Diaquabis(4-formylbenzoato-κO 1)bis(nicotinamide-κN 1)zinc

In the title complex, [Zn(C8H5O3)2(C6H6N2O)2(H2O)2], the ZnII cation is located on an inversion center and is coordinated by two 4-formylbenzoate (FB) anions, two nicotinamide (NA) ligands and two water molecules. The four O atoms in the equatorial plane around the ZnII cation form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxylate group and the adjacent benzene ring is 24.13 (8)°, while the pyridine ring and the benzene ring are oriented at a dihedral angle of 88.52 (4)°. The coordinating water molecule links with the carboxylate group via an O—H⋯O hydrogen bond. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds, and a weak C—H⋯π interaction link the molecules into a two-dimensional network parallel to (010). These networks are linked via C—H⋯O and π–π interactions between inversion-related benzene rings [centroid–centroid distance = 3.8483 (7) Å], forming a three-dimensional supramolecular structure.

In the title complex, [Zn(C 8 H 5 O 3 ) 2 (C 6 H 6 N 2 O) 2 (H 2 O) 2 ], the Zn II cation is located on an inversion center and is coordinated by two 4-formylbenzoate (FB) anions, two nicotinamide (NA) ligands and two water molecules. The four O atoms in the equatorial plane around the Zn II cation form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxylate group and the adjacent benzene ring is 24.13 (8) , while the pyridine ring and the benzene ring are oriented at a dihedral angle of 88.52 (4) . The coordinating water molecule links with the carboxylate group via an O-HÁ Á ÁO hydrogen bond. In the crystal, N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, and a weak C-HÁ Á Á interaction link the molecules into a twodimensional network parallel to (010). These networks are linked via C-HÁ Á ÁO andinteractions between inversionrelated benzene rings [centroid-centroid distance = 3.8483 (7) Å ], forming a three-dimensional supramolecular structure.
In the title mononuclear complex, Zn II cation is located on an inversion center and is coordinated by two 4-formylbenzoate (FB) anions, two nicotinamide (NA) ligands and two water molecules, all ligands coordinating in a monodentate manner ( Fig. 1). The crystal structures of similar complexes of Cu II , Co II , Ni II , Mn II and Zn II ions, (Sertçelik et al., 2012d) have also been reported, where all the ligands coordinate to the metal atoms in a monodentate manner.
In the title complex, the four symmetry related O atoms (O1, O1′, O5 and O5′) in the equatorial plane around the Zn II ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two symmetry related N atoms of the NA ligands (N1 and N1′) in the axial positions. The near equalities of the C1 -O1 [1.2614 (14) Å] and C1-O2 [1.2600 (14) Å] bonds in the carboxylate group indicate a delocalized bonding arrangement, rather than localized single and double bonds. The Zn-O bond lengths are 2.1047 (8) Å (for benzoate oxygens) and 2.1446 (8) Å (for water oxygens), and the Zn-N bond length is 2.1253 (10) Å, close to standard values (Allen et al., 1987). The Zn atom is displaced out of the mean-plane of the carboxylate group (O1/C1/O2) by -0.6114 (1) Å. The dihedral angle between the planar carboxylate group and the adjacent benzene ring A (C2-C7) is 24.13 (8) (Table 1).

Experimental
The title compound was prepared by the reaction of

Refinement
Atoms H8 (for CH), H21 and H22 (for NH 2 ) and H51 and H52 (for H 2 O) were located in a difference Fourier map and were refined freely. The C-bound H-atoms were positioned geometrically and constrained to ride on their parent atoms: C -H = 0.93 Å with U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title molecule with the atom-numbering. Displacement ellipsoids are drawn at the 50% probability level [symmetry code: (′) -x, -y, -z].

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.