2-(2-pyridyl)pyridinium bis(pyridine-2,6dicarboxylato-κ3O,N,O′)aluminate(III) trihydrate

The title compound, (C(10)H(9)N(2))[Al(C(7)H(3)NO(4))(2)] center dot 3H(2)O or (2,2'-bipyH)[Al(pydc)(2)] center dot 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 nonahydrate 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 molecule as a counter- ion, ( 2,2'- bipyH)(+), and three uncoordinated water molecules. The anion is a six-coordinate complex, with the Al III atom in a distorted octahedral geometry coordinated by two tridentate pyridine-2,6- dicarboxylate groups. In the crystal structure, intermolecular O-H center dot center dot center dot O, N-H center dot center dot center dot O, N-H center dot center dot center dot N and C-H center dot center dot center dot O hydrogen bonds, pi-pi stacking between two aromatic rings [centroid - centroid distance = 3.827 ( 10) angstrom], and C=O center dot center dot center dot pi stacking [ with distances of 3.2311 ( 13), 3.4924 ( 14) and 3.5731 ( 13) angstrom], connect the various components to form a supramolecular structure.