Bis(μ-4-methyl-benzoato-κ² O:O′)bis-[aqua-(4- methyl-benzoato-κ² O,O′)zinc(II)]-bis-(μ-4-methyl- benzoato-κ² O:O′)bis-[(4-methyl-benzoato-κO) (nicotinamide-κN)zinc(II)]-water (1/1/2)

The crystal structure of the title compound, [Zn₂(C ₈H₇O₂)₄(H₂O) ₂]·[Zn₂(C₈H₇O ₂)₄(C₆H₆N₂O) ₂]·2H₂O, consists of two kinds of dinuclear Zn ^II complexes (complex A and complex B) and uncoordinated water molecules. In complex A, [Zn₂(C₈H₇O ₂)₄(H₂O)₂], each Zn cation is chelated by a 4-methyl-benzoate (PMB) anion and coordinated by a water molecule, and is further bridged by two PMB anions in a trigonal-bipyramidal geometry. In complex B, [Zn₂(C₈H₇O₂) ₄(C₆H₆N₂O)₂], each Zn^II cation is coordinated by a monodentate PMB anion and one nicotinamide (NA) ligand, and is further bridged by two PMB anions in a tetra-hedral geometry. Weak intra-molecular π-π stacking between adjacent benzene rings is observed in complex B, the centroid-centroid distance being 3.710 (2) Å. Extensive O-H⋯O and N-H⋯O hydrogen bonding and weak C-H⋯O hydrogen bonding is present in the crystal structure. The crystal studied was a racemic twin; the minor twin component refined to 38%.