trans-Tetra-aqua-bis-(isonicotinamide-κN (1))zinc bis-(3-hy-droxy-benzoate) tetra-hydrate.

The asymmetric unit of the title compound, [Zn(C6H6N2O)2(H2O)4](C7H5O3)2·4H2O, contains half of the complex cation with the Zn(II) ion located on an inversion center, a 3-hy-droxy-benzoate counter-anion and two uncoordinating water mol-ecules. 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 octa-hedral geometry is completed by the two N atoms [Zn-N = 2.117 (2) Å] from two isonicotinamide ligands. In the anion, the carboxyl-ate 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 mol-ecule is disordered over two orientations with an occupancy ratio of 0.60:0.40.