Hemipiperazinediium bis-(pyridine-2,6-dicarboxyl-ato-κO,N,O')gallate(III) pyridine-2,6-dicarboxylic acid dihydrate.

The asymmetric unit of the title compound, (C(4)H(12)N(2))(0.5)[Ga(pydc)(2)]·pydcH(2)·2H(2)O, where pydcH(2) is pyridine-2,6-dicarboxylic acid, C(7)H(5)NO(4), contains one half of a centrosymmetric piperazinediium dication, one anion, one uncoord-inated pydcH(2) mol-ecule and two uncoordinated water mol-ecules, one of which is disordered over two sites in a 1:1 ratio. In the anion, the Ga(III) ion is coordinated by four O atoms [Ga-O = 1.9706 (16)-2.0494 (15) Å] and two N atoms [Ga-N = 1.9660 (18) and 1.9709 (17) Å] from two pydc ligands in a distorted octa-hedral geometry. The crystal structure exhibits inter-molecular O-H⋯O, N-H⋯O and O-H⋯N hydrogen bonds and π-π inter-actions [centroid-centroid distances of 3.5359 (13) and 3.6550 (14) Å].