(E)-1-(2,6-Dichlorophenyl)-2-(3-nitrobenzylidene)hydrazine: crystal structure and Hirshfeld surface analysis

In the crystal, face-to-face π-π stacking interactions along the a-axis direction occur between the 2,6-dichlorophenyl ring and nitro-substituted benzene ring of the title molecule. The molecules are further linked by C—H⋯O contacts and N—H⋯O and C—H⋯Cl hydrogen bonds, forming pairs of hydrogen-bonded molecular layers parallel to (100).


Chemical context
Schiff bases as well as hydrazone ligands and their complexes have attracted much attention because of their high synthetic potential for organic and inorganic chemistry and their diverse useful properties Mahmudov et al., 2014). The analytical and catalytic properties of this class of compounds are strongly dependent on the groups attached to the hydrazone moiety (Shixaliyev et al., 2019). On the other hand, intermolecular interactions organize molecular architectures, which play a critical role in synthesis, catalysis, micellization, etc (Akbari et al., 2017;Gurbanov et al., 2018;Mahmoudi et al., 2018 and references cited therein). New types of weak interactions such as halogen, chalcogen, pnictogen and tetrel bonds or their cooperation with hydrogen bonds are able to drive the synthesis and catalysis, as well as improve properties of materials (Mizar et al., 2012;Mahmudov et al., 2019 and references cited therein). For that, the main skeleton of the arylhydrazone ligand should be extended with weak bond-donor centre(s). In order to continue our work in this perspective, we have functionalized a new azo dye, (E)-1-(2,6-dichlorophenyl)-2-(3-nitrobenzylidene)hydrazine, (I), which provides intermolecular non-covalent interactions.

Structural commentary
The title molecule ( Fig. 1) has an E configuration about the C N bond. The 2,6-dichlorophenyl ring and the nitrosubstituted benzene ring of the title compound are inclined at 26.25 (16) , while the nitro group is skewed out of the attached benzene ring plane by 6.3 (2) . The conformation is stabilized by an intramolecular N1-H1NÁ Á ÁCl1 interaction, which forms an S(6) graph-set motif ( Table 1). The conformation of the title compound can be compared with that of the isomeric compound (E)-1-(2,6-dichlorophenyl)-2-(2-nitrobenzylidene)hydrazine (CSD refcode KUWGOB; Ç elikesir et al., 2020). Fig. 2 shows the overlay of the two isomers. The r.m.s. deviation of the overlay between the two isomers is 0.003 Å . In the 2-nitro isomer, the dihedral angles are 21.16 (14) (between the phenyl rings) and 27.06 (18) (between between the nitro group and the phenyl ring). The difference in angles may be due to the steric interaction resulting from the position of the nitro group on the benzene ring to which it is attached.

Figure 4
A general view of the crystal packing of the title compound along the a axis with hydrogen bonds and contacts shown as dashed lines.

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

Hirshfeld surface analysis
The Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and the associated two-dimensional fingerprint plots (McKinnon, et al., 2007) were performed with Crystal Explorer17 (Turner et al., 2017) to investigate the intermolecular interactions and surface morphology. The Hirshfeld surface mapped over d norm in the range À0.2694 to 1.2224 a.u. and corresponding colours from red (shorter distance than the sum of van der Waals radii) over white to blue (longer distance than the sum of van der Waals radii) is shown in Fig. 6. The red points, which represent closer contacts and negative d norm values on the surface, correspond to the N-HÁ Á ÁO, C-HÁ Á ÁO and C-HÁ Á ÁCl interactions ( Table 2). The shape-index of the Hirshfeld surface is a tool for visualizing thestacking by the presence of adjacent red and blue triangles. The plot of the Hirshfeld surface mapped over shape-index shown in Fig. 7 clearly suggests that there areinteractions in the title compound.

Figure 5
A general view of the crystal packing of the title compound along the b axis showing the pairs of hydrogen-bonded molecular layers parallel to (100). Table 2 Summary of short interatomic contacts (Å ) in 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.