Bis(2-amino-5-bromo-pyridinium) fumarate dihydrate

In the title compound, 2C(5)H(6)BrN(2) (+)·C(4)H(2)O(4) (2-)·2H(2)O, the complete fumarate dianion is generated by crystallographic inversion symmetry. The cation is approximately planar, with a maximum deviation of 0.036 (1) Å. In the anion, the carboxyl-ate group is twisted slightly away from the attached plane; the dihedral angle between carboxyl-ate and (E)-but-2-ene planes is 6.11 (14)°. In the crystal, the carboxyl-ate O atoms form bifurcated (N-H⋯O and C-H⋯O) and N-H⋯O hydrogen bonds with the cations. The crystal packing is stabilized by R(2) (2)(8) ring motifs which are generated by pairs of N-H⋯O hydrogen bonds. The crystal structure is further consolidated by water mol-ecules via O(water)-H⋯O and N-H⋯O(water) hydrogen bonds. The components are linked by these inter-actions into three-dimensional network.