Two pyridine-2,5-dicarboxylic acid (pydcH(2)) complexes of nickel(II) with 2,2'-bipyridine and 1,10-phenanthroline were synthesized and characterized by elemental, spectroscopic, thermal analysis, magnetic measurements and single crystal X-ray diffraction techniques. Both [Ni(pydc)(bipy)(2)]center dot 7H(2)O and [Ni(pydc)(phen)(2)]center dot 6.5H(2)O crystallize in the monoclinic system and P2(1)/c space group. The Ni(II) ions are coordinated by two bidentate bipy or phen ligands and one pydc dianion in a distorted octahedral geometry. The pydc ligand is coordinated through the pyridine nitrogen atom and oxygen atom of carboxyl group as a bidentate ligand. Both carboxylate groups of pydc are deprotonated but only the 2-carboxylate is coordinated to the metal. Thermal decompositions of the complexes have been studied over the range 30-600 A degrees C on heating in a static air atmosphere.