Crystal structure, Hirshfeld surface analysis, calculations of intermolecular interaction energies and energy frameworks and the DFT-optimized molecular structure of 1-[(1-butyl-1H-1,2,3-triazol-4-yl)methyl]-3-(prop-1-en-2-yl)-1H-benzimidazol-2-one

In the title molecule, the benzimidazole entity is almost planar (r.m.s. deviation = 0.0262 Å), while the triazole ring is oriented almost perpendicular to the benzimidazole ring. In the crystal, bifurcated C—H⋯O hydrogen bonds link individual molecules into layers extending parallel to the ac plane.


Chemical context
Heterocyclic compounds comprising the benzimidazolone fragment have attracted interest due to their remarkable usefulness in various therapeutic applications.Extensive research has revealed several pharmacological and biological properties associated with these compounds, including antiproliferative (Guillon et al., 2022), antibacterial (Al-Ghulikah et al., 2023;Saber et al., 2020), anticancer (Dimov et al., 2021) and antiviral (Ferro et al., 2017) activities.

Supramolecular features
In the crystal, bifurcated C-H� � �O hydrogen bonds (Table 1, Fig. 3) link individual molecules into layers extending parallel to the ac plane.Two weak C-H� � ��(ring) interactions (Table 1) may also be effective in the stabilization of the crystal packing.

Hirshfeld surface analysis
In order to visualize the intermolecular interactions in the crystal structure of the title compound, a Hirshfeld surface (HS) analysis (Hirshfeld, 1977;Spackman & Jayatilaka, 2009) was carried out using CrystalExplorer (Spackman et al., 2021).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 surfaces contacts shorter (in close contact) or longer (distinct contact), respectively, than the van Schematic synthesis procedure for obtaining benzimidazol-2-one derivatives.

Figure 2
The title molecule with the atom-labelling scheme and displacement ellipsoids drawn at the 50% probability level.

Figure 3
A partial packing diagram of the title compound viewed down the a axis.Non-interacting hydrogen atoms were omitted for clarity.
der Waals radii (Venkatesan et al., 2016).The bright-red spots indicate their roles as the respective donors and/or acceptors; they also appear 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), as shown in Fig. 5.The blue regions indicate positive electrostatic potential (hydrogen-bond donors), while the red regions indicate negative electrostatic potential (hydrogenbond acceptors).The shape-index of the HS does not reveal any relevant �-� interactions (Fig. 6).However, the shapeindex shows C-H� � �� interactions present as 'red p-holes', which are related to the electron ring interactions between the CH groups and the centroids of the aromatic rings of neighbouring molecules (Table 1; Fig. 6).The overall two-dimensional fingerprint plot, Fig. 7a View of the three-dimensional HS of the title compound plotted over d norm .

Figure 5
View of the three-dimensional HS of the title compound plotted over electrostatic potential energy 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
HS of the title compound plotted over shape-index.

Figure 7
The  8a-c, respectively.The HS analysis confirms the importance of H-atom contacts in establishing the packing.The large number of H� � �H, H� � �C/C� � �H and H� � �N/N� � �H interactions suggest that van der Waals and hydrogen-bonding interactions play the major roles in the crystal packing (Hathwar et al., 2015).

Interaction energy calculations and energy frameworks
The intermolecular interaction energies were calculated using the CE-B3LYP/6-311G(d,p) energy model available in Crys-talExplorer (Spackman et al., 2021), where a cluster of molecules is generated by applying crystallographic symmetry operations with respect to a selected central molecule within a radius of 3.8 A ˚by default (Turner et al., 2014).The total intermolecular energy (E tot ) is the sum of electrostatic (E ele ), polarization (E pol ), dispersion (E dis ) and exchange-repulsion (E rep ) energies (Turner et al., 2015) with scale factors of 1.057, 0.740, 0.871 and 0.618, respectively (Mackenzie et al., 2017).Hydrogen-bonding interaction energies (in kJ mol À 1 ) were calculated as À 32.1 (E ele ), À 9.4 (E pol ), À 53.7 (E dis ), 48.4 (E rep ) and À 57.7 (E tot ) for C10-H10B� � �O1 and À 21.0 (E ele ), À 7.7 (E pol ), À 65.2 (E dis ), 51.6 (E rep ) and À 52.8 (E tot ) for the C11-H11B� � �O1 hydrogen bond.Energy frameworks combine the calculation of intermolecular interaction energies with a graphical representation of their magnitude (Turner et al., 2015).Energies between molecular pairs are represented as cylinders joining the centroids of pairs of molecules with the cylinder radius proportional to the relative strength of the corresponding interaction energy.Energy frameworks were constructed for E ele (red cylinders), E dis (green cylinders) and E tot (blue cylinders) (Fig. 9a-c).The evaluation of the electrostatic, dispersion and total energy frameworks indicate that the stabilization is dominated via dispersion energies in the crystal structure of the title compound.

DFT calculations
The molecular structure in the gas phase was optimized using density functional theory (DFT) with the B3LYP functional and 6-311G(d,p) basis-set calculations, as implemented in GAUSSIAN 09 (Frisch et al. 2009).The optimized parameters, including bond lengths and angles, showed satisfactory agreement with the experimental structural data (Table 2).

Figure 9
The energy frameworks for a cluster of molecules of the title compound viewed down the c axis, showing (a) electrostatic energy, (b) dispersion energy and (c) total energy diagrams.The cylindrical radius is proportional to the relative strength of the corresponding energies and they were adjusted to the same scale factor of 80 with cut-off value of 5 kJ mol À 1 within 2�2�2 unit cells.
The largest differences between the calculated and experimental values were observed for the C1-N1 (0.04 A ˚), N1-C7 and N1-C8 (0.02 A ˚) bond lengths, the N4-N3-C12 (0.82 � ) bond angle and the torsion angle N3-C12-C13-N5 (0.3 � ).These differences may be due to the fact that the calculations are based on an isolated molecule at 0 K, while the experimental results were obtained from interacting molecules in the solid state, where intra-and intermolecular interactions with neighbouring molecules are present.

Database survey
A survey of the Cambridge Structural Database (CSD, updated March 2024; Groom et al., 2016) indicates that there are several molecules similar to the title compound (Fig. 10).These include I (CSD refcode YIVWUZ; Zouhair et al., 2023) Saber et al., 2021).The benzimidazol-2-one unit in all of these compounds is almost planar, with the dihedral angle between the constituent rings being less than 1 � , or having the nitrogen atom bearing the exocyclic substituent less than 0.03 A ˚from the mean plane of the remaining nine atoms.

Synthesis and crystallization
To a solution of 2.87 mmol of 1-(prop-1-en-2-yl)-3-(prop-2ynyl)-1H-benzimidazol-2-one and 0.45 mmol of 1-azidobutane in 10 ml of ethanol were added 1.64 mmol of CuSO 4 and 3.73 mmol of sodium ascorbate dissolved in 10 ml of distilled water.The reaction mixture was stirred for 10 h at room temperature and monitored by TLC.After filtration and concentration of the solution under reduced pressure, the residue obtained was chromatographed on a silica gel column using ethyl acetate/hexane (3/1) as eluent.The resulting solid was filtered off, washed with water, dried, and then recrystallized from ethanol, yield: 73%.

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.

Figure 1
Figure 1 Figure 4 full two-dimensional fingerprint plots for the title compound, showing (a) all interactions, and delineated into (b) H� � �H, (c) H� � �C/ C� � �H, (d) H� � �N/N� � �H (e) H� � �O/O� � �H, (f) C� � �N/N� � �C, (g) C� � �C and (h) C� � �O/O� � �C interactions.The d i and d e values are the closest internal and external distances (in A ˚) from given points on the Hirshfeld surface.contribute18.1% to the overall crystal packing, as reflected in Fig.7cwith the tips at d e + d i = 2.66 A ˚.The symmetrical pair of wings in the fingerprint plot delineated into H� � �N/N� � �H contacts (Fig.7d), with 14.9% contribution to the HS, has the tips at d e + d i = 2.66 A ˚.The symmetrical pair of spikes in the fingerprint plot delineated into H� � �O/O� � �H contacts (Fig.7e), 8.3% contribution to the HS, have the tips at d e + d i = 2.22 A ˚. Finally, the C� � �N/N� � �C (Fig.7f), C� � �C (Fig.7g) and C� � �O/O� � �C (Fig.7h) interactions make small contibutions of 0.4%, 0.2% and 0.1%, respectively, to the HS.The nearest neighbour environment of a molecule can be determined from the colour patches on the HS based on how close to other molecules they are.The HS representations with the function d norm plotted onto the surface are shown for the H� � �H, H� � �C/C� � �H and H� � �N/N� � �H interactions in Fig.

Figure 8
Figure 8 The HS representations with the function d norm plotted onto the surface for (a) H� � �H, (b) H� � �C/C� � �H and (c) H� � �N/N� � �H interactions.

Table 3
Experimental details.
Computer programs: CrysAlis PRO

Table 2
Comparison of selected (X-ray and DFT) bond length and angles (A ˚, � ).Fourier map, and were included as riding contributions in idealized positions with U iso (H) = 1.2U eq(C).Aromatic H atoms were treated the same way, and methyl H atoms with U iso (H) = 1.5U eq (C).