Crystal structure and Hirshfeld surface analysis of 1-benzyl-3-(prop-2-yn-1-yl)-2,3-dihydro-1H-1,3-benzodiazol-2-one

In the title compound, the benzodiazole unit is planar while the benzyl and propynyl substituents are rotated significantly out of this plane.

The title compound, C 17 H 14 N 2 O, is built up from the planar benzodiazole unit linked to the benzyl and propynyl substituents. The substituents are rotated significantly out of the benzodiazole plane, where the benzyl group is inclined by 68.91 (7) to the benzodiazole unit. In the crystal, the molecules are linked via intermolecular C-H Bnzdzl Á Á ÁO and C-H Bnzy Á Á ÁO (Bnzdzl = benzodiazole and Bnzy = benzyl) hydrogen bonds, enclosing R 4 4 (27) ring motifs, into a network consisting of rectangular layers parallel to the bc plane which are also stacked along the a-axis direction being associated through C-HÁ Á Á (ring) interactions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from HÁ Á ÁH (43.6%), HÁ Á ÁC/CÁ Á ÁH (42.0%) and HÁ Á ÁO/OÁ Á ÁH (8.9%) interactions.

Hirshfeld surface analysis
In order to visualize the intermolecular interactions in the crystal of the title compound, a Hirshfeld surface (HS) analysis (Hirshfeld, 1977;Spackman & Jayatilaka, 2009) was carried out using CrystalExplorer17.5 (Turner et al., 2017). In the HS plotted over d norm (Fig. 4), the white surface indicates contacts with distances equal to the sum of van der Waals radii, and the red and blue colours indicate distances shorter (in close contact) or longer (distinct contact) than the van der Waals radii, respectively (Venkatesan et al., 2016). The brightred spot appearing near O1 indicates its role as acceptor in the dominant C-HÁ Á ÁO hydrogen bonds. Hydrogen-bond donors and acceptors appear, respectively, as blue and red regions corresponding to positive and negative potentials on the HS mapped over electrostatic potential (Spackman et al., 2008;Jayatilaka et al., 2005) shown in Fig. 5. The shape-index of the HS is a tool to visualize thestacking by the presence of adjacent red and blue triangles; if there are no adjacent red and/or blue triangles, then there are nointeractions. Fig. 6 clearly suggests that there are nointeractions present. The overall two-dimensional fingerprint plot, Fig. 7 Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
Plan view of a portion of one layer seen along the a-axis direction. Intermolecular C-H Bnzdzl Á Á ÁO and C-H Bnzy Á Á ÁO (Bnzdzl = benzodiazole and Bnzy = benzyl) hydrogen bonds are shown by dashed lines.

Figure 3
Elevation view of two layers seen along the b-axis direction. C-HÁ Á ÁO hydrogen bonds are shown by black dashed lines while C-HÁ Á Á(ring) interactions are shown by green dashed lines.

Figure 1
The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
al., 2007) are illustrated in Fig. 7(b)-(g), respectively, together with their relative contributions to the Hirshfeld surface. The most important interaction type is HÁ Á ÁH, contributing 43.6% to the overall crystal packing, which is reflected in Fig. 7(b) as widely scattered points of high density due to the large hydrogen content of the molecule and also due to the short HÁ Á ÁH contacts (Table 2). In the presence of C-HÁ Á Á interactions, the pair of widely scattered points of wings in the fingerprint plot delineated into HÁ Á ÁC/CÁ Á ÁH contacts (42.0% contribution to the HS) have a nearly symmetrical distribution of points, Fig. 7 Fig. 7(f) is due to the CÁ Á ÁC contacts (Table 3) View of the three-dimensional Hirshfeld surface of the title compound plotted over d norm in the range À0.1150 to 1.2702 a.u.

Figure 5
View of the three-dimensional Hirshfeld surface of the title compound plotted over electrostatic potential energy in the range À0.0500 to 0.0500 a.u. using the STO-3 G basis set at the Hartree-Fock level of theory hydrogen-bond donors and acceptors are shown as blue and red regions around the atoms corresponding to positive and negative potentials, respectively.

Figure 6
Hirshfeld surface of the title compound plotted over shape-index.

Synthesis and crystallization
To a solution of 1-(prop-2-ynyl)-1H-benzoimidazol-2(3H)-one (3.42 mmol), benzyl chloride (6.81 mmol) and potassium carbonate (6.42 mmol) in DMF (15 ml) was added a catalytic amount of tetra-n-butylammonium bromide (0.37 mmol) and the mixture was stirred for 24 h. The solid material was removed by filtration and the solvent evaporated under vacuum. The solid product was purified by recrystallization from ethanol to afford colourless crystals in 76% yield.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. Hydrogen atoms were located in a difference-Fourier map and freely refined.

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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness 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 threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) 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.