N′-(5-Bromo-2-hydroxybenzylidene)-3-nitrobenzohydrazide methanol monosolvate

In the title compound, C14H10BrN3O4·CH4O, the dihedral angle between the two benzene rings in the hydrazone molecule is 5.8 (3)° and an intramolecular O—H⋯N hydrogen bond generates an S(6) ring motif. An O—H⋯O hydrogen bond occurs between the hydrazone molecule and the methanol solvent molecule. In the crystal, the components are linked by intermolecular N—H⋯O hydrogen bonds, forming chains along the a axis.

The compound contains a hydrazone molecule and a methanol molecule of crystallization. The dihedral angle between the two benzene rings in the hydrazone molecule is 5.8 (3)°. An intramolecular O-H···N hydrogen bond generates a S(6) ring motif in the hydrazone molecule (Bernstein et al., 1995). Bond lengths in the compound are normal (Allen et al., 1987) and comparable to those in the similar compounds the author has reported previously (Tang, 2010;Tang, 2011). In the crystal structure, the hydrazone molecules are linked by the methanol molecules through intermolecular N-H···O hydrogen bonds (Table 1), forming chains along the a axis ( Fig. 2).
Experimental 5-Bromo-2-hydroxybenzaldehyde (0.1 mmol, 20.1 mg) and 3-nitrobenzohydrazide (0.1 mmol, 18.1 mg) were dissolved in methanol (20 ml). The mixture was stirred at reflux for 10 min to give a clear yellow solution. Yellow needle-shaped crystals of the compound were formed by slow evaporation of the solvent over several days.

Refinement
The amino H atom was located in a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å [U iso (H) = 0.08 Å 2 ]. Other H atoms were constrained to ideal geometries and refined as riding, with Csp 2 -H = 0.93 Å, C(methyl)-H = 0.96 Å, and O-H = 0.82 Å; U iso (H) = 1.2U eq (C) and 1.5U eq (O and C methyl ). Fig. 1. The molecular structure of the compound, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen atoms are shown as spheres of arbitrary radius and hydrogen bonds are drawn as dashed lines.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq