Crystal structure and Hirshfeld surface analysis of 2-(4-nitrophenyl)-2-oxoethyl 2-chlorobenzoate

The title compound, 2-(4-nitrophenyl)-2-oxoethyl 2-chlorobenzoate, is relatively planar with the two aromatic rings being inclined to each other by 3.56 (11)°.

The title compound, C 15 H 10 ClNO 5 , is relatively planar with the two aromatic rings being inclined to each other by 3.56 (11) . The central -C( O)-C-O-C( O)-bridge is slightly twisted, with a C-C-O-C torsion angle of 164.95 (16) . In the crystal, molecules are linked by C-HÁ Á ÁO and C-HÁ Á ÁCl hydrogen bonds, forming layers parallel to the (101) plane. The layers are linked by a further C-HÁ Á ÁO hydrogen bond, forming a three-dimensional supramolecular structure. There are a number of offsetinteractions present between the layers [intercentroid distances vary from 3.8264 (15) to 3.9775 (14) Å ]. Hirshfeld surface analyses, the d norm surfaces, electrostatic potential and two-dimensional fingerprint plots were examined to verify the contributions of the different intermolecular contacts within the supramolecular structure. The shape-index surface shows that two sides of the molecule are involved in the same contacts with neighbouring molecules, and the curvedness plot shows flat surface patches that are characteristic of planar stacking.

Chemical context
Due to their numerous applications in various fields of chemistry, phenacyl benzoates are of great importance (Rather & Reid, 1919;Literá k et al., 2006;Sheehan & Umezawa, 1973;Huang et al., 1996;Gandhi et al., 1995;Zhang et al., 2009). In continuation of our work on such molecules Chidan Kumar et al., 2014), we report herein on the crystal and molecular structures of 2-(4-nitrophenyl)-2-oxoethyl chlorobenzoate (I). Its crystal and molecular structures are compared with those of 2-(4nitrophenyl)-2-oxoethyl benzoate (II) (Sheshadri et al., 2019), published by us recently, and further details of uses and applications of such molecules are described therein.

Structural commentary
The molecular structure of the title compound, I, is shown in Fig. 1. The compound is composed of two aromatic rings (C1-C6 and C10-C15) linked by the -C7( O2)-C8-O1-C9( O3)-bridge. The bond lengths and angles in I are normal and similar to those reported for compound II. The two benzene rings are inclined to each other by 3.56 (11) , indicating that they are almost coplanar, as in the structure of II. The nitro group (N1/O4/O5) lies almost in the plane of the benzene ring (C1-C6), with a dihedral angle between the two ISSN 2056-9890 planes of 5.4 (4) ; the torsion angles C4-C3-N1-O4 and C2-C3-N1-O5 are À5.4 (3) and À5.1 (4) , respectively. Atom Cl1 is displaced by 0.0749 (8) Å from the plane of benzene ring C10-C15.

Supramolecular features
The crystal structure of the title compound, is stabilized by intermolecular hydrogen bonds of the types C-HÁ Á ÁO and C-HÁ Á ÁCl (Table 1). Molecules are linked by the C2-H2Á Á ÁO3 i , C14-H14Á Á ÁO4 i and C13-H13Á Á ÁCl1 iii hydrogen bonds to form layers lying parallel to the (101) plane; see Fig. 2 and Table 1. The layers are linked by C8-H8AÁ Á ÁO3 ii hydrogen bonds and offsetinteractions (see Table 2), forming a supramolecular three-dimensional structure (Fig. 3).

Figure 1
The molecular structure of compound I, with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view normal to the (101) plane of the crystal packing of compound I. The hydrogen bonds are shown as dashed lines (Table 1; symmetry codes as in Table 1), and, for clarity, only the H atoms involved in hydrogen bonding have been included.

Figure 3
The crystal packing of compound I, viewed along the b axis, showing the layered stacking. For clarity, only the H atoms involved in hydrogen bonding have been included, and the hydrogen bonds are shown as dashed lines (Table 1).
Explorer17 (Turner et al., 2017). Hirshfeld surface analysis enables the visualization of intermolecular interactions by different colours and colour intensity, representing short or long contacts and indicating the relative strength of the interactions. Fig. 4(a) shows the Hirshfeld surface mapped over d norm (À0.154 to 1.305) and for Fig. 4(b) the electrostatic potential. The Hirshfeld surface illustrated in Fig. 4(a) reflects the involvement of different atoms with the intermolecular interactions through the appearance of blue and red patches, which correspond to the regions of positive and negative electrostatic potential shown in Fig. 4(b). The shape-index surface (Fig. 5a) clearly shows that the two sides of the molecule are involved in contacts with neighbouring molecules and the curvedness plot (Fig. 5b) shows flat surface patches characteristic of planar stacking. The overall two-dimensional fingerprint plot for the title compound and those delineated into OÁ Á ÁH/HÁ Á ÁO, HÁ Á ÁH, CÁ Á ÁH/HÁ Á ÁC and ClÁ Á ÁH/HÁ Á ÁCl contacts are illustrated in Fig. 6. The percentage contributions from the different interatomic contacts to the Hirshfeld surfaces are as follows: OÁ Á ÁH (34.8%), HÁ Á ÁH (18.8%), CÁ Á ÁH (14.7%) and ClÁ Á ÁH (10.1%), shown in the two-dimensional fingerprint plots, respectively, in Fig. 6. The percentage contributions for other intermolecular contacts are less than 5% in the Hirshfeld surface mapping. A view of the Hirshfeld surface of compound I, mapped over d norm .

Figure 5
Hirshfeld surface of compound I, mapped over (a) the shape-index and (b) the curvedness. Table 2 contacts (Å , ) in the crystal of compound I.

Synthesis and crystallization
The title compound, was synthesized as per the procedure reported earlier by Kumar et al. (2014). A mixture of 2-bromo-1-(4-nitrophenyl)ethanone (0.2 g, 0.5 mmol), potassium carbonate (0.087 g, 0.63 mmol) and 2-chlorobenzoic acid (0.156 g, 0.65 mmol) in dimethylformamide (5 ml) was stirred at room temperature for 2 h. After completion of the reaction, the reaction mixture was poured into ice-cold water. The solid product obtained was filtered, washed with water and recrystallized from ethanol to give colourless block-like crystals (m.p. 386-390 K).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. C-bound H atoms were positioned geometrically (C-H = 0.93-0.97 Å ) and refined using a riding model, with U iso (H) = 1.2U eq (C).   (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010). Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The observed criterion of F 2 > 2sigma(F 2 ) is used only for calculating -R-factor-obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.