research communications
Hirshfeld surface analysis, DFT and molecular of ethyl 5-amino-2-bromoisonicotinate
aDepartment of Physics, Yuvaraja's College, University of Mysore, Mysore, 570005, Karnataka, India, bDepartment of Pharmaceutical Chemistry, Kuvempu University, Shimoga, Karnataka, 577451, India, cDepartment of Physics, Government First Grade College, Chikkabalapura, Karnataka-562101, India, and dDepartment of PG Studies and Research in Physics, Albert Einstein Block, UCS, Tumkur University, Tumkur, Karnataka 572103, India
*Correspondence e-mail: palaksha.bspm@gmail.com
In the title compound, C8H9BrN2O2, the C—O—C—C torsion angle between isonicotine and the ethyl group is 180.0 (2)°. Intramolecular N—H⋯O and C—H⋯O interactions consolidate the molecular structure. In the crystal, N—H⋯N interaction form S(5) zigzag chains along [010]. The most significant contributions to the Hirshfeld surface arise from H⋯H (33.2%), Br⋯H/H⋯Br (20.9%), O⋯H/H⋯O (11.2%), C⋯H/H⋯C (11.1%) and N⋯H/H⋯N (10%) contacts. The topology of the three-dimensional energy frameworks was generated using the B3LYP/6–31 G(d,p) model to calculate the total interaction energy. The net interaction energies for the title compound are Eele = 59.2 kJ mol−1, Epol = 15.5 kJ mol−1, Edis = 140.3 kJ mol−1 and Erep = 107.2 kJ mol−1 with a total interaction energy Etot of 128.8 kJ mol−1. The molecular structure was optimized by density functional theory (DFT) at the B3LYP/6–311+G(d,p) level and the theoretical and experimentally obtained parameters were compared. The frontier molecular orbitals HOMO and LUMO were generated, giving an energy gap ΔE of 4.0931 eV. The MEP was generated to identify active sites in the molecule and molecular carried out with the title compound (ligand) and the covid-19 main protease PDB ID: 6LU7, revealing a moderate binding affinity of −5.4 kcal mol−1.
Keywords: crystal structure; Hirshfeld surface; DFT studies; molecular docking; isonicotinate.
CCDC reference: 2395555
1. Chemical context
The derivatives of isonicotinate are enantiomerically enriched in the R and S configuration. The molecules associated with 2-methylalkyl isonicotinate and nicotinate exhibit R and S configurations at the molecular level. These compounds demonstrate a good anti-fungal activity against different phytopathogenic fungi species and they play significant role in the reduction of the damage at the plant cell and chloroplast levels (Huras et al., 2017). Isonicotinate ligands with an organoruthenium(II) ion form organometallic complexes that exhibit anti-cancer activities (Liu et al., 2012). Silver complexes with nicotinate-based ligands exhibit anti-bacterial activity against clinically isolated pathogens (Abu-Youssef et al., 2007). Various metal complexes with nicotinate moieties have been used to develop phytopathogenic drugs. Most importantly, organotin isonicotinate derivatives are extensively used in the development of antiproliferative drugs, which play a significant role at the innermost layer of cells lining blood vessels and lymphatic vessels (Vieriu et al., 2021). These drugs are used in drug-eluting stents to inhibit vascular smooth muscle cell proliferation possesses, exhibit considerable vasodilator properties and are also used to boost endothelial protective properties (Girgis et al., 2006). The isonicotinate-derived meso-tetraarylporphyrin exhibits anti-oxidant, anti-fungal and allelopathic activities (Dardouri et al., 2024). As part of our studies of this family of materials, we now present the synthesis, structure and Hirshfeld surface analysis of the title compound.
2. Structural commentary
The molecular structure of title compound, which crystallizes in the monoclinic P21/c, is shown in Fig. 1. The amino-2-bromoisonicotinate ring system is essentially planar, with an r.m.s deviation of 0.043 (2) Å. The whole molecule is essentially planar, the dihedral angle between the mean planes defined by the isonocotine moiety and the side chain being 4.30 (2)°. The C6—O1—C7—C8 torsion angle of 175.2 (2)° indicates that the ethyl group is in a planar orientation with the isonocotine ring [see also: C1—C6—O1—C7 = −178.0 (2)° and N2—C2–C1–C6 = −1.2 (4)°]. The molecular structure is consolidated by N2—H2B⋯O2 and C5—H5⋯O1 intramolecular interactions (Table 1).
3. Supramolecular features
In the crystal, N2—H2A⋯N1 interactions (Table 1) link the molecules into S(5) zigzag chains along [010] as shown in Fig. 2a and makes molecular sheets through N—H⋯N interactions between the four independent molecules in the as shown in Fig. 2b.
4. Database survey
A search of the Cambridge Structural Database (CSD, version 5.42, update of November 2020; Groom et al., 2016) was undertaken for molecules containing ethyl 3-aminoisonicotinate, 5-amino-2-bromoisonicotinic acid and ethyl 2-bromoisonicotinate fragments, but no hits were found. However, 29 hits were found in a search for molecules containing an ethyl isonicotinate fragment. Among those, in the structures with CSD refcodes ROMMIQ (Wang et al., 2009), SILPOT (Wan et al., 2007), XEZDEM (Han et al., 2007) and XIMBIF (Li et al., 2007), the C—C—O—C torsion angles associated with the isonicotinate are 177.93 (2), −168.46 (3), −168.46 (3) and 176.82 (2)°, respectively, with the same anti conformation as in the title compound where the comparable torsion angle is 180.0 (2)°.
5. Hirshfeld surface analysis and interaction energies
CrystalExplorer17.5 (Turner et al., 2017) was used to perform a Hirshfeld surface analysis to quantify the various intermolecular interactions. Fig. 3 illustrates the Hirshfeld surface mapped over dnorm with red spots corresponding to electronegative site of the nitrogen through which a short contact N2—H2A⋯N1 forms a hydrogen-bonded chain. The fingerprint plots in Fig. 4 indicate that the major contributions to the Hirshfeld surface of the are from H⋯H (33.2%), Br⋯H/H⋯Br (20.9%), O⋯H/H⋯O (11.2%), C⋯H/H⋯C (11.1%) and N⋯H/H⋯N (10%) contacts. The characteristic spikes in the N⋯H/H⋯N plot indicate the presence of the N2—H2A⋯N1 hydrogen bond listed in Table 1. The three-dimensional interaction energy between the molecules of the title compound were computed using the basis set B3LYP/6-31G(d,p). The net interaction energies are Eele = 59.2 kJ mol−1, Epol = 15.5 kJ mol−1, Edis = 140.3 kJ mol−1, Erep = 107.2 kJ mol−1 with a total interaction energy Etot of128.8 kJ mol−1. The topology of the energy frameworks along the a, b and c axes for the different contributions (Coulombic energy, dispersion energy and total energy) are shown in Fig. 5.
6. DFT Studies
The title compound was studied by DFT calculations in the gas phase at the B3LYP/6-311+G(d,p) level of theory with Gaussian 09W (Frisch et al., 2009). GaussView 5.0 was used to generate the optimized molecular structure (Fig. 6). The optimized bond parameters obtained are in good correlation with those obtained from SCXRD analysis (Table 2). The small deviations observed may be attributed to the gas phase (theoretical calculations) compared to the solid phase of SCXRD analysis. The calculated energies of the frontier molecular orbitals are −6.2700 eV and −2.1769 eV. The energy gap ΔE was found to be 4.0931 eV (Fig. 7). The reactivity descriptors calculated from the energy gap value, (I), (A), (χ), chemical hardness (η), (μ), index (ω) and chemical softness (S) are 6.2700, 2.1769, 4.2234, 2.0465, −4.2234, 4.3580 eV and 0.2440 eV−1 respectively.
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The MEP surface of the optimized structure of the title compound is depicted in Fig. 8. Nucleophilic and electrophilic reactive sites of the molecule are represented by red- and blue-colored regions on the MEP surface. In the MEP surface of the title compound, the pale red color covering the oxygen and nitrogen atoms of the isonicotinate fragment and the pale-blue color over the amino group are active sites for nucleophilic and electrophilic attack, respectively.
7. Molecular docking studies
The interaction of the ligand with the target receptor, covid-19 main protease (PDB ID: 6LU7) was performed using Autodock Vina 4.2 (Morris et al., 2009) software. Biovia Discovery Studio (Biovia, 2017) was used for visualizing the interactions present between ligand and receptor. The docking results of the ligand with the receptor protein reveal that the ligand has a good binding affinity of −5.4 kcal mol−1 and the 2D interaction view shows conventional hydrogen bonding of GLU A:166, LEU A:141, CYS A:145 and SER A:144 with nitrogen and oxygen atoms, van der Waals interactions between the HIS A:163, ASN A:142 amino residues and ethyl −5-amino −2-bromoisonicotinate, Fig. 9. The binding affinity of the title compound with the receptor protein (covid-19 main protease) suggests it to be a potential candidate for pharmaceutical applications. Meanwhile, we have gone through the literature in order to study the efficiency of the title ligand. The docking results of imidazole-anchored azo-imidazole derivatives with the 6LU7 receptor also exhibit a binding affinity of −5.4 kcal mol−1 (Chhetri et al., 2021)
8. Synthesis and crystallization
To a stirred a solution of ethyl 3-aminoisonicotinate (800 mg, 1.0 eq) in DMF (8 mL), N-bromosuccinimide (NBS; 0.937 mg. 1.1 eq) was added, and the reaction mixture was stirred at room temperature for 6 h. The reaction was monitored by TLC (30% EA: hexane) and it confirmed that the reaction was complete. The reaction mixture was then quenched with water and extracted into ethyl acetate. The organic layer was separated and concentrated to obtain the crude product and purified through Combi-Flash using 30% EA. Hexane–ethyl acetate was used as mobile phase to obtain the pure compound as a pale-yellow crystal, yield: 98%. A suitable single crystal was used to collect the X-ray data.1H NMR (500 Hz) in CDCl3, δ 7.96 (s, 1H, Ar-H), 7.78 (s, 1H, Ar-H), 5.69 (s, 2H, NH2), 4.36 (t, J = 7 Hz, 2H, OCH2−), 1.42 (t, J = 7 Hz, 3H, –CH3) ppm. 13C NMR, 125 Hz: δ 165.8, 144.1, 140.3, 126.9, 118.8, 61.6, 14.2 ppm.
9. Refinement
Crystal data, data collection and structure . The hydrogen atoms attached to N were located in difference maps. The distances H2A/H2B—N2 were restrained to 0.82 (2) Å. All other H atoms were positioned with idealized geometry and refined using a riding model with C—H = 0.93–0.97 Å and Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C).
details are summarized in Table 3Supporting information
CCDC reference: 2395555
https://doi.org/10.1107/S2056989024010594/oi2013sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989024010594/oi2013Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989024010594/oi2013Isup3.cml
C8H9BrN2O2 | F(000) = 488 |
Mr = 245.08 | Dx = 1.710 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 4.1538 (9) Å | Cell parameters from 2367 reflections |
b = 8.9978 (16) Å | θ = 2.5–29.0° |
c = 25.487 (5) Å | µ = 4.29 mm−1 |
β = 92.468 (7)° | T = 567 K |
V = 951.7 (3) Å3 | Prism, pale yellow |
Z = 4 | 0.32 × 0.27 × 0.21 mm |
Bruker SMART APEXII CCD diffractometer | 2353 independent reflections |
Radiation source: fine-focus sealed tube | 1910 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.037 |
Detector resolution: 0.97 pixels mm-1 | θmax = 28.3°, θmin = 2.8° |
φ and Ω scans | h = −5→5 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | k = −11→11 |
Tmin = 0.225, Tmax = 0.401 | l = −33→33 |
21643 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.032 | Hydrogen site location: mixed |
wR(F2) = 0.069 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0216P)2 + 0.6676P] where P = (Fo2 + 2Fc2)/3 |
2353 reflections | (Δ/σ)max = 0.001 |
126 parameters | Δρmax = 0.53 e Å−3 |
0 restraints | Δρmin = −0.45 e Å−3 |
0.12 constraints |
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. |
x | y | z | Uiso*/Ueq | ||
Br1 | 0.50981 (7) | 0.23668 (3) | 0.33291 (2) | 0.06255 (12) | |
O1 | 0.6756 (4) | 0.71953 (17) | 0.44789 (6) | 0.0519 (4) | |
O2 | 0.4245 (5) | 0.91607 (19) | 0.41176 (7) | 0.0678 (5) | |
N2 | 0.0811 (7) | 0.8705 (3) | 0.31867 (10) | 0.0679 (7) | |
C1 | 0.3910 (5) | 0.6820 (2) | 0.36780 (8) | 0.0389 (4) | |
C2 | 0.1949 (6) | 0.7303 (2) | 0.32486 (8) | 0.0451 (5) | |
C3 | 0.1106 (6) | 0.6220 (3) | 0.28677 (9) | 0.0511 (6) | |
H3 | −0.019460 | 0.651860 | 0.258076 | 0.061* | |
N1 | 0.2016 (5) | 0.4817 (2) | 0.28864 (7) | 0.0480 (5) | |
C4 | 0.3867 (5) | 0.4403 (2) | 0.32981 (8) | 0.0419 (5) | |
C5 | 0.4870 (5) | 0.5336 (2) | 0.36960 (8) | 0.0414 (5) | |
H5 | 0.617469 | 0.498569 | 0.397470 | 0.050* | |
C6 | 0.4947 (6) | 0.7863 (3) | 0.41030 (8) | 0.0455 (5) | |
C7 | 0.7917 (7) | 0.8112 (3) | 0.49174 (9) | 0.0558 (6) | |
H7A | 0.612483 | 0.860208 | 0.507725 | 0.067* | |
H7B | 0.938171 | 0.886598 | 0.479721 | 0.067* | |
C8 | 0.9601 (8) | 0.7121 (4) | 0.53018 (11) | 0.0737 (8) | |
H8A | 1.039906 | 0.769478 | 0.559719 | 0.111* | |
H8B | 0.812758 | 0.638136 | 0.541835 | 0.111* | |
H8C | 1.137029 | 0.664411 | 0.513954 | 0.111* | |
H2A | −0.018 (6) | 0.889 (3) | 0.2911 (12) | 0.064 (8)* | |
H2B | 0.141 (7) | 0.934 (3) | 0.3432 (12) | 0.067 (9)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.07039 (19) | 0.04411 (15) | 0.0714 (2) | 0.00444 (12) | −0.01747 (13) | −0.01644 (12) |
O1 | 0.0718 (11) | 0.0421 (8) | 0.0399 (8) | 0.0006 (7) | −0.0200 (7) | −0.0075 (7) |
O2 | 0.1044 (15) | 0.0396 (9) | 0.0572 (11) | 0.0078 (9) | −0.0225 (10) | −0.0068 (8) |
N2 | 0.102 (2) | 0.0467 (12) | 0.0519 (14) | 0.0056 (12) | −0.0313 (13) | 0.0091 (10) |
C1 | 0.0475 (12) | 0.0382 (10) | 0.0304 (10) | −0.0056 (9) | −0.0048 (9) | 0.0015 (8) |
C2 | 0.0559 (13) | 0.0426 (11) | 0.0359 (11) | −0.0058 (10) | −0.0073 (9) | 0.0083 (9) |
C3 | 0.0625 (15) | 0.0560 (14) | 0.0334 (11) | −0.0075 (11) | −0.0139 (10) | 0.0050 (10) |
N1 | 0.0569 (12) | 0.0513 (11) | 0.0349 (9) | −0.0085 (9) | −0.0090 (8) | −0.0041 (8) |
C4 | 0.0460 (12) | 0.0399 (11) | 0.0394 (11) | −0.0056 (9) | −0.0026 (9) | −0.0042 (9) |
C5 | 0.0488 (12) | 0.0414 (11) | 0.0331 (10) | −0.0033 (9) | −0.0090 (9) | 0.0005 (8) |
C6 | 0.0589 (14) | 0.0401 (11) | 0.0367 (11) | −0.0036 (10) | −0.0069 (10) | −0.0005 (8) |
C7 | 0.0683 (16) | 0.0557 (14) | 0.0418 (12) | −0.0052 (12) | −0.0159 (11) | −0.0167 (11) |
C8 | 0.080 (2) | 0.091 (2) | 0.0478 (15) | −0.0032 (17) | −0.0203 (14) | −0.0065 (14) |
Br1—C4 | 1.903 (2) | C3—N1 | 1.318 (3) |
O1—C6 | 1.335 (3) | C3—H3 | 0.9300 |
O1—C7 | 1.454 (2) | N1—C4 | 1.327 (3) |
O2—C6 | 1.204 (3) | C4—C5 | 1.368 (3) |
N2—C2 | 1.354 (3) | C5—H5 | 0.9300 |
N2—H2A | 0.82 (3) | C7—C8 | 1.478 (4) |
N2—H2B | 0.87 (3) | C7—H7A | 0.9700 |
C1—C5 | 1.393 (3) | C7—H7B | 0.9700 |
C1—C2 | 1.405 (3) | C8—H8A | 0.9600 |
C1—C6 | 1.483 (3) | C8—H8B | 0.9600 |
C2—C3 | 1.409 (3) | C8—H8C | 0.9600 |
C6—O1—C7 | 117.00 (18) | C1—C5—H5 | 120.5 |
C2—N2—H2A | 117 (2) | O2—C6—O1 | 123.0 (2) |
C2—N2—H2B | 115.9 (19) | O2—C6—O1 | 123.0 (2) |
H2A—N2—H2B | 127 (3) | O2—C6—C1 | 125.0 (2) |
C5—C1—C2 | 118.54 (19) | O2—C6—C1 | 125.0 (2) |
C5—C1—C6 | 120.56 (19) | O1—C6—C1 | 112.08 (19) |
C2—C1—C6 | 120.9 (2) | O1—C7—C8 | 107.4 (2) |
N2—C2—C1 | 124.5 (2) | O1—C7—H7A | 110.2 |
N2—C2—C3 | 119.3 (2) | C8—C7—H7A | 110.2 |
C1—C2—C3 | 116.2 (2) | O1—C7—H7B | 110.2 |
N1—C3—C2 | 125.1 (2) | C8—C7—H7B | 110.2 |
N1—C3—H3 | 117.4 | H7A—C7—H7B | 108.5 |
C2—C3—H3 | 117.4 | C7—C8—H8A | 109.5 |
C3—N1—C4 | 116.92 (19) | C7—C8—H8B | 109.5 |
N1—C4—C5 | 124.2 (2) | H8A—C8—H8B | 109.5 |
N1—C4—Br1 | 116.65 (15) | C7—C8—H8C | 109.5 |
C5—C4—Br1 | 119.19 (16) | H8A—C8—H8C | 109.5 |
C4—C5—C1 | 119.1 (2) | H8B—C8—H8C | 109.5 |
C4—C5—H5 | 120.5 | ||
C5—C1—C2—N2 | 179.0 (2) | C6—C1—C5—C4 | 179.9 (2) |
C6—C1—C2—N2 | −1.2 (4) | C7—O1—C6—O2 | −0.6 (4) |
C5—C1—C2—C3 | 0.2 (3) | C7—O1—C6—O2 | −0.6 (4) |
C6—C1—C2—C3 | −180.0 (2) | C7—O1—C6—C1 | 180.0 (2) |
N2—C2—C3—N1 | −179.0 (3) | C5—C1—C6—O2 | 179.6 (2) |
C1—C2—C3—N1 | −0.1 (4) | C2—C1—C6—O2 | −0.2 (4) |
C2—C3—N1—C4 | 0.1 (4) | C5—C1—C6—O2 | 179.6 (2) |
C3—N1—C4—C5 | −0.2 (3) | C2—C1—C6—O2 | −0.2 (4) |
C3—N1—C4—Br1 | 178.77 (18) | C5—C1—C6—O1 | −1.0 (3) |
N1—C4—C5—C1 | 0.3 (4) | C2—C1—C6—O1 | 179.1 (2) |
Br1—C4—C5—C1 | −178.67 (16) | C6—O1—C7—C8 | 175.2 (2) |
C2—C1—C5—C4 | −0.2 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2B···O2 | 0.87 (3) | 2.07 (3) | 2.746 (3) | 133 (2) |
C5—H5···O1 | 0.93 | 2.37 | 2.694 (3) | 100 (1) |
N2—H2A···N1i | 0.82 (3) | 2.30 (3) | 3.096 (3) | 166 (3) |
Symmetry code: (i) −x, y+1/2, −z+1/2. |
Parameter | SCXRD | DFT |
Br1—C4 | 1.903 (2) | 1.9253 |
O1—C6 | 1.335 (3) | 1.3573 |
O1—C7 | 1.454 (3) | 1.4551 |
N2—C2 | 1.354 (3) | 1.3704 |
C3—N1 | 1.318 (3) | 1.3228 |
N1—C4 | 1.327 (3) | 1.3226 |
C6—O1—C7 | 117.00 (2) | 116.13 |
N2—C2—C1 | 124.5 (2) | 124.95 |
N2—C2—C3 | 119.3 (2) | 118.77 |
C2—C3—N1 | 125.1 (2) | 124.62 |
Br1—C4—N1 | 116.65 (15) | 117.07 |
Br1—C4—C5 | 119.19 (16) | 119.44 |
O1—C6—O2 | 123.0 (2) | 122.35 |
C7—O1—C6—O2 | -0.6 (4) | -0.34 |
C7—O1—C6—C1 | 180.0 (2) | 179.93 |
C3—N1—C4—Br1 | 178.8 (2) | 179.84 |
N2—C2—C3—N1 | -179.0 (3) | -177.72 |
Acknowledgements
HM extends his gratitude to Kishore and Shashikanth SSCU, IISc for their help in collecting the SCXRD data.
Funding information
Funding for this research was provided by: Vision Group of Science and Technology, Government of Karnataka (award No. GRD319 to Palakshamurthy Bandrehalli Siddagangaiah).
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