The asymmetric unit of the title compound, (C3H12N2)- [Zn(C7H3NO5)2]3.5H2O, 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 ZnII atom is distorted octahedral, defined by four O atoms and two N atoms from two Hchel (H3chel = 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 – stacking interactions [centroid–centroid distance = 3.473 (2) A ˚ ] are observed to reinforce the crystal cohesion.
