(E)-N′-[4-(Dimethylamino)benzylidene]-4-hydroxybenzohydrazide hemihydrate

In the title compound, C16H17N3O2·0.5H2O, the two hydrazide molecules are approximately planar: the dihedral angles between the two substituted benzene rings are 7.7 (2) and 4.2 (2)°. Both hydrazone molecules exist in a trans geometry with respect to their methylidene units. In the crystal, the water molecule lies between the two organic molecules and makes bifurcated O—H⋯(N,O) hydrogen bonds to both of them. The hydrazide molecules form N—H⋯O and O—H⋯O hydrogen bonds, resulting in a three-dimensional network.

In the title compound, C 16 H 17 N 3 O 2 Á0.5H 2 O, the two hydrazide molecules are approximately planar: the dihedral angles between the two substituted benzene rings are 7.7 (2) and 4.2 (2) . Both hydrazone molecules exist in a trans geometry with respect to their methylidene units. In the crystal, the water molecule lies between the two organic molecules and makes bifurcated O-HÁ Á Á(N,O) hydrogen bonds to both of them. The hydrazide molecules form N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, resulting in a three-dimensional network.

Comment
In recent years, much attention has been focused on the biological properties of hydrazone compounds (e.g. Banerjee et al., 2009). A number of hydrazone compounds have been prepared and investigated for their structures (Ahmad et al., 2010;Li et al., 2010;Naveenkumar et al., 2010;Zhang, 2009;Fun et al., 2008). In the present work, a new hydrazone compound with interesting structure is reported.
The title compound consists of two hydrazone molecules and one water molecule (Fig. 1). The two hydrazone molecules are approximately parallel to each other, and are linked together by the water molecule through O-H···N and O-H···O hydrogen bonds (Table 1). Both hydrazone molecules exist in trans geometry with respect to the methylidene units. The dihedral angles between the two substituted benzene rings in the hydrazone molecules are 7.7 (2) and 4.2 (2)°.
In the crystal structure, the hydrazone molecules and the water molecules are linked through N-H···O, O-H···O and O-H···N hydrogen bonds (Table 1), forming a three dimensional network (Fig. 2).
Experimental 4-Dimethylaminobenzaldehyde (1.0 mmol, 149 mg) and 4-hydroxybenzohydrazide (1.0 mmol, 152 mg) were mixed in 50 ml methanol. The mixture was stirred at ambient temperature for 2 h and filtered. Colorless blocks of (I) were formed by slow evaporation of the filtrate for a week; presumably water was incorporated from the atmosphere.

Refinement
The amino hydrogen atoms were located in a difference map and refined isotropically, with the N-H distance restrained to 0.90 (1)Å. Other hydrogen atoms were placed in calculated positions (C-H = 0.93 -0.96 Å, O-H = 0.82 Å) and refined as riding with U iso (H) = 1.2U eq (C) and 1.5U eq (O and C methyl ). In the absence of significant anomalous scattering effects, Friedel pairs were averaged.   supplementary materials sup-3

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.