Bis(4,4′-bi­pyridine)­tetra­aqua­cobalt(II) 2,6-naphathalenedi­carboxyl­ate dihydrate

The title compound, [Co(C10H8N2)2(H2O)4](C12H6O4)·2H2O (where C10H8N2 is 4,4′-bi­pyridine, BPY, and C12H6O4 is 2,6-naphthalene­di­carboxyl­ate, NDC2−), (CUmof-6), was synthesized under mild hydro­thermal conditions. The structure contains [Co(BPY)2(H2O)4]2+ complex cations, which stack along the a axis through close face-to-face contacts. Uncoord­inated NDC2− anions are strongly hydrogen bonded to the complex cations. The Co2+ cation and the centre of gravity of NDC2− are located on crystallographic centres of symmetry.