trans-Tetra­aqua­bis­(isonicotinamide-κN (1))zinc bis­(3-hy­droxy­benzoate) tetra­hydrate

The asymmetric unit of the title compound, [Zn(C(6)H(6)N(2)O)(2)(H(2)O)(4)](C(7)H(5)O(3))(2)·4H(2)O, contains half of the complex cation with the Zn(II) ion located on an inversion center, a 3-hy­droxy­benzoate counter-anion and two uncoordinating water mol­ecules. Four water O atoms in the equatorial plane around the Zn(II) ion [Zn—O = 2.089 (2) and 2.128 (2) Å] form a slightly distorted square-planar arrangement and the distorted octa­hedral geometry is completed by the two N atoms [Zn—N = 2.117 (2) Å] from two isonicotinamide ligands. In the anion, the carboxyl­ate group is twisted from the attached benzene ring at 9.0 (2)°. In the crystal, a three-dimensional hydrogen-bonding network, formed by classical O—H⋯O and N—H⋯O and weak C—H⋯O hydrogen bonds, consolidates the crystal packing, which exhibits π–π stacking between the benzene and pyridine rings, with centroid–centroid distances of 3.458 (2) and 3.609 (2) Å. One of the two H atoms of each uncoordinating water mol­ecule is disordered over two orientations with an occupancy ratio of 0.60:0.40.