Propane-1,2-diaminium bis­(pyridine-2,6-dicarboxyl­ato-κ(3) O (2),N,O (6))cadmate dihydrate

The reaction of cadmium nitrate dihydrate, propane-1,2-diamine and pyridine-2,6-dicarb­oxy­lic acid in a 1:1:2 molar ratio in an aqueous solution resulted in the formation of the title compound, (C(3)H(12)N(2))[Cd(C(7)H(3)NO(4))(2)]·2H(2)O or (p-1,2-daH(2))-[Cd(pydc)(2)]·2H(2)O (where p-1,2-da is propane-1,2-diamine and pydcH(2) is pyridine-2,6-dicarb­oxy­lic acid). The Cd(II) ion is coordinated by four O and two N atoms of two pydc ligands in a distorted octa­hedral environment. The structure also contains two uncoordinated water mol­ecules. In the crystal, there are several inter­molecular N—H⋯O, O—H⋯O and weak C—H⋯O hydrogen bonds. There are also π–π stacking inter­actions between the pyridine rings of pydc units, with centroid–centroid distances of 3.4708 (16) Å.