Synthesis, crystal structure and Hirshfeld surface analysis of 5-[2-(dicyanomethylidene)hydrazin-1-yl]-2,4,6-triiodoisophthalic acid ethanol monosolvate

In the crystal, pairs of molecules are linked by O—H⋯O and N—H⋯O hydrogen bonds forming dimers with (14) motifs. These dimers are connected by O—H⋯O hydrogen bonds into chains along the a-axis direction, forming (16) ring motifs. Further O—H⋯O interactions involving the ethanol solvent molecule connect the chains into a three-dimensional network.

The title compound, C 11 H 3 I 3 N 4 O 4 ÁC 2 H 6 O, crystallizes in the triclinic P1 space group with one independent molecule and one ethanol solvent molecule in the asymmetric unit.The benzene ring and the methylcarbonohydrazonoyl dicyanide group of the main molecule makes a dihedral angle of 57.91 ( 16) .In the crystal, O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds link pairs of molecules, forming dimers with R 2 2 (14) motifs.These dimers are connected by O-HÁ Á ÁO hydrogen bonds into chains along the a-axis direction, forming R 2 2 (16) ring motifs.Further O-HÁ Á ÁO interactions involving the ethanol solvent molecule connect the chains into a three-dimensional network.In addition, C-IÁ Á Á interactions are observed.The intermolecular interactions in the crystal structure were quantified and analysed using Hirshfeld surface analysis.

Chemical context
Arylhydrazones of active methylene compounds (AHAMC) have been extensively employed as ligands and precursors for the synthesis of coordination, organic or supramolecular compounds (Gurbanov et al., 2020a,b;Kopylovich et al., 2011).Besides their biological significance (Martins et al., 2017), the transition-metal complexes of AHAMC ligands have been found to possess a wide variety of functional properties, and have applications as catalysts, supramolecular building blocks and analytical reagents (Mahmudov et al., 2010(Mahmudov et al., , 2012(Mahmudov et al., , 2015)).By the functionalization of the active methylene fragment (acetylacetone or barbituric acid) or the aromatic moiety (2,4,6-triiodoisophthalic acid) of the AHAMC molecules, the catalytic properties of their metal complexes can be improved in the nitroaldol reaction between aldehydes and nitroethane (Gurbanov et al., 2022).On the other hand, non-covalent interactions such as hydrogen, halogen and chalcogen bonds as well as -interactions can be employed in the synthesis, catalysis and design of materials (Abdelhamid et al., 2011;Khalilov et al., 2021;Ma et al., 2021;Mahmudov et al., 2022).As well as hydrogen bonds, the cooperation of different weak bonds can act as a driving force for controlling supramolecular networks (Polyanskii et al., 2019;Safarova et al., 2019;Shikhaliyev et al., 2019;Zubkov et al., 2018).Similarly to Schiff base complexes (Mahmoudi et al., 2017a(Mahmoudi et al., ,b, 2019)), the func-tional groups can be involved in various types of intermolecular interactions in metal complexes of arylhydrazone ligands.We have synthesized a new iodine-substituted AHAMC ligand, 5-[2-(dicyanomethylene)hydrazinyl]-2,4,6triiodoisophthalic acid, and studied the intermolecular halogen bonds and other types of weak interactions in its crystal structure.

Structural commentary
The title compound (Fig. 1) crystallizes in the triclinic P1 space group with one independent molecule and one ethanol solvent molecule in the asymmetric unit.The benzene ring (C1-C6) and the methylcarbonohydrazonoyl dicyanide group (N1-N4/ C1/C7-C9) of the main molecule makes a dihedral angle of 57.91 (16) .Geometric parameter values in the molecule are normal and in good agreement with the values in the compounds discussed in the Database survey section.

Supramolecular features and Hirshfeld surface analysis
In the crystal of the title compound, pairs of molecules are linked by O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds, forming dimers with R 2 2 ( 14) motifs (Bernstein et al., 1995; Table 1, Fig. 2).These dimers are connected along the a-axis direction by further O-HÁ Á ÁO hydrogen bonds, forming R 2 2 (16) ring motifs.O-HÁ Á ÁO hydrogen bonds involving the ethanol solvent molecule connect chains into a three-dimensional network.In addition, C-IÁ Á Á interactions are also observed [C2-I1Á Á ÁCg1(1 À x, 1 À y, 1 À z), 3.8441 (15) A ˚].The carbon atoms in the arylhydrazone molecule are magnetically non-equivalent as a result of limited rotation around the C-N bond, thus the NH group is locked and becomes 'asymmetric', which translates into diastereotopic protons and carbons in the title compound.
In order to present the intermolecular interactions in the crystal structure of the title compound in a visual manner, Hirshfeld surfaces and their associated two-dimensional fingerprint plots were generated using CrystalExplorer17.5 (Spackman et al., 2021).The Hirshfeld surface plotted over d norm is shown in Fig. 3, while Fig. 4 shows the full twodimensional fingerprint plot and those delineated into the 796 Aliyeva et al.C 11 H 3 I 3 N 4 O 4 ÁC 2 H 6 O   Acta Cryst. (2023). E79, 795-799 research communications Figure 1 The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 30% probability level.In the crystal of UNUDIR, molecules are linked by O-HÁ Á ÁO hydrogen bonds into a three-dimensional network.An N-HÁ Á ÁO interaction also occurs.One of the amino H atoms is not involved in hydrogen bonding.
In the crystal structure of BOTVUC, molecules are linked into chains by COO-HÁ Á ÁO bonds, and pairs of chains are connected by additional COO-HÁ Á ÁO interactions.This chain bundle shows stacking interactions and weak N-HÁ Á ÁO hydrogen bonds with adjacent chains.

Synthesis and crystallization
Diazotization: 558 mg (1 mmol) of 5-amino-2,4,6-triiodoisophthalic acid were dissolved in 15 mL of water, and the solution was cooled in an ice bath to 273 K, then 69 mg (1 mmol) of NaNO 2 were added followed by 0.2 mL of HCl, and mixed for 1 h.The temperature of the mixture should not exceed 278 K.
Azocoupling: NaOH (40 mg, 1 mmol) was added to a mixture of 1 mmol (66 mg) of malononitrile with 5 mL of water.The solution was cooled in an ice bath, and a suspension of 3,5-bis(methoxycarbonyl)benzenediazonium chloride (prepared according to the procedure described above) was added in two equal portions under vigorous stirring for 1 h.The precipitate was filtered off, recrystallized from methanol and dried in air.Crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution.The title compound: Yield 79% (based on malononitrile), yellow powder soluble in DMSO, methanol, ethanol

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.The hydrogen atoms of the ethanol molecule were placed at idealized positions and refined using a riding model, with U iso (H) values assigned as 1.2U eq or 1.5U eq (methyl only) of the parent atoms, with C-H distances of 0.97 (methylene) and 0.96 A ˚(methyl).The remaining hydrogen atoms bound to nitrogen and oxygen were located in difference-Fourier maps and refined with fixed positional thermal displacement parameters and with U iso (H) values assigned as 1.2U eq (NH) or 1.5U eq (OH) of the parent atoms.One reflection, (001), affected by the incident beam-stop was omitted in the final cycles of refinement.

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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )

Figure 3 (
Figure 3 (a) Front and (b) back sides of the three-dimensional Hirshfeld surface of the title compound mapped over d norm , with a fixed colour scale of À0.8291 to 1.0734 a.u.

Table 2
Experimental details.