4,4'-Bipyridinium bis(perchlorate)-4-aminobenzoic acid-4,4'-bipyridine-water (1/4/2/2).

In the structure of the title compound, C(10)H(10)N(2) (2+)·2ClO(4) (-)·4C(7)H(7)NO(2)·2C(10)H(8)N(2)·2H(2)O, the 4,4'-bipyridinium cation has a crystallographically imposed centre of symmetry. The cation is linked by N-H⋯N hydrogen bonds to adjacent 4,4'-bipyridine mol-ecules, which in turn inter-act via O-H⋯N hydrogen bonds with 4-amino-benzoic acid mol-ecules, forming chains running parallel to [30]. The chains are further connected into a three-dimensional network by N-H⋯O and O-H⋯O hydrogen-bonding inter-actions involving the perchlorate anion, the water mol-ecules and the 4-amino-benzoic acid mol-ecules. In addition, π-π stacking inter-actions with centroid-centroid distances ranging from 3.663 (6) to 3.695 (6) Å are present. The O atoms of the perchlorate anion are disordered over two sets of positions, with refined site occupancies of 0.724 (9) and 0.276 (9).