catena-Poly[[[diaqua­zinc]-bis­{[mu]-N²,N⁶-bis­[(pyridin-3-yl)methyl]pyridine-2,6-dicarboxamide}] dinitrate]

In the title compound, {[Zn(C₁₉H₁₇N₅O₂)₂(H₂O)₂](NO₃)₂}_n, the Zn^II cation is located at an inversion centre within a slightly distorted octa­hedron, ligated by four N atoms from four N²,N⁶-bis­[(pyridin-3-yl)methyl]pyridine-2,6-dicarboxam­ide (L) ligands occupying a plane about the Zn^II atom with the two water O atoms perpendicular to that. In the complex mol­ecule, the bidentate bridging L ligands display helical R and S conformers, and link the Zn^II cations into a one-dimensional centrosymmetric double-chain structure con­taining 32-membered rings. The nitrate anions reside in these rings and are involved in multiple N-H...O hydrogen-bond inter­actions. On excitation at 390 nm, the title compound displays a strong blue emission centred at 449 nm. Investigation of the thermal stability shows that the network structure is stable up to 420 K.