Synthesis,Structure And Propertiesof Complexes Based On 1,2-bis((5H-imidazol-4-Yl)-methylene) Hydrazineand Isoahthalic Acid Derivative

Over the past decade,considerable effort has been invested in the rational design and synthesis of these functional materials.In recent years,based on the respective advantages of nitrogen-containing heterocycles and carboxylic acid ligands,the metal-organic complexes constructed by them have novel structures and potential applications in gas storage and separation,catalysis,magnetics,fluorescence detection and identification,which has attracted much attention.In this paper,We used 1,2-bis??5H-imidazol-4-yl?-methylene?hydrazine?BIm?and isophthalic acid derivative including 5-nitroisophthalic acid,5-methylisophthalic acid,5-tert-butylisophthalic acid as a main and secondary ligand.The complexes can be readily prepared by reacting the BIm ligand and isophthalic acid derivative with various metal nitrate salts under solvothermal conditions or atmospheric temperature volatilization.The structure of seven metal-organic coordination complexes were identified by X-ray crystal analyses,Powder X-Ray Diffraction?PXRD?,infrared spectroscopy and thermogravimetric analysis.The luminescence properties of some complexes and BIm in the solid state were measured at room temperature.The main results are described as follows:Complex 1 is a three-dimensional supramolecular structure,complex 2 is a two-dimensional structure,complexes 3 and 4 are one-dimensional structures,complexes 4,5,and 6 are all zero-dimensional structures,except for complex 1,other complexes all formed a three-dimensional supramolecular network structure through hydrogen bondings.Thermogravimetric analysis?TGA?reveals that complex 1,3 and 4 was thermally stable up to 400°C,and its organic framework collapsed in the temperature of 400°C,complex 5 and 6 was thermally stable up to 350°C,and complex 7 was thermally stable up to 235°C.Powder X-Ray Diffraction?PXRD?measurements were conducted to confirm the phase purity of complexes.Analysis of fluorescence data showed that the fluorescence of complexes 1,3,5,and 6 originated mainly from the interaction of the primary and secondary ligands.Complex 1and 5 can sense nitrobenzene?NB?and selectively detect Fe³⁺ions and Cr₂O₇^2-anions.By contrast,complex 5 was found to be a highly selective and sensitive probe of Fe³⁺in methanol solution.However,complex1 demonstrated the most significant identifying effect to Cr₂O₇^2-anions than complex 5.The luminescent quenching of metal cations and anions may be caused by competitive adsorption of emission wavelength energy between host framework and analytes.