2,6-diaminopyridinium bis(4-hydroxypyridine-2,6-dicarboxylato-κ3O2,N,O6)-ferrate(III) dihydrate

The reaction of iron(II) sulfate heptahydrate with the protontransfer compound (pydaH)(hypydcH) (pyda = pyridine-2,6-diamine; hypydcH(2) = 4-hydroxypyridine-2,6-dicarboxylic acid) in an aqueous solution led to the formation of the title compound, (C5H8N3)[ Fe(C7H3NO5)(2)]center dot 2H(2)O. The anion is a six-coordinated complex with a distorted octahedral geometry around the Fe-III atom. Extensive intermolecular O-H center dot center dot center dot O, N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds, involving the complex anion, (pydaH)(+) counter-ion and two uncoordinated water molecules, and pi-pi [centroid-to-centroid distance 3.323 (11) angstrom] and C-O center dot center dot center dot pi [O-centroid distance 3.150 (15) angstrom] interactions connect the various components into a supramolecular structure.