N′-[(E)-5-Bromo-2-hydroxy-3-methoxybenzylidene]benzohydrazide monohydrate

The title compound, C15H13BrN2O3·H2O, exists in an E conformation with respect to the azomethane C=N double bond. The benzene and phenyl rings form dihedral angles of 0.46 (2) and 4.90 (3)°, respectively with the central C(=O)N2C unit. An intramolecular O—H⋯N hydrogen bond occurs. In the crystal, some hydrazide molecules are replaced by molecules of the 6-bromo isomer. The Br atom from this admixture was refined to give a partial occupancy of 0.0443 (19). A supramolecular network is built in the lattice by means of intermolecular N—H⋯O and two O—H⋯O interactions together with non-classical C—H⋯O interactions involving the lattice water molecule stacking the molecules along the b-axis direction.


Comment
Hydrazone derivatives represent an important class of organic compounds. The research for this class of compounds is an area of great interest due to their biological activities (Sreeja et al., 2004;Rada & Leto, 2008). They have been extensively investigated recently owing to their potential application as antineoplastic, antiviral and antiinflammatory agents (Rakha et al., 1996;Takahama, 1996).
The compound ( Fig. 1) crystallizes in the monoclinic space group P2 1 2 1 2 1 . This molecule adopts an E configuration with respect to the C7=N1 bond and it exists in the amido form with a C8=O3 bond length of 1.222 (5) Å which is very close to the reported C=O bond length of a related structure (Reshma et al., 2012). The O3 and N1 atoms are in a Z configuration with respect to C8-N2 having a torsion angle of -0.3 (7)°. The central C(=O)N 2 C unit has dihedral angles of 0.46 (2) and 4.90 (3)°, respectively with the phenol and phenyl rings.
In the crystal, approximately 4% of the title compound is replaced by molecules of the 6-isomer, the Br1B atom of this admixture molecule was included in the refinement. Since the molecules of the 6-isomer are likely to be non-planar due to sterical factors, it does not occupy the same position as the molecule of the 5-bromo isomer. As a result, Br1B deviates by 0.39 (2) Å from the mean plane of C1-C6 plane, and the distance C6-Br1B is 1.798 (8) Å, much smaller than the typical bond length of C-Br.
The lattice water molecule connects three adjacent molecules via three classical O-H···O and a N-H···O hydrogen bond interactions with D···A distances of 3.178 (5), 3.052 (5), 2.736 (5) and 2.945 (5) Å and two non-classical C-H···O hydrogen bond interactions with D···A distances of 3.304 (8) and 3.333 (7) Å ( Fig. 2, Table 1). Molecules are stacked one over the other by forming a one-dimensional-layer via O-H···O, N-H···O and C-H···O intermolecular hydrogen bonding along a axis (Fig. 3). Such layers are connected by means of a C-H···Br intermolecular hydrogen bonding interaction with D···A distance of 3.649 (5) Å (Fig. 4). These layers arranged in a zig-zag fashion (Fig. 4) forming a threedimensional-supramolecular network in the lattice. The molecule also has a O-H···N intramolecular hydrogen bonding with a D···A distance of 2.637 (5) Å. Although there are very few weak short ring interactions found in the crystal system, they are not significant to support the network since centroid-centroid distances are above 4 Å. Fig. 5 shows a packing diagram of the title compound viewed along the a axis.

Experimental
The title compound was prepared by adapting a reported procedure (Emmanuel et al., 2011). A solution of 5-bromo-3methoxysalicylaldehyde (0.231 g, 1 mmol) in ethanol (10 ml) was mixed with an ethanolic solution (10 ml) of benzhydrazide (0.228 g, 1 mmol). The mixture was boiled under reflux for 3 h and then cooled to room temperature. The for a few days.

Refinement
The bromine atoms Br1 and Br1B of this molecule were refined freely, with the sum of their occupancy factors constrained to 1.0. The atoms H2, Br1B, H1A and H1B were located from a difference Fourier map and N2-H2 distance was restrained to 0.88±0.02. The H5 atom was placed in calculated position with occupancy factor equal to that Br1B, and its coordinates were fixed. The H6 atom was refined with restrained distance of 0.93 with occupancy factor equal to that of Br1. O1W-H1A and O1W-H1B distances were restrained to 0.85±0.02. C6-Br1B distance is restrained to 1.88±0.01 Å. The H atoms on C were placed in calculated positions, guided by difference maps, with C-H bond distances 0.93-0.96 Å. H atoms were assigned as U iso (H) = 1.2U eq (carrier) or 1.5U eq (methyl C). Omitted owing to bad disagreement were the reflections (0 0 2) and (0 1 1).

Computing details
Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 2010); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).     Packing diagram of the compound along the a axis. 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 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 Occ. (