(E)-N′-(3,5-Dibromo-2-hydroxybenzylidene)nicotinohydrazide

In the title Schiff base compound, C13H9Br2N3O2, there is an intramolecular O-H⋯N hydrogen bond involving the hydroxyl substituent and the adjacent hydrazine N atom. The molecule is almost planar, the dihedral angle between the benzene ring and the pyridine ring being 5.7 (2)°. In the crystal structure, symmetry-related molecules are linked via N—H⋯O hydrogen bonds, forming chains propagating in [001].

In the title Schiff base compound, C 13 H 9 Br 2 N 3 O 2 , there is an intramolecular O-HÁ Á ÁN hydrogen bond involving the hydroxyl substituent and the adjacent hydrazine N atom. The molecule is almost planar, the dihedral angle between the benzene ring and the pyridine ring being 5.7 (2) . In the crystal structure, symmetry-related molecules are linked via N-HÁ Á ÁO hydrogen bonds, forming chains propagating in [001].

Structure Reports Online
Recently, we reported on the crystal structures of two new Schiff bases . As a further investigation of the structures of Schiff base compounds the title compound was prepared by the reaction of 3,5-dibromo-2-hydroxybenzaldehyde with nicotinic acid hydrazide in methanol; its crystal structure is reported on here.
In the title compound ( Fig. 1), there is an intramolecular O-H···N hydrogen bond involving the hydroxyl substituent and the adjacent hydrazine N-atom, N2 (Table 1). The benzene ring is inclined to the pyridine ring by 5.7 (2)°. All the bond lengths are comparable with those observed in similar Schiff bases reported on previously (Wen et al., 2009;Mohd Lair et al., 2009;Sun et al., 2009).
In the crystal structure, symmetry related molecules are linked via intermolecular N-H···O hydrogen bonds so forming chains running along the c axis (Table 1, Fig. 2).
Experimental 3,5-Dibromo-2-hydroxybenzaldehyde (1.0 mmol, 280 mg) and nicotinic acid hydrazide (1.0 mmol, 137 mg) were dissolved in methanol (30 mL). The mixture was stirred at room temperature for about 1 h to give a colorless solution. After allowing the solution to evaporate slowly in air for 8 days, colorless block-like crystals, suitable for X-ray analysis, were formed.

Refinement
Atom H2 was located in a difference Fourier map and refined with a N-H distance restraint of 0.90 (1) Å and U iso (H) = 0.08. The other H atoms were placed in idealized positions and constrained to ride on their parent atoms: O-H = 0.82 Å, C-H = 0.93 Å, with U iso (H) = k × U eq (parent atom), where k = 1.2 for C-bound H-atoms and = 1.5 for the hydroxyl H-atom.   Table 1 for details).

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 > σ(F 2 ) is used only for calculating Rfactors(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.