Crystal structure and Hirshfeld surface analysis of 6-((E)-2-{4-[2-(4-chlorophenyl)-2-oxoethoxy]phenyl}ethenyl)-4,5-dihydropyridazin-3(2H)-one

The pyridazine ring in the molecule of the title compound adopts a screw-boat conformation. The whole molecule is flattened, the dihedral angles subtended by the least-suares plane of the central aromatic ring with those of the terminal benzene and pyridazine rings being 15.18 (19) and 11.23 (19)°, respectively. In the crystal, the molecules are linked by pairs of N—H⋯O bonds into centrosymmetric dimers and by C—H⋯π contacts into columns.


Structural commentary
The molecular structure of the title compound is presented in Fig. 1. The bond lengths in the N1-C15 chain (Table 1) are consistent with an alternation of double and single bonds while those in the amide fragment indicate strong -conjugation. The N1-N2 distance of 1.406 (4) Å agrees well with the values for related pyridazinones (Daoui, Ç ınar et al., 2019;Daoui, Baydere et al., 2019). The conformation of the dihydropyridazine ring is close to a screw-boat [Â = 111.9 (6) , ' = 34.6 (6) ]. The whole molecule is flattened with the largest deviations from the least-squares plane of 0.356 (4) and 0.339 (5) Å being observed for atoms C18 and C19, respectively. The central benzene ring forms dihedral angles of 11.23 (19) and 15.18 (19) with the planes of the terminal dihydropyridazine and benzene rings, respectively.

Supramolecular features
In the crystal, the molecules are linked into centrosymmetric dimers by pairs of N-HÁ Á ÁO hydrogen bonds, giving rise to an R 2 2 (8) graph-set motif (Fig. 2a, Table 2). Nointeractions are present in this structure, but the molecules are connected by weak C-HÁ Á Á contacts into stacks running along the aaxis direction (Fig. 2b,c, Table 2). Other contacts of the C-HÁ Á ÁO and C-HÁ Á ÁCl types further stabilize the crystal structure (Table 2).

Hirshfeld surface analysis
In order to visualize and study the intermolecular contacts, a Hirshfeld surface analysis of the title compound was undertaken using Crystal Explorer 17.5 (Turner et al., 2017). Fig. 3a shows the 3D surface mapped over d norm over the range À0.484 (red) to 1.403 (blue) a.u. The pale-red spots on the surface represent short N-HÁ Á ÁO and C-HÁ Á ÁO interactions ( Table 2). The surfaces mapped over d e and d i are presented in Fig. 3b and 3c.
Cg3 is the centroid of the C9-C14 ring.   Molecular structure of the title compound showing the atom labelling and displacement ellipsoids drawn at the 50% probability level.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3 (Macrae et al., 2020); software used to prepare material for publication: WinGX (Farrugia, 2012), SHELXL2018/3 (Sheldrick, 2015b), PLATON (Spek, 2020) and publCIF (Westrip, 2010). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.34 e Å −3 Δρ min = −0.22 e Å −3 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.