Bis(2,3-diamino-pyridinium) bis-(μ-pyridine-2,6-dicarboxyl-ato)-κO,N,O:O;κO:O,N,O-bis-[aqua-(pyridine-2,6-dicarboxyl-ato-κO,N,O)bis-muthate(III)] tetra-hydrate.

In the centrosymmetric dinuclear complex anion of the title compound, (C(5)H(8)N(3))(2)[Bi(2)(C(7)H(3)NO(4))(4)(H(2)O)(2)]·4H(2)O, the Bi(III) atom is eight-coordinated in an N(2)O(6) environment and has a distorted bicapped trigonal-prismatic coordination environment. Extensive inter-molecular O-H⋯O, N-H⋯O and weak C-H⋯O hydrogen bonds lead to the stability of the crystal structure. Inter-actions between one C-H group of the 2,3-diamino-pyridinium [(2,3-dapyH)(+)] cation and the aromatic ring of the pyridine-2,6-dicarboxyl-ate (pydc) ligand (C-H⋯centroid distance = 2.78 Å) and π-π inter-actions between the (2,3-dapyH)(+) cations and between the (2,3-dapyH)(+) cation and the pydc ligand [centroid-centroid distances = 3.489 (5) and 3.694 (5) Å] are observed.