Synthesis, Structures And Properties Of Coordination Complexes Of Pyrazine-2, 3, 5, 6-tetracarboxylic Acid

Pyrazine-carboxylic acid ligands are the biological active substances in biological bodies. Their complexes are broadly researched and applied in the following fields, including solid chemistry, structure, magnetism, spectrum kinetics, reaction mechanism, reaction of ligands and analytical chemistry. There are many reports about complexes with pyrazine-2,3,5,6-tetracarboxylic acid. However, there is no study about complexes with pyrazine-2,3,5,6-tetracaboxylic acid and 2,2-bipyridine 1,10-phenanthroline now.In this studies three complexes [Mn₂(pztc)(phen)₂(H₂O)₂]·4H₂O(I) ,[Mn₂(pztc)(bpy)₂(H₂O)₂]·2H₂O(II) , [Zn2(pztc)(bpy)₂(H₂O)₂]·2H₂O(III) (H4pztc = pyrazine-2,3,5,6-tetracarboxylic acid, phen = 1,10-phenanthroline, bpy = 2,2-bipyrid ine), have been synthesized by and characterized by IR spectrum and single-crystal X-ray diffraction.Complex(I) crystallizes in the triclinic space group P-1, complexes(II),(III) crystallize in the Monoclinic space group P2(1)/c. Zn(II) and Mn(II) are six-coordinated in the complexes, exhibiting distorted octahedral coordination geometry. In the three complexes each pztc4- ligand can be described as tetradenate ligand linking four metal ions through its four carboxylate groups and two N atoms. The coordination mode of the carboxylate groups is monodentate. pztc4- ligands are parallel each other, and 1,10-phenanthroline ligands are parallel each other too. The metal ions are linked through the carboxylate groups to afford 1D chain, these chains are assembled by hydrogen bonds between the uncoordinated carboxylate oxygen atoms of pztc4- ligand and the uncoordinated water molecule to give rise 2D layer supramolecular structure. The structure of complex (I) is analyzed compared with 1,2,4,5-benzenetetracarboxylic acid. The different coordination modes of the carboxylate groups are displayed in coordinating with metal ions. The hydrogen bonding of complex (II) is analyzed compared with complex builted from Mn₂+and 4-Hydroxypyridine-2,6-dicarboxylic acid, and complex builted from pyridine-2,6-dicarboxylic acid ,Ce3+ and Pr3+.