2-(2-Pyrid-yl)pyridinium bis-(pyridine-2,6-dicarboxyl-ato-κO,N,O')aluminate(III) trihydrate.

The title compound, (C(10)H(9)N(2))[Al(C(7)H(3)NO(4))(2)]·3H(2)O or (2,2'-bipyH)[Al(pydc)(2)]·3H(2)O (where 2,2'-bipy is 2,2'-bipyridine and pydcH(2) is pyridine-2,6-dicarboxylic acid), was synthesized by the reaction of aluminium(III) nitrate nona-hydrate with pyridine-2,6-dicarboxylic acid and 2,2'-bipyridine in a 1:2:4 molar ratio in aqueous solution. This compound is composed of an anionic complex, [Al(pydc)(2)](-), a protonated 2,2'-bipyridine mol-ecule as a counter-ion, (2,2'-bipyH)(+), and three uncoordinated water mol-ecules. The anion is a six-coordinate complex, with the Al(III) atom in a distorted octa-hedral geometry coordinated by two tridentate pyridine-2,6-dicarboxyl-ate groups. In the crystal structure, inter-molecular O-H⋯O, N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds, π-π stacking between two aromatic rings [centroid-centroid distance = 3.827†(10)†à ], and C=O⋯π stacking [with distances of 3.2311†(13), 3.4924†(14) and 3.5731†(13)†à ], connect the various components to form a supra-molecular structure.