In the title compound, (C4H14N2)[Cu(C7H3NO4)2]3H2O or (bdaH2)[Cu(pydc)2]3H2O (where bda is butane-1,4-diamine and pydcH2 is pyridine-2,6-dicarboxylic acid), the CuII atom is coordinated by four O atoms [Cu—O = 2.0557 (16)– 2.3194 (16) A ° ] and two N atoms [Cu—N = 1.9185 (18) and 1.9638 (18) A ° ] from two chelating rings of the pydc2 anions, which act as tridentate ligands. The geometry of the resulting CuN2O4 coordination can be described as distorted octahedral. The the two pydc2 fragments are almost perpendicular to one another [77.51 (11)]. To balance the charges, two centrosymmetric protonated butane-1,4-diammonium, (bdaH2)2+ cations are present. In the crystal structure, extensive O—H O, N—H O and C—H O hydrogen bonds [D A = 2.720 (2)–3.446 (3) A ° ], ion pairing, C—O [O = 3.099 (2) A ° ] and – stacking interactions between the pydc2 rings [centroid–centroid distance = 3.5334 (15) A ° ] contribute to the formation of a three-dimensional supramolecular
