Crystal structure and Hirshfeld surface analysis of (E)-1-(2,6-dichlorophenyl)-2-(2-nitrobenzylidene)hydrazine

In the crystal, face-to-face π-π stacking interactions occur along the a-axis direction between the centroids of the 2,6-dichlorophenyl ring and the nitro-substituted benzene ring. In addition, these molecules show intramolecular N—H⋯Cl and C—H⋯O contacts and are linked by intermolecular N—H⋯O and C—H⋯Cl hydrogen bonds, forming pairs of hydrogen-bonded molecular layers parallel to (20).


Chemical context
Arylhydrazones and their complexes have attracted much attention because of their high synthetic potential for organic and inorganic chemistry and diverse useful properties (Maharramov et al., 2009Mahmudov et al., 2010Mahmudov et al., , 2011Mahmudov et al., , 2014a. The analytical and catalytic properties of this class of compounds are strongly dependent on the attached groups to the hydrazone moiety Shixaliyev et al., 2018Shixaliyev et al., , 2019. On the other hand, intermolecular interactions organize the molecular architectures, which play a critical role in synthesis, catalysis, micellization, etc. (Akbari Afkhami et al., 2017;Gurbanov et al., 2017Gurbanov et al., , 2018Kopylovich et al., 2011a,b;Ma et al., 2017a,b;Mahmoudi et al., 2016Mahmoudi et al., , 2017aMahmoudi et al., ,b,c, 2018a. New types of non-covalent bonds such as halogen, chalcogen, pnictogen and tetrel bonds or their cooperation with hydrogen bonds are able to contribute to the synthesis and catalysis, giving materials with improved properties (Mahmudov et al., , 2014b(Mahmudov et al., , 2015(Mahmudov et al., ,b, 2019Mizar et al., 2012;Shixaliyev et al., 2013Shixaliyev et al., , 2014. For that, the main skeleton of the hydrazone ligand should be decorated by non-covalent bond donor centre(s). In a continuation of our work in this regard, we have functionalized a new azo dye, (E)-1-(2,6-dichlorophenyl)-2-(2-nitrobenzylidene)hydrazine, which provides intermolecular non-covalent interactions.

Figure 1
The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 50% probability level.

Figure 3
A partial view ofstacking interactions in the crystal packing of the title compound viewed along the b axis.

Figure 4
A general view of the crystal packing along the a axis of the title compound. Dashed lines indicate the intramolecular N-HÁ Á ÁCl, C-HÁ Á ÁO, intermolecular N-HÁ Á ÁO, C-HÁ Á ÁCl interactions and ClÁ Á ÁH, OÁ Á ÁH contacts. [Symmetry codes: (a) x, 1 + y, z; (b) À 1 2 + x, 3 2 À y, À 1 2 + z; Hirshfeld surface analysis was used to analyse the various intermolecular interactions in the title compound, through mapping the normalized contact distance (d norm ) using Crys-talExplorer (Turner et al., 2017;Spackman & Jayatilaka, 2009). The Hirshfeld surface mapped over d norm using a standard surface resolution with a fixed colour scale of À0.1980 (red) to 1.3500 (blue) a.u. is shown in Fig. 6. The white surface indicates contacts with distances equal to the sum of van der Waals radii, and the red and blue colours indicate distances shorter (in close contact) or longer (distant contact) than the van der Waals radii, respectively (Venkatesan et al., 2016). The darkred spots on the d norm surface arise as a result of short interatomic contacts (Table 2), while the other weaker intermolecular interactions appear as light-red spots. The red points, which represent closer contacts and negative d norm values on the surface, correspond to the C-HÁ Á ÁO and C-HÁ Á ÁCl interactions. The shape-index of the Hirshfeld surface is a tool for visualizing thestacking by the presence of adjacent red and blue triangles; if there are no such triangles, then there are nointeractions. The plot of the Hirshfeld surface mapped over shape-index shown in Fig. 7 clearly suggests that there areinteractions in the crystal packing of the title compound.  Table 2 Summary of short interatomic contacts (Å ) in the title compound.

Figure 5
A general view of the crystal packing with the hydrogen bonds and contacts along the b axis of the title compound, forming pairs of hydrogen-bonded molecular layers parallel to (202).

Figure 6
A view of the Hirshfeld surface mapped for the title compound over d norm in the range À0.1980 to 1.3500 arbitrary units.

Figure 7
View of the three-dimensional Hirshfeld surface of the title compound plotted over shape-index.
The percentage contributions of various contacts to the total Hirshfeld surface are listed in Table 3 and shown in the two-dimensional fingerprint plots in Fig. 8. As revealed by the two-dimensional fingerprint plots (Fig. 8), the crystal packing is dominated by HÁ Á ÁH contacts, representing van der Waals interactions (23.0% contribution to the overall surface), followed by OÁ Á ÁH and ClÁ Á ÁH interactions, which contribute 20.1% and 19.0%, respectively.

Database survey
Six compounds closely resemble the title compound, viz.  (Allen et al., 1987) and angles for the title compound are within normal ranges and are comparable to those observed in these structures. In each one, the configuration of the imine C N bond is E.

Synthesis and crystallization
The title compound was synthesized according to the reported method (Atiog lu et al., 2019;Maharramov et al., 2018;Shixaliyev et al., 2018Shixaliyev et al., , 2019. A mixture of 2-nitrobenzaldehyde (10 mmol), CH 3 COONa (0.82 g), ethanol (50 mL) and (2,6dichlorophenyl)hydrazine (10.2 mmol) was refluxed at 353 K under stirring for 2 h. The reaction mixture was cooled to room temperature and water (50 mL) was added to give a precipitate of the crude product, which was filtered off, washed with diluted ethanol (1:1 with water) and dried in vacuo using a rotary evaporator. Crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution.

(E)-1-(2,6-Dichlorophenyl)-2-(2-nitrobenzylidene)hydrazine
Crystal data 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.