IEFPCM Model Research Articles

Investigation of the electronic properties of solvents (water, benzene, methanol) using IEFPCM model, spectroscopic investigation with docking and MD simulations of a thiadiazole derivative with anti-tumor activities

6-(4-Chlorophenyl)-3-(thiophen-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]-thiadiazole (CLP) was synthesized and spectroscopic investigations have been made experimentally and theoretically. The electrostatic potential maps showed the reactive sites in CLP compound and its halogenated derivatives. The various chemical descriptors and NLO properties are predicted and compared for CLP with its halogenated derivatives. The stability of CLP was studied with NBO analysis. For diverse solvents (water, benzene, and methanol) and gas phase, UV–vis spectra are being used to assess the electronic transition. Binding affinities with target protein were carried out which gave the effects of bio-efficiency due to the halogen substitution. The binding affinity values were increasing from that of the parent molecule and are high for meta substitutions (with chlorine positional changes). The MD simulations and docking studies suggested inhibitory activity against CDK2 and could be considered as anticancer candidates.

Synthesis of benzidine-based conjugated organic materials bearing donor-acceptor groups: DFT studies and photovoltaic applications

Herein, tetraethoxymethyl, diphenyl, and dipyrenyl units have been fused with biphenyl group, via diimine bond, resulting in 3 (2 novel) benzidine derivatives 2, 4a-b. The derivatives were successfully synthesized by condensation of three different aldehydes (formaldehyde, benzaldehyde 3a, and pyrenecarboxaldehyde 3b) with benzidine in high yields. Structural identifications of the newly obtained compounds are determined by NMR, IR, UV–Vis, and HRMS spectroscopic techniques. Then, the photovoltaic properties of the organic compounds were investigated. To obtain insight into the geometric, electronic, and spectroscopic features of compounds 2, 4a-b, theoretical calculations were performed utilizing the B3LYP/6–311G(2d,2p) basis set. Theoretical 1H and 13C NMR resonance signals of compounds 2, 4a-b were estimated in the gas phase and the IEFPCM model in solvent field calculations utilizing the GIAO method at the B3LYP/6–311G(2d,2p) level and showed excellent correlation with the experimental results. A comparison of computed and experimental vibrational frequencies was performed, and significant bands were allocated. The results showed that experimental and theoretical IR frequencies had a good correlation (R2=0.9997 (2), 0.9996 (4a), and 0.9940 (4b)). To explain the relationship between the molecular structure of the compounds and photovoltaic properties, density functional theory (DFT) and its time-dependent form (TD-DFT) were utilized. The HOMO-LUMO energies and energy gap (Eg) helped understand optimal energy levels for electron absorption and transfer. The calculated band-gap of compounds 2, 4a-b were 4.705, 3.679, and 3.006 eV, respectively. The power conversion efficiency (PCE) values for the compounds 2, 4a-b were also calculated as 2.25, 2.70, and 2.80%, respectively. Compared to compounds 2 and 4a, dipyrenyl-bearing benzidine derivative 4b showed a larger redshift in the absorption wavelength with a remarkable high PCE value along with a low Eg value, which can be attributed to the greater stability of 4b due to the extended π-conjugation.Therefore, compound 4b with the d-A-π-A-D architecture is a potential candidate as useful electron transport material for DSSCs.

Electronic properties of solvents (Water, Benzene, Ethanol) using IEFPCM model, spectroscopic exploration with drug likeness and assessment of molecular docking on 1-Octanesulfonic Acid Sodium Salt

Quantum chemical techniques, such as DFT, have become important tools in the examination of molecular structure and vibrational spectrum, and are finding widespread application in biological systems. The antiviral and antioxidant substance 1-Octanesulfonic Acid Sodium Salt has a prospective application in medicine. The current study presents experimental and theoretical reports on the improved geometrical structure, electronic and vibrational properties of 1-Octanesulfonic Acid Sodium Salt using the B3LYP method with the 6–311++G (d, p) basis set. The Infra-Red and Raman spectra of the compound 1-Octanesulfonic Acid Sodium Salt(1OSASS) are explored. UV–vis spectra are being used to assess the electronic transition for different solvents (Water, Benzene, and Ethanol) and gas phase. The geometry of the examined molecule was enhanced. The VEDA programme was used to measure the vibrational assignments and PED (potential energy distribution). The transfer of charges was extensively evaluated by NBO. The electron excitation properties are reflected by the predicted energies of HOMO and LUMO. Electrophilic and nucleophilic sites were discovered during a study of molecular electrostatic potential. ELF and LOL interpretation, as well as drug likeness, environmental toxicity is all accomplished. Molecular docking was used to determine the hydrogen bond lengths, intermolecular energy and binding energy of the investigation title molecule in order to study its biological activity.

Spectroscopy and second hyperpolarizability of odd spin states of acetonitrile: Theoretical study

The present study reports the spectroscopic characterization and second hyperpolarizability of odd spin states of acetonitrile in gas phase and water solvent. The odd spin states of acetonitrile are singlet, triplet and quintet spin state of acetonitrile have been considered for the study. The spectroscopic characterization viz. energy, geometrical parameters, infrared and electronic absorption spectra, molecular orbitals (MOs) their energies and natural transitions orbitals (NTOs) in gas phase and water solvent state reported at B3LYP/aug-cc-pVDZ level of theory. The second hyperpolarizability values are obtained using various methods and basis sets for comparison. It has been observed that the second hyperpolarizability values for the odd spin states of acetonitrile are more positive than the first hyperpolarizability. It is clearly seen that the effect of spin on spectroscopic parameters except on energy. The singlet gas phase acetonitrile calculations are well matching with the available experimental determinations. The TDDFT approach has been used to study electronic absorption spectra of all spin states of acetonitrile in gas phase and in water solvent. The IEFPCM model implemented in studying acetonitrile in water solvent at B3LYP/aug-cc-pVDZ level of theory. It is observed that HOMO to LUMO gap is larger for singlet than the triplet and quintet spin state and it decrease with an increase in strength of an applied field. All these calculations performed using Gaussian 16 program package.

Energy and reactivity profile and proton affinity analysis of rimegepant with special reference to its potential activity against SARS-CoV-2 virus proteins using molecular dynamics

Rimegepant is a new medicine developed for the management of chronic headache due to migraine. This manuscript is an attempt to study the various structural, physical, and chemical properties of the molecules. The molecule was optimized using B3LYP functional with 6-311G + (2d,p) basis set. Excited state properties of the compound were studied using CAM-B3LYP functional with same basis sets using IEFPCM model in methanol for the implicit solvent atmosphere. The various electronic descriptors helped to identify the reactivity behavior and stability. The compound is found to possess good nonlinear optical properties in the gas phase. The various intramolecular electronic delocalizations and non-covalent interactions were analyzed and explained. As the compound contain several heterocyclic nitrogen atoms, they have potential proton abstraction features, which was analyzed energetically. The most important result from this study is from the molecular docking analysis which indicates that rimegepant binds irreversibly with three established SARS-CoV-2 proteins with ID 6LU7, 6M03, and 6W63 with docking scores − 9.2988, − 8.3629, and − 9.5421 kcal/mol respectively. Further assessment of docked complexes with molecular dynamics simulations revealed that hydrophobic interactions, water bridges, and π–π interactions play a significant role in stabilizing the ligand within the binding region of respective proteins. MMGBSA-free energies further demonstrated that rimegepant is more stable when complexed with 6LU7 among the selected PDB models. As the pharmacology and pharmacokinetics of this molecule are already established, rimegepant can be considered as an ideal candidate with potential for use in the treatment of COVID patients after clinical studies.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00894-021-04885-z.

A computational study of mercaptopurine and thioguanine binding to gold clusters Aun (n = 3, 4)

The density functional theory calculations are employed to elucidate the adsorption/desorption behaviours of mercaptopurine (MP) and thioguanine (TG) drugs on the gold surfaces, using Au3 and Au4 clusters as model reactants. The PBE functional in combination with the effective core potential cc-pVTZ-PP basis set for gold atoms and cc-pVTZ basis set for nonmetals have been used to investigated geometric structures, thermodynamic parameters and electronic properties of the obtained complexes. The IEF-PCM model with water solvent was used to include the effect of biological environment on the interactions. The computed results show that the binding is dominated by a covelant bond Au−S and by electrostatic effects, namely a hydrogen bond contribution NH∙∙∙Au. In addition, the drug binding to gold clusters is a reversible process and a drug release mechanism was also clarified. Accordingly, the drugs are willing to separate from the gold surface due to either a slight change of pH in tumor cells or the presence of cysteine residues in protein matrices.

Theoretical investigation on influence of protic and aprotic solvents effect and structural (Monomer, Dimer), Van-der Waals and Hirshfeld surface analysis for clonidine molecule

The protic (water, Ethanol) and aprotic (DMSO) solvent effect on clonidine molecule were investigated by theoretically using DFT/B3LYP method with 6-311 g++(d,p) as a basis set and IEFPCM model. Potential energy surface analysis was carried out for detecting minimum and maximum energy structure. The monomer and dimer structure were optimized and compared geometrical parameters like bond length and angle. Influence of Solvents have been investigated electronic spectral analysis, orbital analysis and reactive site identification as well as hyperpolarizability investigation. Hydrogen bonding attractive and steric repulsive regions are identified by non-covalent interaction (NCI) investigation. Inter and intra molecular interactions are identified by using Hirshfield analysis in various modes.

The vibronic absorption spectrum and electronic properties of Azure B in aqueous solution: TD-DFT/DFT study

The vibronic absorption spectrum of Azure B (AB) in an aqueous solution is calculated using the time-dependent density functional theory (TD-DFT). The results of calculations are analyzed using all hybrid functionals supported by Gaussian16, the 6-31++G(d,p) basis set, and the IEFPCM and SMD solvent models. The solvent model IEFPCM gave significantly underestimated values of λmax in comparison with the experiment. This is a manifestation of the TD-DFT “cyanine failure”. However, the SMD model made it possible to obtain good agreement between the calculation results and experimental data. The best fit was achieved using the X3LYP functional. According to our calculations, the shoulder in the visible absorption spectrum of AB has a vibronic origin. However, the calculated shoulder is weaker than the experimental one. Explicit assignment of two water molecules, which form strong hydrogen bonds with a dye molecule, leads to a shift of the calculated absorption spectrum to longer wavelengths by approximately 17 nm but does not lead to an improvement in its shape. Comparative analysis of the calculated vibronic absorption spectra of Azure B with those obtained earlier for Azure A and methylene blue showed that the presence and intensity of the short-wavelength shoulder are determined by the location of the bands of higher vibronic transitions relative to the band of the 00 → 00 main transitions. Photoexcitation leads to an increase in the dipole moment of the dye molecule. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule.

Tris-isopropyl-sily-ethynyl anthracene based small molecules for organic solar cells with efficient photovoltaic parameters

Four small molecules (Rm1 to Rm4) based on TIPS-anthracene are designed by linking different end-capped acceptors at terminals of thiophene spacer. Photovoltaic properties are inspected under the concepts of density functional theory (DFT) as well as time-dependent (TD) DFT using the MPW1PW91/6-31G (d,p) method to check maximum absorption, presence, and availability of frontier molecular orbitals (FMOs), solution processability, and charge transport effectiveness in TIPS-anthracene based molecules. Comparative inspection between simulated results of newly studied and reference molecules has given an unclouded picture of the better compatibility of novel organic molecules in solar devices. However, among all the designed molecules, Rm4 and Rm2 have marked better λmax (642.3 nm and 597.2 nm) in chloroform by using IEFPCM model. The Rm2 has the lowest reorganization energy that is λe = 0.0038 eV and λh = 0.0072 eV, therefore, has good charge transferability as compared to other molecules. Similarly, Rm2 (µe = 8.7097 Debye) has the highest dipole moment means the highest crystallinity in solution. While open-circuit voltage (Voc) of donor/acceptor interface (Rm2/ PCBM) has shown the highest value (1.75 V). So, Rm2/ PCBM is preferred for charge transfer analysis to make evidence of charge mobility in this interface which is acknowledge competent. Studied TIPS-anthracene based interface Rm2/ PCBM can be utilized in solar devices owing to efficient photovoltaic parameters.

Prediction of the kinetic stability of N‐alkyl‐X‐pyridinium ions in dichloromethane

AbstractGeometries of 20 N‐[4,4′‐bis (dimethylamino)benzhydryl]‐X‐pyridinium ions (DMABh‐X‐pyridinium ions) and of corresponding heterolytic transition structures have been optimized at the M06‐2X/6‐311+G(2d,p) level of theory in the presence of the IEFPCM model with dichloromethane as a solvent. Using the optimized geometries, free energies of activation (∆G‡model) for the model heterolysis of the DMABh‐X‐pyridinium ions in dichloromethane at 20°C have been obtained. A very good correlation between ∆G‡model values for the model heterolysis of five reference DMABh‐X‐pyridinium ions and literature ∆G‡ values for the heterolysis of the same ions in dichloromethane (r = 0.992) validates the procedure for predicting experimental reactivities of the ions (∆G‡calc) in dichloromethane. Accordingly, the correlation has been employed to obtain predicted free energies of activation (∆G‡calc) for heterolyses of other 15 DMABh‐X‐pyridinium ions in dichloromethane from corresponding ∆G‡model values. The high quality of the whole set of the predicted reactivities is confirmed by a very good correlation plot of log kcalc (obtained from ∆G‡calc) versus σ (r = 0.995). Using the previously established correlation equation log k = sf (Ef + Nf), predicted nucleofugality parameters (Nfcalc), which quantitatively describe leaving group abilities, have been determined for various X‐pyridines in dichloromethane, and now can be used not only for comparing leaving group abilities of X‐pyridines with those of other leaving groups on the existing nucleofugality (Nf) scale but also for estimating the reactivity, that is, the kinetic stability, of diverse N‐alkyl‐X‐pyridinium ions in dichloromethane at 20°C.

TD-DFT/DFT study of thionine in aqueous solution: Vibronic absorption spectrum and electronic properties

The vibronic absorption spectrum of thionine (TH) in an aqueous solution is calculated using the time-dependent density functional theory (TD-DFT). The calculations are performed using all hybrid functionals supported by Gaussian16, the 6-31++G(d,p) basis set with IEFPCM and SMD solvent models. IEFPCM gave significantly underestimated values of λmax in comparison with the experiment. However, SMD made it possible to obtain good agreement between the calculation results and experimental data. The best fit was achieved using the X3LYP functional. The shoulder in the visible absorption spectrum of TH has a vibronic origin. Photoexcitation leads to an increase in the dipole moment of the dye molecule. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule. The absorption peak of the TH solution in the visible region of the spectrum is due to the π→π* type electronic transition. Vibronic coupling plays a significant role in the absorption spectra of TH.

Vibronic absorption spectrum and electronic properties of methylene blue in aqueous solution: TD-DFT study

The vibronic absorption spectrum of methylene blue (MB) in an aqueous solution is calculated using the time-dependent density functional theory (TD-DFT). The results of calculations are analyzed using all hybrid functionals supported by Gaussian16, the 6–31++G(d,p) basis set and the IEFPCM and SMD solvent models. The solvent model IEFPCM gave significantly underestimated values of λmax in comparison with the experiment. This is a manifestation of the TD-DFT “cyanine failure”. However, the SMD model made it possible to obtain good agreement between the calculation results and experimental data. The best fit was achieved using the X3LYP functional. According to our calculations, the shoulder in the visible absorption spectrum of MB has a vibronic origin. Explicit assignment of a water molecule strongly bound to the N10 endocyclic nitrogen atom does not change the shape of the absorption band, but shifts its maximum by 7 nm to the long-wavelength region of the spectrum. The dipole moments and atomic charges of the ground and excited states of the MB molecule have been calculated. Photoexcitation leads to an increase in the dipole moment of the dye molecule. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule. In accordance with our results, the absorption peak of the MB solution in the visible region of the spectrum is due to the π → π* type electronic transition. Vibronic coupling plays a significant role in the absorption spectra of MB.

Tuning the optoelectronic properties of oligothienyl silane derivatives and their photovoltaic properties

Four new Donor-Acceptor (D-A) type oligothiophenes based structures (C1–C4) were designed by substituting different acceptors moieties around tetrahedral silicon core to simulate their photovoltaic properties. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) quantum analysis were carried out to reconnoiter various parameters of solar cells. A comparative analysis has conducted between designed structures and reference molecule R to conclude our simulated results. Among all the structures, C2 has displayed highest absorption values (380 nm) with red shift and minimum band gap (ΔH-L) of 4.11 eV in dichloromethane at DFT-CAM-B3LYP/6-31G (d,p) using IEFPCM model. The C2 has also shown the lowest values of electron reorganization energy (λe = 0.018eV) and hole reorganization energy (λh = 0.015eV) therefore, could be suggested for use in organic solar cells because of its most noteworthy charge carrier mobilities. Again, C2 has the different trend in TDM graph because the electron density is present in the lower right part of core unit and in the acceptor moiety due to high electron affinities of end capped acceptor having cyanide groups.

Experimental and Computational Studies on the Electrochemical Behavior of Carvacrol and Menthol

In this study, the effects of solvent on the electrode potentials of menthol and carvacrol species were investigated experimentally and computationally and their antioxidant properties were compared in different solvents by calculating the half-wave potential E1/2 of species, Vand Dissociative Energy (BDE), Ionization Energy (IE), and Electron Affinity (EA). Electrochemical behavior of menthol and carvacrol species in four solvents (MeOH, EtOH, DMSO, and Heptane) were studied using cyclovoltametric technique in a glass electrode as a working electrode and the calculations for obtaining the electrode potential were performed using DFT functional including B3LYP with 6-311+G(d,p)basis set and PCM and IEFPCM models for calculation of solvent energy. Finally, the results were compared and confirmed by experimental methods. Where in the compound carvacrol represent more properties antioxidant than menthol due to lower values E1/2 in gas and solution phases. Also, the lower BDE in the gas phase is 80.19 kcal/mol compared with menthol (98.91 kcal/mol). Moreover, compound carvacrol has the IE value of 1.12 eV smaller than menthol and has the EA value of 0.35 eV higher than menthol. Calculations show that the model had no effect on computational results. Also, according to the results, the antioxidant properties of carvacrol in non-polar solvents were higher due to the smaller amount of E1/2.

Spectroscopic Investigations and DFT Studies of Synthesized 4- Acetamidophenyl 3,4,5-Trimethoxybenzoate and 4-acetyl phenyl 3,4,5- trimethoxybenzoate a Novel Conjugate of Gallic Acid

Gallic acid is abundantly found in amla (Phyllanthus emblica), a deciduous of the family phyllanthaceae. Gallic acid, the major constituent of the plant, was methylated to 3,4,5 trimethoxy gallic acid, which then underwent steglich esterification first with paracetamol and then with 4-hydroxy acetophenone to yield 4-acetamidophenyl 3,4,5-trimethoxybenzoate and 4-acetyl phenyl 3,4,5-trimethoxybenzoate “respectively”. 1H NMR, 13C NMR, UV, FT-IR and mass spectroscopy were used to characterize the synthesized compounds. Density functional theory (B3YLP) using a 6-31G (d,p) basis set has been used for quantum chemical calculations. AIM (Atom in a molecule) approach depicted weak molecular interactions within the molecules, whereas the reactive site and reactivity within the molecule were examined by global and local reactivity descriptors. The HOMO and LUMO energies and frontier orbital energy gaps were calculated by time dependent DFT approach using the IEFPCM model. A small value for the HOMO-LUMO energy gap indicated that easier charge transfer occurs within compound 4. The nucleophilic and electrophilic reactivity was determined by MEP (molecular electrostatic potential) experiment. Polarizability, dipole moment, and first hyperpolarizability values were calculated to depict the NLO (nonlinear optical) property of both the synthesized compounds. The antimicrobial activity was also carried out and broad-spectrum antibacterial activity against several strains of bacteria and certain unicellular fungi were exhibited by synthesized compound 3.

Tuning the optoelectronic properties of dibenzochrysene (DBC) based small molecules for organic solar cells

Four different types of dibenzo chrysene (DBC) based molecules (A1-A4) are designed to investigate their photovoltaic properties via quantum simulation. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analysis is performed to explore various parameter of solar cells i.e. the 3-D geometries of designed molecules, photovoltaic properties, reorganization energies, dipole moment, transition density matrix (TDMs), open-circuit voltage (Voc) and Exciton Binding Energy (Eb). We have performed a comparative study between designed molecules and reference structure to R to conclude our results. Among all designed structures, A4 has shown a red shift with λ max of 797.4 nm and band-gap (ΔH-L) of 1.743eV in CHCl3 by B3LYP/6-31G (d,p) using the IEFPCM model. The internal reorganization energy of all the designed molecules has shown a more effective charge transfer property as compared to R. However, A4 has shown the least value of λe (0.003775 a.u), thus have good charge transferability in the form of electron This high charge transfer ability ascribed to strong electron-withdrawing malononitrile group that enhances the rate of charge transmission among donor and acceptor groups. Transition density matrix (TDM) map results have shown that A2 has weak electrostatic interaction between electron and hole (Eb = 0.1126 eV) showing ease dissociation of exciton in comparison to other molecules. This DFT based quantum simulation explicates that we can amend different properties of solar cells by attachment of different end capped acceptor units around the central donor core. Thus high device performance (PCE) could be achieved by appropriate choice of donor and acceptor units.

Elaborated molecular structure, molecular docking and vibrational spectroscopic investigation of N-((4-aminophenyl)sulfonyl)benzamide with Density functional theory

Abstract The molecule N-((4-aminophenyl)sulfonyl)benzamide was optimized by making use of density functional theory (DFT) with 6-311++G(d,p) basis set. The vibrational frequency and potential energy distribution (PED) of the title compound were calculated and compared with experimental calculations. By using DFT method, the reactivity nature of the molecule was characterized, like as Local reactivity descriptor, Natural bond orbital with a basis set of 6-311++G(d,p), Frontier molecular orbital (FMOs), etc. The electronic properties for HOMO-LUMO, UV-Vis and MEP maps were contemplated by IEFPCM model with various solvation impacts which depends on TD-DFT ((B3LYP for HOMO-LUMO, MEP and M062X for UV)/6-311++G(d,p)) strategies. The Molecular docking analysis reveals the inhibitory nature of title molecule with Aspergillus Niger a fungal protein, SARS CoV-1 and SARS CoV-2 viral proteins. Hence, the present study reveals that the title compound has structural behavior and bioactive (antifungal and antiviral) nature.

Isatin-derived non-fullerene acceptors for efficient organic solar cells

Geometries optimization, electronic structure, electronic absorption spectra, charge transport rate, morphology, and photovoltaic properties of indacenodithiophene as donor core unit tie with isatin derive different end-capped electron acceptor groups have been performed using Density Functional Theory (DFT) and time dependent density functional theory (TD-DFT). Isatin unit connected with 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile in M1, 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile in M2, 2-thioxothiazolidin-4-one in M3, 2-(4-fluorothiophen-2-yl)acetonitrile in M4 and geometries, opto-electronic properties have been computed at TD-DFT MPW1PW91/6-31G level of theory and compared with reference molecule R. Among all novel structures, M2 has lowest value of energy band gap (1.99 eV) and has maximum absorption (λmax = 824.0 nm) in chloroform by TD-MPW1PW91/6-31G (d,p) using IEFPCM model. The red shift in M2 was due presence of strong electron withdrawing acceptor moiety and more extended conjugation as compared to other structures. Indeed, electron withdrawing functionality i.e fluorine and cyno moieties in M2 structure stabilized its LUMO orbital and hence improved its opto-electronic properties. Transition density matrix (TDM) maps results revealed obvious influence of end-capped acceptor group on the exciton. M2 has lower probability of coupling of electron and hole owing easy exciton dissociation as compared to other designed molecules. Theoretically calculated reorganization energy indicates that M1 has the highest hole transfer rate due to the lowest value of λh (0.0068 eV). Similarly, M4 has the highest electron mobility due to lowest value of λe (0.0053 eV). In short, choice of appropriate electron withdrawing end capped acceptor groups is very important for improving the performance of organic solar cells.

Chrysazin semiquinone radical anion. A theoretical study of the influence of the solvent on the electron spin resonance spectrum

The strong influence of the solvent on the hyperfine coupling constants of the semiquinone radical anion derived from chrysazin (1,8-dihydroxy-9,10-anthraquinone) was investigated by theoretical calculations, using the polarizable continuum models IEFPCM and IPCM. The current implementation of the popular IEFPCM model does not describe the influence of specific interactions between solute and solvent molecules. This model thus requires incorporation of hydrogen-bonded solute–solvent clusters to approximate the situation in alcoholic and aqueous solvents. The results using the IPCM model suggest that it may be used as a tool to simulate the effect of rapidly changing formation and breaking of solute–solvent complexes by means of an average electrostatic reaction field at the position of the solute species, thus approximating the influence of specific effects within the polarizable continuum picture.

Croweacin and Ammi visnaga (L.) Lam Essential Oil derivatives as green corrosion inhibitors for brass in 3% NaCl medium: Quantum Mechanics investigation and Molecular Dynamics Simulation Approaches

<p class="Mabstract"><span lang="EN-US">The computational study was carried out to understand the anti-corrosion properties of Croweacin, a major chemical component of two essential oils of <em>Ammi visnaga</em> (L.) Lam collected from northern Morocco in 2016 (EO16) and 2018 (EO18) against brass corrosion in a 3% NaCl medium. The study, moreover, considers the inhibitory effect of some minor compounds of EO18 such as Eugenol, Trans-Anethole, α-Isophorone, and Thymol. In this context, the quantum mechanics modelling using the density functional theory (DFT) method with B3LYP /6-31G (d, p) were conducted in the aqueous medium by the use of the IEFPCM model and SCRF theory. The DFT method was adopted to identify, analyze and interpret several elements such as the electronic features, the Frontier Molecular Orbitals (FMO) diagram, Molecular Electrostatic Potential (MEP), contours maps of the electrostatic potential (ESP), and the Mulliken population analysis. The DFT demonstrated that the studied compounds are excellent corrosion inhibitors.</span></p><p class="Mabstract"><span lang="EN-US">Furthermore, the Monte Carlo (MC) type simulation of molecular dynamics (MD) was carried out to provide information on the adsorption mechanism of the studied inhibitors through the active sites on the metal surface. This method informed us that the studied inhibitors have high adsorption energy when interacting with the metal surface, especially for Croweacin (-68.63 kcal/mol). The results obtained from DFT and the MC type simulations are in good agreement.</span></p>