Influence of Preparation Conditions on the Formation of Copper (II) Architectures with Pyrazine-2,3,5-tricarboxylic Acid

Three new metal-organic copper(II) complexes, [Cu(H_2PZTC)_2]_n·2nH_2O (1), [Cu(HPZTC)·2H_2O]_n·2nH_2O (2),and Cu_2[(PZHD)(OH)(H_2O)_2]_n (3) (H_3PZTC = pyrazine-2,3,5-tricarboxylic acid, PZHD^3− = 2-hydroxypyrazine-3,5-dicarboxylate), have been synthesized from Cu(II)/H3PZTC system under different synthetic conditions, and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. In complexes 1 and 2, H_3PZTC ligands loose one and two protons, which were transformed into H_2PZTC− anion and HPZTC^2− dianion under different preparation condition, respectively. Furthermore, two ligands coordinate with Cu(II) cations in different modes, leading to the formation of the different chain structures. In complex 3, H_3PZTC ligand was converted into a new ligand-PZHD by in situ decarboxylation and hydroxylation under a higher pH value than that for complexes 1 and 2. PZHD ligands link the Cu(II) cations to form a 2D layer structure. These results demonstrate that the preparation conditions,including pH value and reaction temperature etc, play an important role in the construction of complexes based on H_3PZTC ligand. KCI Citation Count: 0