N′-(2-Hydroxy-5-chlorobenzylidene)-4-nitrobenzohydrazide methanol solvate

The title compound, C14H10ClN3O4·CH4O, was synthesized from the reaction of 5-chlorosalicylaldehyde with 4-nitrobenzohydrazide in methanol. The Schiff base molecule is nearly planar, with a dihedral angle of 9.1 (3)° between the two benzene rings. The methanol solvent molecules are linked to the Schiff base molecules by N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds, forming chains running parallel to the a axis.

The title compound, C 14 H 10 ClN 3 O 4 ÁCH 4 O, was synthesized from the reaction of 5-chlorosalicylaldehyde with 4-nitrobenzohydrazide in methanol. The Schiff base molecule is nearly planar, with a dihedral angle of 9.1 (3) between the two benzene rings. The methanol solvent molecules are linked to the Schiff base molecules by N-HÁ Á ÁO, O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds, forming chains running parallel to the a axis.

Comment
Schiff base compounds have been found to have potential pharmacological and antitumor properties (Brückner et al., 2000;Harrop et al., 2003;Ren et al., 2002). Recently, a few Schiff base compounds derived from the reaction of aldehydes with benzohydrazides have been reported (Diao 2007;Diao, Huang et al., 2008;Diao, Shu et al., 2007;Diao, Zhen et al., 2008;Huang et al., 2007;Li et al., 2007;Ma et al., 2008;Wang et al., 2008). As a further study of such compounds, we report here the crystal structure of the title compound.
The asymmetric unit of the title compound consists of a Schiff base molecule and a lattice methanol molecule. The Schiff base molecule is nearly planar with the dihedral angle between the two benzene rings of 9.1 (3)°. The dihedral angle between the C1-C6 benzene ring and the O1/N1/O2 nitryl plane is 6.4 (3) °. The torsion angles C9-C8-N3-N2 and C4-C7-N2-N3 are 179.8 (2)° and -173.6 (2)°, respectively. The methanol solvent molecules are linked to the Schiff base molecules by N-H···O, O-H···N and O-H···O hydrogen bonds (Table 1), forming chains running along the a axis (Fig. 2).
Experimental 5-Chlorosalicylaldehyde (0.1 mmol, 15.7 mg) and 4-nitrobenzohydrazide (0.1 mmol, 18.1 mg) were dissolved in a methanol solution (20 ml). The mixture was stirred at reflux for 1 h and cooled to room temperature. After keeping the solution in air for a week, yellow block-like crystals were formed.

Refinement
Atom H2A was located from a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å. All other H atoms were placed in idealized positions and constrained to ride on their parent atoms, with C-H = 0.93-0.96 Å, O-H = 0.82 Å, and with U iso (H) = 1.2U eq (C) or 1.5U eq (O and methyl C). Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.

Special details
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 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.