4,4'-Bipyridine-1,1'-diium 2,3,5,6-tetra-bromo-terephthalate dihydrate.

The title compound, C(10)H(10)N(2) (2+)·C(8)Br(4)O(4) (2-)·2H(2)O, consists of a tetra-bromo-terephthalate dianion, a 4,4'-bipyridinium dication and two solvent water mol-ecules. Crystallographic inversion centers are situated at the center of the aromatic ring of the dianion as well as at the midpoint of the carbon-carbon bond connecting the pyridine rings in the dication. In the crystal, inter-molecular N-H⋯O hydrogen-bonding inter-actions between tetra-bromo-terephthalate dianions and protonated 4,4'-bipyridinium dications result in the formation of a chain-like structure. Further O-H⋯O hydrogen bonds between carboxyl-ate O atoms and water mol-ecules lead to the formation of a two-dimensional network in the crystal structure.