Bis(dimethyl­malonato-κ(2) O,O′)bis­[4-(4-pyridylamino-κN (4))pyridinium]nickel(II) hexa­hydrate

In the title compound, [Ni(C(5)H(6)O(4))(2)(C(10)H(10)N(3))(2)]·6H(2)O, divalent nickel ions situated on the crystallographic twofold axis are octa­hedrally coordinated by four O atoms from two dimethyl­malonate ligands in a 1,3-chelating mode and two N atoms from two protonated monodentate 4,4′-dipyridylamine mol­ecules. The mol­ecules link into chains via N—H⋯O hydrogen bonding mediated by protonated pyridyl groups. The chains form layer patterns via π–π stacking [centroid–centroid distance = 3.777 (2) Å] . Water mol­ecule hexa­mers are generated from the unligated water mol­ecules (three per asymmetric unit) by inversion centers at Wyckoff position d. These clusters are situated between the pseudolayers, providing hydrogen-bonding pathways that build up the three-dimensional structure.