N′-(3-Hydroxybenzylidene)-4-nitrobenzohydrazide

The title molecule, C14H11N3O4, is approximately planar, with an interplanar angle between the two benzene rings of 5.8 (2)°. In the crystal, four molecules are linked by an R 4 4(12) motif with pairs of strong O—H⋯O and N—H⋯O hydrogen bonds. The motif is situated about the crystallographic centres of symmetry and it is composed of two pairs of parallel molecules. This quadruplet of molecules is further extended by symmetry-equivalent hydrogen bonds to form layers parallel to the (10) plane. In addition to the hydrogen bonds, there is also a weak π–π interaction between the benzene rings.

The title molecule is shown in Fig. 1. The molecule is approximately planar, with the interplanar angle between the two benzene rings equal to 5.8 (2)°. The bond lengths and angles are comparable with the hydrazone compounds cited above.
Four title molecules are linked by the motif R 4 4 (12) (Etter et al., 1990) with pairs of strong O-H···O and strong N-H···O hydrogen bonds (Desiraju & Steiner, 1999). For the hydrogen bonds, see Table 1. The motif R 4 4 (12) is situated about the crystallographic centres of symmetry with the Wyckoff position 2c for the present setting. This motif is composed of two pairs of parallel molecules. This quadruplet of the title molecules is further extended by the symmetry equivalent H-bonds into the layers parallel to the planes (101). In addition to the hydrogen bonds there is also a weak π-electron ring-π-electron ring interaction (Table 2) between the benzene rings in the structure (Spek, 2009).
Experimental 4-Nitrobenzohydrazide (0.181 g, 1 mmol) and 3-hydroxybenzaldehyde (0.122 g, 1 mmol) were mixed in 50 ml of methanol at room temperature. The mixture was stirred at room temperature for 30 min to give a yellow solution of the product. After keeping the above solution in air for 5 d, yellow block-shaped crystals with average size of 0.1 mm × 0.2 mm × 0.2 mm developed.

Refinement
All the H atoms were discernible in the difference electron density maps. However, the aryl H atoms were positioned into idealized positions and refined in riding atom approximation. The used constraints: C-H = 0.93 Å; U iso (H) = 1.2U eq (C).
The positional parameters of the H atoms H1 and H2 involved in the strong hydrogen bonds were refined freely, however, with the constraints of the displacement parameters U iso (H) = 1.5U eq (O or N).

Special details
Geometry. All e.s. 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.  Overview of π-π ring interactions in the structure Centroid-centroid * Distance (Å) Symmetry code Cg1-Cg2 3.6803 (16) 1 -x, -y, 1 -z * Cg1 and Cg2 are the centroids of the C1-C6 and C9-C14 benzene rings, respectively.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
supplementary materials sup-7