2,6-Diamino-pyridinium bis-(4-hydroxy-pyridine-2,6-dicarboxyl-ato-κO,N,O)ferrate(III) dihydrate

The reaction of iron(II) sulfate hepta-hydrate with the proton-transfer compound (pydaH)(hypydcH) (pyda = pyridine-2,6-diamine; hypydcH(2) = 4-hydroxy-pyridine-2,6-dicarboxylic acid) in an aqueous solution led to the formation of the title compound, (C(5)H(8)N(3))[Fe(C(7)H(3)NO(5))(2)]·2H(2)O. The anion is a six-coordinated complex with a distorted octa-hedral geometry around the Fe(III) atom. Extensive inter-molecular O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, involving the complex anion, (pydaH)(+) counter-ion and two uncoordinated water mol-ecules, and π-π [centroid-to-centroid distance 3.323 (11) Å] and C-O⋯π [O-centroid distance 3.150 (15) Å] inter-actions connect the various components into a supra-molecular structure.