N′-(2,6-Dichlorobenzylidene)-2-hydroxybenzohydrazide

In the title compound, C14H10Cl2N2O2, the dihedral angle between the two aromatic rings is 17.39 (4)°. An intramolecular O—H⋯O hydrogen bond forms a six-membered R(6)1 1 ring motif. In the crystal structure, intermolecular N—H⋯O and O—H⋯O hydrogen-bonding interactions occur.

HLS is grateful to the Institute of Chemistry, University of the Punjab, for financial support.  (Mookherjee et al., 1989). Related compounds have also shown to exhibit biological activities such as antibacterial, antimicrobial (El-Masry et al., 2000), and were investigated as herbicides (Samadhiya et al., 2001). Further, Schiff bases have also been employed as ligands for complexation of metal ions (Kumar et al., 2009). With this perspective of widespread applications of Schiff bases we embarked on the synthesis, characterization and biological evaluation of this class of compounds (Siddiqui et al., 2006;Iqbal et al., 2007). Herein, we report the synthesis and crystal structure of the title compound.
The title compound is presented in Fig.1. The two aromatic ring systems in the hydrazide are inclined at an angle of 17.39 (0.04) ° with respect to each other. The structure possesses classical inter and intra molecular hydrogen bonding. The intramolecular O-H···O type hydrogen bonding forms six membered ring motif R(6) 1 1 (Bernstein et al., 1995) which inclines at an angle of 9.73 (0.14) ° with respect to aromatic C1-C6. The intermolecular C-H···O and N-H···N type of hydrogen bonding forms nine membered ring motif R(9) 2 2 (Bernstein et al., 1995) where N-H···O type of hydrogen bonding interveins to form a six and a five membered ring system R(6) 2 1 and R(5) 1 2 (Bernstein et al., 1995), respectively ( Fig. 2, table 1).

Experimental
A mixture of 2-hydroxy-benzoic acid hydrazide (1.5 g, 10.0 mmol) and 2,6-dichlorobenzaldehyde (1.7 g, 10.0 mmol) in absolute ethanol (20 ml) was heated to reflux (2 hrs.), cooled to room temperature and filtered. The off-white precipitates were washed with the same solvent and dried at room temperature to yield 2.8 g of off-white, needle-like crystals of the title compound (9.1 mmol, 90.6%). Suitable crystals were grown from a solution of CH 3 OH by slow evaporation at room temperature.

Refinement
All aromatic H-atoms were positioned geometrically with C-H = 0.95 Å and refined using riding model with U iso (H) = 1.2 U eq (C), while the imine hydrogen was located in difference map and was refined with C-H = 0.95 (2) Å and U iso (H)

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > 2σ(F 2 ) is used only for calculating Rfactors(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.