3-Bromo-N′-(3,5-dibromo-2-hydroxybenzylidene)benzohydrazide methanol solvate

The title compound, C14H9Br3N2O2·CH4O, was prepared by the reaction of 3,5-dibromo-2-hydroxybenzaldehyde and 3-bromobenzohydrazide in methanol. The asymmetric unit of the crystal consists of a Schiff base molecule and a methanol molecule of crystallization. The dihedral angle between the two benzene rings is 5.5 (2)°. An intramolecular O—H⋯N hydrogen bond is observed. In the crystal structure, pairs of adjacent Schiff base molecules are linked by two methanol molecules through intermolecular N—H⋯O and O—H⋯O hydrogen bonds.

The title compound, C 14 H 9 Br 3 N 2 O 2 ÁCH 4 O, was prepared by the reaction of 3,5-dibromo-2-hydroxybenzaldehyde and 3bromobenzohydrazide in methanol. The asymmetric unit of the crystal consists of a Schiff base molecule and a methanol molecule of crystallization. The dihedral angle between the two benzene rings is 5.5 (2) . An intramolecular O-HÁ Á ÁN hydrogen bond is observed. In the crystal structure, pairs of adjacent Schiff base molecules are linked by two methanol molecules through intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds.

Comment
Schiff bases are readily synthesized by the reaction of aldehydes with primary amines (Lodeiro et al., 2003;Annigeri et al., 2002;Rao et al., 2003). We have previously reported some Schiff bases and their complexes Wang et al., 2006). In this paper, the preparation and crystal structure of the new Schiff base title compound (I) , Fig 1, is reported.
The C═N bond length in the title molecule is comparable with those observed in other Schiff bases (Yehye et al., 2008;Odabaşoğlu et al., 2007;Yathirajan et al., 2007). All bond lengths are within normal ranges and are comparable to those observed in the related compounds (Zhu et al., 2009;Bao & Wei, 2008). The dihedral angle between C1-C6 and C9-C14 phenyl rings is 5.5 (2)°, indicating that the molecule is nearly coplanar. An intramolecular O1-H1···N1 hydrogen bond is observed and may contribute to the overall planarity of the molecule.
Experimental 3,5-Dibromo-2-hydroxybenzaldehyde (1.0 mmol) and 3-bromobenzohydrazide (1.0 mmol) were dissolved in methanol (30 ml). The mixture was stirred at reflux for 10 min to give a clear colourless solution. After keeping this solution in air for a week, colourless block-shaped crystals were formed.

Refinement
The H atom bound to N2 was located in a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å. All other H atoms were positioned geometrically (C-H = 0.93-0.96 Å and O-H = 0.82 Å) and refined as riding, with U iso (H) values set at 1.2U eq (C) and 1.5U eq (O and C15). The crystals were small and weakly diffracting which accounts for the low measured data fraction of 96% out to θ = 27.0 °.

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.