trans-Tetraaquabis(isonicotinamide-κN1)zinc bis(3-hydroxybenzoate) tetrahydrate

The asymmetric unit of the title compound, [Zn(C6H6N2O)2(H2O)4](C7H5O3)2·4H2O, contains half of the complex cation with the ZnII 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 ZnII ion [Zn—O = 2.089 (2) and 2.128 (2) ] form a slightly distorted square-planar arrangement and the distorted octahedral geometry is completed by the two N atoms [Zn—N = 2.117 (2) ] 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) . 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.