Propane-1,2-diammonium bis­(6-carboxy­pyridine-2-carboxyl­ate) dihydrate

The reaction of propane-1,2-diamine (pn) and pyridine-2,6-dicarboxylic acid (pydcH(2)) in a 1:2 molar ratio in aqueous solution resulted in the formation of the title compound, C(3)H(12)N(2) (2+)·2C(7)H(4)NO(4)·2H(2)O or (pnH(2))(pydcH)(2)·2H(2)O. The structure contains two monoanionic deprotonated forms of pyridine-2,6-dicarboxylic acid molecules (pydcH)(-), a diprotonated propane-1,2-diamine (pnH(2))(2+), and two water mol-ecules. A significant π-π stacking inter-action is observed between the pyridyl rings of the (pydcH)(-) fragments, with a face-to-face distance of 3.6194 (9) Å. In the crystal structure, a wide range of non-covalent inter-actions consisting of ion pairing, hydrogen bonding [of the types of O-H⋯O, N-H⋯O, N-H⋯N and C-H⋯O, with D⋯A distances in the range 2.454 (2)-3.222 (2)Å] and π-π stacking inter-actions [centroid-centroid distance = 3.6194 (9) Å] connect the components into a supra-molecular structure.