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

In the title compound, [Ni(C(12)H(6)N(2)O(4))(H(2)O)(4)]·2H(2)O, 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.