Unoccupied Molecular Orbitals Research Articles

N-H Bond Activation Catalyzed by an Anderson-Type Polyoxometalate-Based Compound: Key Role of Transition-Metal Heteroatom.

Polyoxometalates (POMs) have a broad array of applied platforms with well-characterized catalysis to achieve N-H bond activation. Herein, the mechanism of the Anderson-type POM-based catalyst [FeIIIMoVI6O18{(OCH2)3CNH2}2]3- ([TrisFeIIIMoVI6O18]3-, Tris = {(OCH2)3CNH2}2) for the N-H bond activation of hydrazine (PhHNNHPh) was investigated by density functional theory calculations. The results reveal that [TrisFeIIIMoVI6O18]3- as the active species is responsible for the continuous abstraction of two electrons and two protons of PhHNNHPh via a proton-coupled electron transfer pathway, resulting in the activation of two N-H bonds in PhHNNHPh and thus the product PhNNPh. H2O2 acts as an oxidant to regulate catalyst regeneration. Based on the proposed catalytic mechanism, the key role of the heteroatom FeIII in [TrisFeIIIMoVI6O18]3- was disclosed. The d-orbital of FeIII in [TrisFeIIIMoVI6O18]3- acts as an electron receptor to promote the electron transfer (ET) in the rate-determining step (RDS) of the catalytic cycle. The substitution of the heteroatom FeIII of [TrisFeIIIMoVI6O18]3- with CoIII, RuIII, or MnIII is expected to improve the catalytic activity for several reasons: (i) the unoccupied molecular orbitals of POM-based compounds containing CoIII or RuIII are low, which is beneficial for the ET of RDS; (ii) For N-H bond activation catalyzed by the MnIII-containing POM-based compound, the transition state of RDS is stable because the d-orbital of its active site is half-filled, which results in a low free-energy barrier.

Experimental and theoretical investigation of structure activity relationship on L-Lysine Monohydrate for antioxidant efficacy

Comprehensive spectroscopic research has been undertaken to investigate the structural behaviour of the l-lysine monohydrate molecule. The spectral properties of the l-lysine monohydrate molecule in solid phase were examined using Fourier Transform Infrared (FTIR) and Fourier Transform Raman methods. The B3LYP/6–311++G (d, p) computations were used to optimize the structure of the molecule. To provide complete vibrational spectral assignments, vibration energy distribution analysis (VEDA) was used. The Natural bond orbital (NBO) analysis explains the stability and distinct forms of hydrogen bonds with in the molecule. The chemical stability of the molecule is predicted by Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) analysis. Non-Covalent Interaction (NCI) analysis was done to identify weak interactions according to density of electron of the title compound. The fukui function identified the chemical reactivity sites. To predict its antioxidant efficacy, docking studies were done.

Indapamide analogue a promising drug: Synthesis, a novel crystal structure, HSA/DFT/XRD, greener pastures biological study

A new indoline derivative, N-allyl-4-chloro-3-(N,N-diallylsulfamoyl)-N-(2-methylindolin-1-yl)benzamide (ASIB), indapamide analogue, has been synthesized via the N-allylation reaction and characterized by ESI-MS, IR, 1H & 13C NMR. The geometric parameters of the title compound, whose crystallographic structure has been defined by X-ray diffraction, have been calculated by Density Functional Theory (DFT), B3LYP, 6–311++G(d,p) basis set. For these operations, the data obtained by X-ray diffraction was used as initial values, and the calculated geometric parameters and experimental results were compared. In order to understand intermolecular interactions, Molecular Electrostatic Potential (MEP) and Hirshfeld Surface Analysis (HSA) studies were figured out for the molecule. Frontier Molecular Orbitals (FMO's) were created, and Energy Gap between Lowest Unoccupied Molecular Orbital (LUMO) and Highest Occupied Molecular Orbital (HOMO) was calcculated. Adapting Greener Pastures Biological Study (GPBS) aims to conduct a fair comparative study using accessible computer-aided software. ASIB, Indapamide, Asunaprevir, Danoprevir, and Vaniprevir were docked together using the same conditions and parameters to ensure a fair comparison. The binding scores against 6LU7 were −6.6, −7.1, −8.4, 7.6, and −7.9 kcal/mol−1 for ASIB, Indapamide, Asunaprevir, Danoprevir, and Vaniprevir, respectively. A relation between the molecule's binding score was due to the hydrophobic and hydrogen interactions between the ligand and the receptor's active amino acid residues. Worth pointing out here that the free energy and environmentally friendly in Silico molecular docking method aims mainly to rank ASIB, and Indapamide with respect to the approved drugs used in this study. Results support further investigation of ASIB as non-toxic a Diuretic, anti-COVID-19 and powerful antiviral drug as an indapamide derivative. Way2drug-PASS, Pro Tox-II and SwissADME are online software tools used in this study. Absorption, distribution, metabolism, excretion and toxicity (ADMET) properties of ASIB and its starting material (Indapamide) were compared.

New Insight into the Electronic Effect for Cu Porphyrin Catalysts in Electrocatalytic of CO2 into CH4.

Perturbation of the copper (Cu) active site by electron manipulation is a crucial factor in determining the activity and selectivity of electrochemical carbon dioxide (CO2 ) reduction reaction (e-CO2 RR) in Cu-based molecular catalysts. However, much ambiguity is present concerning their electronic structure-function relationships. Here, three molecular Cu-based porphyrin catalysts with different electron densities at the Cu active site, Cu tetrakis(4-methoxyphenyl)porphyrin (Cu─T(OMe)PP), Cu tetraphenylporphyrin (Cu─THPP), and Cu tetrakis(4-bromophenyl)porphyrin (Cu─TBrPP), are prepared. Although all three catalysts exhibit e-CO2 RR activity and the same reaction pathway, their performance is significantly affected by the electronic structure of the Cu site. Theoretical and experimental investigations verify that the conjugated effect of ─OCH3 and ─Br groups lowers the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbitals (LUMO) gap of Cu─T(OMe)PP and Cu─TBrPP, promoting faster electron transfer between Cu and CO2 , thereby improving their e-CO2 RR activity. Moreover, the high inductive effect of ─Br group reduces the electron density of Cu active site of Cu─TBrPP, facilitating the hydrolysis of the bound H2 O and thus creating a preferable local microenvironment, further enhancing the catalytic performance. This work provides new insights into the relationships between the substituent group characteristics with e-CO2 RR performance and is highly instructive for the design of efficient Cu-based e-CO2 RR electrocatalysts.

Effect of solvent role in electronic properties, band gap, electron injection barrier, charge transport nature, topology studies (ELF, LOL, RDG), and optical properties of azoles for multifunctional applications

The ground state geometries of oxazole compounds, i.e., 3,5-Bis-(4-chloro-phenyl)-7a-methyl-dihydro-oxazolo[3,4-c]oxazole (Compound1) and 3,5-Bis-(4-methoxy-phenyl)-7a-methyl-dihydro-oxazolo[3,4-c]oxazole (Compound2) were optimized using Density functional theory employing B3LYP/6-31G++ level for comparing the geometric parameters (torsion angles, bond angles & bond lengths) with the X-ray crystallographic information. We explored the charge transport nature, wave functional properties, optical and electronic properties of both the oxazoles. The computed geometric parameters are rational to the experimental data. The time-domain TD - B3LYP/6-31G++ & the B3LYP/6-31G++ levels were used to reveal the electronic characteristics and absorption wavelength. Intra-molecular charge transfer was perceived in studied compounds. The IEFPCM (Integral Equation Formalism Polarizable Continuum Model) model was used to calculate the solvation UV spectrum. The effect of various solvents (acetone, acetonitrile, DMF(Dimethylformamide), DMSO (Dimethyl sulfoxide) and methanol) was examined on the excitation energies but solvent polarity has no discernible impact on the wavelengths of absorption. From HOMO-LUMO (Highest Occupied Molecular Orbital – Lowest Unoccupied Molecular Orbital) orbitals with various solvent molecules, band gap energies with the solvation effect are determined. Additionally, through the use of topological analytics like RDG (Reduced Density Gradient), ELF (Electron Localisation Function) & LOL (Localised Orbital Locator), the energy concentration of electrons was elucidated. Furthermore, the outcome of electron-donating cluster (–OCH3) and electron-withdrawing cluster (–Cl) was studied on open-circuit voltage, bandgap alignment, electron coupling constants, excitons dissociation values, ΔGinject – electron injection, LHE-Light Harvesting Efficiency and electron coupling constants (|VRP|).

Laser Ablation of the Flexible Graphite: A New Way to Create a Graphene‐Based Flexible Substrate

The morphological and structural changes of an ablated flexible graphite in air and acetone ablation environments are studied here. From field emission scanning electron microscopy images, vertically aligned graphene nanosheets are found on the surface of ablated target in acetone. Measured ablation depth values for the ablated target in water are generally higher than those for the ablated target in air. X‐ray diffraction analysis reveals that the (002) peak position and full‐width at half‐maximum of this peak in the ablated flexible graphite in the air increase. The gap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals, i.e., the bandgap of the ablated target, indicating that the energy bandgap of the ablated target in two ablation media increased compared to the nonirradiated target. Raman analysis from different points of the surface of the ablated target in both ablation media demonstrates the presence of bulk defects on the ablated target in the air, instead the edge defects are found for the ablated target in acetone. From Raman spectra, there are no single‐layer graphene nanosheets pinned on the surface of the target in acetone.

Multi-Mode Photoluminescence Regulation in a Zero-Dimensional Organic-Inorganic Hybrid Metal Halide Perovskite─[(CH3)4N]2SnCl6.

Metal ion-doped zero-dimensional halide perovskites provide good platforms to generate broadband emission and explore the fundamental dynamics of emission regulations. Recently, Sb3+-doped zero-dimensional halide perovskites have attracted considerable attention for the high quantum yield of yellow emission; however, the triplet state recombination is activated and the singlet state emission is usually absent. Herein, we fabricate an Sb3+-doped zero-dimensional [(CH3)4N]2SnCl6 perovskite that can induce singlet and triplet emission. Density functional theory calculation shows that there are some overlaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals, which may induce a large energy separation between the lowest excited triplet states (T1) and the lowest excited singlet states (S1) [ΔE(S1 - T1)], impeding all the carriers' transfer from the singlet state to the triplet state. As a result, the reserved singlet emission together with the triplet emission can be regulated by excitation wavelength in situ. In addition, different Bi3+ ratios are co-doped into Sb3+@[(CH3)4N]2SnCl6, resulting in a photoluminescence ex situ regulation. Single-phase white light LED and optical anti-counterfeiting are developed further.

Exploration of Coumarin Derivative: Experimental and Computational Modeling for Dipole Moment Estimation and Thermal Sensing Application.

The Optical properties of the FBTC (1-((4-((5-chlorobenzo[d]oxazol-2-ylthio)methyl)-1H-1,2,3-triazol-1-yl)methyl)-3H-benzo[f]chromen-3-one) molecule were studied experimentally and theoretically. The spectra of absorption and fluorescence were recorded in various solvents to explore their Solvatochromic behavior and dipole moment at room temperature. To determine the ground and excited state of dipole moment experimentally and theoretically, we employed different Solvatochromic techniques, including microscopic solvent polarity functions developed by Lippert, Bakhshiev, Kawaski-Chamma-Viallet, and Reichardt's, as well as density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The stability of the excited state dipole moment in FBTC is higher. Using prime functional, FBTC was optimized in its ground state, and its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital), energies were estimated. These values were then compared with those obtained through cyclic voltammetry. Based on the HOMO and LUMO values given, we calculated the global reactivity parameter and energy gap, which was found to be low at 3.77eV. This study also includes an estimation of electron absorption energies and oscillator strength. Natural population analysis (NPA), Milliken atomic charge, and molecular electrostatic potential (MESP) map are correlated. In addition, FBTC exhibited exceptional physiological temperature sensing behaviour from 20°C -65°C with high relative sensitivity and firm stability. Hence these results confirm that FBTC is a potential candidate for photonic devices and it's also applicable in optical temperature sensing.

Molecular structure, electronic, structural, topological analyses with solvents (water, chloroform, acetone and benzene) based on IEFPCM investigation and Hirshfeld analysis on 2-acetyl pyridine

In this study, theoretical investigations of the molecule 2-Acetyl Pyridine have been DFT technique. The geometrical optimization, spectral investigations (FT-IR and FT-R), electronic transitions and the energy gap between Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) and chemical nature of the title molecule by UV–Vis analysis and non-linear optical behavior of the molecule using urea as NLO protocol and Molecular Electrostatic Potential for assessing local reactivity properties were calculated and analyzed using gas and solvent phases such as water, chloroform, acetone and benzene. In NLO analysis, the highest hyperpolarizability has been shown in water solvent (6.0283 × 10−30 e.s.u). In UV analysis, results of excitation electronic analysis of 2AP were observed to have wavelength absorption in the order gas:water: 241.699 nm > acetone:241.609 nm > chloroform: 241.135 nm > 240.401 nm among which benzene solvent possessed the highest transition energy (41597.238 cm−1) with contribution of 78%. The Natural Bond Orbital (NBO) analysis depicted the prominent acceptor–donor interaction in terms of stabilization energies. The local reactivity descriptors such as Fukui functions were performed to determine the reactive sites within the molecule. Topological studies like Electron Localization Function, Localized Orbital Locator, Non-covalent Interaction, Atoms in molecule, Electrostatic Potential were carried out. Hirshfeld Surface analysis was employed to analyze the intermolecular interactions in the crystal structure.

Effect of microplastics on the degradation of tetracycline in a soil microbial electric field

The degradation of organic pollutants and the adsorption of organic pollutants onto microplastics (MPs) in the environment have recently been intensively studied, but the effects of biocurrents, which are widespread in various soil environments, on the environmental behavior of MPs and antibiotic pollutants have not been reported. In this study, it was found that polylactic acid (PLA) and polyvinyl chloride (PVC) MPs accelerated the mineralization of humic substances in microbial electrochemical systems (MESs). After tetracycline (TC) was introduced into the MESs, the internal resistance of the soil MESs decreased. Additionally, the presence of MPs enhanced the charge output of the soil MESs by 40% (PLA+TC) and 18% (PVC+TC) compared with a control group without MPs (424 C). The loss in MP mass decreased after TC was added, suggesting a promotion of TC degradation rather than MP degradation for charge output. MPs altered the distribution of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of TC molecules and reduced the energy barrier for the TC hydrolysis reaction. The microbial community of the plastisphere exhibited a greater ability to degrade xenobiotics than the soil microbial community, indicating that MPs were hotspots for TC degradation. This study provides the first glimpse into the influence of MPs on the degradation of TC in MESs, laying a theoretical and methodological foundation for the systematic evaluation of the potential risks of environmental pollutants in the future.

A Ground-State Dual-Descriptor Strategy for Screening Efficient Singlet Fission Systems.

Exploration of singlet fission (SF) materials is vital for enhancing the photoelectric conversion efficiency of photovoltaic devices, and the development of an effective screening means is in great demand. In this work, we for the first time propose a promising dual-descriptor strategy to predict the SF energetics (ΔESF) from ground-state electronic properties, the gap (GapHL) and exchange energy (KHL) between the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), where GapHL plays a dominant role and KHL acts as a correction. This strategy is statistically verified through exploring the effect of N-doping on the electronic/energetic properties of the N-doped tetracene derivatives and isomers. Several rules of thumb are suggested, and the reliability of this strategy is validated by comparison with experiments. This work proposes a novel strategy for exploring SF chromophores with insights into the SF energetics from ground-state properties and certainly has fundamental interest and generality in exploring efficient SF-capable materials.

Interpretable Fragment‐Based Molecule Design with Self‐Learning Entropic Population Annealing

Self‐learning entropic population annealing (SLEPA) is a recently developed method used for achieving interpretable black‐box optimization via density‐of‐states estimation. Applying SLEPA to a chemical space is not straightforward, however, because of its dependence on Markov chain Monte Carlo sampling in the space of generated entities. Herein, SLEPA is applied to optimal molecule generation by combining an irreducible Markov chain in the space of fragment multisets and a probabilistic fragment assembler such as MoLeR. The weighted samples from SLEPA are used to identify salient fragments for the highest occupied molecular orbitals‐lowest unoccupied molecular orbitals (HOMO‐LUMO) gap maximization and minimization, and the relationship between the identified fragments and the electronic structures is elucidated. This approach offers a viable platform to reconcile the incompatible goals of optimization and interpretation during molecular design.

Concentration induced modulation of solvation structure for efficient lithium metal battery by regulating energy level of LUMO orbital

Nitrile electrolytes have attracted extensive attention for achieving high-voltage lithium metal batteries. However, the poor compatibility of nitrile electrolyte with Li anode remains a huge challenge owing to severe side reactions. Herein, changing concentration of LiTFSI in succinonitrile (SN) is proposed to improve interface compatibility by regulating the solvation structure. The higher coordination number (1.3) of TFSI− in high concentration electrolytes results in a LiF-rich SEI film, accounting for the superior performance of LiNi0.8Co0.1Mn0.1O2|Li cell with negligible capacity fade after 100 cycles at 0.5 C. Density functional theory (DFT) suggests that the solvation structure with a high coordination number of TFSI− towards Li+ leads to a reduced Lowest Unoccupied Molecular Orbital (LUMO) energy level, which promotes the decomposition of TFSI− to form LiF-rich film. Also, a reduced decomposition energy barrier of anion is demonstrated. This work provides an encouraging way to enhance interface stability via modulating the solvation structure achieved by regulating concentration.

Synthesis, photophysical, electrochemical and morphological properties of a novel cross-linked chitosan-based fluorescent polymer: A fluorescence sensor for single-stranded DNA

This report details the first-time use of the perylene-3,4,9,10-tetracarboxylic dianhydride as a cross-linker to synthesize a novel fluorescent, chitosan-based cross-linked polymer (3). The polymer has single-stranded DNA (ssDNA) binding properties that can be used in sensor production for detecting salmon sperm DNA. Chitosan polymer's solubility is poor and restrictedto only acidic media. In contrast, this new fluorescent chitosan polymer was soluble in various organic solvents and aqueous solutions at different pHs. Its absorption, photophysical, electrochemical and morphological properties were investigated in detail. Gel permeation chromatography determined the weight average molecular mass (Mw) of polymer 3 as 21300 g/mol. Seventeen hydrophobic perylene units were determined in the cross-linked network. The energy levels of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of the new polymer 3 were calculated as −6.24 and −3.96 eV, corresponding to the band gap of 2.28 eV. Fluorescence and ultraviolet spectroscopy techniques were used to study the interaction between ssDNA and polymer 3. The interaction pointed to the intercalative mode, and the cross-linked chitosan can be used as a stable and sensitive platform for ssDNA detection. These results show a new class of organic biopolymers that could yield promising potential in many biomedical applications.

Calculation of the one- and two-photon absorption spectra of water-soluble stilbene derivatives using a multiscale QM/MM approach.

We calculated the one- (OPA) and two-photon absorption (TPA) spectra of two large water-soluble stilbene derivatives presenting TPA cross sections of about 400 GM. However, the reported experimental TPA spectra present a spectral gap region, and a theoretical study of these promising molecules seems now timely and relevant. These molecules are composed of 200 or more atoms, becoming a challenge to obtain the TPA spectra even using density functional theory at the time-dependent quadratic response formalism. Thus, both OPA and TPA were also calculated using the INDO-S semi-empirical method. We used explicit solvent molecules using the sequential-quantum mechanics/molecular mechanics to include the solvent effects. Our results show that different transitions are participating in the OPA and TPA processes and that exchange-correlation functionals, including larger Hartree-Fock contributions, provide a better description of the OPA spectra; however, the opposite trend is observed on the TPA spectra. Alternatively, INDO-S/CISD, including contributions from single and double excitations, systematically describes both OPA and TPA bands with similar shifts and better reproduces the relative intensities of the two TPA bands compared to the experimental ones. The OPA spectra are characterized by a Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) excitation, while the low-energy TPA band is ascribed to a single transition encompassing the (HOMO-1)-LUMO and HOMO-(LUMO+1) excitations and the high-energy one is a combination of several transitions. Thus, although more studies are required to better assess the capability of the INDO-S/CISD method in describing the TPA spectra of large molecules, our results corroborate that it is a promising alternative.

Adsorption configurations and electronic properties of self-assembled C60 and C70 molecules on a semiconductor CuSe monolayer with periodic nanopores

Two-dimensional (2D) supramolecular self-assembly architectures are considered one of the most significant and challenging topics in nanotechnology and modern organic chemistry. The study of these processes on surfaces is vital to achieving a higher degree of control in the design of supramolecular architecture. Herein, we report on the 2D self-assembly monolayer architectures based on C60 and C70 molecules on a semiconductor CuSe monolayer with periodic nanopores, which are essential for providing ideas for surface template chemistry. With the aid of low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS) and density functional theory (DFT) calculation methods, we systematically investigate the adsorption configurations and electronic properties of C60 and C70 on CuSe monolayer with periodic nanopores. Our results show that both the C60 and C70 molecules above the nanopores will fall into the nanopores, while those on the CuSe surface will show well-defined self-assembly with various adsorption configurations. Besides, through STS measurement, the lowest unoccupied molecular orbitals (LUMOs) and characteristic peaks of fullerene molecules will be slightly different due to different adsorption configurations. This work helps us to study the adsorption behavior of the fullerene family on various kinds of semiconductor substrates, and also provides vigorous support for the development of fullerene electrical devices in the future.

Electronic coarse-graining of long conjugated molecules: Case study of non-fullerene acceptors.

By considering only one electronic state per molecule, charge transport models of molecular solids neglect intramolecular charge transfer. This approximation excludes materials with quasi-degenerate spatially separated frontier orbitals, such as non-fullerene acceptors (NFAs) and symmetric thermally activated delayed fluorescence emitters. By analyzing the electronic structure of room-temperature molecular conformers of a prototypical NFA, ITIC-4F, we conclude that the electron is localized on one of the two acceptor blocks with the mean intramolecular transfer integral of 120meV, which is comparable with intermolecular couplings. Therefore, the minimal basis for acceptor-donor-acceptor (A-D-A) molecules consists of two molecular orbitals localized on the acceptor blocks. This basis is robust even with respect to geometry distortions in an amorphous solid, in contrast to the basis of two lowest unoccupied canonical molecular orbitals withstanding only thermal fluctuations in a crystal. The charge carrier mobility can be underestimated by a factor of two when using single site approximation for A-D-A molecules in their typical crystalline packings.

Synthesis of novel pyrazole-4-carboxylates by rearrangement reaction: Experimental and theoretical characterization

In this study, alkyl pyrazole-4-carboxylate compounds (5a-d) were synthesized from the esterification reaction of pyrazole-5-carboxylic acid compound by rearrangement. Molecules 5a-d have been studied in detail both experimentally (x-ray, FT-IR and NMR) and theoretically. Optimization of the structure for all compounds, Highest Occupied Molecular Orbital (HOMO)-Lowest Unoccupied Molecular Orbital (LUMO) values and distributions and Molecular Electrostatic Potential (MEP) analyzes for only 5d (most stable energy and single crystal) were performed by DFT theory at B3LYP functional and 6–311++G(d,p) basis set. Possible crystallization of the structure (5d) from experimental crystal was carried out by Hirshfeld surface analysis. In the next step, the interactions between the 5a, 5b, 5c and 5d molecules, the proposed molecule from the similarity and the target were made by molecular docking calculations. Then, drug-likeness and ADME properties were investigated.

Computational study of the interaction of metal ions (Na+, K+, Mg2+, Ca2+, and Al3+) with Quercetin and its antioxidant properties

In recent years, the chelation between quercetin and transition metals has attracted much attention because the complexes formed have higher antioxidant and medicinal activities. However, the theoretical investigation of the mechanisms of flavonoid functioning along with the structures of quercetin–metal complexes is still not sufficiently studied. In this research work, quercetin–complexes with Na+, K+, Mg2+, Ca2+, and Al3+ are studied theoretically by using density functional theory (DFT) method in order to investigate the stability, reactivity, nature of interaction, and the application of the quercetin-metal complexes as potential antioxidants. From the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) results, the K-quercetin salt was observed to be more stable as compared to the other metals while Ca seemed to be the most reactive with the least values in the neutral form of the metal - quercetin interaction. The results of the antioxidant activity in the neutral state present Ca and Mg to have the higher values of ionization potential (IP) indicating that the antioxidant activity of Ca/Mg complexes with quercetin are less pronounced, while K-complex with the least value indicating the higher the electron donating reactivity. In comparison, it is worth to note that Mg-Q and Ca-Q in the deprotonated state of quercetin showcase lower IP, higher ability of H-atom transfer and electron transfer reactivity, therefore, better antioxidant candidates of the quercetin complexes than their other counterparts.

In English

This study determined the corrosion inhibition levels of benzimidazole (BIA), 1-hydroxybenzotriazole (HBT), methylbenzimidazole (MBI) and 4-phenylimidazole (PIZ). By using simulation, it was possible to have a complete relationship with the experimental work because the results were completely consistent. Density functional theory (DFT) and Monte Carlo simulations were used to calculate several quantum chemical parameters. The molecules are simulated using quantum chemical calculations with Gaussian09 software. Fundamental factors determining the corrosion order of molecules are the highest-energy occupied and lowest-energy unoccupied molecular orbitals (HOMO and LUMO), frontier molecular orbital energy, back donating energy, electrophilicity, nucleophilicity, energy gap ∆E, absolute electronegativity (χ), softness, the number of electrons (∆N) transferred from inhibitors to iron, the dipole moment (μ), the global hardness (η) and the total energy.