Crystal structure of (E)-N′-(5-bromo-2-hydroxybenzylidene)nicotinohydrazide monohydrate

The title compound, has an E conformation about the C=N bond and the molecules is planar (r.m.s. deviation for all non-H atoms = 0.021 Å). In the crystal, the lattice water molecule (Ow) links the molecules via Ow—H⋯O, Ow—H⋯N and N—H⋯Ow hydrogen bonds, forming sheets lying parallel to (100).

In the title compound, C 13 H 10 BrN 3 O 2 ÁH 2 O, the conformation about the azomethine double bond is E. The molecule exists in the amido form with a C O bond length of 1.229 (2) Å . There is an intramolecular O-HÁ Á ÁN hydrogen bond forming an S(6) ring motif. The whole molecule is almost planar, with an r.m.s. deviation of 0.021 Å for all non-H atoms, and the dihedral angle between the planes of the pyridine and benzene rings is 0.74 (12) . In the crystal, the water molecule of crystallization links the organic molecules via Ow-HÁ Á ÁO, Ow-HÁ Á ÁN and N-HÁ Á ÁOw hydrogen bonds and short C-HÁ Á ÁOw contacts, forming sheets lying parallel to (100). Within the sheets there is a weak interaction involving the pyridine and benzene rings [centroid-to-centroid distance = 3.8473 (15) Å ]. The sheets are linked via C-HÁ Á ÁBr interactions, forming a three-dimensional network.

Chemical context
Aroylhydrazones can coordinate to transition metals either in the amido form (Bessy Raj & Kurup, 2007) or in the iminolato form (Ghosh et al., 2005;Galić et al., 2011), leading to the formation of two types of complexes. Hydrazones derived from isonicotinoyl hydrazides are potential drugs for the treatment of the iron-overload associated diseases (Macková et al., 2012). They are associated with a broad spectrum of biological activities, and studies have shown that nicotinic acid hydrazones could be considered as anti-inflammatory and analgesic agents (Navidpour et al., 2014;Kheradmand et al., 2013) and as a novel pharmacophore in the design of anticonvulsant drugs (Sinha et al., 2011). Hydrazones have been used in chemical processes, in non-linear optics and as sensors as well as in catalytic processes (Hosseini-Monfared et al., 2013;Du & Hong, 2014). Their potential as analytical reagents (Galić et al., 2011) and their uses as molecular switches, metallo-assemblies and sensors have also been reported (Su & Aprahamian, 2014). Salicylaldehyde isonicotinoylhydrazone has also been used for the spectrophotometric determination of gallium(III) and indium(III) (Reddy et al., 2011).

Supramolecular features
In the crystal, the water molecule forms three hydrogen bonds with three different nicotinic hydrazone molecules (Table 1 and Fig. 2). This compound is an example of a system where a single atom acts both as donor and acceptor. There are also C-HÁ Á ÁO(water) contacts present enclosing R 1 2 (6) and R 1 2 (7) ring motifs (Fig. 2). Finally sheets are formed lying parallel to (100). There are weakinteractions within the sheets involving the bromine-bearing aromatic ring of one molecule and the pyridine ring of another, with a centroid-centroid distance of 3.8473 (15) Å (Fig. 2). The sheets are linked via C-HÁ Á ÁBr interactions, forming a three-dimensional network (Table 1 and Fig. 3).

Database survey
A search of the Cambridge Structural Database (Version 5.36, update Feb. 2015;Groom & Allen, 2014) yielded 22 hits for the substructure N 0 -(2-hydroxybenzylidene)nicotinohydrazide. The crystal structure of N 0 -(2-hydroxybenzylidene)nicotinohydrazide itself is reported as a monohydrate (IDASUB; Galić et al., 2001), and the crystal structure of the chloro derivative of the title compound, which crystallized with two independent molecules in the asymmetric unit, has also been reported (MOZPIB; Ren, 2009 A view of the molecular structure of the title compound, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Table 1 Hydrogen-bond geometry (Å , ).

Figure 3
A view along the c axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed lines (see Table 1 for details) and H atoms not involved in hydrogen bonding have been omitted for clarity.
compounds, an intramolecular O-HÁ Á ÁN hydrogen bond is also present. The molecules are also relatively planar, with the benzene and pyridine rings being inclined to one another by ca 4.2 in IDASUB, and by ca 12.8 and 1.9 in the two independent molecules of MOZPIB. This last dihedral angle is similar to that in the title compound [cf. 0.74 (12) ]. In the crystal structure of N 0 -(2-hydroxybenzylidene)nicotinohydrazide monohydrate (IDASUB), the water molecule forms three hydrogen bonds and is another example of a system where a single atom acts both as donor and acceptor.

Synthesis and crystallization
The title compound was prepared by adapting a reported procedure (Mathew & Kurup, 2011). A methanolic solution of 5-bromosalicylaldehyde (0.10051 g, 0.5 mmol) and nicotinic hydrazide (0.06857 g, 0.5 mmol) was refluxed for 3 h with two drops of glacial acetic acid. Light-yellow block-shaped crystals of the title compound were obtained by slow evaporation of the solvent.

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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )