catena-Poly[[tetra­aqua­nickel(II)]-μ-(9,10-dioxo-9,10-dihydro­anthracene-1,4,5,8-tetra­carboxyl­ato)-κ2 O 1:O 8-[tetra­aqua­nickel(II)]-μ-4,4′-bipyridine-κ2 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 coord-in-ated by four water mol-ecules in the equatorial plane, and is further bridged by an 9,10-dioxo-9,10-dihydro-anthracene-1,4,5,8-tetra-carb-oxy-l-ate anion and a 4,4'-bipyridine ligand in the axial directions, forming a distorted octa-hedral geometry. The 9,10-dioxo-9,10-dihydro-anthracene-1,4,5,8-tetra-carboxyl-ate 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-dihydro-anthracene-1,4,5,8-tetra-carboxyl-ate 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 mol-ecules are involved in O-H⋯O hydrogen bonding.