(E)-5-(4-Chlorobenzylidene)-1-phenyl-4,5,6,7-tetrahydro-1H-indazol-4-one: crystal structure and Hirshfeld surface analysis

The title 1,2-diazole derivative is highly twisted with the dihedral angle between the pendant rings being 74.5 (1)°. In the crystal, weak C—H⋯O interactions feature predominantly within the three-dimensional architecture.

In the title compound, C 20 H 15 ClN 2 O, the non-aromatic six-membered ring adopts a distorted envelope conformation with methylene-C atom nearest to the five-membered ring being the flap atom. The dihedral angle between the phenyl and chlorobenzene rings is 74.5 (1) . The heterocyclic ring forms dihedral angles of 37.9 (1) and 64.3 (1) with the phenyl and chlorobenzene rings, respectively. In the crystal, weak C-HÁ Á ÁO interactions feature predominantly within the three-dimensional architecture. The intermolecular interactions are further analysed with the calculation of the Hirshfeld surfaces highlighting the prominent role of C-HÁ Á ÁO interactions, along with HÁ Á ÁH (36.8%) and CÁ Á ÁH/HÁ Á ÁC (26.5%) contacts.
The non-aromatic six-membered ring adopts a distorted envelope conformation with the methylene-C10 atom being the flap atom, Fig. 1. The heterocyclic ring forms dihedral angles of 37.9 (1) and 64.3 (1) with the phenyl and chlorobenzene rings, respectively. The data reports dihedral angle between the pendant rings is 74.5 (1) . The molecular structure features a weak intramolecular interaction through C14-H14Á Á ÁO1 (Table 1).
The intermolecular interactions in the crystal state can be visualized through the calculation of the Hirshfeld surfaces and associated two-dimensional fingerprint plots. These were generated by Crystal Explorer (Wolff et al., 2012). The Hirshfeld surface is colour-mapped with the normalized contact distance, d norm , i.e. from red (distances shorter than the sum of the van der Waals radii) through white to blue (distances longer than the sum of the van der Waals radii). The different types of intermolecular interactions can be identified by colour-coding distances from the surface to the nearest atom exterior (d e ) or interior (d i ) plots to the surface. The three-dimensional Hirshfeld surfaces and selected twodimensional fingerprint plots (with percentage contributions) are given in Fig. 4.

Figure 2
A view of the unit-cell contents viewed in projection down the b-axis.

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids

Figure 4
Hirshfeld three-dimensional surfaces (showing d norm , d i and d e ) and selected two-dimensional fingerprint plots interactions contribute 36.8% with widely scattered points of high density, which is consistent with the large number of hydrogen atoms at the surface of the molecule. The ClÁ Á ÁH/ HÁ Á ÁCl contacts also make a notable contribution to the total Hirshfeld surfaces, comprising about 12.9%. The large number of HÁ Á ÁH, ClÁ Á ÁH/HÁ Á ÁCl, OÁ Á ÁH/HÁ Á ÁO interactions suggest that van der Waals interactions play a significant role in the packing in the crystal.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

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. data reports data-2 IUCrData (2021). 6, x211195 Refinement. The hydrogen atoms were included in their geometrically calculated positions and refined isotropically with C-H = 0.93 or 0.97 Å and U iso (H) = 1.2U eq (C).