1-{(E)-[(2E)-3-(4-Methoxyphenyl)-1-phenylprop-2-en-1-ylidene]amino}-3-phenylurea: crystal structure and Hirshfeld surface analysis

An intramolecular amine-N—H⋯N(imine) hydrogen bond is found in the disubstituted aminourea residue; the conformations about the imine and ethylene double bonds are E. The packing features amide-N—H⋯O(carbonyl) hydrogen bonds, leading to centrosymmetric aggregates, as well as C—H⋯O and C—H⋯π interactions, which significantly influence the packing.

The title compound, C 23 H 21 N 3 O 2 , is constructed about an almost planar disubstituted aminourea residue (r.m.s. deviation = 0.0201 Å ), which features an intramolecular amine-N-HÁ Á ÁN(imine) hydrogen bond. In the 'all-trans' chain connecting this to the terminal methoxybenzene residue, the conformation about each of the imine and ethylene double bonds is E. In the crystal, amide-N-HÁ Á ÁO(carbonyl) hydrogen bonds connect centrosymmetrically related molecules into dimeric aggregates, which also incorporate ethylene-C-HÁ Á ÁO(amide) interactions. The dimers are linked by amine-phenyl-C-HÁ Á Á(imine-phenyl) and methoxybenzene-C-HÁ Á Á(amine-phenyl) interactions to generate a three-dimensional network. The importance of C-HÁ Á Á interactions in the molecular packing is reflected in the relatively high contributions made by CÁ Á ÁH/HÁ Á ÁC contacts to the Hirshfeld surface, i.e. 31.6%.

Chemical context
Chalcones are natural or synthetic compounds comprising an open-chain flavonoid structure in which the two aromatic rings are connected via a three-carbon-atom ,-unsaturated carbonyl system. These compounds have attracted much attention due to their diverse pharmacological and biological activities (Gaonkar & Vignesh, 2017), including their anticancer (Mahapatra et al., 2015), anti-malarial (Syahri et al., 2017), anti-inflammatory (Li et al., 2017), anti-microbial (Kumar et al., 2017), xanthine oxidase inhibitory (Xie et al., 2017) and aldol reductase inhibitory (Zhuang et al., 2017) properties. The present work is part of an on-going project on the synthesis of chalcone-derived Schiff bases, their ultilization in the synthesis of new transition metal complexes and their investigation as anti-proliferative and anti-bacterial agents. In this context, crystal-structure determinations of a chalcone-derived thiosemicarbazone and a zinc complex have been published (Tan et al., 2015(Tan et al., , 2017. In this contribution, a chalcone residue has been incorporated into a semicarbazide skeleton to form the title chalconesemicarbazone, (I). While chalconesemicarbazone derivatives have shown potential anti-convulsant (Sharma et al., 2014), anti-inflammatory (Singha et al., 2010) and anti- ISSN 2056-9890 oxidant activities (Singhal et al., 2011), no crystal structures of chalconesemicarbazone derivatives have been published. Herein, the crystal and molecular structures of (I) have been determined and the study augmented by an analysis of the calculated Hirshfeld surfaces.

Structural commentary
The molecular structure of (I), Fig. 1, comprises a doubly substituted aminourea residue which is close to planar (r.m.s. deviation of CN 3 O = 0.0201 Å ), owing in part to an intramolecular amine-N-HÁ Á ÁN(imine) hydrogen bond, Table 1. The amine-bound phenyl ring is inclined to the CN 3 O plane, forming a dihedral angle of 46.88 (4) . The imine/ethylene sequence of bonds, i.e. N3 C8-C9 C10-C11, has an alltrans conformation but the N3-C8-C9-C10 and C8-C9-C10-C11 torsion angles of 154.62 (12) and À169.19 (11) , respectively, indicate some twisting in this residue, especially about the C8-C9 bond; the conformation about each of the double bonds is E. The imine-bound phenyl ring forms a dihedral angle of 63.30 (7) with the C 4 N atoms of the imine/ ethylene sequence, and the corresponding angle for the terminal methoxybenzene ring is significantly less, at 8.29 (13) . The methoxy group is twisted out of the plane of the ring to which it is connected as seen in the value of the C17-O18-C14-C15 torsion angle of 15.55 (17) .

Analysis of the Hirshfeld surface
The Hirshfeld surface was calculated for (I) in accord with a recent report on a related molecule (Tan et al., 2017) to provide more detailed information on the relative significance of the various intermolecular interactions. The donors and acceptors of intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO interactions in (I) are viewed as the bright-red spots near the ethylene-H9, amide-H2N and carbonyl-O1 atoms on the Hirshfeld surface mapped over d norm in Fig. 3a. The appearance of diminutive red spots near the N3 and C17 atoms, Fig. 3a, and the tiny faint-red spots near the C9 and H82 atoms in Fig. 3b, indicate the influence of short interatomic N3Á Á ÁC17 and C9Á Á ÁH82 contacts, Table 2. The donors and acceptors of intermolecular hydrogen bonds also appear as blue and red regions, respectively, around the participating atoms on the Hirshfeld surface mapped over the calculated electrostatic potential in Fig. 4. The involvement of the imine-phenyl (C81-C86) and amine-phenyl (C2-C7) rings as acceptors for C-HÁ Á Á interactions are also evident through the light-red regions around these rings on the Hirshfeld surfaces in the views of Fig. 4. Referring to Fig. 5a, the concave region around the imine-phenyl ring on one side and the biconcave region around the amine-phenyl ring indicate their involvement in one and two C-HÁ Á Á contacts, respectively. The short interatomic OÁ Á ÁH/HÁ Á ÁO contacts (Table 3) as well as N-HÁ Á ÁO and C-HÁ Á ÁO interactions about a reference molecule within shape-index mapped Hirshfeld surface, and the HÁ Á ÁH, CÁ Á ÁH/HÁ Á ÁC and CÁ Á ÁN/NÁ Á ÁC contacts within the d normmapped Hirshfeld surface are shown in Fig. 5b and c, respectively.
The CÁ Á ÁH/HÁ Á ÁC contacts in the crystal make the second largest contribution, i.e. 31.6%, to the Hirshfeld surface of (I), Fig. 6c, which is due to the presence of a significant number of C-HÁ Á Á interactions involving the imine-and amine-phenyl rings, as well as short interatomic CÁ Á ÁH/HÁ Á ÁC contacts, Table 3, between the atoms of the methoxy-phenyl and iminephenyl rings, Fig Table 2 Summary of short interatomic contacts (Å ) in (I).

Figure 3
Two views of the Hirshfeld surface for (I) mapped over d norm in the ranges (a) À0.225 to +1.332 a.u. and (b) À0.110 to +1.332 a.u.

Figure 4
Two views of the Hirshfeld surface for (I) mapped over the electrostatic potential in the range À0.095 to +0.108 a.u. The red and blue regions represent negative and positive electrostatic potentials, respectively.  Fig. 6e, as their interatomic distances are greater than their van der Waals separations, they do not make a specific contribution to the molecular packing. The participation of the methyl-C17 atom in two close interatomic contacts, Table 2, brings into close proximity the methyl-C17 and imine-N3 atoms, Table 2, but these are interspersed by the H17A and H17B atoms so are not surface contacts. Finally, the small contributions from other interatomic contacts summarized in Table 3 have a negligible effect on the structure.

Database survey
The title compound was prepared from the dehydrogenation reaction of 4-phenylsemicarbazide and 4-methoxychalcone. A search of the Cambridge Structural Database (Groom et al., 2016) revealed no direct precedents for this type of molecule. The most closely related structure is one where the ethylene bond is incorporated within a five-membered pyrazolone ring (Chai et al., 2005).

Synthesis and crystallization
Analytical grade reagents were used as procured without further purification. 4-Phenylsemicarbazide (1.51 g, 0.01 mol) and 4-methoxychalcone (2.38 g, 0.01 mol) were dissolved separately in hot absolute ethanol (30 ml) and mixed with stirring. A few drops of concentrated hydrochloric acid were added as a catalyst. The reaction mixture was heated and stirred for about 20 min., then stirred for a further 30 min. at room temperature. The resulting yellow precipitate was filtered, washed with cold ethanol and dried in vacuo; yield: 75%. Single crystals were grown at room temperature from the slow evaporation of mixed ethanol and acetonitrile solvents (

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. The carbon-bound H atoms were placed in calculated positions (C-H = 0.95-0.98 Å ) and were included in the refinement in the riding-model approximation, with U iso (H) set to 1.2-1.5U eq (C). The nitrogen-bound H atoms were located in a difference-Fourier map but were refined with a distance restraint of N-H = 0.88AE0.01 Å , and with U iso (H) set to 1.2U eq (N). Singh

1-{(E)-[(2E)-3-(4-Methoxyphenyl)-1-phenylprop-2-en-1-ylidene]amino}-3-phenylurea
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.