Crystal structure, Hirshfeld surface analysis and interaction energy and DFT studies of 2-chloroethyl 2-oxo-1-(prop-2-yn-1-yl)-1,2-dihydroquinoline-4-carboxylate

The title compound consists of a 1,2-dihydroquinoline-4-carboxylate unit with 2-chloroethyl and propynyl substituents, where the quinoline moiety is almost planar and the propynyl substituent is nearly perpendicular to its mean plane. In the crystal, the molecules form zigzag stacks along the a-axis direction through slightly offset π-stacking interactions between inversion-related quinoline moieties, which are tied together by intermolecular C—HPrpnyl⋯OCarbx and C—HChlethy⋯OCarbx (Prpnyl = propynyl, Carbx = carboxylate and Chlethy = chloroethyl) hydrogen bonds.

Recently, substituted quinolines have also been reported to act as antagonists for endothelin (Cheng et al., 1996), 5HT3 (Anzini et al., 1995), NK-3 (Giardina et al., 1997) and leukotriene D4 (Gauthier et al., 1990) receptors. They are also used as inhibitors of gastric (H + /K + )-ATPase (Ife et al., 1992), dihydroorotate dehydrogenase (Chen et al., 1990) and 5-lipoxygenase (Musser et al., 1987). As a continuation of our ISSN 2056-9890 research on the development of N-substituted quinoline derivatives and the assessments of their potential pharmacological activities (Filali Baba et al., 2016Bouzian et al., 2018Bouzian et al., , 2019a, we have studied the condensation reaction of propargyl bromide with 2-chloroethyl 2-oxo-1,2-dihydroquinoline-4-carboxylate under phase-transfer catalysis conditions using tetra-n-butylammonium bromide (TBAB) as catalyst and potassium carbonate as base. We report herein on the synthesis and the molecular and crystal structures of the title compound along with the Hirshfeld surface analysis and the intermolecular interaction energies and the density functional theory (DFT) computational calculation carried out at the B3LYP/6-311 G(d,p) level.

Supramolecular features
In the crystal, the molecules form zigzag stacks along the aaxis direction through slightly offset -stacking interactions between inversion-related quinoline moieties (Fig. 2) The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 4
View of the three-dimensional Hirshfeld surface of the title compound plotted over d norm in the range À0.2177 to 1.3626 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. , while the red regions indicate the negative electrostatic potential (hydrogen-bond acceptors). The shape-index of the HS is a tool to visualizestacking 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 suggest that there areinteractions in (I).
The overall two-dimensional fingerprint plot, Fig. 7a, and those delineated into H Á Á Á H, HÁ Á ÁO/OÁ Á ÁH, HÁ Á ÁC/CÁ Á ÁH, HÁ Á ÁCl/ClÁ Á ÁH, CÁ Á ÁC, CÁ Á ÁN/N Á Á Á C and OÁ Á ÁCl/ClÁ Á ÁO contacts (McKinnon et al., 2007) are illustrated in Fig. 7 b-h, respectively, together with their relative contributions to the Hirshfeld surface. The most important interaction is HÁ Á ÁH (Table 2), contributing 29.9% to the overall crystal packing, which is reflected in Fig. 7b as widely scattered points of high density due to the large hydrogen content of the molecule with the tip at d e = d i = 1.22 Å . The pair of characteristic wings in the fingerprint plot delineated into HÁ Á ÁO/OÁ Á ÁH contacts (21.4% contribution, Fig. 7c) are viewed as a pair of spikes with the tips at d e + d i = 2.28 Å . In the absence of C-HÁ Á Á interactions, the pairs of characteristic wings in Fig. 7d    The Hirshfeld surface analysis confirms the importance of H-atom contacts in establishing the packing. The large number of HÁ Á ÁH, HÁ Á ÁO/OÁ Á ÁH, H Á Á Á C/CÁ Á ÁH and HÁ Á ÁCl/ClÁ Á ÁH interactions suggest that van der Waals interactions and hydrogen bonding play the major roles in the crystal packing (Hathwar et al., 2015).

DFT calculations
The optimized structure of the title compound in the gas phase was generated theoretically via density functional theory (DFT) using the standard B3LYP functional and 6-311 G(d,p) basis-set calculations (Becke, 1993) as implemented in GAUSSIAN 09 (Frisch et al., 2009). The theoretical and experimental results were in good agreement (Table 3). The highest-occupied molecular orbital (HOMO), acting as an electron donor, and the lowest-unoccupied molecular orbital (LUMO), acting as an electron acceptor, are very important parameters for quantum chemistry. When the energy gap is small, the molecule is highly polarizable and has high chemical reactivity. The DFT calculations provide some important information on the reactivity and site selectivity of the molecular framework. E HOMO and E LUMO clarify the inevitable charge-exchange collaboration inside the studied material, and are recorded in Table 4 Table 3 Comparison of selected (X-ray and DFT) geometric data (Å , ).
Bonds/angles X-ray B3LYP/6-311G(d,p)   ness (). The significance of and is to evaluate both the reactivity and stability. The electron transition from the HOMO to the LUMO energy level is shown in Fig. 9. The HOMO and LUMO are localized in the plane extending from the whole 2-chloroethyl 2-oxo-1-(prop-2-yn-1-yl)-1,2-dihydroquinoline-4-carboxylate ring. The energy band gap [ÁE = E LUMO À E HOMO ] of the molecule is 3.6984 eV, and the frontier molecular orbital energies, E HOMO and E LUMO are À6.3024 and À2.6040 eV, respectively.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 5. Hydrogen atoms were positioned geometrically (C-H = 0.95 and 0.99 Å , for CH and CH 2 H atoms, respectively) and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C). The largest peak and hole in the final difference map are +0.73 e Å À3 (1.00 Å away from Cl1) and À0.35 e Å À3 (0.64 Å away from C14), and are associated with the 2-chloroethylcarboxy group and may indicate a slight degree of disorder here but it was not considered serious enough to model.

Figure 9
The energy band gap of the title compound.

2-Chloroethyl 2-oxo-1-(prop-2-yn-1-yl)-1,2-dihydroquinoline-4-carboxylate
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.73 e Å −3 Δρ min = −0.35 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. 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. Hatoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å) and included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms. The largest peaks and holes in the final difference map are < +/-1 e --/%A -3 and are associated with the 2-chloroethylcarboxy group and may indicate a slight degree of disorder here but it was not considered serious enough to model.