(Propane-1,3-diammonium) bis­(4-hydroxy­pyridine-2,6-dicarboxyl­ato-κ(3) O (2),N,O (6))zinc(II) 3.5-hydrate

The asymmetric unit of the title compound, (C(3)H(12)N(2))[Zn(C(7)H(3)NO(5))(2)]·3.5H(2)O, contains two formula units. The compound consists of an anionic complex, a doubly protonated propane-1,3-diamine as a counter-ion and 3.5 uncoord­inated water mol­ecules. The coordination polyhedron around the Zn(II )atom is distorted octa­hedral, defined by four O atoms and two N atoms from two Hchel (H(3)chel = 4-hydroxy­pyridine-2,6-dicarboxylic acid) ligands. In the crystal structure, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds along with π–π stacking inter­actions [centroid–centroid distance = 3.473 (2) Å] are observed to reinforce the crystal cohesion.