Tetraaqua(2,2′-bipyridine-5,5′-dicarboxylato-κ2N,N′)nickel(II) dihydrate

In the title compound, [Ni(C12H6N2O4)(H2O)4]·2H2O, obtained from a basic solution of 2,2′-bipyridine-5,5′-dicarboxylate and nickel(II) chloride in water, the central Ni(II) cation (site symmetry 2) is coordinated by two N atoms from the 2,2′-bipyridine-5,5′-dicarboxylate ligand and four aqua O atoms. The N—Ni—N angle is 78.64 (8)°. Weak but significant π–π stacking interactions exist between the pyridine rings with a centroid–centroid distance of 3.652 (8) Å. In addition, four O atoms of the two carboxyl groups form hydrogen bonds with both coordinated and uncoordinated water molecules, forming an infinite three-dimensional network