Synthesis, Structure And Properties Of Coordination Polymers Of Pyrazine-2,3,5,6-tetracarboxylic Acid

In recent years, considerable interests have been focused on the coordinationpolymers because of their novel structures and unique physical properties. In addition,these complexes exhibit promising applications in magnetic materials, catalysis,electrochemistry, molecular recognition, ion-exchange and gas storage as well.Pyrazine carboxylate ligands have attracted intense interest due to their strongcoordination capability and varieties of coordination modes.Pyrazine-2,3,5,6-tetracarboxylic acid is a multifunctional N-heterocyclic ligandwith N/O-donors and could be employed in linking different metal atoms withdifferent coordinative modes, resulting in unexpected complexes with novelstructures. In this dissertation, pyrazine-2,3,5,6-tetracarboxylic acid (H4PZTC) isselected as the building block, two coordination polymers have been synthesizedunder solvent evaporation method at room temperature. They were[Cu2(PZTC)(NH3)2(H2O)2]·2H2O (2),[Eu0.5Tb0.5(H2PZTC)(H2O)6(NO3)]·HNO3·H2O(5).They were well characterized by single crystal X-ray diffraction, infrared (IR)spectroscopy, luminescent analysis, elemental analysis, and Inductively CoupledPlasma-Atomic Emission Spectrometer (ICP)，respectively. Luminescent studies onhetero-metal coordination polymer (5) showed that the emission of complex (5) isassigned to the emission of metal-to-ligand charge transfer (MLCT). In addition,complex (5) had relative obvious luminescent enhancement effect comparing tosingle complexes.In addition, we explore the possibility of3d-4f hetero-metal coordinationpolymers, which was synthesized under solvent evaporation method and acidicconditions. Only single lanthanide complex was obtained and characterized byInductively Coupled Plasma-Atomic Emission Spectrometer (ICP). Results indicatedthat RE(III) ions are easier to coordinate with pyrazine-2,3,5,6-tetracarboxylic acidthan transition metal ions under this weak acid condition.