Crystal structure and Hirshfeld surface analysis of 4-(2,6-dichlorobenzyl)-6-phenylpyridazin-3(2H)-one

In the crystal, the molecules are linked by a pair of N—H⋯O hydrogen bonds, forming inversion dimers with an (8) ring motif. The dimers are linked by C—H⋯O hydrogen bonds, forming layers parallel to the bc plane and by weak π–π interactions, forming layers parallel to the ab plane.

The asymmetric unit of the title compound, C 17 H 12 Cl 2 N 2 O, contains one independent molecule. The molecule is not planar, the phenyl and pyridazine rings are twisted with respect to each other, making a dihedral angle of 29.96 (2) and the dichlorophenyl ring is nearly perpendicular to the pyridazine ring, with a dihedral angle of 82.38 (11) . In the crystal, pairs of N-HÁ Á ÁO hydrogen bonds link the molecules to form inversion dimers with an R 2 2 (8) ring motif. The dimers are linked by C-HÁ Á ÁO interactions, forming layers parallel to the bc plane. The intermolecular interactions were investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots, and the molecular electrostatic potential surface was also analysed. The Hirshfeld surface analysis of the title compound suggests that the most significant contributions to the crystal packing are by HÁ Á ÁH (31.4%), ClÁ Á ÁH/HÁ Á ÁCl (19.9%) and CÁ Á ÁH/HÁ Á ÁC (19%) contacts.

Structural commentary
As the molecular structure of the title compound is illustrated in Fig. 1; the asymmetric unit contains one independent molecule. The molecule is not planar, the benzene ring (C12-C17) and the pyridazine ring are twisted relative to each other, making a dihedral angle of 29.96 (2) and the phenyl ring (C1-C6) is nearly perpendicular to the pyridazine ring with a dihedral angle of 82.38 (11) (Fig. 1). The C9 O1 bond length is 1.248 (4) Å while the C9-N1 and C11-N2 bond lengths are 1.360 (4) and 1.307 (4) Å , respectively.

Figure 2
A view along the a axis of the crystal packing of the title compound. Dashed lines denote the N-HÁ Á ÁO hydrogen bonds (Table 1) forming an inversion dimer with an R 2 2 (8) ring motif. The C-HÁ Á ÁO interactions are shown as blue dashed lines.

Figure 3
A view along the a axis of the crystal packing of the title compound. The hydrogen bonds (Table 1) are shown as dashed lines and theinteractions as pink dashed lines.

Figure 1
The molecular structure of the title compound, with the atom labelling. Displacement ellipsoids are drawn at the 20% probability level. weak offsetstacking interactions stabilize the packing. In QANVOR, the phenyl and pyridazinone rings are approximately coplanar with a dihedral angle of 4.84 (13) and in the crystal, centrosymmetrically related molecules form dimers through non-classical intermolecular C-HÁ Á ÁO hydrogen bonds (Fig. 5).

Hirshfeld surface analysis
The Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and the associated two-dimensional fingerprint plots (McKinnon et al., 2007) were performed with Crystal-Explorer17 (Turner et al., 2017). In Fig. 6, the mappings of d norm , shape-index and curvedness for the title compound are shown. Fig. 7 illustrates the Hirshfeld surface of the molecule in the crystal, with the evident hydrogen-bonding interactions indicated by intense red spots. Fig. 8a shows the two-dimensional fingerprint of the sum of the contacts contributing to the Hirshfeld surface represented in normal mode. Two-dimensional fingerprint plots provide information about the major and minor percentage contributions of interatomic contacts in the compound. The blue colour refers to the frequency of occurrence of the (d i , d e ) pair and the grey colour is the outline of the full fingerprint. The fingerprint plot in Fig. 8b shows that the HÁ Á ÁH contacts clearly make the most significant contribution to the Hirshfeld surface (31.4%). In addition, ClÁ Á ÁH/HÁ Á ÁCl, CÁ Á ÁH/HÁ Á ÁC, OÁ Á ÁH/HÁ Á ÁO and NÁ Á ÁH/HÁ Á ÁN contacts contribute 19.9%, 19%, 9.3% and 6.7%, respectively, to the Hirshfeld surface. In particular, the OÁ Á ÁH/HÁ Á ÁO contacts indicate the presence of intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO interactions. Much weaker ClÁ Á ÁC/CÁ Á ÁCl (6.1%) and CÁ Á ÁC (3.7%) contacts also occur.
A view of the molecular electrostatic potential, in the range À0.0500 to 0.0500 a.u. using the 6-31G(d,p) basis set with DFT method, for the title compound is shown in Fig. 9, where the N-HÁ Á ÁO hydrogen-bond donors and acceptors are shown as blue and red areas around the atoms related with positive (hydrogen-bond donors) and negative (hydrogen-bond acceptors) electrostatic potentials, respectively. The crystal packing of YOTVIN (Oubair et al., 2009). The N-HÁ Á ÁO hydrogen bonds with an R 2 2 (8) graph set motif are shown as pink dashed lines.   The Hirshfeld surfaces of the title compound mapped over d norm , shapeindex and curvedness.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The nitrogen-bound H atom was located in a difference-Fourier map and refined subject to a DFIX restraint of N-H = 0.86 Å . The C-bound H atoms were positioned geometrically and refined using a riding model: C-H = 0.93-0.97 Å with U iso (H) = 1.2U eq (C).

Figure 8
Two-dimensional fingerprint plots for the title compound, with a d norm view and the relative contribution of the atom pairs to the Hirshfeld surface.

4-(2,6-Dichlorobenzyl)-6-phenylpyridazin-3(2H)-one
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.15 e Å −3 Δρ min = −0.20 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.