Synthesis, Characterization, Crystal Structures, and Solution Studies of Ni(II), Cu(II) and Zn(II) Complexes Obtained from Pyridine-2,6-dicarboxylic Acid and 2,9- Dimethyl-1,10-Phenanthroline

The homonuclear water-soluble and air stable compounds (dmpH) (H5O2) [M(pydc)2].0.5H2O (M = Ni(II) (1), Cu(II) (2),Zn(II) (3); pydcH2 = pyridine-2,6-dicarboxylic acid, dipicolinic acid, dmp = 2,9-dimethyl-1,10-phenanthroline) have been prepared by self-assembly synthesis in aqueous solution at room temperature, and characterized by IR, 1H NMR, 13C NMR, elemental analysis and X-ray diffraction single crystal analyses for 1, 2 and 3. The complexes 1-3 represent the isostructural features. Extensive hydrogen bonding interactions involving all aqua ligands, dipicolinate oxygens and lattice water molecules further stabilize the complex units by linking them to form three dimensional polymeric networks. The stoichiometry and stability of the all three complexes in aqueous solution were investigated by potentiometric pH titration