·10. In addition, the luminescence properties of 1 in the solid state and the fluorescence sensing of metal ions in suspension were studied. Significantly, compound 1 shows potential application as a fluorescent sensor with sensing properties for Zr4+ and Cu2+ ions.