N′-(5-Bromo-2-hydroxy-3-methoxybenzylidene)-4-hydroxy-3-methoxybenzohydrazide dihydrate

In the title compound, C16H15BrN2O5·2H2O, the dihedral angle between the two aromatic rings is 2.9 (2)° and an intramolecular O—H⋯N hydrogen bond is observed. One of the water molecule is disordered over two positions, with occupancies of 0.83 (3) and 0.17 (3). In the crystal structure, molecules are linked into a three-dimensional network by intermolecular O—H⋯O, O—H⋯(O,O), O—H⋯N and N—H⋯O hydrogen bonds. π–π interactions involving Br-substituted benzene rings, with a centroid–centroid distance of 3.552 (3) Å are also observed.

The title compound ( Fig. 1) consists of a Schiff base molecule and two water molecules of crystallization. The bond lengths have normal values (Allen et al., 1987) and are comparable to those observed in related structures (Abdul Alhadi et al., 2009;Mohd Lair et al., 2009;Narayana et al., 2007). The dihedral angle between the two aromatic rings is 2.9 (2)°, indicating that they are approximately coplanar. An intramolecular O-H···N hydrogen bond is observed (Fig. 1).
In the crystal structure, the molecules are linked into layers parallel to the ab direction by intermolecular N-H···O and O-H···O hydrogen bonds (Table 1 and Fig. 2).

Experimental
The title compound was prepared by the Schiff base condensation of 5-bromo-2-hydroxy-3-methoxybenzaldehyde (0.1 mol) and 4-hydroxy-3-methoxybenzohydrazide (0.1 mmol) in 95% ethanol (50 ml). The excess ethanol was removed by distillation. The colourless solid obtained was filtered and washed with ethanol. Single crystals suitable for X-ray diffraction were obatined by slow evaporation of a 95% ethanol solution at room temperature.
The U ij parameters of atoms O6B and O7 were restrained to an approximate isotropic behaviour. The H atoms of the water molecules were located in a difference map and refined with O-H and H···H distance restraints of 0.85 (1) and 1.37 (2) Å, respectively. The disordered water O atoms O6A and O6B share the same H atoms. All other H atoms were positioned geometrically (O-H = 0.82 Å and N-H = 0.90 Å and C-H = 0.93 or 0.96 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C) and 1.5U eq (C methyl , O).

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.