Crystal structure of (E)-N’-[1-(4-aminophenyl)ethylidene]-2-hydroxy-5-iodobenzohydrazide methanol monosolvate

The synthesis and crystal structure of a new N-substituted hydrazide are reported. In the crystal packing, O—H⋯O and N—H⋯O hydrogen bonds predominate together with π–π stacking interactions.


Chemical context
N-substituted hydrazides have been attracted much attention for their structures, coordination ability, biological activities and transformations to heterocyclic compounds (Majumdar et al., 2014;Asif & Husain, 2013;Khan et al., 2017). Derivatives of salicylic acid act as antibacterial (Kumar et al., 2012;Cui et al., 2014;Sarshira et al., 2016), antifungal (Wodnicka et al., 2017;Abbas et al., 2017) and antitumor (Murty et al., 2014) agents. In addition, some salicylhydrazones exhibit significant antitrypanosomal activity with IC 50 ranging from 1 to 34 mM. N-substituted hydrazides containing the typical -C(O)-NH-N C< functional group can be prepared by a condensation reaction between a hydrazide and a carbonyl compound (an aldehyde or a ketone).
As a continuation of our research work to synthesize derivatives of 5-iodosalicylohydrazide (Nguyen et al., 2012), the new compound (E)-N'-[1-(4-aminophenyl)ethylidene]-2-hydroxy-5-iodobenzohydrazide methanol monosolvate was synthesized. The structure of the compound was determined by IR, 1 H NMR, 13 C NMR and HR-MS spectroscopy as well as X-ray diffraction and the crystal structure is reported herein.

Structural commentary
The title compound ( Fig. 1) crystallizes as a methanol monosolvate in the monoclinic space group P2 1 /c with one hydrazide molecule and a methanol solvate molecule in the asymmetric unit. The OH group of methanol is hydrogen bonded to the hydrazide oxygen atom O4 (Fig. 1, Table 1). The dihedral angle between the aromatic rings is 10.53 (8) . This relatively planar character of the molecule is caused by an intramolecular hydrogen bond, N2-H2Á Á ÁO11 (Table 1), and the presence of the hydrazide functional group and the C13 N1 double bond. The r.m.s. deviation from a plane through all 21 non-Hatoms is 0.291 Å [with a maximum deviation of 0.838 (1) Å observed for atom O4]. The torsion angles about the bonds of the hydrazide link between the two aromatic rings are: C15-C13 N1-N2 = À175.48 (15) , C13 N1-N2-C3 = 178.71 (16) and N1-N2-C3-C5 = À172.18 (15) . The stereochemistry about the imine function C13 N1 is E. The planar character causes short contacts for the H atoms of methyl group C14 with the H atoms on atoms N2 and C20. As a consequence, this methyl group displays rotational disorder with occupancies of 0.66 (2) and 0.34 (2).

Figure 2
Part of the crystal packing of the title compound, showing the chain along the c-axis direction formed by O-HÁ Á ÁO hydrogen-bonding interactions [see Table 1; symmetry code: (i) x, y, z À 1]. Only the major component of the disordered methyl group C14 is shown.

Figure 5
Views of the Hirshfeld surface for the title compound mapped over d norm over the range À0.740 to 1.296 a.u. showing the closest methanol molecules.

Synthesis and crystallization
The reaction scheme used to synthesize the title compound, 5, is shown in Fig. 8. Methyl salicylate, methyl 2-hydroxy-5iodobenzoate and 2-hydroxy-5-iodobenzohydrazide were prepared from salicylic acid according to the method described in our earlier work (Nguyen et al., 2012).
Methyl    Reaction scheme for the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The H atoms attached to atoms N2, N21, O11 and O23 were found in a difference-Fourier map and refined freely. The other H atoms were placed at calculated positions and refined in riding mode, with C-H distances of 0.95 (aromatic) and 0.98 Å (CH 3 ), and isotropic displacement parameters equal to 1.2U eq of the parent atoms (1.5U eq for CH 3 ). The difference-Fourier map indicated disorder for the H atoms of methyl group C14. The final occupancy factors for the two sets of H atoms are 0.66 (2) and 0.34 (2). In the final cycles of refinement, two reflections showing very poor agreement were omitted as outliers.

Funding information
LVM thanks VLIR-UOS (project ZEIN2014Z182) for financial support.

(E)-N′-[1-(4-Aminophenyl)ethylidene]-2-hydroxy-5-iodobenzohydrazide methanol monosolvate
Crystal data 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.