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

Two similar molecules make up the asymmetric unit of the title compound. The crystal structure features short C—H⋯Cl and C—H⋯O contacts and C—H⋯π and van der Waals interactions.


Chemical context
Azo dyes have found a wide range of applications, including as ligands, sensors, optical data storage, liquid crystals, non-linear optical materials, color-changing materials, molecular switches, and dye-sensitized solar cells Mahmudov et al., 2016;Viswanathan et al., 2019). The functional properties of azo dyes are strongly dependent on the groups attached to the -N N-synthon. Moreover, noncovalent bond donors or acceptors attached to N-donor azo/ hydrazone ligands are of interest because of their high solubility in polar solvents, functional properties, photoactivity in the solid state, coordination ability, and high thermal and oxidative stability (Gurbanov et al., 2020a,b;Kopylovich et al., 2011;Mac Leod et al., 2012;Mahmoudi et al., 2017aMahmoudi et al., ,b, 2018a. The functionalization of N-donor ligands with -COOH or -SO 3 H groups can improve the catalytic activity of the corresponding metal complexes in oxidation and C-C coupling reactions Ma et al., 2017aMa et al., ,b, 2020Ma et al., , 2021Mahmudov et al., 2013;Mizar et al., 2012;Shixaliyev et al., 2014). Thus, in the current work we have synthesized a new azo dye, (E)-1-[2,2-dichloro-1-(4-methylphenyl)ethenyl]-2-(4-methoxyphenyl)diazene, which displays multiple intermolecular non-covalent interactions.

Supramolecular features
In the crystal, no classical hydrogen bonds are observed. The molecules are self-assembled via C-HÁ Á ÁCl short contacts, yielding supramolecular chains along the b-axis direction. Adjacent chains are linked by C-HÁ Á ÁO contacts, generating a two-dimensional array parallel to the bc plane (Table 1, Fig. 2). In addition, molecules are connected by C-HÁ Á Á interactions [ Molecules A and B in the asymmetric unit with the atom-labeling scheme and ellipsoids drawn at the 30% probability level. Table 1 Hydrogen-bond geometry (Å , ).

Figure 3
A general view of the C-HÁ Á Á interactions in the title compound.

Figure 2
The crystal packing of the title compound viewed along the b axis, showing the C-HÁ Á ÁCl and C-HÁ Á ÁO interactions as dashed lines.

Hirshfeld surface analysis
To visualize the intermolecular interactions in the title molecule, CrystalExplorer17 (Turner et al., 2017) was used to generate Hirshfeld surfaces (McKinnon et al., 2007) and their corresponding two-dimensional fingerprint plots (Spackman & McKinnon, 2002). In the Hirshfeld surfaces mapped over d norm for molecules A and B of the title compound ( Fig. 4), the bright-red spots near atoms Cl1, Cl3, Cl4 and O1 indicate the short C-HÁ Á ÁCl and C-HÁ Á ÁO contacts (Table 1). Other contacts are equal to or longer than the sum of van der Waals radii. The Hirshfeld surfaces for molecules A and B mapped over electrostatic potential (Spackman et al., 2008) are shown in Fig. 5. 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). The overall two-dimensional fingerprint plot and those delineated into HÁ Á ÁH, ClÁ Á ÁH/HÁ Á ÁCl and CÁ Á ÁH/HÁ Á ÁC contacts in molecules A and B are illustrated in Fig. 6. The most important interaction is HÁ Á ÁH, contributing 38.2% for molecule A and 36.0% for molecule B to the overall crystal packing (Fig. 6b). The ClÁ Á ÁH/HÁ Á ÁCl interactions appear as two symmetrical broad wings with d e + d i = 2.70 Å and contribute 24.6% to the Hirshfeld surface for molecule A, and with d e + d i = 2.70 Å and contribute 26.7% to the Hirshfeld surface for molecule B (Fig. 6c). The pair of characteristic wings in the fingerprint plot delineated into HÁ Á ÁC/CÁ Á ÁH contacts ( Fig. 6d;   Views of the three-dimensional Hirshfeld surfaces of (a) molecule A and (b) molecule B 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. The hydrogen-bond donors and acceptors are shown as blue and red regions, respectively, around the atoms corresponding to positive and negative potentials. Table 2 Summary of short interatomic contacts (Å ) in the title compound.

Contact
Distance Symmetry operation  of all interactions are listed in Table 3. The fact that the same interactions make different contributions to the HS for molecules A and B can be attributed to the different molecular environments of the A and B molecules in the crystal structure.

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. Refined as a 2-component inversion twin.