catena-Poly[[tetra­aqua­nickel(II)]-μ-(9,10-dioxo-9,10-dihydro­anthracene-1,4,5,8-tetra­carboxyl­ato)-κ(2) O (1):O (8)-[tetra­aqua­nickel(II)]-μ-4,4′-bipyridine-κ(2) N:N′]

In the crystal of the title polymeric complex, [Ni(2)(C(18)H(4)O(10))(C(10)H(8)N(2))(H(2)O)(8)](n), each Ni(II) cation is coord­in­ated by four water mol­ecules in the equatorial plane, and is further bridged by an 9,10-dioxo-9,10-dihydro­anthracene-1,4,5,8-tetra­carb­oxy­l­ate anion and a 4,4′-bipyridine ligand in the axial directions, forming a distorted octa­hedral geometry. The 9,10-dioxo-9,10-dihydro­anthracene-1,4,5,8-tetra­carboxyl­ate anion is centrosymmetric with the centroid of the quinone ring located about an inversion center; the 4,4′-bipyridine ligand is also centrosymmetric with the mid-point of the C—C bond linking two pyridine rings located about another invertion center. The 9,10-dioxo-9,10-dihydro­anthracene-1,4,5,8-tetra­carboxyl­ate anion and bypiridine ligand bridge the Ni(II) cations, forming a polymeric chain along the b axis. π–π stacking is observed between pyridine and benzene rings [centroid–centroid distance = 3.705 (2) Å]. All of the coordinating water mol­ecules are involved in O—H⋯O hydrogen bonding.