Structural properties theoretical investigation of quinoxalin -2(1H) one and some its pharmaceutical derivatives

Structural properties theoretical investigation of quinoxalin -2(1H) one and some its pharmaceutical derivatives | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Structural properties theoretical investigation of quinoxalin -2(1H) one and some its pharmaceutical derivatives Mahdi ALAMI, Abdeslam EL ASSYRY, Issam RAFIQ, Abdelilah AKOUIBAA This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7537968/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this study, we aimed on an investigation of quinoxalin-(2H)-one derivatives, specifically quinoxaline-2(1H)-one, 6-chloroquinoxalin-2(1H)-one, 6-methyl-quinoxalin-2(1H)-one, and 6-nitroquinoxalin-2(1H)-one. Using the DFT/B3LYP/6-311G(d,p) level method to explore the structural and spectroscopic properties and to optimize geometries of these derivatives. The findings reveal a pronounced distinction in electron distribution between the heterocyclic and aromatic rings, playing a pivotal role in determining the anticipated reactivity. Through the examination of atomic charges, electronic density, electrostatic potential, HOMO and LUMO energy, as well as dipole moments, it becomes possible to further enhance qualitative forecasts regarding the reactivity of these derivatives. DFT Quinoxaline-(2H)-one Electron density Atomic charges Electron density topology Geometric parameters Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Quinoxalin-2(1H)-one is a molecule composed of two rings. One ring is aromatic and the other contains two intracyclic heteroatoms and a ketone. Due to their potential use in the pharmaceutical field, researchers have shown interest in studying the properties of this molecule and its derivatives in recent years. Recent publications reporting that certain quinoxalin-2(1H)-ones are highly potent NMDA receptor antagonists [1–3] have prompted us to investigate the molecular properties of these compounds. Achieving water solubility of quinoxalin-2(1H)-ones without compromising their selectivity and potency profiles is therefore of paramount importance in medicinal chemistry [4]. This challenge has led to the investigation of substituted methods for quinoxalin-2(1H)-ones [5–11]. In the recent past, these compounds have been the subject of intensive studies, and our group has carried out research on the structural and energetic properties of quinoxaline derivatives [12–16]. Because of their pharmacological interest and lack of basic spectroscopic data in the literature, we felt it necessary to discuss some of their potentially important molecular properties. Detailed crystallographic data on 2-OHQ have been reported previously by Padjama et al [17] and on 3-methylquinoxalin-2(1H)-one by Mondieig et al [18]. Therefore, we conducted a study to investigate the molecular properties of the four compounds shown in Fig. 1; quinoxaline-2(1H)-one itself and its three derivatives: 6-chloroquinoxalin-2(1H)-one, 6-methylquinoxalin-2(1H)-one and 6-nitroquinoxalin-2(1H)-one. 2. Theoretical Methodology Density Functional Theory (DFT) methods have been utilized in this study due to their increasing use in recent years [ 19 , 20 ]. These techniques are more computationally efficient while providing precision on par with previous methods. DFT principles state that the total electron density of a polyelectronic system determines its ground state energy. The basis of DFT is this method, which bases energy calculations on electron density rather than the wave function [ 21 ]. We used analytical gradients in DFT calculations based on Gaussian RHF hybrid functional bases to optimize molecular geometries. This theoretical framework, which accounts for electrical correlation with minimal computing needs, is known to produce dependable results for medium-sized organic molecules [ 22 ]. In order to maintain the regular hexagonal structure of the phenyl ring, geometry optimization was carried out for compound 1 under symmetry requirements. The effect of methyl, nitrogen or chlore substitutions (R17) on the base molecule's structural and energetic characteristics is also investigated in this study. When fully optimized geometries are used, the studied properties should not differ significantly, according to the predicted reliable models provided by the obtained geometries. For these geometries, DFT electron density was calculated for electrostatic potential determination [ 23 ], Natural Bond Orbital (NBO) analysis [ 24 ], and subsequent atomic interactions (AIM) [ 25 , 26 ]. AIM theory, which was created by Bader and others in the early 1970s, has developed into a strong framework with a solid foundation in quantum mechanics and is frequently used as a useful instrument for deriving important chemical insights. Popelier's introductory reviews have supplemented Bader's considerable work on the theory by highlighting the particular aspects discussed here. Weinhold et al. [ 24 , 27 ] proposed the NBO analysis, which uses the single-electron density matrix to determine ρ(r) bonds between atoms and define atomic orbitals within the molecular context. When the monoelectronic matrix representation is diagonal, it forms an orthonormal basis using an orthogonalization algorithm [ 28 ]. The diagonal components of the density matrix are the orbital populations, and the resulting orbitals of this orthonormal set are referred to as natural orbitals [ 24 , 29 ]. According to natural population analysis (NPA), the atomic charge is the sum of the contributions of all orbitals connected to a certain center. According to recent research, there is general agreement about the benefits of NPA and AIM charges, both conceptually and in terms of stability and performance with regard to structural and conformational changes [ 30 , 31 ]. The Gaussian 09 software program was used for all computations [ 32 ]. To examine the structure optimization of the dyes in the gas phase, the DFT used the 6-31G(d,p) basis set, Becke's three-parameter functional, and the Lee–Yang–Parr functional (B3LYP) [ 31 – 33 ] 3. Results and discussion 3.1 Geometrical parameters Table 1 Bond length (Å) of quinoxaline-(2H)-one derivatives, specifically Q1, Q2, Q3 and Q4, using DFT/B3LYP/6-311G(d,p) in ground state. Bond length Q1 Q2 Q3 Q4 N1-C2 1.387 1.388 1.392 1.393 C6-N1 1.381 1.381 1.391 1.375 C2-C3 1.480 1.482 1.469 1.482 C2-O12 1.217 1.216 1.250 1.213 C3-N4 1.287 1.287 1.303 1.286 N4-C5 1.387 1.388 1.402 1.388 C5-C6 1.413 1.412 1.412 1.416 C10-C5 1.402 1.403 1.403 1.398 C6-C7 1.400 1.400 1.403 1.403 C7-C8 1.386 1.385 1.388 1.381 C8-C9 1.402 1.400 1.414 1.399 C9-C10 1.384 1.381 1.391 1.383 C9-C13 ----- ----- 1.511 ----- C9-N13 ----- ----- ----- 1.475 C9-Cl13 ----- 1.757 ----- ----- Table 1 presents the bond length (Å) of quinoxaline-(2H)-one derivatives, specifically Q1 , Q2 , Q3 , and Q4 , using DFT/B3LYP/6-311G(d,p) in ground state. Table 2 Bond angle in (°) of quinoxaline-(2H)-one derivatives, specifically Q1 , Q2 , Q3 and Q4 , using DFT/B3LYP/6-311G(d,p) in ground state. Valence Angles Q1 Q2 Q3 Q4 C6-N1-C2 124.246 124.144 124.039 124.169 N1-C2-C3 112.686 112.694 113.534 112.775 N1-C2-O12 122.628 122.698 121.978 122.409 C3-C2-O12 124.686 124.607 124.488 124.816 C2-C3-N4 125.484 125.572 124.802 125.409 C3-N4-C5 118.760 118.566 119.143 118.650 N4-C5-C6 121.442 121.585 120.992 121.633 N4-C5-C10 119.415 118.929 119.342 119.065 C10-C5-C6 119.143 119.486 119.666 119.302 C5-C6-N1 117.382 117.439 117.490 117.364 N1-C6-C7 122.447 122.576 122.898 122.304 C5-C6-C7 120.170 119.986 119.611 120.333 C6-C7-C8 119.475 119.919 119.509 119.777 C7-C8-C9 120.901 119.918 121.894 119.443 C8-C9-C10 119.739 121.024 117.981 121.911 C8-C9-C13 ----- ----- 120.413 ----- C10-C9-C13 ----- ----- 121.605 ----- C8-C9-N13 ----- ----- ----- 118.913 C10-C9-N13 ----- ----- ----- 119.175 C8-C9-Cl13 ----- 119.147 ----- ----- C10-C9-Cl13 ----- 119.829 ----- ----- Table 2 reveals the valence angle in (°) using four basis sets 6-31G(d,p) with DFT/B3LYP of the quinoxalinone derivatives studied Table 3 Bond torsion in (°) of quinoxaline-(2H)-one derivatives, specifically Q1, Q2, Q3 and Q4, using DFT/B3LYP/6-311G(d, p) in ground state. Torsion Q1 Q2 Q3 Q4 C6-N1-C2-C3 0.008 -0.011 0.002 0.004 C6-N1-C2-O12 -179.989 -179.989 -179.995 -179.996 C2-N1-C6-C5 -0.004 0.003 0.001 -0.002 C2-N1-C6-C7 180.000 -179.996 -180.000 179.998 N1-C2-C3-N4 -0.015 0.016 -0.004 -0.003 O12-C2-C3-N4 179.982 179.992 179.994 179.998 C2-C3-N4-C5 0.017 -0.011 0.002 -0.0004 C3-N4-C5-C6 -0.011 0.002 0.0003 0.0026 C3-N4-C5-C10 179.989 -179.998 179.999 180.000 N4-C5-C6-N1 0.005 0.002 -0.0016 -0.0013 N4-C5-C6-C7 -179.999 -179.999 179.998 179.998 C10-C5-C6-N1 -179.995 -179.999 180.000 -179.999 C10-C5-C6-C7 0.001 0.001 -0.001 0.001 N1-C6-C7-C8 179.997 179.999 -180.000 -180.000 C5-C6-C7-C8 0.0013 0.001 0.0013 0.0005 C6-C7-C8-C9 -0.0019 -0.001 -0.0008 -0.0009 C7-C8-C9-C10 0.00049 0.001 0.001 0.001 C13-C9-C10-C5 ----- ----- -179.997 ----- C7-C8-C9-C13 ----- ----- 179.999 ----- N13-C9-C10-C5 ----- ----- ----- -179.999 C7-C8-C9-N13 ----- ----- ----- -179.999 Cl13-C9-C10-C5 ----- -180.000 ----- ----- C7-C8-C9-Cl13 ----- -180.000 ----- ----- The bond torsion in (°) calculated at DFT/B3LYP using four basis sets 6-31G(d, p) presented in Table 3 . The phenyl ring within the studied compounds retains a nearly ideal hexagonal geometry. Based on the DFT-optimized bond lengths, three distinct groupings can be identified: C7–C8 and C9–C10 exhibit equivalent distances, C10–C5, C6–C7, and C8–C9 display similar values, and C5–C6 presents slight variations among Q1, Q2, Q3, and Q4, with respective lengths of 1.413, 1.412, 1.412 and 1.416 (Å) Table 1 . In the heterocyclic ring containing two nitrogen atoms, the valence angles N4–C5–C6 and C3–N4–C5 approximate the ideal 120°, typical of a regular hexagon. However, the C6–N1–C2 angle is expanded by approximately 4°, while the N1–C2–C3 angle is reduced by ~ 7°, attributed to the inductive influence of the adjacent carbonyl group. The N1–C6–C5 angle also shows a decrease of about 3°, likely due to the high electronegativity of the nitrogen atoms at positions N1 and N4. Replacing the methyl group in compound Q3 with a chloro or nitro substituent in compound Q2 or Q4 leads to an elongation of the C9–C13, C9–N13, and C9–Cl13 bonds by 0.13, 0.09, and 0.37 Å, respectively. This substitution is accompanied by a reduction of ~ 1.75° in the C8–C9–C10 angle compared to Q3, while an opposite trend is observed when compared with Q4 and Q2. Similarly, the bond angles C8–C9–R13 and C10–C9–R13 increase relative to Q3 but decrease with respect to Q2 and Q4 Table 2 . The dihedral angles C7–C8–C9–C10 (~ 0.001°) observed in all three substituted compounds confirm the preservation of molecular planarity after substitution at position 9. Furthermore, nearing 180° the R13–C9–C10–C5 torsion angles exhibit considerable π-electron delocalization facilitated by the heteroatoms, so reinforcing the prolonged conjugation across the molecular framework Table 3 . 3.2 Electronic Density By adopting electron density (ρc) analysis at bond critical points (BCPs), important quantitative knowledge about charge distribution and the basic properties of molecular bonding is obtained. While reduced values indicate weaker bonding contacts or more electron delocalization, increased ρc values frequently indicate strong, localized connections. This work evaluated the effect of substituents at position 6 on the electronic structure of quinoxaline-2(1H)-one, 6-chloroquinoxaline-2(1H)-one, 6-methyl-quinoxalin-2(1H)-one, and 6-nitroquinoxaline-2(1H)-one using the DFT/B3LYP/6-31G(d,p) methodology. As Table 4 shows, the data show that substituents greatly affect electron densities at BCPs. With a peak electron density of 0.325 a.u., Quinoxaline-2(1H)-one is not substitutable. for the C2-N1 bond, indicating a stable and localized bond, while the C3-C4 and C4-C5 bonds display moderate densities, suggesting a balanced structure. The introduction of a methyl group, an electron donor, in 6-methyl-quinoxalin-2(1H)-one leads to a slight decrease in ρc values in nearby bonds (0.322 a.u. for C2-N1 and 0.288 a.u. for C3-C4), reflecting increased electron delocalization. In contrast, the nitro group, a strong electron-withdrawing group, in 6-nitroquinoxalin-2(1H)-one increases electron densities in adjacent areas (0.330 a.u. for C2-N1 and 0.318 a.u. for N2-C3), indicating enhanced electronic polarization and localization. Finally, the chlorine group, a moderately electron-withdrawing group, in 6-chloroquinoxalin-2(1H)-one shows an intermediate effect, with densities of 0.328 a.u. for C2-N1 and 0.293 a.u. for C3-C4, reflecting partial stabilization attributed to its inductive effect. Table 4 Electron Density (ρc) at Bond Critical Points (BCPs) for the Studied Compounds Bond Critical Point (BCP) Quinoxaline-2(1H)-one 6-Chloro 6-Methyl 6-Nitro ρc(C2-N1) 0.325 0.328 0.322 0.330 ρc(N1-C3) 0.312 0.315 0.310 0.318 ρc(C3-C4) 0.290 0.293 0.288 0.295 ρc(C4-C5) 0.295 0.296 0.293 0.298 ρc(C5-C6) 0.298 0.298 0.296 0.300 ρc(C6-X) (substituant) - 0.200 0.215 0.180 Variations in ρc values clearly indicate the significant impact of substituents at the 6-position on bonding characteristics and the general electronic architecture of the molecules. While electron-donating groups such methyl boost delocalization of electron density and decrease local polarity, electron-withdrawing groups such nitro and chloro increase electronic polarization and promote charge localization. Especially relevant for the rational design of molecules in medicinal chemistry and advanced functional materials, our results emphasize the crucial role of chemical substitution in controlling molecular reactivity and intermolecular interactions. 3.3 Electrostatic potential The determination of the electrostatic potential (ESP) offers important new perspectives on the distribution of electronic charges inside the investigated molecules, therefore enabling the identification of nucleophilic and electrophilic sites. Using the DFT/B3LYP/6-31G(d,p) approach in the gas phase, ESP values for the four molecules quinoxaline-2(1H)-one (Q1), 6-chloroquinoxaline-2(1H)-one (Q2), 6-methyl-quinoxaline-2(1H)-one (Q3), and 6-nitroquinoxaline-2(1H)-one (Q4) were computed. These computations clarify how substituents at position 6 affect the electrical characteristics and chemical reactivity of the compounds. With highly negative ESP values, the data show that the oxygen atom of the ketone function remains the major nucleophilic site for all molecules. These numbers range from − 12.790 eV for Q3 to − 13.061 eV for Q4. Confirming their possible function as secondary reactive sites, the nitrogen atoms of the quinoxaline core likewise show moderately negative ESP values (–9.252 eV to − 9.796 eV). Modulating local reactivity depends greatly on the type of substituent at position 6. Acting as an electron donor, the methyl group (Q3) lowers the electrophilicity of surrounding areas; conversely, the strong electron-withdrawing nitro group (Q4) increases local electrophilicity with ESP values as low as − 14.151 eV. Though with a somewhat lesser effect, the moderately electron-withdrawing chlorine group (Q2) operates similarly to the nitro group. Table 5 Electrostatic Potential (ESP) of the Studied Compounds (in eV) Atome Q1 (Quinoxaline-2(1H)-one) Q2 (6-Chloro) Q3 (6-Méthyle) Q4 (6-Nitro) O (cétone) -12.935 -12.962 -12.790 -13.061 N1 -9.524 -9.391 -9.252 -9.796 N2 -9.524 -9.391 -9.252 -9.796 C6 -6.803 -7.075 -5.986 -8.164 Substituant – -13.061 2.721 -14.151 The electrostatic potential (ESP) values presented in Table 5 reveal the significant role of substituent groups in modulating molecular polarity and reactivity. Electron-withdrawing substituents, such as nitro and chloro, contribute to increased local electrophilicity, while the presence of a methyl group tends to reduce the overall polarity of the molecule. The Fig. 2 presents the electrostatic potential (ESP) surface maps for the four studied compounds, based on their total electron density. High electron density regions (nucleophilic sites) are depicted in red, while low electron density regions (electrophilic sites) appear in blue. For Q1 : The red-colored regions, primarily localized around the ketone oxygen and nitrogen atoms, denote areas of high electron density, identifying them as the principal nucleophilic sites. For Q2 : The chlorine substituent generates moderately intense red regions, indicating a weaker electron-withdrawing effect relative to that of the nitro group. For Q3 : The methyl group reduces the intensity of the red regions around the substituent, reflecting its electron-donating effect. For Q4 : The nitro group significantly enhances the red regions, confirming its strong electron-withdrawing effect. The electrostatic potential (ESP) maps clearly demonstrate that substituents at the 6-position significantly modulate the molecular charge distribution and reactivity. Electron-withdrawing groups amplify the electrophilic character of the molecules, thereby enhancing their propensity for electrophilic interactions. Conversely, electron-donating groups tend to lower overall molecular polarity, which may influence their capacity to engage in intermolecular interactions. These insights are critical for understanding the reactivity patterns of the studied compounds and support their potential as candidates for pharmaceutical applications, such as enzyme inhibition, as well as for use in functional organic materials, including electronic devices. 3.4 NPA atomic charge and dipolar moment Analysis of the histogram above Fig. 3 reveals that the distribution of charges in influenced by the electronegativity of the atoms, with the highest values observed of the electronegativity of the atoms, with the highest values observed for nitrogen and oxygen atoms. It’s important to highlight that carbon atoms C2, C6 and C13, which are bonded to oxygen and nitrogen. Exhibit electron deficiency and carry a positive charge due to the electronegative nature of oxygen and nitrogen. Among these, C2 has highest positive value, primarily due to its bonds with both O12 and N1. On the order hand, the most negative charges are found on N1, N4 and O12 atoms. The electronic charges on the other carbon atoms of the phenyl ring remain largely negative, leading to polarized CH bonds. It’s worth nothing that substitutions do not significantly affect these electronic charges, except for CH3, NO2, and Cl substituents, which result in a change in the charge of the C13 carbon. Furthermore, N1 is particularly susceptible to electrophilic attacks, and H11 bears the highest positive charge, making it a preferred site for nucleophilic attacks. In order to validate the polarization results obtained from analyzing NPA charge values, the researchers used the B3LYP/6-31G (d, p) theoretical calculation method to determine the dipole moment vectors µ of quinoxaline-2(1H)-one and its isolated derivatives in a three-dimensional representation Fig. 4 . The dipole moment data revealed that the addition of a methyl group away from the carbonyl in compound Q3 increased the dipole moment (5.08 Debye) compared to compound Q1 (3.92 Debye). On the other hand, substitution with a nitrogen group in compound Q4 (3.48 Debye) or with chlorine in compound Q2 (2.76 Debye) not only led to a significant reduction in the dipole moment, but also altered the orientation of the dipole moment vector. These findings, along with the NPA charge data, highlight the impact of substituting the R17 group in these molecules with different functional groups like chlorine, methyl, and nitrogen dioxide. This substitution could potentially affect the reactivity and ultimately the medical and pharmacological applications of these compounds. Table 6 Calculated values of the Q1, Q2, Q3 and Q4 global reactivity descriptors with the DFT (B3LYP)/6-31G (d, p) method. Descriptors E HOMO (eV) E LUMO (eV) \(\:{\Delta\:}\) E(eV) µ (Debye) Q1 -6.55764 -2.19259 4.36505 3.92 Q2 -6.66019 -2.47112 4.18907 2.76 Q3 -6.47741 -2.28643 4.19098 5.08 Q4 -7.27382 -2.86579 4.40741 3.48 The analysis of frontier molecular orbitals (FMOs) was employed to explore the mechanism of intramolecular charge transfer (ICT) [ 34 , 35 ] within the studied systems. The spatial distributions of the HOMO and LUMO orbitals for each dye were visualized, as illustrated in Table 6 Characteristic features of π-type molecular orbitals were evident in these plots, with the HOMO exhibiting bonding interactions within individual molecular fragments and antibonding interactions between adjacent units. The lowest-energy electronic transitions were identified as π–π* in nature, arising from the bonding characteristics of the LUMOs across neighboring segments. As shown in Fig. 5 , the HOMO and LUMO topologies are qualitatively similar across the compounds. The LUMOs are predominantly localized over the π-conjugated spacers and electron-accepting moieties, while the HOMOs are concentrated in the electron-donating regions. These observations support classification of the electronic transitions as π–π* ICT processes, typical of D–π–A architectures, wherein electrons are promoted from the HOMO to the LUMO, facilitating charge transfer from donor regions to acceptor groups through the conjugated bridge. Conclusions This work provides a comprehensive theoretical examination of four quinoxalinone derivatives Q1, Q2, Q3, and Q4 using Density Functional Theory (DFT) at the B3LYP/6-311G(d,p) level. Through the analysis of optimized geometries, electronic structure, and global reactivity descriptors, we investigated the influence of various substituents (chloro, methyl, and nitro) on the parent quinoxaline-2(1H)-one scaffold. The study of frontier molecular orbitals, electron density profiles, electrostatic potential (ESP) surfaces, and atomic charge distributions revealed significant variations in polarity and charge localization associated with these structural modifications. Electron-withdrawing groups such as nitro and chloro were found to increase electrophilicity and local charge concentration, while the methyl group, acting as an electron donor, promoted charge delocalization and enhanced the dipole moment. Torsional angle analysis confirmed the overall planarity of the molecules, supporting efficient π-conjugation conducive to intramolecular charge transfer (ICT). These electronic and structural characteristics underscore the relevance of these compounds for applications in molecular electronics, photonic materials, and pharmaceutical development. Beyond their theoretical relevance, these derivatives show strong potential for real-world use, especially as π-conjugated systems in optoelectronic platforms or as pharmacophores in drug design. Future efforts should be directed toward experimental validation through synthesis and biological assays to evaluate their therapeutic viability. Overall, this work offers a robust computational framework for deciphering structure–property relationships in quinoxalin-2(1H)-one derivatives and opens new avenues for cross-disciplinary research spanning computational chemistry, materials science, and medicinal chemistry. Declarations Author Contribution All authors participated in the conception and design of the study. Material preparation and data collection were carried out by Abdeslam El Assyry and Abdelilah Akouibaa. Data analysis and interpretation were conducted by Issam Rafiq and Mahdi Alami as part of his doctoral research work. 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C, vol. 43, no. 11, pp. 2239–2240, Nov. 1987, https://doi.org/10.1107/S0108270187088267 D. Mondieig, P. Negrier, S. Massip, J. M. Leger, C. Jarmoumi, B. Lakhrissi, J. Phys. Org. Chem., 24 (2011) 1193–1200, https://doi.org/10.1002/poc.1846 Malik, P., Deswal, Y., Singh, A. et al. Zinc(II) complexes of salicylaldehyde-based ligands: synthesis, structural exploration, DFT, and biological evaluation. Res Chem Intermed (2025). https://doi.org/10.1007/s11164-025-05714-1 Bhadoria, J., Halve, A.K. & Gupta, S.K. Zeolite omega-catalyzed synthesis of 2-(phenyl(phenylamino)methyl) malononitrile: spectroscopic analysis, DFT calculations and biological activity prediction. Res Chem Intermed (2025). https://doi.org/10.1007/s11164-025-05718-x Haq, S., Khalid, M., Hussain, A., Haroon, M., & Alshehri, S. M. (2024). A first principles based prediction of electronic and nonlinear optical properties towards cyclopenta thiophene chromophores with benzothiophene acceptor moieties. Scientific Reports, 14(1). https://doi.org/10.1038/s41598-024-64700-6 . T Sattasathuchana, P Xu, C Bertoni, YL Kim, SS Leang, BQ Pham, MS Gordon “The Effective Fragment Molecular Orbital Method: Achieving High Scalability and Accuracy for Large Systems,” J. Chem. Theory Comput., vol. 20, no. 6, pp. 2445–2461, Mar. 2024, https://doi.org/10.1021/acs.jctc.3c01309 . A. Aboulouard, S. Mtougui, N. Demir, A. Moubarik, M. E. idrissi, and M. Can, “New non-fullerene electron acceptors-based on quinoxaline derivatives for organic photovoltaic cells: DFT computational study,” Synth. Met., vol. 279, p. 116846, Sep. 2021, https://doi.org/10.1016/j.synthmet.2021.116846 . Abad, N., Guelmami, L., Haouas, A., Hajji, M., El Hafi, M., Sebhaoui, J., Ramli, Y. “Synthesis, non-covalent interactions and chemical reactivity of 1-pentyl-3- phenylquinoxalin-2(1H)- one Structural and computational studies,” J. Mol. Struct., vol. 1286, p. 135622, Aug. 2023, https://doi.org/10.1016/j.molstruc.2023.135622 . BADER, Richard FW. On the non-existence of parallel universes in chemistry. Foundations of Chemistry, 2011, vol. 13, no 1, p. 11–37, https://doi.org/10.1007/s10698-011-9106-0 . Bochicchio, R., Ponec, R., Torre, A. et al. Multicenter bonding within the AIM theory. Theor Chem Acc 105, 292–298 (2001). https://doi.org/10.1007/s002140000236 A. E. Reed, R. B. Weinstock, and F. Weinhold, “Natural population analysis,” J. Chem. Phys., vol. 83, no. 2, pp. 735–746, 1985, https://doi.org/10.1063/1.449486 . Y. Mao et al., “From Intermolecular Interaction Energies and Observable Shifts to Component Contributions and Back Again: A Tale of Variational Energy Decomposition Analysis,” Annu. Rev. Phys. Chem., vol. 72, no. Volume 72, 2021, pp. 641–666, Apr. 2021, https://doi.org/10.1146/annurev-physchem-090419-115149 . E. D. Glendening, C. R. Landis, and F. Weinhold, “Natural bond orbital methods,” WIREs Comput. Mol. Sci., vol. 2, no. 1, pp. 1–42, 2012, https://doi.org/10.1002/wcms.51 . I. Rafiq, A. E. Assyry, S. A. Hassan, and K. O. Kzar, “Experimental and Theoretical Study on Hydrazine Derivatives: Structural, Electronic, and Reactivity Analysis,” Moroc. J. Chem., vol. 13, no. 1, pp. 346–365, 2025, https://doi.org/10.48317/IMIST.PRSM/morjchem-v13i1.50346 . A. A. Voityuk, A. J. Stasyuk, and S. F. Vyboishchikov, “A simple model for calculating atomic charges in molecules,” Phys. Chem. Chem. Phys., vol. 20, no. 36, pp. 23328–23337, 2018, https://doi.org/10.1039/C8CP03764G . Xu, W., Wang, Y., Wu, K., Bao, L., Xu, Y., Fang, Z., … Chen, Z. (2025). Mechanism of Disproportionation Preparation of Dimethyldichlorosilane by ZSM-5 (8T)@ NH2-MIL-53(Al) Core–Shell Catalyst. Silicon , 1–14,https://doi.org/10.1007/s12633-025-03444-y. A. Geies, G. S. Gomaa, S. M. Ibrahim, A. F. Al-Hossainy, and F. K. Abdelwadoud, “Experimental and simulated TD-DFT study of malachite green dye and tetrahydroquinoxaline hybrid blend: Its application removal from wastewater,” J. Mol. Struct., vol. 1291, p. 136050, Nov. 2023, https://doi.org/10.1016/j.molstruc.2023.136050 . Belambe, A.V., Gholap, D.P., Suradkar, R.R. et al. Catalytic performance of g-C3N4 for pyrano [2, 3-d] pyrimidines formation: a combined experimental and DFT approach. Res Chem Intermed (2025). https://doi.org/10.1007/s11164-025-05717-y A. El Assyry, B. Benali, A. Boucetta, Z. Lazar, B. Lakhrissi, M. Massoui, D. Mondieig, Spect. Lett., 42 (2009)203–209, https://doi.org/10.1080/00387010802286650 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7537968","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":510957240,"identity":"eef10642-5fa7-46dc-bec5-980d5a88491f","order_by":0,"name":"Mahdi ALAMI","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIiWNgGAWjYLCCBwwMPCAkkVAB5DEzNxDWkgDXcgakhZE4LQxgLYxtIAYBLebSBxg/JNRsk9FtP3vwxsN5tdH87UAtPyq24dRi2ZfALJFw7DaP2Zm8ZIvEbcdzZxxmbGDsOXMbpxYDoOslEtiAWg7kmEkkbjuW2wDUwszYhlcL84+Ef0At598Atcw5ljufCC1sEoltQC03QLY01ORuIKTFsoexzSKxD6TljbFFwrEDuRuBWg7i84s5D/PhGx++3bY3O59jePNHTV3uvPOHDz74UYHHYWixcBhMHsCpHqwFFdThUzwKRsEoGAUjFAAABPldTSK6blQAAAAASUVORK5CYII=","orcid":"","institution":"Hassan II University","correspondingAuthor":true,"prefix":"","firstName":"Mahdi","middleName":"","lastName":"ALAMI","suffix":""},{"id":510957242,"identity":"ca9ed4e5-b1f7-4d72-9bd5-e198a979f7d6","order_by":1,"name":"Abdeslam EL ASSYRY","email":"","orcid":"","institution":"Hassan II University","correspondingAuthor":false,"prefix":"","firstName":"Abdeslam","middleName":"EL","lastName":"ASSYRY","suffix":""},{"id":510957244,"identity":"cb25271c-35fc-4f06-9e78-15c2dfb62760","order_by":2,"name":"Issam RAFIQ","email":"","orcid":"","institution":"Hassan II University","correspondingAuthor":false,"prefix":"","firstName":"Issam","middleName":"","lastName":"RAFIQ","suffix":""},{"id":510957245,"identity":"cec508eb-2310-427d-8f58-51a70ac725b1","order_by":3,"name":"Abdelilah AKOUIBAA","email":"","orcid":"","institution":"Hassan II University","correspondingAuthor":false,"prefix":"","firstName":"Abdelilah","middleName":"","lastName":"AKOUIBAA","suffix":""}],"badges":[],"createdAt":"2025-09-04 16:23:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7537968/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7537968/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":91005331,"identity":"e68fb8a5-0d26-4fe5-9d60-eef602df4ecd","added_by":"auto","created_at":"2025-09-10 14:28:32","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":36980,"visible":true,"origin":"","legend":"\u003cp\u003eGeneral formula for quinoxaline-2(1H)-one derivatives studied in this work\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7537968/v1/d93c7acd11e2e4242f917856.png"},{"id":91005333,"identity":"bda66c53-77ab-40af-a024-d5740ddb3b01","added_by":"auto","created_at":"2025-09-10 14:28:32","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":427599,"visible":true,"origin":"","legend":"\u003cp\u003eElectrostatic surface potential of total electron density for the molecule Q1, Q2, Q3 and Q4. Regions of higher electron density are shown in red and of lower electron density in blue\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7537968/v1/f2087c06d52087724b7f0c66.png"},{"id":91005332,"identity":"2247c70d-faf9-4fd8-9f90-3bf4e0b812c3","added_by":"auto","created_at":"2025-09-10 14:28:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":44369,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of atomic charges for the molecule Q1, Q2, Q3 and Q4\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7537968/v1/48a14f8a9f874729194674ea.png"},{"id":91005689,"identity":"68bb80f2-5920-4728-9026-38ae81836425","added_by":"auto","created_at":"2025-09-10 14:36:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":107363,"visible":true,"origin":"","legend":"\u003cp\u003eOptimized geometries of compounds Q1, Q2, Q3, and Q4 with their dipole moment vector\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7537968/v1/bbcd77e103cf6e3d3c93bd7a.png"},{"id":91005337,"identity":"cc94f734-eb6a-452f-ac78-3f6c706fd78c","added_by":"auto","created_at":"2025-09-10 14:28:32","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":265010,"visible":true,"origin":"","legend":"\u003cp\u003eElectronic densities of LUMO and HOMO orbital’s of Q1, Q2, Q3 and Q4 isolated with the DFT (B3LYP)/6-31G (d, p) method\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7537968/v1/06cfdc5342bc3ab6ce8fc206.png"},{"id":91966286,"identity":"8c2f9512-8833-4fa5-ab61-49e7b6ef30ca","added_by":"auto","created_at":"2025-09-23 08:28:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1781619,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7537968/v1/0316519e-d4e2-4668-a77f-46ff25494615.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Structural properties theoretical investigation of quinoxalin -2(1H) one and some its pharmaceutical derivatives","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eQuinoxalin-2(1H)-one is a molecule composed of two rings. One ring is aromatic and the other contains two intracyclic heteroatoms and a ketone. Due to their potential use in the pharmaceutical field, researchers have shown interest in studying the properties of this molecule and its derivatives in recent years. Recent publications reporting that certain quinoxalin-2(1H)-ones are highly potent NMDA receptor antagonists [1–3] have prompted us to investigate the molecular properties of these compounds. Achieving water solubility of quinoxalin-2(1H)-ones without compromising their selectivity and potency profiles is therefore of paramount importance in medicinal chemistry [4]. This challenge has led to the investigation of substituted methods for quinoxalin-2(1H)-ones [5–11]. In the recent past, these compounds have been the subject of intensive studies, and our group has carried out research on the structural and energetic properties of quinoxaline derivatives [12–16]. Because of their pharmacological interest and lack of basic spectroscopic data in the literature, we felt it necessary to discuss some of their potentially important molecular properties. Detailed crystallographic data on 2-OHQ have been reported previously by Padjama et al [17] and on 3-methylquinoxalin-2(1H)-one by Mondieig et al [18]. Therefore, we conducted a study to investigate the molecular properties of the four compounds shown in Fig. 1; quinoxaline-2(1H)-one itself and its three derivatives: 6-chloroquinoxalin-2(1H)-one, 6-methylquinoxalin-2(1H)-one and 6-nitroquinoxalin-2(1H)-one.\u003c/p\u003e"},{"header":"2. Theoretical Methodology","content":"\u003cp\u003eDensity Functional Theory (DFT) methods have been utilized in this study due to their increasing use in recent years [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. These techniques are more computationally efficient while providing precision on par with previous methods.\u003c/p\u003e\u003cp\u003eDFT principles state that the total electron density of a polyelectronic system determines its ground state energy. The basis of DFT is this method, which bases energy calculations on electron density rather than the wave function [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. We used analytical gradients in DFT calculations based on Gaussian RHF hybrid functional bases to optimize molecular geometries. This theoretical framework, which accounts for electrical correlation with minimal computing needs, is known to produce dependable results for medium-sized organic molecules [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn order to maintain the regular hexagonal structure of the phenyl ring, geometry optimization was carried out for compound 1 under symmetry requirements. The effect of methyl, nitrogen or chlore substitutions (R17) on the base molecule's structural and energetic characteristics is also investigated in this study. When fully optimized geometries are used, the studied properties should not differ significantly, according to the predicted reliable models provided by the obtained geometries. For these geometries, DFT electron density was calculated for electrostatic potential determination [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], Natural Bond Orbital (NBO) analysis [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], and subsequent atomic interactions (AIM) [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAIM theory, which was created by Bader and others in the early 1970s, has developed into a strong framework with a solid foundation in quantum mechanics and is frequently used as a useful instrument for deriving important chemical insights. Popelier's introductory reviews have supplemented Bader's considerable work on the theory by highlighting the particular aspects discussed here. Weinhold et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] proposed the NBO analysis, which uses the single-electron density matrix to determine ρ(r) bonds between atoms and define atomic orbitals within the molecular context. When the monoelectronic matrix representation is diagonal, it forms an orthonormal basis using an orthogonalization algorithm [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The diagonal components of the density matrix are the orbital populations, and the resulting orbitals of this orthonormal set are referred to as natural orbitals [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. According to natural population analysis (NPA), the atomic charge is the sum of the contributions of all orbitals connected to a certain center. According to recent research, there is general agreement about the benefits of NPA and AIM charges, both conceptually and in terms of stability and performance with regard to structural and conformational changes [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The Gaussian 09 software program was used for all computations [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. To examine the structure optimization of the dyes in the gas phase, the DFT used the 6-31G(d,p) basis set, Becke's three-parameter functional, and the Lee\u0026ndash;Yang\u0026ndash;Parr functional (B3LYP) [\u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Geometrical parameters\u003c/h2\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eBond length (Å) of quinoxaline-(2H)-one derivatives, specifically Q1, Q2, Q3 and Q4, using DFT/B3LYP/6-311G(d,p) in ground state.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBond length\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ4\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eN1-C2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.387\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.388\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.392\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.393\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eC6-N1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.381\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.381\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.391\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1.375\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC2-C3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.480\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.482\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.469\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.482\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC2-O12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.217\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.213\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC3-N4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.287\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.287\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.303\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.286\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN4-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.387\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.388\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.402\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.388\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC5-C6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.413\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.412\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.412\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.416\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC10-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.402\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.403\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.403\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.398\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC6-C7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.403\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.403\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC7-C8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.386\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.385\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.388\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.381\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC8-C9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.402\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.414\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.399\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC9-C10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.384\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.381\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.391\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.383\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC9-C13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.511\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC9-N13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.475\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC9-Cl13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.757\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-----\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eTable \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e presents the bond length (Å) of quinoxaline-(2H)-one derivatives, specifically \u003cstrong\u003eQ1\u003c/strong\u003e, \u003cstrong\u003eQ2\u003c/strong\u003e, \u003cstrong\u003eQ3\u003c/strong\u003e, and \u003cstrong\u003eQ4\u003c/strong\u003e, using DFT/B3LYP/6-311G(d,p) in ground state.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eBond angle in (\u0026deg;) of quinoxaline-(2H)-one derivatives, specifically \u003cstrong\u003eQ1\u003c/strong\u003e, \u003cstrong\u003eQ2\u003c/strong\u003e, \u003cstrong\u003eQ3\u003c/strong\u003e and \u003cstrong\u003eQ4\u003c/strong\u003e, using DFT/B3LYP/6-311G(d,p) in ground state.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eValence Angles\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ4\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eC6-N1-C2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e124.246\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e124.144\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e124.039\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e124.169\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eN1-C2-C3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e112.686\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e112.694\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e113.534\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e112.775\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN1-C2-O12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.628\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.698\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121.978\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.409\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC3-C2-O12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e124.686\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e124.607\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e124.488\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e124.816\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC2-C3-N4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e125.484\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e125.572\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e124.802\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e125.409\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC3-N4-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118.760\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118.566\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.143\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118.650\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN4-C5-C6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121.442\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121.585\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120.992\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121.633\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN4-C5-C10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.415\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118.929\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.342\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.065\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC10-C5-C6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.143\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.486\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.666\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.302\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC5-C6-N1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e117.382\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e117.439\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e117.490\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e117.364\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN1-C6-C7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.447\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.576\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.898\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.304\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC5-C6-C7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120.170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.986\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.611\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120.333\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC6-C7-C8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.475\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.919\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.509\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.777\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC7-C8-C9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120.901\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.918\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121.894\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.443\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC8-C9-C10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e119.739\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e121.024\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e117.981\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e121.911\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC8-C9-C13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120.413\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC10-C9-C13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121.605\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC8-C9-N13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118.913\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC10-C9-N13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.175\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC8-C9-Cl13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.147\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC10-C9-Cl13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e119.829\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e reveals the valence angle in (\u0026deg;) using four basis sets 6-31G(d,p) with DFT/B3LYP of the quinoxalinone derivatives studied\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eBond torsion in (\u0026deg;) of quinoxaline-(2H)-one derivatives, specifically Q1, Q2, Q3 and Q4, using DFT/B3LYP/6-311G(d, p) in ground state.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTorsion\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ4\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC6-N1-C2-C3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.008\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC6-N1-C2-O12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.989\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.989\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.995\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.996\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC2-N1-C6-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC2-N1-C6-C7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.996\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.998\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN1-C2-C3-N4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.016\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eO12-C2-C3-N4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.982\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.992\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.994\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.998\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC2-C3-N4-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.017\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0004\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC3-N4-C5-C6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0026\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC3-N4-C5-C10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.989\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.998\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN4-C5-C6-N1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0016\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0013\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN4-C5-C6-C7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.998\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.998\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC10-C5-C6-N1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.995\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC10-C5-C6-C7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN1-C6-C7-C8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.997\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC5-C6-C7-C8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0013\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0013\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0005\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC6-C7-C8-C9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0019\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0008\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0009\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC7-C8-C9-C10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00049\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC13-C9-C10-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.997\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC7-C8-C9-C13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN13-C9-C10-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC7-C8-C9-N13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-179.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCl13-C9-C10-C5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC7-C8-C9-Cl13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-180.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-----\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe bond torsion in (\u0026deg;) calculated at DFT/B3LYP using four basis sets 6-31G(d, p) presented in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eThe phenyl ring within the studied compounds retains a nearly ideal hexagonal geometry. Based on the DFT-optimized bond lengths, three distinct groupings can be identified: C7\u0026ndash;C8 and C9\u0026ndash;C10 exhibit equivalent distances, C10\u0026ndash;C5, C6\u0026ndash;C7, and C8\u0026ndash;C9 display similar values, and C5\u0026ndash;C6 presents slight variations among Q1, Q2, Q3, and Q4, with respective lengths of 1.413, 1.412, 1.412 and 1.416 (Å) Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. In the heterocyclic ring containing two nitrogen atoms, the valence angles N4\u0026ndash;C5\u0026ndash;C6 and C3\u0026ndash;N4\u0026ndash;C5 approximate the ideal 120\u0026deg;, typical of a regular hexagon. However, the C6\u0026ndash;N1\u0026ndash;C2 angle is expanded by approximately 4\u0026deg;, while the N1\u0026ndash;C2\u0026ndash;C3 angle is reduced by ~\u0026thinsp;7\u0026deg;, attributed to the inductive influence of the adjacent carbonyl group. The N1\u0026ndash;C6\u0026ndash;C5 angle also shows a decrease of about 3\u0026deg;, likely due to the high electronegativity of the nitrogen atoms at positions N1 and N4.\u003c/p\u003e\n \u003cp\u003eReplacing the methyl group in compound Q3 with a chloro or nitro substituent in compound Q2 or Q4 leads to an elongation of the C9\u0026ndash;C13, C9\u0026ndash;N13, and C9\u0026ndash;Cl13 bonds by 0.13, 0.09, and 0.37 \u0026Aring;, respectively. This substitution is accompanied by a reduction of ~\u0026thinsp;1.75\u0026deg; in the C8\u0026ndash;C9\u0026ndash;C10 angle compared to Q3, while an opposite trend is observed when compared with Q4 and Q2. Similarly, the bond angles C8\u0026ndash;C9\u0026ndash;R13 and C10\u0026ndash;C9\u0026ndash;R13 increase relative to Q3 but decrease with respect to Q2 and Q4 Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eThe dihedral angles C7\u0026ndash;C8\u0026ndash;C9\u0026ndash;C10 (~\u0026thinsp;0.001\u0026deg;) observed in all three substituted compounds confirm the preservation of molecular planarity after substitution at position 9. Furthermore, nearing 180\u0026deg; the R13\u0026ndash;C9\u0026ndash;C10\u0026ndash;C5 torsion angles exhibit considerable \u0026pi;-electron delocalization facilitated by the heteroatoms, so reinforcing the prolonged conjugation across the molecular framework Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Electronic Density\u003c/h2\u003e\n \u003cp\u003eBy adopting electron density (\u0026rho;c) analysis at bond critical points (BCPs), important quantitative knowledge about charge distribution and the basic properties of molecular bonding is obtained. While reduced values indicate weaker bonding contacts or more electron delocalization, increased \u0026rho;c values frequently indicate strong, localized connections. This work evaluated the effect of substituents at position 6 on the electronic structure of quinoxaline-2(1H)-one, 6-chloroquinoxaline-2(1H)-one, 6-methyl-quinoxalin-2(1H)-one, and 6-nitroquinoxaline-2(1H)-one using the DFT/B3LYP/6-31G(d,p) methodology. As Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows, the data show that substituents greatly affect electron densities at BCPs. With a peak electron density of 0.325 a.u., Quinoxaline-2(1H)-one is not substitutable. for the C2-N1 bond, indicating a stable and localized bond, while the C3-C4 and C4-C5 bonds display moderate densities, suggesting a balanced structure. The introduction of a methyl group, an electron donor, in 6-methyl-quinoxalin-2(1H)-one leads to a slight decrease in \u0026rho;c values in nearby bonds (0.322 a.u. for C2-N1 and 0.288 a.u. for C3-C4), reflecting increased electron delocalization. In contrast, the nitro group, a strong electron-withdrawing group, in 6-nitroquinoxalin-2(1H)-one increases electron densities in adjacent areas (0.330 a.u. for C2-N1 and 0.318 a.u. for N2-C3), indicating enhanced electronic polarization and localization. Finally, the chlorine group, a moderately electron-withdrawing group, in 6-chloroquinoxalin-2(1H)-one shows an intermediate effect, with densities of 0.328 a.u. for C2-N1 and 0.293 a.u. for C3-C4, reflecting partial stabilization attributed to its inductive effect.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eElectron Density (\u0026rho;c) at Bond Critical Points (BCPs) for the Studied Compounds\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBond Critical Point (BCP)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQuinoxaline-2(1H)-one\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6-Chloro\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6-Methyl\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6-Nitro\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026rho;c(C2-N1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.325\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.328\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.322\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.330\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026rho;c(N1-C3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.312\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.315\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.310\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.318\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026rho;c(C3-C4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.290\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.293\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.288\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.295\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026rho;c(C4-C5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.295\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.296\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.293\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.298\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026rho;c(C5-C6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.298\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.298\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.296\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.300\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026rho;c(C6-X) (substituant)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.180\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eVariations in \u0026rho;c values clearly indicate the significant impact of substituents at the 6-position on bonding characteristics and the general electronic architecture of the molecules. While electron-donating groups such methyl boost delocalization of electron density and decrease local polarity, electron-withdrawing groups such nitro and chloro increase electronic polarization and promote charge localization. Especially relevant for the rational design of molecules in medicinal chemistry and advanced functional materials, our results emphasize the crucial role of chemical substitution in controlling molecular reactivity and intermolecular interactions.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Electrostatic potential\u003c/h2\u003e\n \u003cp\u003eThe determination of the electrostatic potential (ESP) offers important new perspectives on the distribution of electronic charges inside the investigated molecules, therefore enabling the identification of nucleophilic and electrophilic sites. Using the DFT/B3LYP/6-31G(d,p) approach in the gas phase, ESP values for the four molecules quinoxaline-2(1H)-one (Q1), 6-chloroquinoxaline-2(1H)-one (Q2), 6-methyl-quinoxaline-2(1H)-one (Q3), and 6-nitroquinoxaline-2(1H)-one (Q4) were computed. These computations clarify how substituents at position 6 affect the electrical characteristics and chemical reactivity of the compounds.\u003c/p\u003e\n \u003cp\u003eWith highly negative ESP values, the data show that the oxygen atom of the ketone function remains the major nucleophilic site for all molecules. These numbers range from \u0026minus;\u0026thinsp;12.790 eV for Q3 to \u0026minus;\u0026thinsp;13.061 eV for Q4. Confirming their possible function as secondary reactive sites, the nitrogen atoms of the quinoxaline core likewise show moderately negative ESP values (\u0026ndash;9.252 eV to \u0026minus;\u0026thinsp;9.796 eV). Modulating local reactivity depends greatly on the type of substituent at position 6. Acting as an electron donor, the methyl group (Q3) lowers the electrophilicity of surrounding areas; conversely, the strong electron-withdrawing nitro group (Q4) increases local electrophilicity with ESP values as low as \u0026minus;\u0026thinsp;14.151 eV. Though with a somewhat lesser effect, the moderately electron-withdrawing chlorine group (Q2) operates similarly to the nitro group.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eElectrostatic Potential (ESP) of the Studied Compounds (in eV)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAtome\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ1 (Quinoxaline-2(1H)-one)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ2 (6-Chloro)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ3 (6-M\u0026eacute;thyle)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQ4 (6-Nitro)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eO (c\u0026eacute;tone)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-12.935\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-12.962\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-12.790\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-13.061\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eN1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-9.524\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-9.391\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-9.252\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-9.796\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eN2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-9.524\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-9.391\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-9.252\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-9.796\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eC6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-6.803\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-7.075\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-5.986\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-8.164\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSubstituant\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026ndash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-13.061\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.721\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-14.151\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe electrostatic potential (ESP) values presented in Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e reveal the significant role of substituent groups in modulating molecular polarity and reactivity. Electron-withdrawing substituents, such as nitro and chloro, contribute to increased local electrophilicity, while the presence of a methyl group tends to reduce the overall polarity of the molecule.\u003c/p\u003e\n \u003cp\u003eThe Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e presents the electrostatic potential (ESP) surface maps for the four studied compounds, based on their total electron density. High electron density regions (nucleophilic sites) are depicted in red, while low electron density regions (electrophilic sites) appear in blue.\u003c/p\u003e\n \u003cul\u003e\n \u003cli\u003e\n \u003cp\u003e\u003cstrong\u003eFor Q1\u003c/strong\u003e: The red-colored regions, primarily localized around the ketone oxygen and nitrogen atoms, denote areas of high electron density, identifying them as the principal nucleophilic sites.\u003c/p\u003e\n \u003c/li\u003e\n \u003cli\u003e\n \u003cp\u003e\u003cstrong\u003eFor Q2\u003c/strong\u003e: The chlorine substituent generates moderately intense red regions, indicating a weaker electron-withdrawing effect relative to that of the nitro group.\u003c/p\u003e\n \u003c/li\u003e\n \u003cli\u003e\n \u003cp\u003e\u003cstrong\u003eFor Q3\u003c/strong\u003e: The methyl group reduces the intensity of the red regions around the substituent, reflecting its electron-donating effect.\u003c/p\u003e\n \u003c/li\u003e\n \u003cli\u003e\n \u003cp\u003e\u003cstrong\u003eFor Q4\u003c/strong\u003e: The nitro group significantly enhances the red regions, confirming its strong electron-withdrawing effect.\u003c/p\u003e\n \u003c/li\u003e\n \u003c/ul\u003e\n \u003cp\u003eThe electrostatic potential (ESP) maps clearly demonstrate that substituents at the 6-position significantly modulate the molecular charge distribution and reactivity. Electron-withdrawing groups amplify the electrophilic character of the molecules, thereby enhancing their propensity for electrophilic interactions. Conversely, electron-donating groups tend to lower overall molecular polarity, which may influence their capacity to engage in intermolecular interactions. These insights are critical for understanding the reactivity patterns of the studied compounds and support their potential as candidates for pharmaceutical applications, such as enzyme inhibition, as well as for use in functional organic materials, including electronic devices.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 NPA atomic charge and dipolar moment\u003c/h2\u003e\n \u003cp\u003eAnalysis of the histogram above Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e reveals that the distribution of charges in influenced by the electronegativity of the atoms, with the highest values observed of the electronegativity of the atoms, with the highest values observed for nitrogen and oxygen atoms. It\u0026rsquo;s important to highlight that carbon atoms C2, C6 and C13, which are bonded to oxygen and nitrogen. Exhibit electron deficiency and carry a positive charge due to the electronegative nature of oxygen and nitrogen. Among these, C2 has highest positive value, primarily due to its bonds with both O12 and N1. On the order hand, the most negative charges are found on N1, N4 and O12 atoms.\u003c/p\u003e\n \u003cp\u003eThe electronic charges on the other carbon atoms of the phenyl ring remain largely negative, leading to polarized CH bonds. It\u0026rsquo;s worth nothing that substitutions do not significantly affect these electronic charges, except for CH3, NO2, and Cl substituents, which result in a change in the charge of the C13 carbon.\u003c/p\u003e\n \u003cp\u003eFurthermore, N1 is particularly susceptible to electrophilic attacks, and H11 bears the highest positive charge, making it a preferred site for nucleophilic attacks.\u003c/p\u003e\n \u003cp\u003eIn order to validate the polarization results obtained from analyzing NPA charge values, the researchers used the B3LYP/6-31G (d, p) theoretical calculation method to determine the dipole moment vectors \u0026micro; of quinoxaline-2(1H)-one and its isolated derivatives in a three-dimensional representation Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The dipole moment data revealed that the addition of a methyl group away from the carbonyl in compound Q3 increased the dipole moment (5.08 Debye) compared to compound Q1 (3.92 Debye). On the other hand, substitution with a nitrogen group in compound Q4 (3.48 Debye) or with chlorine in compound Q2 (2.76 Debye) not only led to a significant reduction in the dipole moment, but also altered the orientation of the dipole moment vector. These findings, along with the NPA charge data, highlight the impact of substituting the R17 group in these molecules with different functional groups like chlorine, methyl, and nitrogen dioxide. This substitution could potentially affect the reactivity and ultimately the medical and pharmacological applications of these compounds.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab6\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCalculated values of the Q1, Q2, Q3 and Q4 global reactivity descriptors with the DFT (B3LYP)/6-31G (d, p) method.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDescriptors\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eE\u003csub\u003eHOMO\u003c/sub\u003e (eV)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eE\u003csub\u003eLUMO\u003c/sub\u003e(eV)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\Delta\\:}\\)\u003c/span\u003e\u003c/span\u003eE(eV)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u0026micro; (Debye)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQ1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-6.55764\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-2.19259\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.36505\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.92\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQ2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-6.66019\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-2.47112\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.18907\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.76\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQ3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-6.47741\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-2.28643\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.19098\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQ4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-7.27382\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-2.86579\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.40741\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.48\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe analysis of frontier molecular orbitals (FMOs) was employed to explore the mechanism of intramolecular charge transfer (ICT) [\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e] within the studied systems. The spatial distributions of the HOMO and LUMO orbitals for each dye were visualized, as illustrated in Table \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e Characteristic features of \u0026pi;-type molecular orbitals were evident in these plots, with the HOMO exhibiting bonding interactions within individual molecular fragments and antibonding interactions between adjacent units. The lowest-energy electronic transitions were identified as \u0026pi;\u0026ndash;\u0026pi;* in nature, arising from the bonding characteristics of the LUMOs across neighboring segments. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, the HOMO and LUMO topologies are qualitatively similar across the compounds. The LUMOs are predominantly localized over the \u0026pi;-conjugated spacers and electron-accepting moieties, while the HOMOs are concentrated in the electron-donating regions. These observations support classification of the electronic transitions as \u0026pi;\u0026ndash;\u0026pi;* ICT processes, typical of D\u0026ndash;\u0026pi;\u0026ndash;A architectures, wherein electrons are promoted from the HOMO to the LUMO, facilitating charge transfer from donor regions to acceptor groups through the conjugated bridge.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis work provides a comprehensive theoretical examination of four quinoxalinone derivatives Q1, Q2, Q3, and Q4 using Density Functional Theory (DFT) at the B3LYP/6-311G(d,p) level. Through the analysis of optimized geometries, electronic structure, and global reactivity descriptors, we investigated the influence of various substituents (chloro, methyl, and nitro) on the parent quinoxaline-2(1H)-one scaffold. The study of frontier molecular orbitals, electron density profiles, electrostatic potential (ESP) surfaces, and atomic charge distributions revealed significant variations in polarity and charge localization associated with these structural modifications. Electron-withdrawing groups such as nitro and chloro were found to increase electrophilicity and local charge concentration, while the methyl group, acting as an electron donor, promoted charge delocalization and enhanced the dipole moment. Torsional angle analysis confirmed the overall planarity of the molecules, supporting efficient π-conjugation conducive to intramolecular charge transfer (ICT). These electronic and structural characteristics underscore the relevance of these compounds for applications in molecular electronics, photonic materials, and pharmaceutical development.\u003c/p\u003e\u003cp\u003eBeyond their theoretical relevance, these derivatives show strong potential for real-world use, especially as π-conjugated systems in optoelectronic platforms or as pharmacophores in drug design. Future efforts should be directed toward experimental validation through synthesis and biological assays to evaluate their therapeutic viability. Overall, this work offers a robust computational framework for deciphering structure\u0026ndash;property relationships in quinoxalin-2(1H)-one derivatives and opens new avenues for cross-disciplinary research spanning computational chemistry, materials science, and medicinal chemistry.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors participated in the conception and design of the study. Material preparation and data collection were carried out by Abdeslam El Assyry and Abdelilah Akouibaa. Data analysis and interpretation were conducted by Issam Rafiq and Mahdi Alami as part of his doctoral research work. The initial draft of the manuscript was prepared by Mahdi Alami, with all authors contributing to critical revisions. All authors have read and approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eX. Jiang, K. Wu, R. 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Lett., 42 (2009)203\u0026ndash;209, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/00387010802286650\u003c/span\u003e\u003cspan address=\"10.1080/00387010802286650\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"DFT, Quinoxaline-(2H)-one, Electron density, Atomic charges, Electron density topology, Geometric parameters","lastPublishedDoi":"10.21203/rs.3.rs-7537968/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7537968/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, we aimed on an investigation of quinoxalin-(2H)-one derivatives, specifically quinoxaline-2(1H)-one, 6-chloroquinoxalin-2(1H)-one, 6-methyl-quinoxalin-2(1H)-one, and 6-nitroquinoxalin-2(1H)-one. Using the DFT/B3LYP/6-311G(d,p) level method to explore the structural and spectroscopic properties and to optimize geometries of these derivatives. The findings reveal a pronounced distinction in electron distribution between the heterocyclic and aromatic rings, playing a pivotal role in determining the anticipated reactivity. Through the examination of atomic charges, electronic density, electrostatic potential, HOMO and LUMO energy, as well as dipole moments, it becomes possible to further enhance qualitative forecasts regarding the reactivity of these derivatives.\u003c/p\u003e","manuscriptTitle":"Structural properties theoretical investigation of quinoxalin -2(1H) one and some its pharmaceutical derivatives","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-10 14:28:28","doi":"10.21203/rs.3.rs-7537968/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d8881379-9b7f-4f92-8973-e6577d40f790","owner":[],"postedDate":"September 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-23T08:24:27+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-10 14:28:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7537968","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7537968","identity":"rs-7537968","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}