Crystal structure and Hirshfeld surface analysis of (E)-4-amino-N′-[1-(4-methylphenyl)ethylidene]benzohydrazide

The title substituted benzohydrazide Schiff base compound is essentially planar, with a trans configuration between the benzene ring molecular components, while the Hirshfeld surface analysis has been used to examine the molecular interactions within the hydrogen-bonded structure


Chemical context
Schiff bases are an important class of compounds in the medicinal and pharmaceutical fields and have played a role in the development of coordination chemistry as they readily form stable complexes with most transition metals. These complexes show interesting properties, e.g. their ability to reversibly bind oxygen, catalytic activity in the hydrogenation of olefins and transfer of an amino group, photochromic properties, and complexation ability towards toxic metals (Karthikeyan et al., 2006;Khattab et al., 2005;Kü çü kgü zel et al., 2006). Hydrazone Schiff base compounds (Cao et al., 2009;Zhou & Yang, 2010;Zhang et al., 2009), derived from the reaction of aldehydes with hydrazines have been shown to possess excellent biological activities, such as anti-bacterial, anti-convulsant and anti-tubercular (Bernhardt et al., 2005;Armstrong et al., 2003). As part of our studies in this area, the title Schiff base compound (E)-4-amino-N 0 -(1-(p-tolyl)ethylidene)benzohydrazide, was prepared and the crystal structure is reported herein. Hirshfeld surface analysis was also performed for visualizing and quantifying intermolecular interactions in the crystal packing of the compound.

Supramolecular features
In the crystal, two types of intermolecular hydrogen-bonding interactions are present (Table 1). The N3-H1N3Á Á ÁO1 i hydrogen bond between the amino group and a symmetryrelated carbonyl group generates zigzag chains extending along the b-axis direction, as shown in Fig. 2. The secondary weak methyl C9-H9AÁ Á ÁO1 ii hydrogen-bonding interactions extend the structure across a (Fig. 3), generating a layer lying parallel to (001). No reasonable acceptors could be identified for either the second amine N3 H atom or the hydrazide N1 H atom.

Hirshfeld surface analysis
Hirshfeld surfaces and their associated two-dimensional fingerprint plots (Soman et al., 2014) have been used to quantify the various intermolecular interactions in the title compound. The Hirshfeld surface of a molecule is mapped using the descriptor d norm which encompasses two factors: one is d e , representing the distance of any surface point nearest to the internal atoms, and the other one is d i , representing the distance of the surface point nearest to the exterior atoms and also with the van der Waals radii of the atoms (Dalal et al., 1030 Sivajeyanthi et al.  Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) Àx; y þ 1 2 ; Àz þ 3 2 ; (ii) x þ 1; y; z.

Figure 2
Crystal packing of the title compound in the unit cell, showing molecules linked across b via N-HÁ Á ÁO hydrogen bonds (dashed lines).

Figure 3
The crystal packing in the title compound in which molecules are linked across a via weak C-HÁ Á ÁO hydrogen bonds (dashed lines). H atoms not involved in hydrogen-bonding interactions have been omitted.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.

Figure 4
Hirshfeld surfaces mapped over d norm for the title compound.

Synthesis and crystallization
The title compound was synthesized by the reaction of a 1:1 molar ratio mixture of a hot methanolic solution (20 mL) of 4-aminibenzoichydrazide (0.151 mg, Aldrich) and a hot methanolic solution of 4-methylacetophenone (0.134 mg, Aldrich), which was refluxed for 8 h. The solution was then cooled and kept at room temperature after which colourless Two-dimensional fingerprint plots of the title compound.

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.  (7) 0.0706 (10) −0.0063 (7) −0.0069 (8) 0.0095 (7)  N2 0.0532 (9) 0.0386 (7) 0.0638 (9) −0.0062 (7) −0.0056 (7) 0.0055 (7)