In methylaminium 4',7-dihydroxyisoflavone-3'-sulfonate di- hydrate, CH6N+·C15H9O7S-·2H2O, 11 hydrogen bonds exist between the methylaminium cations, the isoflavone-3'-sulfonate anions and the solvent water molecules. In hexaaquairon(II) bis(4',7-diethoxyisoflavone-3'-sulfonate) tetra- hydrate, [Fe(H2O)6](C19H17O7S)2·4H2O, 12 hydrogen bonds exist between the centrosymmetric [Fe(H2O)6]2+ cation, the isoflavone-3'-sulfonate anions and the solvent water molecules. Additional π-π stacking interactions generate three-dimensional supramolecular structures in both compounds. [ABSTRACT FROM AUTHOR]