Synthesis, Structure And Properties Of Novel Coordination Polymers Derived With Pyrazinetetracarboxylic Acid And Lanthanide Compounds

Coordination polymers are varieties of supramolecular complexes self-assembled by coordination bonding among metal ions and organic ligands. Due to their novel structures and fascinating properties, coordination polymers have potential applications in molecular recognition, ion exchange, catalysis, adsorption and magnetic, optical, electrical materials. Pyrazine tetracarboxylic acid (PTCA) is a multi-dentate organic ligand containing N, O atoms, which can provide different coordination modes with metal ions. Thus it is a good candidate for synthesizing novel complexes. Considering rare earth elements have empty f-orbits, they exhibit unique fluorescent and magnetic properties when they coordinate with organic ligands.In this paper, a series of coordination polymers were synthesized by the reactions of PTCA and rare earth nitrates (dysprosium nitrate, europium nitrate, terbium nitrate, gadolinium nitrate) through hydrothermal method or solvent evaporation method and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis and fluorescence analysis.The main works is listed as below:1、Pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) was prepared by the oxidization of phenazine with potassium permanganate2、Two rare earth complexes2and3have been synthesized by the hydrothermal reactions of H4pztc with dysprosium nitrate and europium nitrate. Complexes2is orthorhombic, space group is Pbcn. Single crystal X-ray analysis shows that the structures of complexes2and3are similar. Ten-coordinated Eu(III) or Dy(III) center, hexa-dentate pztc4-and H2O formed a1D linear chain structure. The potassium cations connected these chains by coordinated with the oxygen atoms of carboxyl of pztc4-to form a2D framework.3、Complexes4and5have been synthesized at room temperature by the reactions of H4pztc with terbium nitrate and gadolinium nitrate, respectively. Single crystal X-ray analysis shows that the structures of complexes4,5are similar to the structure of complex2.