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

In the crystal, C—H⋯N, C—Cl⋯π interactions and face-to-face π–π stacking interactions connect the molecules, forming ribbons along the a-axis direction.


Chemical context
Azo dyes find numerous applications in a diversity of areas, including as antimicrobial agents, in molecular recognition, optical data storage, molecular switches, non-linear optics, liquid crystals, dye-sensitized solar cells, color-changing materials, etc., mainly due to the possibility of the cis-to-trans isomerization and the chromophoric properties of the -N Nsynthon Viswanathan et al., 2019). Not only azo-hydrazone tautomerisim, but also E/Z isomerization are important phenomena in the synthetic chemistry of azo dyes (Ma et al., 2017a,b;Mahmoudi et al., 2018a,b). The design of azo dyes with functional groups led to multifunctional ligands, the corresponding transition-metal complexes of which have been used effectively as catalysts in C-C coupling and oxidation reactions (Ma et al., 2020(Ma et al., , 2021Mahmudov et al., 2013;Mizar et al., 2012). Moreover, the functional properties of azo dyes can be improved by attaching substituents with non-covalent bond donor or acceptor site(s) to the -N N-synthon (Gurbanov et al., 2020a,b;Kopylovich et al., 2011;Mahmudov et al., 2020;Shixaliyev et al., 2014). Thus, we have attached halogen-bond donor centres to the -N N-moiety, leading to a new azo dye, (E)-1-[2,2-dichloro-1-(4-fluorophenyl)ethenyl]-2-(2,4-dichlorophenyl)diazene, which provides multiple intermolecular non-covalent interactions.

Hirshfeld surface analysis
Crystal Explorer (Turner et al., 2017) was used to perform a Hirshfeld surface analysis and generate the associated twodimensional fingerprint plots, with a standard resolution of the three-dimensional d norm surfaces plotted over a fixed colour scale of À0.1450 (red) to 1.1580 (blue) a.u (Fig. 5). In the Hirshfeld surface mapped over d norm (Fig. 5), the bright-red spots near atoms Cl1, Cl3, H4, N2 and F1 indicate the short C-HÁ Á ÁN, C-HÁ Á ÁCl and ClÁ Á ÁF contacts (Table 2). Other contacts are equal to or longer than the sum of van der Waals radii. The Hirshfeld surface of the title compound mapped over the electrostatic potential (Spackman et al., 2008 Table 1 Hydrogen-bond geometry (Å , ).

Figure 3
The crystal packing of the title compound viewed along the b axis with intermolecular C-HÁ Á ÁN and C-ClÁ Á Á interactions andstacking interactions 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.
shown in Fig. 6. The positive electrostatic potential (blue regions) over the surface indicates hydrogen-donor potential, whereas the hydrogen-bond acceptors are represented by negative electrostatic potential (red regions).

Table 2
Summary of short interatomic contacts (Å ) in the title compound.

Figure 4
The crystal packing of the title compound viewed along the c axis with intermolecular C-HÁ Á ÁN and C-ClÁ Á Á interactions andstacking interactions shown as dashed lines.

Figure 6
View of the three-dimensional Hirshfeld surface of the title compound plotted over electrostatic potential energy in the range À0.0500 to 0.0500 a.u. using the STO-3 G basis set at the Hartree-Fock level of theory. Hydrogen-bond donors and acceptors are shown as blue and red regions around the atoms, corresponding to positive and negative potentials, respectively.

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 4. The Moscow synchrotron radiation source was used for the data collection. H atoms were positioned geometrically and treated as riding atoms where C-H = 0.95 Å with U iso (H) = 1.2U eq (C). Five outliers 3 2 2, 3 2 2, 2 11 3, 2 2 1 and 2 2 1 were omitted during the final refinement cycle because of large differences between observed and calculated intensities.    (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2020).

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.