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Oxidative stress, associated with excessive production of reactive oxygen and nitrogen species (ROS, RNS), contributes to the development and progression of many ailments, such as aging, cardiovascular diseases, Alzheimer's disease, Parkinson's disease, diabetes, cancer, preeclampsia or multiple sclerosis. While phenols and polyphenols are the most studied antioxidants structurally similar compounds such as anilines or thiophenols are sporadically analyzed despite their radical scavenging potential. This work assesses the impact of structural features of phenols and thiophenols on their antioxidant activity. Seventeen pairs of phenol/thiophenol analogues, possessing both electron-donating and withdrawing groups were selected for this study. Several physicochemical properties of the compounds were determined by density functional theory (DFT) calculations at the (U)B3LYP/6-311++G(d,p) level of theory for gas phase calculations and at the (U)B3LYP/6-311++G(d,p) scrf = (smd, solvent = water) level for the solvated ones. Correlations between calculated properties and experimental radical scavenging activities were investigated to identify the pivotal physical characteristics contributing to antioxidant efficiency. These include S–H and O–H bond distances and bond dissociation enthalpies (BDE), dipole moments, logP values, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) orbital energies, and the HOMO–LUMO gap energies that were calculated at the M06-2X/6-311++G(d,p) level of theory, and Fukui functions. The experimental activity was evaluated using the 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and 2,2-diphenyl-1picrylhydrazyl (DPPH) radical scavenging assays. Several compounds exhibited superior scavenging abilities, surpassing that of the reference antioxidant Trolox. The extensive DFT calculations revealed that in the gas phase, lower BDE values, compared to IP and PA, suggested that the HAT mechanism predominates in case of these compound groups. In contrast, in water, significant reductions in PA due to solvent effects suggested that the SPLET mechanism is dominant under aqueous conditions. [ABSTRACT FROM AUTHOR]

The catalytic efficiency of M−H2tpda pincer complexes (M=Mn(I), Fe(II), Co(III)) in CO2 hydrogenation, emphasizing the role of transition metal variability have been discussed. The DFT analysis demonstrates that complexes with low αR values form weaker M−H bonds, enhancing catalyst reactivity with the elongation of M−H bond. The analysis further displays excellent catalytic performance for Mn−H2tpda (ΔE=20.3 kcal/mol), Fe−H2tpda (ΔE=21.0 kcal/mol) and Co−H2tpda (ΔE=23.6 kcal/mol) for CO2 to formic acid formation. The Co−H2tpda (ΔE=16.7 kcal/mol) is comparatively better than Mn−H2tpda (ΔE=20.7 kcal/mol) and Fe−H2tpda (ΔE=19.6 kcal/mol) in formaldehyde formation. All three catalysts exhibit excellent catalytic performance in the conversion of formaldehyde to methanol. The condensed Fukui function calculations of these catalyst complexes establish direct relationship between the ΔE for the rate limiting catalytic cycle and the electrophilicity of the metal centers. The TOF calculations further helped to understand the catalytic performance of the catalysts at various temperatures. [ABSTRACT FROM AUTHOR]

Context: The corrosion of mild steel is a significant issue in various industries, prompting the need for effective corrosion inhibitors. This study focuses on understanding the corrosion inhibition properties of organic compounds derived from isoxazole, namely series Iso(a), Iso(b), Iso(c), Iso(d), Iso(e), Iso(f), Iso(g), and Iso(h), which could have implications for materials science and industrial applications. By investigating the influence of different substitutions on these compounds, valuable insights can be gained into designing better corrosion inhibitors for practical use. Methods: Theoretical studies were conducted using density functional theory (DFT) with the B3LYP functional and the 6-31G (d,p) basis set. These calculations enabled the evaluation of various parameters including frontier orbital energies (EHOMO, ELUMO), energy gap (∆E), electronegativity (χ), absolute hardness (η), softness (σ), fraction of transferred electrons (∆N), as well as local properties such as natural atomic populations and Fukui indices. Additionally, molecular dynamics simulations were performed to study the adsorption behavior of the inhibitors on the surface of Fe (110). The simulations were conducted using Materials Studio version 8.0 software package using COMPASS force field to understand the impact of different functional groups on the inhibitors before and after adsorption on the iron surface. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations and molecular docking have been carried out on natural products containing eugenol, gingerol, ascorbic acid, oleurpoein, piperine, hesperidin, quercetin, Luteolin, and curcumin in order to predict their biological activities and to analyze their pancreatic lipase inhibition. The biological activity predictions are based on the global and local chemical descriptors, namely, HOMO–LUMO gaps, chemical hardness, chemical potential, electrophilicity, dipole moment, and Fukui functions. Our findings show that the studied compounds can be divided into two groups based on the chemical descriptors; the first group is composed of eugenol, gingerol, ascorbic acid, and oleuropein and the second one is composed of piperine, hesperidin, quercetin, Luteolin, and curcumin depending on the HOMO–LUMO gaps and electrophilicity values predicting best reactivity for the second group than the first one. The frontier orbitals offer a deeper insight concerning the electron donor and electron acceptor capabilities, whereas the local descriptors resulting from Fukui functions put emphasis on the active sites of different candidate ligands. The molecular docking was performed in order to compare and identify the inhibition activity of the natural candidate ligands against pancreatic lipase which were compared to that of synthesized ones. The molecular docking results revealed that the Luteolin compound has the best binding affinity of −8.56 kcal/mol due to their unique molecular structure and the position of -OH aromatic substituents. [ABSTRACT FROM AUTHOR]

To study asphalt aging and its anti-aging mechanism, the Frontier Orbital theory, Fukui Function, and Density Functional Theory are applied.The data reveals that 65 nm UV light can dissociate O2 into O radicals during UV aging. Among the resin components, sulfur (S) exhibits the highest radical attack index (f0) of 0.131. Resin molecules absorb UV light at 344 nm and 311 nm, leading to π electron transitions in S with a 28% probability. This result aligns with f0, indicating that f0 adequately reflects chemical reactivity. Resin molecules with electron transitions in S can form sulfoxide by creating a new delocalized π bond with unpaired electrons from oxygen radicals. Thermal oxidative aging at a temperature of 241 K has the potential to form carbonyl, hydroxyl, and peroxide bridge bonds. Ageing-resistant agents with a high f0 value on their outer layer compete with resin molecules in radical reactions, thereby exhibiting anti-aging effects. Calculation results indicate a slight increase in the number of carbonyl and peroxide bridge bonds after short-term aging, which becomes more prominent under pressure aging. UV aging is expected to result in a significant increase in sulfoxide, carbonyl, and ether bonds. The combination of experimental and calculated findings suggests that using quantum chemistry for qualitative analysis of aging mechanisms is a feasible approach. This method aids the investigation of asphalt anti-aging measures and enhances the efficiency of optimizing asphalt anti-aging agents.

Dyes are naked-eye detectable even at low concentration levels and can cause environmental damage when released into aquatic effluents; therefore, methods for removing the residual color from the aquatic media are always a current issue. In this paper, degradation of three xanthene dyes, Rhodamine B, Eosin Y, and Sodium Fluorescein, using photoactivated persulfate was evaluated at pH 3.0 and 11.0. The dyes' degradation followed a pseudo-first-order reaction. Although the solution is completely decolorized in 40 min at pH 3.0, achieving 75% mineralization requires a longer reaction time of 180 min. Furthermore, GC–MS analyses indicate that degradation products are mainly low-molecular weight acids, CO2 and H2O. Experiments carried out in dark and under UV irradiation showed substantial contribution of radical (SO4•− and HO•) and non-radical pathways to dye degradation in both pH. Additionally, to get more insights into the degradation pathways, HOMO–LUMO energy gaps of the dyes were calculated by DFT using MPW1PW91/MidiXo level of theory and, in general, the lower the bandgap, the faster the degradation. Fukui functions revealed that the preferential sites to radical attack were the xanthene or the benzoate portion depending on the pH, wherein attack to the xanthene ring provided better kinetic and mineralization results. [ABSTRACT FROM AUTHOR]

In this manuscript, we postulate a possible relationship of philicity within a molecular set of electrocyclic reactions. Philicity has been studied by Chattaraj and co‐workers (J. Phys. Chem. A. 2003, 107, 25). This important concept was obtained using the electrophilicity index and Fukui functions. Recently, the present author has published a possible way to quantify philicity using molecular quantum similarity and chemical reactivity indices (see, J. Math. Chem. 2023, 61, 165). In this work, philicity was related with the molecular quantum similarity framework to obtain a possible way to relate philicity using 21 electrocyclic reactions using the cyclobutene reaction as a reference. The main idea is to postulate philicity scales. This methodology can open up a possible path to find systematic relationships in each molecular ensemble using the selectivity defined in the density functional theory context. With these scales, we can relate the effect of the substituent on the electrocyclic opening reaction on the molecular set. [ABSTRACT FROM AUTHOR]

The prospective compound pencycuron (PNC) was probed using FT-IR, FT-Raman, NMR, and UV-Vis spectra and quantum chemical computation. Vibrational assignment pertaining to different modes of vibration with potential energy distribution has been augmented by normal coordinate analysis (NCA). The most stable minimum energy conformer was identified by performing potential energy surface scan (PES) along the rotational bonds at the B3LYP/6-311++G(d,p) level of theory. The chemical reactivity and stability of PNC were estimated based on the HOMO-LUMO energy gap and NBO approach. The overall picture of accumulation of charges on individual atoms of the molecule was predicted by molecular electrostatic potential (MEP) surface map which in turn identifies the nucleophilic and electrophilic region or sites. The intermolecular interaction in the PNC was confirmed by using Hirshfeld surfaces. Antifungal activity of the compound with different bacterial strains was validated by the agar well diffusion method. Ligand-protein interaction was explored by using molecular docking studies, while the pharmacokinetic aspects of the compound were probed using drug likeness and Absorption, Distribution, Metabolism, Excretion, and Toxicity properties. The stability of the title compound has been investigated via molecular dynamics simulation (MDS). [ABSTRACT FROM AUTHOR]

The prospective antimicrobial molecule N-(2-Hydroxyphenyl)-4-methylbenzene sulfonamide has been synthesized and characterized by single crystal XRD, FT-IR, FT-Raman, UV-Vis spectra and antimicrobial analysis. The quantum chemical computations of energies, geometrical structure, charge transfer and vibrational wavenumbers were carried out using density functional method (DFT/B3LYP) with 6-311 G (d, p) basis set. The complete vibrational assignment for the vibrational modes were performed with vibrational energy distribution analysis (VEDA4) and these assignments were compared with the experimental FT-IR and FT-Raman spectrum. In FT-IR spectrum, strong intense absorption bands are observed at 3408 and 3273 cm−1 corresponding to OH and NH group, which is involved in N–H...O and C–H...O intermolecular interaction. Hirshfeld surface analysis determines the stability of crystal packing within the crystal packing ensured by C–H...O and O–H...O intermolecular interactions. The 2 D fingerprint plot shows that H...H, C...H and O...H interaction exhibit the most significant contribution. Natural bond orbital (NBO) analysis suggests that the electronic transitions are mainly attributed to π→π* transitions. The strength of N–H...O and C–H...O intermolecular interactions were analyzed using reduced density gradient (RDG) analysis and atom in molecule (AIM) analysis. The frontier molecular orbital analysis reveals the possibility of charge transfer within the molecule. Electrophilic and nucleophilic sites were found by molecular electrostatic potential (MEP) analysis and Fukui analysis. Molecular docking shows that sulfonamide and hydroxyl groups are biologically active through their hydrogen bonding interaction with amino acids, which reveals the antimicrobial activity of the compound. Antimicrobial activity of the compound was confirmed by the Kirby Bauer disk diffusion method. The band gap energy and antimicrobial evaluation of the title molecule were compared with the reported relative compounds, which reveals the significant antimicrobial activity. Besides, drug likeness and ADMET (absorption, distribution, metabolism, excretion and toxicity) prediction analysis suggest that the title compound can be used as an antimicrobial drug. [ABSTRACT FROM AUTHOR]

The polarizable continuum model was used for four different compounds to investigate the impact of substituent groups, of the number of π-electrons, of the electron-accepting and electron-donating properties on the corrosion inhibiting properties in both aqueous and gas phases for the neutral and cationic forms of the studied subsdtances. Measures for the corrosion prevention of metals are of great importance in the industrial, environmental (or ecologic), aesthetic, and economic fields. The use of inhibitors is the best way to preserve metals and alloys from corrosion. The purpose of this study was to apply quantum chemical calculations in the research of the corrosion inhibition and adsorption properties of four compounds with various heteroatoms or substituent groups but with similar chemical skeleton structures: 2-mercaptoimidazole, 2-mercapto-5-methyl benzimidazole, 2-mercaptobenzoimidazole, and 2-mercapto-5-nitrobenzimidazole, shown in Figs. 1 and 2 and designated as A, C, B, and D, respectively. The quantum chemical computations sector of the study gives complete calculation details and discussion on the correlation between corrosion inhibition and global reactivity descriptors such as the energy of the highest occupied molecule orbital, the energy of the lowest unoccupied molecule orbital, total energy, ionization energy, electron affinity, electronegativity, energy gap, hardness, softness, dipole moment, electron transfer, chemical potential, electrophilicity, nucleophilicity, and back-donation energy. The calculations were carried out using the general purpose computational chemistry software package Gaussian 09. The total calculations have been done based on the density functional theory at 6-311++G(d, p) basis set and applying the hybrid functional B3LYP level taking into account the exchange and the correlation with three parameters defining the hybrid Becke's functional (Becke—the exchange part, and Lee, Yang and Parr—the correlation part). Based on the calculations performed in this paper, the following summary ranking was obtained for the corrosion inhibition efficiency: A > B > C ≈ D for neutral forms and A > B > C > D for cationic forms in the gas phase, A > C ≈ D > B for neutral forms and A ≈ B > C > D for cationic forms in the aqueous phase. Thus, inhibitor A should be considered to be the best one in all cases. [ABSTRACT FROM AUTHOR]

We have here presented an extended theoretical and experimental study of hydroxyl radical (HR) trapping assay by ascorbic acid (AA). 2,4-Dimethoxyaniline (DMA) in the presence of hydrogen peroxide and horseradish peroxidase (HRP) produces an imine form of 2,4-DMA (DMA*), a violet colored product with an UV–Vis absorption maximum at 540 nm. The formation of the violet colored product was inhibited by the addition of AA. Fukui functions and dual descriptor enumerating the local and global electron densities of the atoms on the DMA, AA, and HR systems were calculated. The preferential electron density pattern on DMA, AA, and HR was assessed by left and right Fukui functionals at constant external potential. Highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap for DMA and AA were found to be 8.834 and 10.908 eV, respectively, and singly occupied molecular orbital–highest occupied molecular orbital (SOMO–HOMO) gap for HR was 16.872 eV. The global softness for DMA, HR, and AA was 12.99, 6.10, and 11.70, respectively. The electronic transitions (n to π* and π to π*) of the proposed colored product were simulated by time dependent-density functional theory (TD-DFT) calculation with its correlation with the practical UV–Vis data. Natural bond order analysis (NBO) and electrostatic potential (ESP) providing theoretical information on the relative electron density over the atomic position of AA and DMA were presented. This article can provide a unique way of understanding the position of HR radical attack on AA and DMA. [ABSTRACT FROM AUTHOR]

In this work, the structural conformation of pyrrole-2-carboxaldehyde was evaluated using potential energy surface (PES) scan employing DFT computations using B3LYP method with 6-311++G(d,p) level of basis set. The molecule assumed cis form in conformational ground state being more stable than the trans by 15.21 kJ mol−1 due to the orientation of the N–C–C = O dihedral angle. Existence of hydrogen bonds due to intra- and inter-molecular interactions was envisaged. The geometrical parameters of optimized monomeric and dimeric forms have been computed. The computational structural parameters of monomer are in good agreement with its experimental counterparts. The HOMO-LUMO energies were employed for determination of chemical reactivity descriptors. The electronic properties such as frontier molecular orbitals and Global reactivity descriptors were predicted using TD-DFT method. The local reactivity descriptors such as Fukui functions were investigated to determine the electrophilic and nucleophilic attacks within the molecule. The calculated first order hyperpolarizability value exhibited its suitability for non-linear optical applications. Furthermore, the electrophilic and nucleophilic regions of the molecule were studied by molecular electrostatic potential and Fukui functions. 1H and 13C NMR chemical shifts were evaluated using GIAO method employing the same level of theory. NPA analysis and thermodynamic parameters were also calculated. Determined the structure for monomer in cis form and dimer; and intra- and inter-molecular hydrogen bonding. NLO behavior was demonstrated from HOMO-LUMO band gap energy and first order hyperpolarizability. The reactivity sites for electrophilic, nucleophilic and radical attack were found from Fukui functions. MEP and NPA analysis were carried out. NMR chemical shifts, thermodynamic parameters and rotational constants were evaluated. [ABSTRACT FROM AUTHOR]

The goal of this study is to look at the development and use of green inhibitors in the electropolishing process (EP), as well as their potential as an anti-corrosive coating for C-steel in an acidic medium. We can replace environmentally dangerous substances with inexpensive, effective molecules that have little or no negative environmental impact like amino acids which are employed as safe inhibitors. The EP characteristics of C-steel were measured by galvanostatic techniques with different concentrations of amino acids over a wide range of (1-1000 × 10−6 mol/l) and temperatures (298–313 K). The findings indicate that the electropolishing behavior of C-steel is governed by mass transfer, with Fe2+ being proposed as the governing species for the salt film mechanism during anodic dissolution in the limiting current plateau. The experimental results indicate that increases in the amino acid concentrations inhibit the EP by 83.33% in the case of L-Methionine at 298 K. Density Functional Theory (DFT) was used to optimize geometry in the gas and liquid phases. The inhibition efficiency was associated with global reactivity descriptors, Fukui indices and dual local descriptors. The inhibitory performance is in good agreement with the estimated quantum chemical parameters, according to our findings.

A condensation reaction between formyl-containing spiropyrans and iodides of 1,2,3,3-tetramethyl-3H-indolium derivatives was studied. The reaction results in a mixture of products with a strong predominance of one of them irrespective of the structure of the starting compounds. The structures of the compounds formed during the reaction were determined based on the NMR, IR, and mass spectroscopy data. The dependence of the yield of the major reaction product on the structure of the starting compounds was studied. The prerequisites for the observed reaction pathway were established and the reaction mechanism was proposed using the results of quantum-chemical calculations based on analysis of the molecular electrostatic potential and the dual descriptor of reactivity. [ABSTRACT FROM AUTHOR]

Anthocyanidins, leucoanthocyanidins, and flavonols are natural compounds mainly known due to their reported biological activities, such as antiviral, antifungal, anti-inflammatory activities, and antioxidant activity. In the present study, we performed a comparative structural, conformational, electronic, and nuclear magnetic resonance analysis of the reactivity of the chemical structure of primary anthocyanidins, leucoanthocyanidins, and flavonoids. We focused our analysis on the following molecular questions: (i) differences in cyanidin catechols (+)-catechin, leucocyanidin, and quercetin; (ii) the loss of hydroxyl presents in the R1 radical of leucoanthocyanidin in the functional groups linked to C4 (ring C); and (iii) the electron affinity of the 3-hydroxyl group (R7) in the flavonoids delphinidin, pelargonidin, cyanidin, quercetin, and kaempferol. We show unprecedented results for bond critical point (BCP) of leucopelargonidin and leucodelphirinidin. The BCP formed between hydroxyl hydrogen (R2) and ketone oxygen (R1) of kaempferol has the same degrees of covalence of quercetin. Kaempferol and quercetin exhibited localized electron densities between hydroxyl hydrogen (R2) and ketone oxygen (R1). Global molecular descriptors showed quercetin and leucocyanidin are the most reactive flavonoids in electrophilic reactions. Complementary, anthocyanidins are the most reactive in nucleophilic reactions, while the smallest gap occurs in delphinidin. Local descriptors indicate that anthocyanidins and flavonols are more prone to electrophilic attacks, while in leucoanthocyanidins, the most susceptible to attack are localized in the ring A. The ring C of anthocyanidins is more aromatic than the same found in flavonols and leucoanthocyanidins. Methods: For the analysis of the molecular properties, we used the DFT to evaluate the formation of the covalent bonds and intermolecular forces. CAM-B3LYP functional with the def2TZV basis set was used for the geometry optimization. A broad analysis of quantum properties was performed using the assessment of the molecular electrostatic potential surface, electron localization function, Fukui functions, descriptors constructed from frontier orbitals, and nucleus independent chemical shift. [ABSTRACT FROM AUTHOR]

The present study aims to provide deeper knowledge about the structural, vibrational, chemical, antimicrobial activity, molecular dynamic simulation and drug likeness of synthesized compound 4-Methoxy-N-(nitrobenzylidene)-aniline. The FT-IR and FT-Raman spectra of 4-Methoxy-N-(nitrobenzylidene)-aniline have been recorded in the powder form in the region 4000–500 cm−1 and 3500–50 cm−1. The vibrational analysis were carried out with the help of normal coordinate analysis (NCA). The molecular geometry, hydrogen bonding interaction and vibrational frequencies have been calculated using the density functional method (DFT/B3LYP) with 6-311 G (D) basis set. The natural bond orbital (NBO), atoms in molecule (AIM), and Hirshfeld surface analysis and RDG were applied to evaluate the relative strength of hydrogen bond interactions and represent their effect on the stabilities of molecular arrangements. Related molecules were compared by computation in order to understand the effect of non-bonded interactions (i.e. intermolecular and intramolecular hydrogen bonding). The HOMO and LUMO analysis was used to determine the charge transfer within the molecule. Furthermore, the in vitro antimicrobial study was carried out for the title compound against Aspergillus niger and Staphylococcus aureus. The antimicrobial activity was confirmed on the compounds with molecular docking (A.niger, S.aureus, Homosapians, Sars-Cov-19 and anticancer) studies and molecular dynamic simulation. The non-linear optical (NLO) properties were also analyzed for the molecules. [ABSTRACT FROM AUTHOR]

Pyridine-3-carboxylic (or nicotinic) (P3CA) acid has been recorded by using different spectroscopic tools like NMR (13C, 1H), UV–Vis, FT-IR and FT-Raman spectral analysis. The structural conformation examined by potential energy scan for the titled compound was obtained by using DFT computations through B3LYP method with 6–311++G(d,p) basis set. Using optimized monomer structure, the dimeric structures (head-to-tail and tail-to-tail) are obtained. The title compound exhibits inter-molecular as well as intra-molecular hydrogen bonding forming a supramolecular network. The geometrical parameters of both monomer and dimer are coinciding with the observed ones. Using vibrational frequencies, Infrared and Raman intensities were computed. The rms error between the experimental and scaled quantum mechanical frequencies is 9.77 cm−1 for P3CA. From the scaled quantum mechanical method, reliable vibrational assignments were made using PED. The site of chemical reactivity and selectivity of the title compound were estimated from frontier molecular orbitals and local reactivity descriptors. The reactive areas around the compound were evaluated by using MESP. The interactions of donor and acceptor are studied by NBO analysis. The 13C and 1H NMR chemical shifts of the title compound were determined using the gauge independent atomic orbital (GIAO) method in DMSO-d6 solution. By using UV–visible spectrum, the maximum absorption wavelength was obtained and compared with the TD-DFT method. [ABSTRACT FROM AUTHOR]

Herein, we report a quantum chemistry investigation of the interaction between µ-truxinic acid, referred to as TXA0, and Y+ (Y = Li, Na, K) and Z− (Z = F, Cl, Br) ions using M06-2X, B3LYP and ω B97XD functionals in conjunction with the 6–31 + + G(d,p), aug-cc-pVDZ(-X2C) and 6–311 + + G (d, p) basis sets. Our computations suggest that Y+ cations can bind to TXA0 through several combinations of cation...O and cation-π interactions, while Z− anions generally establish anion...H–O contacts. Predicted binding energies at the M06-2X/6–311 + + G(d,p) level range between − 26.6 and − 70.2 kcal/mol for cationic complexes and − 20.4 and − 62.3 kcal/mol for anionic ones. As such, TXA0 appears as an amphoteric molecule with a slight preference for electrophilic (cation... O) attacks. Furthermore, the most favourable binding site for cations allows for the formation of O...cation...O interactions where the cation is trapped between O37 and O38 atoms of TXA0. Anions do not behave uniformly towards TXA0: while the fluoride anion F− induces the deprotonation of TXA0, Br− and Cl− do not. All of these structural insights are supported by topological calculations in the context of the quantum theory of atoms in molecules (QTAIM). Finally, SAPT0 analyses suggest that TXA0...Y+ and TXA0...Z− complexes are mainly stabilized by electrostatic and inductive effects, whose combined contributions account for more than 60 percent of the total interaction energy. [ABSTRACT FROM AUTHOR]

• A diversity of novel annulated pyrido[2,3- d ]pyrimidines were synthesized. • DFT calculations using B3LYP/6–311++ G (d,p) basis set support the experimental data. • Molecular reactive sites were discovered using MEP and Fukui functions. • The ADME analysis and molecular docking were carried out. • In vitro anticancer efficiency was examined. 6-Amino-1,3-dimethyluracil (1) has two electron donating centres (NH 2 and C-5) and its chemical reactivity was investigated towards a variety of electrophilic reagents hoping to construct some novel heteroannulated pyrido[2,3- d ]pyrimidines. The key precursor 1 reacted with some o -chloroaldehydes through condensation between activated C-5 and the formyl group followed by heterocyclization with elimination of HCl. Also, reaction of compound 1 with some o -aminoaldehydes occurred through a similar mechanism. In addition, reaction of precursor 1 with some arylidenes took place through addition of C-5 to the activated double bond followed by cycloaddition of the amino group onto the cyano function with concomitant aromatization. The synthesized compounds were characterized using spectroscopic techniques and evaluated for in vitro anticancer activity against HepG-2 cell lines where compound 4 was found to be the most potent (IC 50 =3.99 µM). The optimized structures, HOMO-LUMO energies and chemical reactivity descriptors of the synthesized compounds were computed by density functional theory (DFT) calculations using the B3LYP/6–311++ G (d,p) basis set. Compound 13 has the lowest energy gap (2.90 eV) and therefore is more the reactive and polarizable than other compounds. The sites for electrostatic interactions are identified using molecular electrostatic potential (MEP). The frequencies calculated by FT-IR showed good agreement with those derived from the experimental findings. Theoretical 1H and 13C NMR chemical shift values were calculated using GIAO method and compared with experimental values using linear correlation factor (R2). Moreover, the nucleophilic and electrophilic reactive sites were probed by Fukui functions accompanying the optimized structures using DFT. The first hyperpolarizabilities (β tot) of the prepared compounds are higher than the reference urea; indicating good nonlinear optical properties and are excellent materials for NLO applications. All the current compounds adhered to the Lipinski, Veber and Ghose rules that were a set of parameters used in ADME studies. In addition, the binding interactions of the synthesized compounds were investigated by molecular docking studies with aromatase enzymatic protein (PDB id: 31G7) receptor and correlated with anticancer activity. [Display omitted] [ABSTRACT FROM AUTHOR]

The compounds N-(2-nicotinoylhydrazine-1-carbonothioyl)benzamide (H3L1) and its isomer N-(2-isonicotinoylhydrazine-1-carbonothioyl)benzamide (H3L2) type N, S, O donors, by reaction of benzoyl isothiocyanate with nicotinic hydrazide and isoniazid respectively were synthesized. The H3L1 and H3L2 compounds were characterized by 1H-NMR, 13C-NMR, FT-IR and elemental analysis. Computational analysis using the Fukui functions were performed to determine the reasons why the 1,2,4-triazoles were not formed. Preliminary tests of the synthesized compounds were carried out against Staphylococcus aureus (Gram+) and Escherichia coli (Gram-), having demonstrated signifi cant activity against such bacteria. [ABSTRACT FROM AUTHOR]

Herein, a screen–printed diamond electrode (SPDE) coupled with a "point-of-care" platform (30 µL-drop concepts, single-drop-detection approach) was successfully applied for the electrochemical determination of pterostilbene (PTS). Cyclic voltammetry identified irreversible oxidation of PTS, where oxidation peak was shown to be strongly dependent on the pH of the working environmental. Although the proposition of the detailed electrochemical oxidation mechanism of PTS goes out of the scope of the present research, we have determined the most probable reactive site of our analyte, by utilizing DFT-based reactivity descriptors (Fukui functions). For electrochemical quantification of PTS, oxidation peak at 0.32 V (vs. Ag/AgCl) was followed in presence of 0.5 mol L−1 of Briton–Robinson buffer solution (pH = 9). Coupled with the optimized parameters of differential pulse voltammetry (DPV), SPDE detected PTS in two linear ranges (first range was from 0.011 to 0.912 µmol L−1; second range was from 0.912 to 4.420 µmol L−1), providing the LOD and LOQ on a nanomolar level (3.1 nmol L−1 and 10.0 nmol L−1, respectively). The selectivity of the optimized DPV method was found to be excellent, with the current changes of less than 7%, in the presence of ten times higher concentrations of the certain interferences. The practical applicability of the SPDE and single-drop-detection approach in dietary supplements (with a declared PTS content of 50 mg/tablet), with the recovery values ranging from 95 to 102%, shows that the developed method has high potential for precise and accurate PTS detection, as well as exceptional miniaturization possibilities of relevant equipment for on-site sensing. [ABSTRACT FROM AUTHOR]

Interactions between alumina and cryolite clusters were investigated using chemical reactivity descriptors based on conceptual DFT such as global hardness, η, global softness, S, fukui functions, f, and local softness, s. Hard and Soft Acids and Bases (HSAB) Principle was applied for identifying clusters that are most likely to interact with alumina, Al2O3. Local reactivity descriptors were employed to predict the most probable regions of interaction within the cluster. [ABSTRACT FROM AUTHOR]

Glycerol (G) is the major co-product in the transesterification process of biodiesel. As clean energy demand increases, the production of G also increases and new ways of re-using it are needed. In the last decade, some experimental studies claimed that G and its derivative, malonic acid (MA), could be used as corrosion inhibitors. Yet, presently, there is little evidence of it and more studies are needed to confirm that G and MA could have a good performance in metal protection. The present work aims to study the reactivity of G and MA, since reactivity and inhibition are intimately linked. The density functional theory (DFT) at the B3YLP/6-31G** level of theory was used to study the reactivity of both molecules. The global and local quantum parameters derived were used to assess the reactivity of both molecules. Analysis of the calculated reactivity descriptors suggest that G and MA should exhibit an acceptable corrosion efficiency, but MA showed have a greater potential as a corrosion inhibitor.

Six amino acids were studied for their corrosion inhibition properties, taking into account the experimental results. The computed quantum chemical descriptors gave almost the same trend in high precision, and this matching reveals the reliability of computational calculations in this field of research. The reactivity of the investigated amino acids was found to be in the order; tryptophan > methionine > proline > leucine > valine > alanine, where alanine showed the lowest inhibition efficiency while the tryptophan showed the highest efficiency and that may be due to its π system which enables to donate π electrons to the metal surface or accept through antibonding π* character through back donation process. QSAR also gave the same expectations with high correlation with the experimental results. Also, The Monte Carlo simulation predicted the best adsorption mode for the investigated compounds which looks planner on the metal surface. [ABSTRACT FROM AUTHOR]

The goal of this study is to look at the development and use of green inhibitors in the electropolishing process (EP), as well as their potential as an anti-corrosive coating for C-steel in an acidic medium. We can replace environmentally dangerous substances with inexpensive, effective molecules that have little or no negative environmental impact like amino acids which are employed as safe inhibitors. The EP characteristics of C-steel were measured by galvanostatic techniques with different concentrations of amino acids over a wide range of (1-1000 × 10−6 mol/l) and temperatures (298–313 K). The findings indicate that the electropolishing behavior of C-steel is governed by mass transfer, with Fe2+ being proposed as the governing species for the salt film mechanism during anodic dissolution in the limiting current plateau. The experimental results indicate that increases in the amino acid concentrations inhibit the EP by 83.33% in the case of L-Methionine at 298 K. Density Functional Theory (DFT) was used to optimize geometry in the gas and liquid phases. The inhibition efficiency was associated with global reactivity descriptors, Fukui indices and dual local descriptors. The inhibitory performance is in good agreement with the estimated quantum chemical parameters, according to our findings. [ABSTRACT FROM AUTHOR]

• Thirteen N,N -disubstituted chloroacetamides were synthesized as covalent inhibitors • Several chloroacetamides effectively activated both extrinsic and intrinsic apoptotic pathways • 3D QSAR and pharmacophoric similarity search suggested alcohol-metabolizing enzymes as promising targets • Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) identified as potential anticancer targets through pharmacophoric similarity search. • Docking studies demonstrated hydrogen bonds and hydrophobic interactions with ADH and ALDH. The recent FDA approval of afatanib, ibrutinib, and osimertinib, which covalently bind to specific cysteine residues in target kinases, has renewed interest in covalent drug discovery. Besides α,β -unsaturated carbonyls, chloroacetamides have emerged as popular warheads for designing targeted covalent inhibitors. In this study, we synthesized thirteen N,N -disubstituted chloroacetamides (1 – 13) by acylating secondary amines with chloroacetyl chloride, selecting substituents to provide a wide range of lipophilicity. We evaluated their anticancer and antimicrobial activity, finding five compounds with significant cytotoxicity against HeLa, K562, and A549 cell lines (IC 50 <10 μM). Notably, compound 10 activated caspases 3, 8, and 9, promoting both intrinsic and extrinsic apoptotic pathways, while compounds 9 – 12 were strong apoptosis inducers. A 3D QSAR model showed that aromatic substituents on nitrogen atoms reduced HeLa potency, whereas the overall molecular shape had a positive effect. ChemBL and pharmacophoric similarity searches suggested potential anticancer targets, including alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), glycogen synthase kinase-3β, and calmodulin. Docking studies indicated that chloroacetamides bind to ADH and ALDH via hydrogen bonds and hydrophobic interactions. Pharmacokinetics predictions suggest that chloroacetamides are druglike molecules with promising ADMET properties. [ABSTRACT FROM AUTHOR]

• The reactivity of substrate 3 was investigated towards binucleophiles. • Chromone moieties are more reactive than α,β-unsaturated ketone segment. • DFT/B3LYP/6-311G++(d,p) was used to discuss theoretical calculations. • ADME analysis and molecular docking studies were assessed. • The NMR were estimated theoretically and well-matched with experimental results. The electron deficient centers in α,β-unsaturated ketone 3 are C-2 and C=O of chromone moieties as well as C=O and H-β of α,β-unsaturated ketone segment. To investigate the reactivity of various electron deficient centers and to synthesize some heterocyclic systems, compound 3 was allowed to react with some binucleophilic reagents. The antimicrobial activity of some compounds showed a notable inhibitory effect on the microorganisms that were being studied. The synthesized compounds were verified by spectral and analytical data. The structure of the prepared compounds were optimized at the DFT/B3LYP level of theory employing 6-311G(d,p). Density Functional Theory (DFT) was used to compute the chemical reactivity descriptors. Compound 9 is more stable and less reactive than other compounds. MEP mapping was applied at the same computational level to identify the favored locations for electrophilic and nucleophilic assault, providing additional insight into the regioselectivity in the desired reaction. Moreover, the most reactive sites of compound 3 were investigated by Fukui function descriptor using Mulliken charges. The 13C and 1H-NMR spectra of the prepared compound were measured experimentally in DMSO, and correlated with the theoretical calculations that performed by 6-311G(d,p) of DFT-B3LYP method. All compounds met Veber's and Lipinski's requirements according to in silico predictions made with the SwissADME online server, suggesting the possibility for usage as oral active drugs. The synthesized compounds were also subjected to molecular docking studies to investigate their binding pattern and affinity for the CDKs active site and correlated with antimicrobial data. [ABSTRACT FROM AUTHOR]

• Experimental and theoretical spectral investigation of dihydro-pyrimidines. • Experimental and theoretical Fourier transform infrared (FT-IR) spectra were recorded and compared. • Experimental and theoretical IRaman were also calculated and compared. • A benchmark analysis was performed by employing DFT functions by estimating HOMO to LUMO UV transitions, band gaps (eV) and oscillator strength φ by comparing with experimental λ max. Theoretical 1H and 13C NMR chemical shift values. • In addition, Muliken charges, natural population analysis (NPA), fukui functions, and thermodynamic parameters were calculated. In this article, theoretical and experimental study is presented for eight derivatives of dihydro-pyrimidinones (symbolized as U1-U6, U10 and U11). The Fourier transform infrared (FT-IR) spectra of dihydro-pyrimidinones were recorded in the range of 4000cm−1 to 400cm−1 in solid phase and compared with experimental vibrational assignments. The potential energy distributions (PED) was assigned to each scaled vibrational wavenumber value by using Vibrational Energy Distribution Analysis (VEDA4) program. In order to get insight into electronic properties and a good UV absorber compound Time Dependent Density Functional Theory (TF-DFT) approach was taken into consideration. A benchmark analysis was performed by employing DFT functional B3LYP, HSEH1PBE, MPW1PW91, WB97XD by estimating HOMO to LUMO UV transitions, band gaps (eV) and oscillator strength φ by comparing with experimental λ max. Theoretical 1H and 13C NMR chemical shift was calculated using GIAO method and compared with already published experimental NMR chemical shift values by using linear correlation factor R2. Electron poor, rich and reactive sites were probed by Mulliken atomic charge, natural population analysis (NPA) and fukui functions accompanying the optimized structures by utilizing density functional theory (DFT) methods with B3LYP function and 6–311 G (d, p) as basis set. In last vibrational assignments were subjected to thermodynamic parameter calculations using Moltran v.2.5. program. [Display omitted] [ABSTRACT FROM AUTHOR]

This work presents a significant investigation involving both electrochemical experiment and quantum chemical simulation approaches. The objective was to characterize the electrochemical detection of dopamine (DA). The detection was carried out using a modified carbon paste electrode (CPE) incorporating bentonite (Bent) and l -cysteine (CySH) (named as CySH/Bent/CPE). To understand and explain the oxidation mechanism of DA on the CySH/Bent modified electrode surface, the coupling of the two approaches were exploited. The CySH/Bent/CPE showed excellent electroactivity toward DA such as good sensibility, selectivity, stability, and regenerative ability. The developed sensor shows a dynamic linear range from 0.8 to 80 μM with a limit of detection and quantification of 0.5 μM and 1.5 μM, respectively. During the quantitative analysis of DA in presence of ascorbic acid (AA) and uric acid (UA) the electrochemical oxidation signals of AA, DA, and UA distinctly appear as three separate peaks. The potential differences between the peaks are 190 mv, 150 mv, and 340 mV for the AA–DA, DA–UA, and AA–UA oxidation pairs, respectively. These observations stem from square wave voltammetry (SWV) studies, along with the corresponding redox peak potential separations. The developed sensor is simple and accurate to monitor DA in human serum samples. On the other hand, CySH acts as an electrocatalyst on the CySH/Bent/CPE surface by increasing its active electron transfer sites, as suggested by the quantum chemical modeling with analytical results of Fukui. Furthermore, the voltammetric results obtained agree well with the theoretical calculations. [Display omitted] • Electrochemical experiments and quantum chemical simulations were performed. • Bent and CySH were employed to modify CPE. • The device is simple and precise to monitor DA in serum. • The analytical results from Fukui suggests that CySH acts as an electrocatalyst. • The sensor showed excellent response to DA with an LOD of 0.5 μM. [ABSTRACT FROM AUTHOR]

The cyclic anhydrides are broadly employed in several fields, such as the chemical, plastic, agrochemical, and pharmaceutical industries. This study describes the chemical reactivity of 4,5-dichlorophthalic anhydride towards several nucleophiles, including thiosemicarbazide and different amines, to produce the carboxylic acid derivatives resulting from anhydride's opening, namely, phthalimide and dicarboxylic acid (1–12) products. Their chemical structures are confirmed by NMR, IR and MS spectra analyses. Density–functional theory (DFT) studies are performed using (DFT/B3LYP) with the 6-311G(d, p) basis sets to recognize different chemical and physical features of the target compounds. [ABSTRACT FROM AUTHOR]

An experimental and theoretical study based on DFT/TD-DFT approximations is presented to understand the nature of electronic excitations, reactivity, and nonlinear optical (NLO) properties of reactive orange 16 dye (RO16), an azo chromophore widely used in textile and pharmacological industries. The results show that the solvent has a considerable influence on the electronic properties of the material. According to experimental results, the absorption spectrum is formed by four intense transitions, which have been identified as π → π ∗ states using TD-DFT calculations. However, the TD-DFT results reveal a weak n → π ∗ in the low-lying spectral region. Continuum models of solvation indicate that these states suffer from bathochromic (ca. 15 nm) and hypsochromic shifts (ca. 4 nm), respectively. However, the expected blue shift for the absorption n → π ∗ is only described using long-range or dispersion-corrected DFT methods. RO16 is classified as a strong electrophilic system, with electrophilicity ω > 1.5 eV. Concerning the nucleophilicity parameter (N), from vacuum to solvent, the environment is active and changes the nucleophilic status from strong to moderate nucleophile (2.0 ≤ N ≤ 3.0 eV). The results also suggest that all electrical constants are strongly dependent on long-range and Hartree-Fock exchange contributions, and the absence of these interactions gives results far from reality. In particular, the results for the NLO response show that the chromophore presents a potential application in this field with a low refractive index and first hyperpolarizability ca. 214 times bigger than the value usually reported for urea (β = 0.34 × 10− 30 esu), which is a standard NLO material. Concerning the solvent effects, the results indicate that the polarizability increases ∼ 20 × 1 0 − 24 esu from gas to solvent while the first hyperpolarizability is calculated as ∼ 45 × 1 0 − 30 esu, ca. 180%, regarding the vacuum. The results suggest RO16 is a potential compound in NLO applications. [ABSTRACT FROM AUTHOR]

We review the early works which were precursors of the Conceptual Density Functional Theory. Starting from Thomas–Fermi approximation and from the exact formulation of Density Functional Theory by Hohenberg and Kohn's theorem, we will introduce electronegativity and the theory of hard and soft acids and bases. We will also present a general introduction to the Fukui functions, and their relation with nucleophilicity and electrophilicity, with an emphasis towards the importance of these concepts for chemical reactivity. [ABSTRACT FROM AUTHOR]

In this study, the structure and various molecular parameters of 4-bromo-3-(methoxymethoxy) benzoic acid are determined at the B3LYP/6-311++G(d,p) level of theory. Present study provides comparision and discussion of calculated and experimental optimized parameters. The values of descriptors such as ionization energy, hardness, electrophilicity, condensed Fukui function and energy were determined to predict the reactivity of 4-bromo-3-(methoxymethoxy) benzoic acid. The influence of the solvent on reactivity parameters has been studied  adopting the PCM model. The analysis shows that solvation alters the values of reactivity descriptors. A vibrational assessment of the molecule has also been performed. To gain a better understanding of the properties of the title molecule, parameters such as the molecular electrostatic potential surface and the HOMO-LUMO band gap have been computed. The dipole moment, polarizability and hyperpolarizability were also estimated to probe into non-linear optical properties of the chemical. [ABSTRACT FROM AUTHOR]

Heterocyclic compounds are mostly used in pharmaceutical purposes. In this present study, we investigated molecular structure properties, delocalization of charge and energy density of atoms of 6-phenylpteridine 2,4,7-triamine. The topological properties like as the electron localization function and the laplacian of the electron density are calculated with the help of Bader's Atoms in Molecules theory. Linear polarizability parameters are calculated. Band gap energy (Bgap= 3.9253 eV) of headline compound is predicted from the highest occupied molecular orbital and lowest unoccupied molecular orbital's (HOMO-LUMO) energies. Reactive sites are identified from molecular electrostatic potential. Drug likeness and absorption, distribution, metabolism, excretion and toxicity (ADMET) properties are studied. Molecular docking is performed to explore the detailed biological information of headline compound. Protein ligand interaction is found with two bacterial targets. [ABSTRACT FROM AUTHOR]

The structural and biological mechanism of a drug material was investigated by spectroscopic techniques and molecular modeling methods. The experimental spectroscopic techniques, namely Fourier Transform Infrared and Fourier Transform Raman spectroscopies are recorded for the structural confirmation and were also compared with computed values. The stability of the compound, the intermolecular and intra molecular interactions is studied using the density functional theory tool Gaussian 16 W. The optimized molecular geometry, vibrational wavenumbers, infrared intensities, and Raman scattering activities are calculated. Natural Bond Orbital analysis has been carried out to explain the charge transfer (or) delocalization of charge due to the intra molecular interactions. The Time dependent-Density functional theory is used to evaluate the excitations between different energy levels, the interpretation which affords good information about D-(-)-alpha-Phenylglycine's electronic properties with different solvation effects. Reactive sites were also analyzed using topological studies. To explore the biological activities docking studies of D-(-)-alpha-Phenylglycine is performed with Prolactinoma and hyperprolactinemia diseases. [ABSTRACT FROM AUTHOR]

Both intramolecular [4 + 2] and intermolecular [3 + 2] cycloaddition reactions for the synthesis of 1,3-dioxoepoxyisoindole and epoxypyrrolo[3,4-g]indazoles, respectively, experimentally explored by Alizadeh and co-workers, were studied theoretically at the M06-2X/6-311G(d,p) computational level in both gaseous and solution (acetonitrile, benzene and DMSO) phases. In the first stage, it was studied the intramolecular [4 + 2] cycloaddition reaction generating potentially two diastereomeric adducts and it was confirmed the formation of experimentally reported product, 1,3-dioxoepoxyisoindole DEI-1 by the local reactivity indices as well as potential energy surface analysis. In the second stage, the [3 + 2] cycloaddition reaction of DEI-1 with three nitrilimines including NI–H, NI-C and NI–N, which generates potentially four possible regio- and stereoisomeric adducts was studied. The local reactivity indices described satisfactorily the experimentally observed regioselectivities. The results of potential energy surface analysis indicated that among the four possible products, only two exo regioisomeric adducts (namely, epoxypyrrolo[3,4-g]indazoles, CA-x1 and CA-x2) can be formed. In fact, for the reaction of DEI-1 with NI–H, NI-C and NI–H, the ratio of CA-x1:CA-x2 was estimated to be 57:43, 86:14 and 39:61, respectively, which is in satisfactory agreement with the experimental outcomes. The structural variations during the reactions were also studied and the results indicated that the transition states are not completely synchronous. [ABSTRACT FROM AUTHOR]

The pollution of water bodies with ciprofloxacin (CF) and other antibiotics has resulted in undesirable characteristics, such as color, odor and microbial resistance in environmental waters. Using agricultural waste as biosorbents for the removal of antibiotics from wastewater is a promising treatment approach. This research was based on the treatment of CF-polluted water by utilizing acid-modified Dialium guineense (tamarind) seed waste (HA-DGS), prepared by hydrochloric acid treatment of Dialium guineense seed (DGS). HA-DGS exhibited a maximum CF uptake of 125 mg/g, which was higher than most adsorbents reported in the literature. The DGS and HA-DGS were characterized by the FTIR, SEM, EDX, TGA and BET analyses. The acid modification was optimized by the application of response surface methodology using central composite design. Batch methodology showed that HA-DGS had higher CF uptake than DGS at variations of pH, temperature, contact time, adsorbent dosage and CF concentration. The Freundlich isotherm with R2 > 0.9795 was more applicable to both adsorbents, while DGS conformed to the pseudo-second-order kinetic (R2 > 0.9939) and HA-DGS (R2 > 0.9085), to the pseudo-first-order kinetics. Thermodynamics showed a physical and exothermic uptake of CF on the adsorbents. HA-DGS exhibited a maximum CF uptake of 125 mg/g, which was higher than most adsorbents reported in the literature. Quantum chemical parameters and condensed Fukui functions revealed efficient interaction between CF molecules and the prepared materials. Over 60% desorption of CF was obtained from the CF-loaded adsorbents using water and HCl solution. The results of this research showed HA-DGS as an efficient, low-cost, waste material that can be optimally valorized in the treatment of wastewater contaminated with CF. [ABSTRACT FROM AUTHOR]

Quantum chemical study, based on DFT methods at B3LYP/6-31G (d, p) level of theory, of four tetrazole compounds, denoted Ph-T, Me-Ph-T, MeO-Ph-T, Cl-Ph-T and reported as corrosion inhibitors in acidic medium, has been investigated in an attempt to find relationships between their molecular electronic properties and their corresponding experimental corrosion inhibition efficiencies. The global reactivity descriptors, such as the frontier molecular orbital energies (EHOMO and ELUMO), energy gap ∆E, electronegativity χ, absolute hardness η and softens σ, fraction of electrons transferred ∆N as well as local selectivity parameters such as Natural Atomic Populations and Fukui indices were also calculated and discussed. The calculations were undertaken in both gaseous and aqueous states for a better approach of the experimental conditions. The results showed that Cl-Ph-T presented the lowest ELUMO and the highest χ indicating its high electron acceptor ability, which can explain its good corrosion inhibition efficiency when compared to the three-other studied tetrazole derivatives. [ABSTRACT FROM AUTHOR]

An attempt was made to determine the ground state and excited state dipole moments and quantum chemical computations of two coumarin compounds, namely 3‐hydroxy‐3‐[2‐oxo‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐ethyl]‐1,3‐dihydro‐indol‐2‐one (3HOCE) and 3‐[2‐(8‐methoxy‐2‐oxo‐2H‐chromen‐3‐yl)‐2‐oxo‐ethylidene]‐1,3‐dihydro‐indol‐2‐one (3MOCE). Both compounds displayed a red shift with enhancement in solvent polarity. The larger excited state dipole moment indicated the more polar nature of the selected compounds in the excited state than in the ground state. Kinetic stability and chemical reactivity of the selected compounds were studied with help of the quantum chemical properties of the compounds such as frontier molecular orbital analysis using density functional theory calculations with B3LYP/6–311+G (d, p) basis sets. Molecular electrostatic potential, Mulliken charges, natural bond orbital, and nonlinear optical properties were further studied. NBO analysis showed proton transfer within the selected donor–acceptor, depicting the large energy of stabilization for the compounds. The calculated Fukui function inferred the local softness and electrophilicity indices of used solute compounds. [ABSTRACT FROM AUTHOR]

The solvatochromic studies in a Quinoline derivative molecule namely Quinolin-8-ol (QO) have been carried out at ambient temperature using absorption and fluorescence spectroscopy. The QO molecule shows the bathochromic shift with increase in solvent polarity demonstrating π → π* transition. The solvatochromic data coupled with quantum mechanical calculations has been used to estimate change in dipole moment of the molecule after excitation. It has been found that excited state dipole moment is greater than the corresponding ground state dipole moment. Further, it is observed that excited and ground state dipole moments are parallel. The chemical reactivity and kinetic stability of QO molecule are investigated using Frontier molecular orbital (FMO) analysis. Natural bond orbital (NBO) analysis shows proton transfer within the selected donor-acceptor depicting large energy of stabilization for QO molecule. The calculated Fukui functions infer the local softness and local eletrophilicity index of QO molecule. The theoretically simulated UV-Vis absorption spectrum of QO molecule matches well with the experimental spectrum. [ABSTRACT FROM AUTHOR]

Quercetin is the most abundant flavonoid with potent antioxidant activities. In the current research, the antioxidant properties of quercetin and quercetin-DNA complex were investigated theoretically and experimentally. Free radical scavenging experiments with thiobarbituric acid–reactive substances (TBARS) and 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) indicate that quercetin can protect DNA from free radical damage, and the antioxidant activity of the quercetin-DNA complex is stronger than quercetin. Deoxyriboseadenine-quercetin-dimethylphosphinic acid (DA-Q-P) model was extracted from molecular docking. The contributions of hydroxyl groups in quercetin and DA-Q-P model molecules to the antioxidant activity were investigated by computation of bond dissociation enthalpy (BDE) parameter and Fukui function, at B3LYP/6-311++G(2d,2p) level of theory. The results outlined that the hydroxyl groups from the B ring (3′-OH and 4′-OH) have a lower BDE compared with the ones from the A and C rings (3-OH, 5-OH, and 7-OH) and hence define antioxidant activity. The computational result based on Fukui function shows that the B ring is an electrophilic region. The interaction of antioxidant with DNA discovered at the molecular level could provide the structural basis of the antioxidant property of active ingredients in the flavonoids. It is of great significance to study the interaction mechanism between the small drug molecules with DNA at the molecular level. [ABSTRACT FROM AUTHOR]

Obtaining reactivity information from the molecular electronic structure of a chemical system is a computationally intensive process. As a way of probing reactivity information around that, there exist electron density response variables, such as the Fukui functions (FFs), which are well‐established descriptors that summarize the local susceptibility to react. These properties only require few single‐point quantum chemical calculations, but even then, the intrinsic high cost and unfavorable computational complexity with respect to the number of atoms in the system makes this approach available only to small fragments and systems. In this study, we explore the computation of FFs, showing that semiempirical quantum chemical methods can be used to obtain the reactivity information equivalent to that of a Density Functional Theory (DFT) functional, for the eight entire polypeptide chains. The combination of semiempirical methods with the frozen orbital approximation allows for the obtention of these reactivity descriptors for biological systems with reasonable accuracy and speed, unlocking the utilization of these methods for such systems. These results for the frozen orbital approximation can be additionally improved when other molecular orbitals from the frontier band are employed in the computation. We also show the potential of this computational protocol in the ligand–protein complexes of HIV‐1 protease, predicting which of those ligands are active inhibitors. [ABSTRACT FROM AUTHOR]

The B3LYP/6-31G(d,p) calculations were conducted to establish a correlation between structural electronic properties and corrosion inhibition efficiencies of four quinoxaline derivatives. The Fukui functions reflecting the local reactivity centers were investigated to determine the Fe-complexes by the studied ligands. Three spin multiplicities were examined and the quintet complexes were the most stable. Five types of interactions between Fe and quinoxaline compounds were studied, i.e., Fe–2S, Fe–2O, Fe–ϕ, Fe–S, and Fe–O among 10 complexes. While the calculated binding energies of the chelating bidentate complexes Fe–2O/2S were the lowest, Fe–ϕ presented a higher energy value without loss of aromaticity. [ABSTRACT FROM AUTHOR]