Crystal structure and Hirshfeld surface analysis of (E)-1-(4-chlorophenyl)-2-[2,2-dichloro-1-(4-fluorophenyl)ethenyl]diazene

The dihedral angle between the 4-fluorophenyl ring and the 4-chlorophenyl ring is 56.13 (13)°. In the crystal, molecules are linked by C—H⋯Cl hydrogen bonds stacking in a column along the a axis. The crystal packing is further stabilized by face-to-face π–π stacking interactions between the centres of the similar aromatic rings of the adjacent molecules.


Chemical context
Azo compounds provide ubiquitous motifs in synthetic chemistry and are widely used as organic dyes, indicators, molecular switches, pigments, ligands, food additives, radical reaction initiators, therapeutic agents etc. (Gurbanov et al., 2017;Maharramov et al., 2018;Mahmudov et al., 2019). Azo dyes are also convenient model compounds to study both E/Z isomerization and noncovalent interactions (Mahmudov et al., 2015;Shixaliyev et al., 2018). Thus, decorating the structure of dyes with tailored functionalities (noncovalent bond donor centres) can be a pivotal strategy for controlling and tuning their functional properties . Herein we report the molecular structure and noncovalent interactions in the title compound.

Supramolecular features and Hirshfeld surface analysis
In the crystal, molecules are linked by a weak C-HÁ Á ÁCl hydrogen bond (Table 1), forming a column along the a axis (Figs. 2 and 3). The column is further stabilized by face-to-face stacking interactions; the centroid-centroid distances between the adjacent C3-C8 rings and between the adjacent C9-C14 rings are 3.8615 (18) and 3.8619 (18) Å , respectively. Moreover, the columns are linked by intermolecular ClÁ Á ÁCl short contacts, with distances of 3.3756 (11) and 3.3841 (11) Å (Table 2), forming a layer parallel to the bc plane (Fig. 2).
Hirshfeld surfaces and fingerprint plots were generated for the title compound using CrystalExplorer (McKinnon et al., 2007). The Hirshfeld surface mapped over d norm using a standard surface resolution with a fixed colour scale of À0.0941 (red) to 1.4174 a.u. (blue) is shown in Fig. 4. This plot was generated to quantify and visualize the intermolecular interactions and to explain the observed crystal packing. The dark-red spots on the d norm surface arise as a result of the C-HÁ Á ÁCl interaction and short interatomic contacts (Tables 1  and 2), while the other weaker intermolecular interactions appear as light-red spots. The shape index of the Hirshfeld surface is a tool to visualize thestacking by the presence of adjacent red and blue triangles; if there are no adjacent red and/or blue triangles, then there are nointeractions. Fig. 5 clearly suggests that there areinteractions in the title compound.
The percentage contributions of the various contacts to the total Hirshfeld surface are shown in the 2D fingerprint plots in Fig. 6. The reciprocal ClÁ Á ÁH/HÁ Á ÁCl interactions appear as two symmetrical broad wings with d e + d i ' 2.7 Å and contribute 31.2% to the Hirshfeld surface (Fig. 6b) The molecular structure of the title compound, with the atom-labelling scheme and 50% probability displacement ellipsoids.

Figure 4
View of the Hirshfeld surface of the title compound plotted over d norm in the range from À0.0941 to 1.4174 a.u. points in the 2D fingerprint plots, with an overall contribution to the Hirshfeld surface of 14.8% (Fig. 6c). The CÁ Á ÁH/HÁ Á ÁC interactions, with a 14.0% contribution, are present as bump symmetrical spikes at diagonal axes (Fig. 6d). The FÁ Á ÁH/ HÁ Á ÁF interactions, with a 12.8% contribution, are present as sharp symmetrical spikes at diagonal axes d e + d i ' 2.55 Å (Fig. 6e). The CÁ Á ÁC interactions appear in the middle of the scattered points in the 2D fingerprint plots with an overall contribution to the Hirshfeld surface of 9.0% (Fig. 6f). The small percentage contributions from the other different interatomic contacts to the Hirshfeld surfaces are as follows: ClÁ Á ÁCl (6.7%) (Fig. 6g), NÁ Á ÁH/HÁ Á ÁN (3.4%) (Fig. 6h),  View of the Hirshfeld surface of the title compound plotted over shape index.

Figure 6
The full 2D fingerprint plots for the title compound, showing (a) all interactions, and those delineated into (
Red solid (

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.