Guanidinium (aqua-2κO)(4-hydr­oxy-6-carboxy­pyridine-2-carboxyl­ato-2κ(3) O (2),N,O (6))(μ-4-hydroxy­pyridine-2,6-dicarboxyl­ato-1:2κ(4) O (2),N,O (6):O (2))(4-hydroxy­pyridine-2,6-dicarboxyl­ato-1κ(3) O (2),N,O (6))dizincate(II) dihydrate

The title compound, (CH(6)N(3))[Zn(2)(C(7)H(3)NO(5))(2)(C(7)H(4)NO(5))(H(2)O)]·2H(2)O, has an anionic binuclear complex of Zn(II) balanced with a guanidinium cation. There are two uncoord­inated water mol­ecules in the structure. The asymmetric unit of the compound has two different coordination types (the coordination of Zn1 is distorted trigonal-bipyramidal, while that of Zn2 is distorted octahedral) of Zn(II) in the crystal structure that are bridged to each other via one hypydc(2−) group (hypydcH(2) is 4-hydroxy­pyridine-2,6-dicarboxylic acid). A variety of inter­molecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds involving water mol­ecules, cations and anions, and also a weak π–π inter­action [3.798 (1) Å], are responsible for extending the structure into a three-dimensional network.