{2,2′-[Pyridine-3,4-diylbis(nitrilomethylidyne)]diphenolato}zinc(II)

The title compound, [Zn(C19H13N3O2)], has been synthesized by the reaction of Zn(ClO4)2·6H2O and the tetradentate Schiff base ligand 2,2′-[pyridine-3,4-diylbis(nitrilomethylidyne)]diphenol (L). The coordination geometry of the ZnII ion is slightly distorted square-planar, formed by two N atoms and two O atoms from the L ligand.

The title compound, [Zn(C 19 H 13 N 3 O 2 )], has been synthesized by the reaction of Zn(ClO 4 ) 2 Á6H 2 O and the tetradentate Schiff base ligand 2,2 0 -[pyridine-3,4-diylbis(nitrilomethylidyne)]diphenol (L). The coordination geometry of the Zn II ion is slightly distorted square-planar, formed by two N atoms and two O atoms from the L ligand.

N. Sheng
Comment Schiff base complexes have attracted much attention due to their interesting structures and wide potential applications. They play an important role in the development of coordination chemistry as well as inorganic biochemistry, catalysis and optical materials (Aurangzeb et al., 1994, Hulme et al., 1997Li et al., 2008;Fei et al., 2008;Zhang & Janiak, 2001). Here, we report the structure of a new zinc complex based on a tetradentate Schiff base ligand. The molecular structure of title compound is shown in Fig. 1. As can be seen, the whole molecule of the title complex is essentially planar. The Zn ion is four-coordinate with the four positions occupied by two N atoms and two O atoms of the Schiff base ligand. The mean deviation of the plane formed by ZnN 2 O 2 unit is 0.0121 Å. The Zn-O and Zn-N bond lengths are all consistent with those found in other Zn Schiff base complexes (Chen, 2005;Li, et al., 2004).

Experimental
The Schiff base ligand was synthesized by condensation 3,4-diaminopyridine and 2-hydroxy-benzaldehyde with the ratio 1:2 in ethanol.The synthesis of the title complex was carried out by reacting Zn(ClO 4 ) 2 .6H 2 O (1 mmol, 373 mg) and the schiff-base ligand (1 mmol, 317 mg) in methanol under the stirring condition at room temperature. The filtrated solution was left to slowly evaperate in air to obtain single-crystal suitable for X-ray diffraction with the yield about 228 mg, 60%.

Refinement
All the H atoms bonded to the C atoms were placed using the HFIX commands in SHELXL-97, with C-H distances of 0.93 Å, and were allowed for as riding atoms with U iso (H) = 1.2U eq (C). Fig. 1. View of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

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.