Crystal structure and Hirshfeld surface analysis of methyl 4-[(E)-2-(5-bromo-2-methoxybenzylidene)hydrazinyl]-3-nitrobenzoate

The title compound is a novel halogen-substituted hydrazine derivative. Intramolecular N—H⋯O interactions form S(6) graph-set motifs, while C—H⋯O and C—H⋯N interactions form S(5) graph-set motifs.

The title compound, C 16 H 14 BrN 3 O 5 , is a novel halogen (Br) substituted hydrazine derivative. The hydrazine derivatives were the group of compounds with the general structure, R 1 R 2 C NNH 2 (Uppal et al., 2011), with the central RC NNH 2 moiety bridging two different groups on both sides. An all-trans configuration of the backbone (RC NNH 2 ) results in an extended molecular conformation. The dihedral angle between the 5-bromo-2-methoxyphenyl ring and the nitrophenyl ring is 4.4 (3) . Intramolecular N-HÁ Á ÁO interactions form S(6) graph-set motifs, while C-HÁ Á ÁO and C-HÁ Á ÁN interactions form S(5) graph-set motifs. Symmetry-related molecules are linked by C-HÁ Á ÁO intermolecular interactions forming an R 2 1 (10) graph-set motif. There are nearly faceto-face directional specificstacking interactions between the centroids of the nitrophenyl ring and the benzene ring of the 5-bromo-2-methoxy group [centroid-centroid distance = 3.6121 (5) Å and slippage = 1.115 Å ], which also contributes to the molecular packing. The Hirshfeld surface analysis was performed in order to visualize, explore and quantify the intermolecular interactions in the crystal lattice of the title compound.

Chemical context
Hydrazine and its derivatives have attracted much attention due to their synthetic potential for organic and inorganic chemical reactions and diverse useful properties (Levrand et al., 2007;Li et al., 2011). Hydrazine-based coupling methods are used in medical biotechnology to couple drugs to targeted antibodies, e.g. antibodies against a certain type of cancer cell (Wu et al., 2005). Hydrazine possesses diverse biological and pharmacological properties, such as antimicrobial, antiinflammatory, analgesic, antifungal, antitubercular, antiviral, anticancer, antiplatelet, antimalarial, anticonvulsant, cardioprotective, antihelmintic, antiprotozoal (Rollas & Kü çü kgü zel, 2007), antitrypanosomal and antischistosomiasis (Narang et al., 2012). These compounds contain a C N bond, which is conjugated with a lone pair of electrons of the functional N atom (Corey & Enders, 1976). The N atom of the hydrazine is nucleophilic and the C atom has both an electrophilic and a nucleophilic nature (Corey & Enders, 1976). The -hydrogen of hydrazine is more potent than that of acidic ketones (Belskaya et al., 2010). The combination of hydrazine with other functional groups results in new compounds with unique physical and chemical characteristics (Xavier et al., 2012). Owing to their biological and pharmacological properties, ISSN 2056-9890 hydrazine derivatives play an important role for the synthesis of heterocyclic compounds (Banerjee et al., 2009). Fig. 1 displays the title molecule with the atom-labelling scheme. Intramolecular N2-H2AÁ Á ÁO4 interactions form S(6) graph-set motifs and C3-H3Á Á ÁO1 and C6-H6Á Á ÁN3 interactions form S(5) graph-set motifs. The central bridging moiety R 2 C NNHR 1 adopts an all-trans conformation about the C10-C9, C9-N3, N3-N2 and N2-C5 bonds, with torsion angles of 176.0 (6), À178.1 (5), À177.0 (6) and 173.6 (6) , leading to an extended molecular conformation, thereby causing the terminal bromomethoxyphenyl ring and nitrophenylring to occupy almost the same plane; the dihedral angle between the rings is 4.4 (3) .

Figure 1
The molecular structure of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. and slippage = 1.115 Å ], which also contributes to the molecular packing. The Br atom does not take part in any interactions. The nearest BrÁ Á ÁC7(Àx + 1 2 , y À 1 2 , Àz + 1 2 ) distance in the molecular structure is 3.6112 (7) Å .
Hirshfeld surface analysis serves as a powerful tool for gaining additional insight into intermolecular interactions of molecular crystals. The Hirshfeld surfaces are mapped with 2D fingerprint plots presented using CrystalExplorer3.1 and it provides a summary of the intermolecular contacts in the crystal (McKinnon et al., 2004;Spackman & Jayatilaka, 2009). The 2D fingerprint plots (Fig. 3) show that the intermolecular HÁ Á ÁH and OÁ Á ÁH interactions dominate and complement the Hirshfeld surfaces. The fingerprint plots can also be decomposed to highlight particular atom-pair close contacts (Luo et al., 2013) and enables separation of contributions from different interaction types. Two sharp spikes pointing towards the upper left of the plot are typical C-HÁ Á ÁO hydrogen bonds. This portion corresponds to HÁ Á ÁO interactions comprising 25.1% of the total Hirshfed surfaces. Two sharp spikes pointing towards the lower left of the plot are typical BrÁ Á ÁH hydrogen bonds. This portion corresponds to BrÁ Á ÁH interactions comprising 11.7% of the total Hirshfeld surfaces. The broad region bearing short and narrow spikes at the middle of plot is reflected as HÁ Á ÁH interaction comprising 27.2% of the total Hirshfeld surfaces. Apart from these, the presence of BrÁ Á ÁC, BrÁ Á ÁN, BrÁ Á ÁO, CÁ Á ÁO, HÁ Á ÁN, NÁ Á ÁO and OÁ Á ÁO interactions were observed (Pi chart; Fig. 4g), which are summarized in Table 2 (Li et al., 2013;Luo & Sun, 2014;Seth et al., 2011).   and in DUSNUB, both molecules form inversion dimers linked by pairs of N-HÁ Á ÁO hydrogen bonds, thereby generating R 2 2 (16) motif rings (Bernstein et al., 1995). In the title compound, intramolecular N-HÁ Á ÁO and only intermolecular C-HÁ Á ÁO hydrogen bonds are present; there are no C-HÁ Á Á interactions. Very few similar hydrazine derivatives are reported in the literature (Corté s et al., 2013;Dey & Chopra, 2017). In those crystal structures, a halogen group (Cl and F, respectively) is present, while in this crystal structure, Br is present.

Synthesis and crystallization
The title compound was synthesized in one step by heating the hydrazine derivative 3-nitrobenzohydrazide (0.181 mg) with a slight excess of 5-bromo-2-methoxybenzaldehyde (0.215 mg) in an acetic acid solution (10 ml). The reaction mixture was refluxed for 8 h. The solid product formed during reflux was filtered off, washed and dried over anhydrous calcium chloride in a vacuum desiccator (yield 75%). The final product was soluble in acetone, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), methanol, ethanol and ethyl acetate, etc. Transparent orange-coloured needle-shaped diffractionquality single crystals of the title compound were grown by slow evaporation using methanol as the solvent at room temperature.

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Acta Cryst. (2018). E74, 1239-1243 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.