4-Chloro-N′-[(Z)-4-nitrobenzylidene]benzohydrazide monohydrate

In the title compound, C14H10ClN3O3·H2O, the benzohydrazide group is not planar and the molecule exists in a cis configuration with respect to the methylidene unit. The dihedral angle between the two substituted benzene rings is 38.7 (3)°. In the crystal structure, molecules are linked by O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds into a two-dimensional network parallel to the (100) plane. The crystal structure is further stabilized by weak C—H⋯O interactions.

In the title compound, C 14 H 10 ClN 3 O 3 ÁH 2 O, the benzohydrazide group is not planar and the molecule exists in a cis configuration with respect to the methylidene unit. The dihedral angle between the two substituted benzene rings is 38.7 (3) . In the crystal structure, molecules are linked by O-HÁ Á ÁO, O-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds into a twodimensional network parallel to the (100) plane. The crystal structure is further stabilized by weak C-HÁ Á ÁO interactions.
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003). Hydrazones have been demonstrated to possess antimicrobial, anticonvulsant, analgesic, antiinflammatory, antiplatelet, antitubercular, anticancer and antitumor activities (e.g. Bedia et al., 2006). Hydrazones possessing an azometine -NHN=CH-proton constitute an important class of compounds for new drug development. Many researchers have therefore synthesized these compounds as target structures and evaluated their biological activities. These observations have served as guides for the development of new hydrazones that possess varied biological activities. These compounds are synthesized by heating the appropriate substituted hydrazines/hydrazides with aldehydes and ketones in solvents like ethanol, methanol, tetrahydrofuran, butanol, glacial acetic acid, ethanol-glacial and acetic acid. Another synthetic route for the synthesis of hydrazones is the coupling of aryldiazonium salts with active hydrogen compounds (Rollas & Kοuçοukgοuzel, 2007).
The water molecule is involved in O-H···O, O-H···N and N-H···O hydrogen bonds (Table 1). These hydrogen bonds linked the molecules into two dimensional networks parallel to the (100) plane as shown in Fig. 2. The crystal is further stabilized by weak C-H···O interactions (Table 1).

S2. Experimental
The title compound was prepared by refluxing 4-chlorophenyl hydrazide (0.01 mol), 4-nitro benzaldehyde (0.01 mol) in ethanol (30 ml) and 3 drops of concentrated sulfuric acid for 3 hrs. Excess ethanol was removed from the reaction mixture under reduced pressure. The solid product obtained was filtered, washed with water and dried. Colorless needles of (I) were obtained from an ethanol solution by slow evaporation (Yield 53%), M.p. 488 K.

S3. Refinement
All the H atoms were placed in calculated positions (N-H = 0.85Å, O-H = 0.88-0.89Å, C-H = 0.93Å) and refined as riding with U iso (H) = 1.2U eq (carrier). The highest residual electron density peak is 1.88 Å from H13A and the deepest hole is 0.87 Å from C7.  The molecular structure of (I), showing 50% probability displacement ellipsoids for the non-hydrogen atoms. The N-H···O hydrogen bond is shown as a dashed line.

Figure 2
The packing diagram of (I), viewed along the a axis. Hydrogen bonds are shown as dashed lines. Special details Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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.