Crystal structure and Hirshfeld surface analysis of ethyl 2-[5-(3-chlorobenzyl)-6-oxo-3-phenyl-1,6-dihydropyridazin-1-yl]acetate

In the title pyridazinone derivative, the unsubstituted phenyl ring and the pyridazine ring are inclined to each other, making a dihedral angle of 17.41 (13)°, whereas the Cl-substituted phenyl ring is nearly orthogonal to the pyridazine ring [88.19 (13)°], C21H19ClN2O3, contains one independent molecule. C—H⋯O hydrogen bonds, weak C—H⋯π and weak offset π–π stacking interactions stabilize the packing.


Figure 2
A view along the a axis of the crystal structure of the title compound. Black dashed lines symbolize intermolecular C-HÁ Á ÁO hydrogen bonds; C-HÁ Á Á interactions are shown as green dashes lines.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.
molecule is illustrated in Fig. 3a. The pale-red spots symbolize short contacts and negative d norm values on the surface and correspond to the C-HÁ Á ÁO interactions (Table 1). The shape-index map of the title molecule was generated in the range À1 to 1 Å (Fig. 3b). The convex blue regions symbolize hydrogen-donor groups and the concave red regions hydrogen-acceptor groups.interactions are generally indicated by adjacent red and blue triangles in the shape-index map, as is the case for the title molecule.
The curvedness map of the title complex was generated in the range À4.0 to 0.4 Å (Fig. 3c). The curvedness plot of the title complex shows large regions of green with a relatively flat (i.e. planar) surface area, indicating the presence ofstacking interactions, while the blue regions demonstrate areas of curvature.
The overall two-dimensional fingerprint plot is illustrated in Fig. 4a, delineated into HÁ Á ÁH, HÁ Á ÁC/ CÁ Á ÁH, HÁ Á ÁO/OÁ Á ÁH, HÁ Á ÁCl/ClÁ Á ÁH, CÁ Á ÁC contacts associated with their relative contributions to the Hirshfeld surface in Fig. 4b-f, respectively. The most important intermolecular interaction is HÁ Á ÁH, contributing 44.5% to the overall crystal packing, with the centre of the peak d e = d i = 1.18 Å (Fig. 4b). HÁ Á ÁC/ CÁ Á ÁH contacts, with a 18.5% contribution to the Hirshfeld surface, indicate the presence of the weak C-HÁ Á Á interaction (Table 1). Two pairs of characteristic wings in the fingerprint plot with pairs of tips at d e + d i $2.8 Å are present (Fig. 4c). HÁ Á ÁO/OÁ Á ÁH contacts arising from intermolecular C-HÁ Á ÁO hydrogen bonding make a 15.6% contribution to the Hirshfeld surface and are represented by a pair of sharp spikes in the region d e + d i $2.35 Å The CÁ Á ÁC contacts are a measure of -\p stacking interactions and contribute 2.8% of the Hirshfeld surface. They appear as an arrow-shaped distribution at d e + d i $3.3 Å . Another contact to the Hirshfeld surface is from HÁ Á ÁCl/ClÁ Á ÁH interactions (10.6%).

Synthesis and crystallization
To a solution (0.99 g, 3 mmol) of 4-(3-dichlorobenzyl)-6phenylpyridazin-3(2H)-one in 30 ml of tetrahydrofuran (THF), potassium carbonate (0.5 g, 3.5 mmol) was added. The mixture was refluxed for 1 h. After cooling, ethyl bromoacetate (0.66 g, 4 mmol) was added and the mixture was refluxed for 8 h. The precipitated material was removed by filtration and the solvent evaporated under vacuum. The residue was purified through silica gel column chromatography using hexane/ethyl acetate (4:6 v/v). Slow evaporation at room temperature led to formation of single crystals with a yield of 70%.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq