The phase transition of pyridine-2-6-dicarboxylateo nickel (II), rehydrate at different temperatures

A nickel complex with pyridine-2,6-dicarboxylic acid formulated as [Ni(pydcH)2].3H2O was synthesized and its crystal structure determined with single-crystal X-ray at diffraction temperatures (296 K and 120 K). Pyridine-2,6-dicarboxyli acid deprotonated on one group of COOH and two pydcH- anion is coordinated to Ni(II) atom as a tridentate ligand forming a distorted octahedral environment. The phase transition in crystal system is obtained with differ in temperature. The title compound is crystallized in monoclinic system with P21/c space group at 296 K, while it is crystallized in triclinic system with CAWT IMAGE space group at 120 K.