N′-(5-Bromo-2-hydroxy-3-methoxybenzylidene)isonicotinohydrazide

The title compound, C14H12BrN3O3, was prepared by reaction of 5-bromo-3-methoxysalicylaldehyde and isonicotinohydrazide in methanol. The molecule is not planar and adopts a trans configuration with respect to the C=N bond. There is an intramolecular O—H⋯N hydrogen bond in the molecule. The dihedral angle between the benzene and pyridine rings is 12.2 (2)°. In the crystal structure, molecules are linked through intermolecular N—H⋯N hydrogen bonds, forming chains running along the c-axis direction.

The title compound, C 14 H 12 BrN 3 O 3 , was prepared by reaction of 5-bromo-3-methoxysalicylaldehyde and isonicotinohydrazide in methanol. The molecule is not planar and adopts a trans configuration with respect to the C N bond. There is an intramolecular O-HÁ Á ÁN hydrogen bond in the molecule. The dihedral angle between the benzene and pyridine rings is 12.2 (2) . In the crystal structure, molecules are linked through intermolecular N-HÁ Á ÁN hydrogen bonds, forming chains running along the c-axis direction.
In the molecule of the title compound (I) the C7═N1 length of 1.275 (3) Å indicates a typical C═N bond. The molecule exists in a trans configuration with respect to the methylidene unit (C7═N1), as observed in other similar compounds (Han et al., 2006;Lu et al., 2008). There is an intramolecular O-H···N hydrogen bond in the molecule. The dihedral angle between the benzene and pyridine rings is 12.2 (2)°, indicating the molecule is not planar. The bond lengths are in normal ranges (Allen et al., 1987).
In the crystal structure, molecules are linked through intermolecular N-H···N hydrogen bonds (Table 1), forming chains running along the c direction (Fig. 2).
Experimental 5-Bromo-3-methoxysalicylaldehyde (0.231 g, 1 mmol) was dissolved in methanol (50 ml), then isonicotinohydrazide (0.137 g, 1 mmol) was added slowly to the solution, and the mixture was heated at reflux with continuous stirring for 1 h. The solution was cooled to room temperature, yielding colorless crystallites. Recrystallization from an absolute methanol yielded block-like single crystals of the compound.

Refinement
H2 was located in a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å, and with U iso set at 0.08 Å 2 . Other H atoms were placed in calculated positions with C-H distances of 0.93-0.96 Å, O-H distance of 0.82 Å, and refined in riding mode with U iso (H) = 1.2U eq (C) and 1.5U eq (O). Fig. 1. The molecular structure of the title compound with 30% probability displacement ellipsoids for non-H atoms; the intramolecular hydrogen bond is drawn as a dashed line.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.