Guanidinium (aqua-2κO)(4-hydr­oxy-6-carboxy­pyridine-2-carboxyl­ato-2κ3 O 2,N,O 6)(μ-4-hydroxy­pyridine-2,6-dicarboxyl­ato-1:2κ4 O 2,N,O 6:O 2)(4-hydroxy­pyridine-2,6-dicarboxyl­ato-1κ3 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 uncoord-inated water mol-ecules 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-hydroxy-pyridine-2,6-dicarboxylic acid). A variety of inter-molecular O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds involving water mol-ecules, cations and anions, and also a weak π-π inter-action [3.798 (1) Å], are responsible for extending the structure into a three-dimensional network.