Quantum Theory Of Atoms In Molecules Analysis Research Articles

Theoretical study on the capture of toxic gases by ionic liquids encapsulated in assembled belt[14[pyridine

In the current study, self-assembled belt[14]pyridine (BP) encapsulated IL (tetramethylammonium chloride (TMACl)) is theoretically explored to capture greenhouse gases (GHGs) at B3LYP-D3/6-311G(d,p) level of theory. The encapsulation of TMACl in assembled belt[14]pyridine is thermodynamically feasible as revealed through high interaction energy value of −50.7 kcal/mol. Moreover, the results of capturing of gas molecules (SO2, CO2, CO and CH4) show that attractive forces involved in capturing of gases are strong van der Waals forces i.e., London dispersion forces and electrostatic interactions. The synergic effect of self-assembled belts and ionic liquid results in significantly high interaction energy values ranging from −7.88 to −25.92 kcal/mol for capturing of gas molecules. Furthermore, the interaction between BP-TMACl and gas molecules is studied in detail through natural bond orbital (NBO) analysis. NBO results show the charge transfer between the fragments (BP-TMACl and gases) which is further validated through EDD analysis. The charge shifts towards all of the captured gas molecules but the most prominent change in NBO charges is shown by captured SO2. The successful charge transfer indicates better interaction in the designed systems. Additionally, the type and strength of interactions involved in the process of encapsulation is studied through quantum theory of atoms in molecules (QTAIM) and noncovalent interactions (NCI) analysis. NCI analysis clearly shows that gases are captured by BP-TMACl complex through strong van der Waals forces. However, in capturing of SO2, strong electrostatic attractive forces are also involved. The nature of attractive forces is confirmed through QTAIM analysis. Furthermore, the relation between recovery time and desorption energy of captured gas molecules has been studied. The strongest absorption for SO2 results in prolonged recovery time for it (as compared to the other gas molecules). AIMD analysis is performed to find the dynamical stability of assembled-belts before and after loading ionic liquids along with gases to be captured. These results reveal that assembled-belts are suitable for encapsulation of ionic liquids along with capturing of gases. Overall, the best results are shown for SO2 capture. The study intends to deliver valuable information on the important progress in the environmental-remediation field and we hope our work is going to inspire more investigators to provide novel research on such challenging tasks.

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ContextMicro-hydration of the aminobenzoic acid is essential to understand its interaction with surrounding water molecules. Understanding the micro-hydration of the aminobenzoic acid is also essential to study its remediation from wastewater. Therefore, we explored the potential energy surfaces (PESs) of the para-aminobenzoic acid-water clusters, ABWn\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_n$$\\end{document}, n=1-10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n=1-10$$\\end{document}, to study the microsolvation of the aminobenzoic acid in water. In addition, we performed a quantum theory of atoms in molecules (QTAIM) analysis to identify the nature of non-covalent bondings in the aminobenzoic acid-water clusters. Furthermore, temperature effects on the stability of the located isomers have been examined. The located structures have been used to calculate the hydration free energy and the hydration enthalpy of the aminobenzoic acid using the cluster continuum solvation model. The hydration free energy and the hydration enthalpy of the aminobenzoic acid at room temperature are evaluated to be −7.0 kcal/mol and −18.1 kcal/mol, respectively. The hydration enthalpy is in perfect agreement with a previous experimental estimate. Besides, temperature effects on the calculated hydration enthalpy and free energy are reported. Finally, we calculated the gas phase binding energies of the most stable structures of the ABWn\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_n$$\\end{document} clusters using twelve functionals of density functional theory (DFT), including empirical dispersion. The DFT functionals are benchmarked against the DLPNO-CCSD(T)/CBS. We have found that the three most suitable DFT functionals are classified in the following order: PW6B95D3 > MN15 > ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega $$\\end{document}B97XD. Therefore, the PW6B95D3 functional is recommended for further study of the aminobenzoic acid-water clusters and similar systems.MethodsThe exploration started with classical molecular dynamics simulations followed by complete optimization at the PW6B95D3/def2-TZVP level of theory. Optimizations are performed using Gaussian 16 suite of codes. QTAIM analysis is performed using the AIMAll program.

Investigations of the reaction mechanism of sodium with hydrogen fluoride to form sodium fluoride and the adsorption of hydrogen fluoride on sodium fluoride monomer and tetramer.

The reaction between Na and HF is a typical harpooning reaction which is of great interest due to its significance in understanding the elementary chemical reaction kinetics. This work aims to investigate the detailed reaction mechanisms of sodium with hydrogen fluoride and the adsorption of HF on the resultant NaF as well as the (NaF)4 tetramer. The results suggest that the reaction between Na and HF leads to the formation of sodium fluoride salt NaF and hydrogen gas. Na interacts with HF to form a complex HF···Na, and then the approaching of F atom of HF to Na results in a transition state H···F···Na. Accompanied by the broken of H-F bond, the bond forms between F and Na atoms as NaF, then the product NaF is yielded due to the removal of H atom. The resultant NaF can further form (NaF)4 tetramer. The interaction of NaF with HF leads to the complex NaF···HF; the form I as well as II of (NaF)4 can interact with HF to produce two complexes (i.e., (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF), but the form III of (NaF)4 can interact with HF to produce only one complex (NaF)4(III)···HF. These complexes were explored in terms of noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. NCI analyses confirm the existences of attractive interactions in the complexes HF···Na, NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF. QTAIM analyses suggest that the F···Na interaction forms in the HF···Na complex while the F···H hydrogen bonds form in NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF complexes. Natural bond orbital (NBO) analyses were also applied to analyze the intermolecular donor-acceptor orbital interactions in these complexes. These results would provide valuable insight into the chemical reaction of Na and HF and the adsorption interaction between sodium fluoride salt and HF. The calculations were carried out at the M06-L/6-311++G(2d,2p) level of theory which were performed using the Gaussian16 program. Intrinsic reaction coordinate (IRC) calculations were carried out at the same level of theory to confirm that the obtained transition state was true. The molecular surface electrostatic potential (MSEP) was employed to understand how the complex forms. Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) analysis was used to know the topology parameters at bond critical points (BCPs) and intermolecular interactions in the complex and intermediate. The topology parameters and the BCP plots were obtained by the Multiwfn software.

Electronic properties and collision cross sections of AgOkHm± (k, m = 1-4) aerosol ionic clusters.

Experimental evidence shows that hydroxylated metal ions are often produced during cluster synthesis by atmospheric pressure spark ablation. In this work, we predict the ground state equilibrium structures of AgOkHm± clusters (k and m = 1-4), which are readily produced when spark ablating Ag, using the coupled cluster with singles and doubles (CCSD) method. The stabilization energy of these clusters is calculated with respect to the dissociation channel having the lowest energy, by accounting perturbative triples corrections to the CCSD method. The interatomic interactions in each of the systems have been investigated using the frontier molecular orbital (FMO), natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) methods. Many of the ground states of these ionic clusters are found to be stable, corroborating experimental observations. We find that clusters having singlet spin states are more stable in terms of dissociation than the clusters that have doublet or triplet spin states. Our calculations also indicate a strong affinity of the ionic and neutral Ag atom towards water and hydroxyl radicals or ions. Many 3-center, 4-electron (3c/4e) hyperbonds giving rise to more than one resonance structure are identified primarily for the anionic clusters. The QTAIM analysis shows that the O-H and O-Ag bonds in the clusters of both polarities are respectively covalent and ionic. The FMO analysis indicates that the anionic clusters are more reactive than the cationic ones. Using the cluster structures predicted by the CCSD method, we calculate the collision cross sections of the AgOkHm± family, with k and m ranging from 1 to 4, by the trajectory method. In turn, we predict the electrical mobilities of these clusters when suspended in helium at atmospheric pressure and compare them with experimental measurements.

Unravelling performance of honeycomb structures as drug delivery systems for the isoniazid drug using DFT-D3 correction dispersion and molecular dynamic simulations.

In this study, the potential of aluminum nitride (h-AlN), boron nitride (h-BN) and silicon carbide (h-SiC) nanosheets as the drug delivery systems (DDS) of isoniazid (INH) was scrutinized through density functional theory (DFT) and molecular dynamic (MD) simulations. We performed DFT periodic calculations on the geometry and electronic features of nanosheets adsorbed with INH by the DFT functional (DZP/GGA-PBE) employed in the SIESTA code. In the energetically favorable model, an oxygen atom of the C-O group of the INH molecule interacts with a Si atom of the h-SiC at 2.077 Å with an interaction energy of -1.361 eV. Charge transfer (CT) calculation by employing the Mulliken, Hirshfeld and Voronoi approaches reveals that the monolayers and drug molecules act as donors and acceptors, respectively. The density of states (DOS) calculations indicate that the HOMO-LUMO energy gap (HLG) of the h-SiC nanosheet declines significantly from 2.543 to 1.492 eV upon the adsorption of the INH molecule, which causes an electrical conductivity increase and then produces an electrical signal. The signal is linked to the existence of INH, demonstrating that h-SiC may be an appropriate sensor for INH sensing. The decrease in HLG for the interaction of INH and h-SiC is the uppermost (up to 41%) representing the uppermost sensitivity, whereas the sensitivity trend is σ(h-SiC) > σ(h-AlN) > σ(h-BN). Quantum theory of atoms in molecules (QTAIM) investigations is employed to scrutinize the nature of the INH/nanosheet interactions. The QTAIM analysis reveals that the interaction of the INH molecule and h-SiC has a partially covalent nature, while INH/h-AlN model electrostatic interaction occurs in the system and noncovalent and electrostatic interaction for the INH/h-BN model. Finally, the state-of-the-art DFT-MD simulations utilized in this study can mimic ambient conditions. The results obtained from the MD simulation show that it takes more time to bond the INH drug and h-SiC, and the INH/h-SiC system becomes stable. The results of the current research demonstrate the potential of h-SiC as a suitable sensor and drug delivery platform for INH drugs to remedy tuberculosis.

Adsorption of some cationic dyes onto two models of graphene oxide

Context:The search for highly efficient adsorbent materials remains a significant requirement in the field of adsorption for wastewater treatment. Computational study can highly contribute to the identification of efficient material. In this work, we propose a computational approach to study the adsorption of four cationic basic dyes, basic blue 26 (BB26), basic green 1 (BG1), basic yellow 2 (BY2), and basic red 1 (BR1), onto two models of graphene oxide as adsorbents. The main objectives of this study are the assessment of the adsorption capacity of the graphene oxide towards basic dyes and the evaluation of the environmental and temperature effects on the adsorption capacity. Quantum theory of atoms in molecules (QTAIM) analysis has been used to understand the interactions between the dyes and graphene oxides. In addition, adsorption free energies of the dyes onto graphene oxides are calculated in gas and solvent phases for temperatures varying from 200 to 400 K. As a result, the adsorption free energy varies linearly depending on the temperature, highlighting the importance of temperature effects in the adsorption processes. Furthermore, the results indicate that the environment (through the solvation) considerably affects the calculated adsorption free energies. Overall, the results show that the two models of graphene oxide used in this work are efficient for removing dyes from wastewater.Methods:We have optimized the complexes formed by the interaction of dyes with graphene oxides at the PW6B95-D3/def2-SVP level of theory. The SMD solvation model realizes the implicit solvation, and water is used as the solvent. Calculations are performed using the Gaussian 16 suite of program. QTAIM analysis is performed using the AIMAll program. Gibbs free energies as function of temperature are calculated using the TEMPO program.

Structural properties of newly 4,7-dihydroxycoumarin derivatives as potential inhibitors of XIIa, Xa, IIa factors of coagulation

Some coumarin derivatives show notable anticoagulant properties through their ability to interrupt the enzymatic function of vitamin K epoxide reductase. The current challenge lies in the development of novel derivatives that are more efficient and less harmful, specifically targeting the direct inhibition of coagulation factors. This study examined the direct inhibitory potential of two recently synthesized coumarin derivatives, 3-(1-(3-hydroxy-4-methoxyphenyl)-amino)-ethyldiene)-2,4-dioxochroman-7-yl acetate (A-3OH) and 3-(1-(4-hydroxy-3-methoxyphenyl)-amino)-ethyldiene)-2,4-dioxochroman-7-yl acetate (A-4OH), according to coagulation factors IIa, Xa, and XIIa. Accurately defining the structural properties of compounds is of great importance for a comprehensive understanding of the biological activity of pharmaceutical agents. In regard, this study aimed to analyze the structural (Potential Energy Surface (PES)), spectroscopic (FT-IR, NMR, and UV–Vis), and electronic properties (Quantum Theory of Atoms in Molecules (QTAIM)) of two newly synthesized compounds. These properties are determined using a combination of experimental and theoretical methods (B3LYP-D3BJ/6–311++G(d,p) level of theory). The investigated compounds deviate from planarity based on the results of structural properties. The results of QTAIM analysis show the presence of partially covalent hydrogen bonds and closed-shell van der Waals interactions that stabilize the examined compounds. Based on the large correlation coefficient (R) and low mean absolute error (MAE) of the spectroscopic data showed that the applied level of theory effectively replicated the experimental finding. The results from the molecular docking study suggest that both compounds demonstrate similar inhibitory effects on IIa when compared to the standard inhibitor dabigatran (DAB). The efficacy of A-3OH in inhibiting Xa is similar to that of conventional inhibitors apixaban (API), and rivaroxaban (RIV). The observed inhibitory effect of both compounds on coagulation factor XIIa was more potent than that of the conventional co-crystallized inhibitor. The results of this study add to the understanding of the structure-activity relationship of coumarin derivatives and provide possibilities for enhancing anticoagulant therapy and clinical outcomes for coagulation-related illnesses. The findings lay a foundation for further in vitro and in vivo investigations into the anticoagulant activities of the compounds, contributing to their potential pharmaceutical application.

Structures, Bonding Analyses and Reactivity of a Dicationic Digallene and Diindene Mimicking trans-bent Ditetrylenes.

The reaction of bisdicyclohexylphosphinoethane (dcpe) and the subvalent MI sources [MI (PhF)2 ][pf] (M=Ga+ , In+ ; [pf]- =[Al(ORF )4 ]- ; RF =C(CF3 )3 ) yielded the salts [{M(dcpe)}2 ][pf]2 , containing the first dicationic, trans-bent digallene and diindene structures reported so far. The non-classical MI ⇆MI double bonds are surprisingly short and display a ditetrylene-like structure. The bonding situation was extensively analyzed by quantum chemical calculations, QTAIM (Quantum Theory of Atoms in Molecules) and EDA-NOCV (Energy Decomposition Analysis with the combination of Natural Orbitals for Chemical Valence) analyses and is compared to that in the isoelectronic and isostructural, but neutral digermenes and distannenes. The dissolved [{Ga(dcpe)}2 ]2+ ([pf]- )2 readily reacts with 1-hexene, cyclooctyne, diphenyldisulfide, diphenylphosphine and under mild conditions at room temperature. This reactivity is analyzed and rationalized.

Triquinoxalinylene and benzoquinone based covalent organic framework as robust material for mitigation of environmental pollutants-A theoretical approach

The physisorption of pollutant gases (NH3, HCN, H2S and PH3) on TQBQ-COF has been explored using DFT calculations. The strength and nature of interactions were determined through interaction energy, non-Covalent interactions- Reduced Density Gradient (NCI-RDG) plots, Frontier Molecular Orbital (FMO), Natural bond orbital (NBO), Electron Density Difference (EDD) and Quantum Theory of Atoms In Molecule (QTAIM) analysis. The optimized geometries and interaction energy calculations revealed that the analytes interacted with Oxygen and Nitrogen atoms of TQBQ-COF leading to adsorption energy ranging from −10.66 to −5.85 kcal/mol. The values of recovery time were in agreement to that of interaction energy and decreased with the increase in temperature. The NCI-RDG plots and QTAIM analysis revealed the presence of weak van der Waals forces in all complexes and partial covalent character in H2S@TQBQ-COF. Charge transfer study (employing NBO and EDD analysis) depicted the transfer of charge from surface to analytes. The study of HOMO-LUMO energy gap in FMO analysis depicted the high sensitivity of TQBQ-COF for H2S and NH3 compared to HCN and PH3 due to significant lowering of HOMO-LUMO energy gap upon the adsorption of H2S and NH3 on TQBQ-COF.

Conjugation-modulated optoelectronic and anti-corrosion properties of pyrrole oligomer: Insights from DFT/TD-DFT analysis

To investigate the influence of π-conjugation on optical properties, models of Pyrrole oligomers with varying π-bridge lengths, ranging from 1 to 5, were constructed. The π-bridge plays a crucial role in tuning and modulating the optoelectronic characteristics of these molecules. By employing FMO (Frontier Molecular Orbital) analysis, the band gap values were determined. Notably, the pyrrole oligomer with a 1π-bridge exhibited a higher band gap (2.68 eV) compared to the 5π-bridge variant (1.53 eV). Moreover, the calculated hyperpolarizability (β°) values exhibited a substantial increase from 37 esu to 1876 esu as the extent of π-conjugation was augmented. This suggests that enhanced π-conjugation promotes greater nonlinear optical properties. Further analysis revealed that the pyrrole oligomer with 5π-bridges displayed maximal absorption at a longer wavelength, specifically 1024 nm. This information provides valuable insights into the absorption characteristics of these molecules. Additionally, the NBO (Natural Bond Orbital) analysis successfully captured the stable donor-acceptor interactions responsible for the ground state stabilization observed in pyrrole oligomers. On the other hand, the QTAIM (Quantum Theory of Atoms in Molecules) analysis provided detailed information regarding weak interactions, such as hydrogen bonding, which contribute to the stabilization of the modeled monomers. In summary, the creation of Pyrrole oligomer models with varying π-bridge lengths facilitated the evaluation of the impact of π-conjugation on the optical properties. The findings indicate that increasing the π-conjugation leads to a decrease in the band gap, an increase in hyperpolarizability, and absorption at longer wavelengths. Additionally, the stability of the ground state and the nature of weak interactions were elucidated through NBO and QTAIM analyses, respectively.

Synthesis, characterization, DFT/M06 studies, NBO, QTAIM and RDG analyses of new copper (II) complexes with bis-phosphonamide obtained under microwave irradiation

We have devised a novel one-step approach for synthesizing bis-phosphonamides utilizing primary amines and phenylphosphonic dichloride (PPDC) under ultrasound irradiation. The bis-phosphonamides obtained were used as organophosphorus ligands for the synthesis of new copper (II) complexes with metal ions. The synthesis of these complexes was accomplished via a novel eco-friendly method employing microwave irradiation. The desired complex obtained, as a green powder in 65% yield, which were fully characterized by spectroscopic methods (FT-IR, UV–vis, XDR). To gain and further insights into structure and properties of studied complexes, several calculations such as Natural Atomic Orbitals (NAO), Natural Bond orbitals(NBO), Quantum Theory of Atoms in Molecules (QTAIM) analysis were performed at M06/6-311++g(d, p) level. Using the Reduced electron Density Gradient (RDG) approach, the non-covalent interactions were explored and visualized in two and three-dimensional spaces.

To understand the miglitol adsorption behavior on BC3, BN, and GNS nanosheets using DFT and QTAIM analysis for drug delivery applications

Utilizing nanomaterials in the drug delivery system has a potential impact on administering a drug to a patient’s body, and that helps to reduce the severe adverse effect by carrying them into the targeted cell location. The implementation of boron carbide (BC3), boron nitride (BN), and graphene nanosheet (GNS) as miglitol (MT) drug carriers in both gaseous and fluid phases has been evaluated using density functional theory. We methodically looked at the optimum adsorption energy, frontier molecular orbital, density of state, dipole moment, and UV–vis spectroscopy analysis to grasp the targeted drug delivery capability of these nanostructures. The adsorption energy analysis displayed that MT drug adsorption occurs stably on the nanosheet both in gas (−57.86 kj mol−1) and water (−43.72 kj mol−1) media. This physical interaction is suitable for an undeniable offloading of MT drugs to the targeted site. The outcomes of the quantum theory of atoms in molecules (QTAIM) have also supported these assessments. Our study reveals that the BC3 nanosheet exhibits more stable adsorption of MT drugs than that of BN and GNS.

Analysis of Fe2+ and Mn2+ ions in DES and water: A theoretical study using molecular dynamic simulations, QTAIM and NCI-RDG

This work was essential to analyze the behavior of Fe2+ and Mn2+ ions in water and deep eutectic solvent (DES) based on choline chloride and ethylene glycol (1ChCl:2EG (choline chloride and ethylene glycol, DES)) to evaluate the electrodeposition of metallic ions. Due to their low toxicity, high solubility, biodegradability and thermal stability, DES have shown promise as alternatives to traditional solvents such as water in various applications, including biological studies. They also dissolve insoluble substances in other types of solvents, working from the purification of chemicals to the manufacture of semiconductor devices. Water, choline and ethylene glycol molecules were optimized by Density Functional Theory (DFT) through B3LYP/6–311 +G(d,p) model implemented with the Gaussian 09 W software. Molecular Dynamics (MD) simulations were performed by GROMACS software 2020.04 in a cubic box of dimensions 8 nm × 8 nm × 8 nm. Quantum Theory of Atoms in Molecules (QTAIM) and analysis of Non-covalent Interactions (NCI) used Multiwfn 3.8 software. The preliminary results of MD simulations showed that gradually adding water increased the interaction between the metal center and water. Fe2+ and Mn2+ ions were placed in water (OW) and 1ClCh:2EG, indicating that the interaction between the cations and the chloride anion in DES was strong, followed by the ethylene glycol molecules (O1, O2). In the presence of water, however, Fe-OW and Mn-OW interactions were more substantial in all systems, either with the ions alone or in a mixture. Electrostatic forces acting on the electrons in the last filled layer of the iron atom provided the formation of shorter and stronger bonds than the Mn2+ ions. When placed in a 1:1 equimolar mixture, they showed little difference from when they were isolated. Thus, the Mn-Cl interaction was more significant in the presence of a eutectic solvent than the Fe-Cl interaction. QTAIM analysis showed for the FeDES and MnDES systems that the Electron Localization Function (ELF) values increased for the Fe-(O1, O2) and Mn-(O1, O2) interactions but decreased for the Fe-Cl and Mn-Cl interactions in the metal mixture. It revealed strong hydrogen bonding interactions between the water molecules, Fe2+ and Mn2+, which may affect their chemical reactivity, as the Fe-Cl interaction in DES was stronger than Fe-Cl in any water. The Laplacians of the electronic densities were positive, and so were the ELF values, indicating a predominance of non-covalent interactions of the van der Waals forces type. Considering the two metal ions alone, in the presence of DES, the interaction strength followed Fe-Cl > Mn-Cl > Fe-(O1, O2) > Mn-(O1, O2). In the mixture, Fe-Mn followed the pattern Mn-Cl > Fe-Cl > Fe-(O1, O2) > Mn-(O1, O2). Thus, comparing the 3 systems, the interaction strength was Fe-Cl > Mn-Cl > Mn-Clmixture > Fe-Cl mixture e Fe-(O1, O2) mixture > Fe-(O1, O2) > Mn-(O1, O2)mixture > Mn-(O1, O2). The interaction strength for the systems with water was Fe-Clmixture > Fe-Cl > Mn-Cl > Mn-Clmixture. However, for the interaction with OW, the observed behaviors were: W300, Mn-OW > Fe-OWmixture > Mn-OWmixture > Fe-OWmixture; W600, Mn-OWmixture > Fe-OWmixture > Mn-OW > Fe-OW; W900, Mn-OW > Fe-OW > Mn-OWmixture > Fe-OWmixture; W1200, Mn-OW > Mn-OWmixture > Fe-OWmixture > Fe-OWmixture; W5580, Mn-OW > Fe-OW > Mn-OWmixture > Fe-OWmixture. The mixtures in the 1:1 molar ratio of the cations presented a little discrepant from their isolated ions, suggesting a new approach to observing the behavior of these systems and the coordination possibilities. One of the prospects for expanding the study will be temperature variation, modification of metal ions and molar proportions, and the effects of these changes.

Host–Guest Inclusion Systems of Vanillic Acid into α-Cyclodextrin: Structures, Electronic Properties, QTAIM, NCI and IGM Analyses with Dispersion Corrected Calculations

In this work, a theoretical study of the host–guest inclusion process involving the vanillic acid (VA) into α-cyclodextrin (α-CD) was investigated by the semi empirical methods PM6 and its modern variant PM6-D3H4 and density functional theory with the BP86-D3/6-31G+(d,p) functional to elucidate the relationship between host, guest and their molecular structures. According to the results from theoretical calculation, the model in which the VA molecule points it’s the carboxylic acid group toward the wider rim of α–CD is energetically preferred. The global reactivity descriptors were calculated and analyzed. The electronic transitions of the two complexes computed with the TD-DFT approach on the optimized geometries at BP86-D3/6-31G+ (d, p) level of theory including the CPCM model were investigated. Finally, quantum theory of atoms in molecules (QTAIM) analysis, the non-covalent interactions analysis (NCI) and the independent gradient model (IGM) results confirms that the van der Waals interactions and hydrogen bonds play a major role in the stabilization of the complexes.

Covalent Triazine Framework C6N6 as an Electrochemical Sensor for Hydrogen-Containing Industrial Pollutants. A DFT Study

Industrial pollutants pose a serious threat to ecosystems. Hence, there is a need to search for new efficient sensor materials for the detection of pollutants. In the current study, we explored the electrochemical sensing potential of a C6N6 sheet for H-containing industrial pollutants (HCN, H2S, NH3 and PH3) through DFT simulations. The adsorption of industrial pollutants over C6N6 occurs through physisorption, with adsorption energies ranging from -9.36 kcal/mol to -16.46 kcal/mol. The non-covalent interactions of analyte@C6N6 complexes are quantified by symmetry adapted perturbation theory (SAPT0), quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analyses. SAPT0 analyses show that electrostatic and dispersion forces play a dominant role in the stabilization of analytes over C6N6 sheets. Similarly, NCI and QTAIM analyses also verified the results of SAPT0 and interaction energy analyses. The electronic properties of analyte@C6N6 complexes are investigated by electron density difference (EDD), natural bond orbital analyses (NBO) and frontier molecular orbital analyses (FMO). Charge is transferred from the C6N6 sheet to HCN, H2S, NH3 and PH3. The highest exchange of charge is noted for H2S (-0.026 e-). The results of FMO analyses show that the interaction of all analytes results in changes in the EH-L gap of the C6N6 sheet. However, the highest decrease in the EH-L gap (2.58 eV) is observed for the NH3@C6N6 complex among all studied analyte@C6N6 complexes. The orbital density pattern shows that the HOMO density is completely concentrated on NH3, while the LUMO density is centred on the C6N6 surface. Such a type of electronic transition results in a significant change in the EH-L gap. Thus, it is concluded that C6N6 is highly selective towards NH3 compared to the other studied analytes.

Unconventional Dual Donor-Acceptor Topologies of Aromatic Rings in Amine-Based Polymeric Tetrahedral Zn(II) Compounds Involving Unusual Non-Covalent Contacts: Antiproliferative Evaluation and Theoretical Studies

Two Zn(II) coordination polymers, viz., [Zn2Cl2(H2O)2(µ-4-AmBz)2]n (1) and [ZnCl2(µ-3-AmPy)2]n (2) (4-AmBz = 4-aminobenzoate, 3-AmPy = 3-aminopyridine) have been prepared at room temperature and characterized using elemental analysis, FT-IR, electronic spectroscopy, TGA (thermogravimetric analysis) and single crystal XRD. Crystal structure analyses of the polymers unfold the presence of non-covalent anion–π, π-stacking and unusual NH2(amino)⋯π interactions which provide rigidity to the crystal structures. Unconventional Type I Cl⋯Cl interactions also play a pivotal role in the stability of compound 1. Molecular electrostatic potential (MEP) surface analysis reveals that the MEP values over the center of the aromatic rings of coordinated 4-AmBz and 3-AmPy moieties are positive on one side and negative on the other side which confirms the dual non-covalent donor-acceptor topologies of the aromatic rings and explains the concurrent formation of unusual non-covalent NH2···π and anion–π interactions. DFT (density functional theory) calculations, QTAIM (quantum theory of atoms in molecules) and NCI plot (non-covalent index) index analyses reveal that among various non-covalent contacts involved in the crystal packing of the compounds, H-bonds in compound 1 and π-interactions (NH2···π, π-π, anion–π) in compound 2 are energetically significant. We have explored in vitro cytotoxic potential of the compounds in Dalton’s lymphoma (DL) cancer cells using trypan blue and apoptosis assays. The studies show that compounds 1 and 2 can significantly exhibit cytotoxicity in DL cells with minimum cytotoxicity in healthy PBMC cells. Molecular docking studies reveal that the compounds effectively bind with the antiapoptotic target proteins; thereby establishing a structure activity relationship of the compounds.

Novel copper (II) and zinc (II) complexes with enrofloxacin and oxolinic acid: synthesis, characterization, Hirshfeld surface and DFT/CAM-B3LYPD3BJ studies: NBO, QTAIM and RDG analysis

This study aimed to investigate the crystal structure of the synthesized complexes of Cu (II) and Zn (II) with enrofloxacin and oxolinic acid. The characterization of the complexes was carried out using single–crystal x-ray diffraction, Hirshfeld surface and 1H NMR spectroscopy. In addition, a DFT/6-31g(d) investigation was conducted to assess the performance of two exchange-correlation functionals CAM-B3LYP and CAM-B3LYPD3BJ to predict both covalent and non-covalent bonds lengths, and the vibrational frequencies of the metallic complexes.The main findings of this study indicate that the interaction between each metallic ion and the corresponding ligand leads to significant modifications in bond lengths, Mulliken charge distribution and electrostatic potential values in the complex molecules as compared to the ligands alone. To gain further insights into these complexes, several calculations were performed, such as Natural Atomic orbitals (NAO), Natural Bond orbitals (NBO), and Quantum Theory of Atoms in Molecules (QTAIM) analysis. The non-covalent interactions were explored and visualized in two and three-dimensional spaces with the help of the Reduced electron Density Gradient (RDG) approach.

An atoms-in-molecules characterization of the nature of the OO bond in peroxides and nitroxide dimers.

The quantum theory of atoms-in-molecules (QTAIM) method is used to examine the OO bond in peroxides (RO-OR) and nitroxide dimers (R2 NO-ONR2 ), including Fremy's salt. The electron density (ρ), electron kinetic energy density [K(ρ)], and Laplacian of the electron density (∇2 ρ) at bond critical points characterize the nature of the OO bond. The data distinguish OO bonding of two kinds. Large values of ρ and positive ∇2 ρ and K(ρ) suggest that simple peroxides have charge-shift bonds. Nitroxide dimers, with smaller ρ, positive ∇2 ρ, and near-zero K(ρ), show a lack of shared electron density, suggesting there is no conventional OO bonding in these molecules. QTAIM analysis at the B3LYP/6-311+G(d,p) level of theory gives results in agreement with valence-bond theory and X-ray diffraction characterizations of peroxide OO bonds as charge-shift bonds. In contrast, CCSD/cc-pVDZ calculations fail to agree with previous results because of an insufficient, single-determinant treatment of the charge-shift bond.

Unraveling the Nature of Hydrogen Bonds of "Proton Sponges" Based on Car-Parrinello and Metadynamics Approaches.

The nature of intra- and intermolecular non-covalent interactions was studied in four naphthalene derivatives commonly referred to as "proton sponges". Special attention was paid to an intramolecular hydrogen bond present in the protonated form of the compounds. The unsubstituted "proton sponge" served as a reference structure to study the substituent influence on the hydrogen bond (HB) properties. We selected three compounds substituted by methoxy, amino, and nitro groups. The presence of the substituents either retained the parent symmetry or rendered the compounds asymmetric. In order to reveal the non-covalent interaction properties, the Hirshfeld surface (HS) was computed for the crystal structures of the studied compounds. Next, quantum-chemical simulations were performed in vacuo and in the crystalline phase. Car-Parrinello molecular dynamics (CPMD), Path Integral Molecular Dynamics (PIMD), and metadynamics were employed to investigate the time-evolution changes of metric parameters and free energy profile in both phases. Additionally, for selected snapshots obtained from the CPMD trajectories, non-covalent interactions and electronic structure were studied. Quantum theory of atoms in molecules (QTAIM) and the Density Overlap Regions Indicator (DORI) were applied for this purpose. It was found based on Hirshfeld surfaces that, besides intramolecular hydrogen bonds, other non-covalent interactions are present and have a strong impact on the crystal structure organization. The CPMD results obtained in both phases showed frequent proton transfer phenomena. The proton was strongly delocalized in the applied time-scale and temperature, especially in the PIMD framework. The use of metadynamics allowed for tracing the free energy profiles and confirming that the hydrogen bonds present in "proton sponges" are Low-Barrier Hydrogen Bonds (LBHBs). The electronic and topological analysis quantitatively described the temperature dependence and time-evolution changes of the electronic structure. The covalency of the hydrogen bonds was estimated based on QTAIM analysis. It was found that strong hydrogen bonds show greater covalency, which is additionally determined by the proton position in the hydrogen bridge.

Efficient Detection of Nerve Agents through Carbon Nitride Quantum Dots: A DFT Approach.

V-series nerve agents are very lethal to health and cause the inactivation of acetylcholinesterase which leads to neuromuscular paralysis and, finally, death. Therefore, rapid detection and elimination of V-series nerve agents are very important. Herein, we have carried out a theoretical investigation of carbon nitride quantum dots (C2N) as an electrochemical sensor for the detection of V-series nerve agents, including VX, VS, VE, VG, and VM. Adsorption of V-series nerve agents on C2N quantum dots is explored at M05-2X/6-31++G(d,p) level of theory. The level of theory chosen is quite adequate in systems describing non-bonding interactions. The adsorption behavior of nerve agents is characterized by interaction energy, non-covalent interaction (NCI), Bader's quantum theory of atoms in molecules (QTAIM), frontier molecular orbital (FMO), electron density difference (EDD), and charge transfer analysis. The computed adsorption energies of the studied complexes are in the range of -12.93 to -17.81 kcal/mol, which indicates the nerve agents are physiosorbed onto C2N surface through non-covalent interactions. The non-covalent interactions between V-series and C2N are confirmed through NCI and QTAIM analysis. EDD analysis is carried out to understand electron density shifting, which is further validated by natural bond orbital (NBO) analysis. FMO analysis is used to estimate the changes in energy gap of C2N on complexation through HOMO-LUMO energies. These findings suggest that C2N surface is highly selective toward VX, and it might be a promising candidate for the detection of V-series nerve agents.