Density Functional B3LYP Research Articles

Supramolecular structure, DFT calculation and vibrational characterization of melamin-1-ium oxalurate monohydrate

Crystallization from an aqueous solution of melamine with parabanic acid was taken in a molar ratio of 1:1 leads to the formation of melamin-1-ium oxalurate monohydrate (MOX) crystals. The compound crystallizes in the centrosymmetric space group P21/n of the monoclinic system with four molecules per unit cell. The molecular geometry and vibrational frequencies of MOX in the ground state have been calculated by using the density functional hybrid function B3LYP 6–31+G(d) basis set. The results of optimized molecular structure are presented and compared with the experimental X-ray diffraction data. Furthermore, Fourier Transform Infrared (FT-IR) and Raman Spectra were used to conduct vibrational characterization to study the compound's structural groups. The calculated Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies show that charge transfer occurs in the molecule and other related electronic properties have also been calculated. Besides, Molecular Electrostatic Potential (MEP) was performed to identify the possible electrophilic and nucleophilic sites. First order hyperpolarizability results establish the nonlinear response of the grown MOX crystal with respect to the electric field. Further, the crystal packing behaviour of MOX was studied quantitatively with the aid of Hirshfeld surface analysis.

Analysis of electronic properties and sensing applications in Graphene/BC3 heterostructures

Many research studies have been conducted into the applications of the heterostructures of graphene (Gr) and boron carbide (BC3) in real-world devices after they were synthesized successfully by researchers. Thanks to their unique electronic attributes and high surface-to-volume ratio, the above-mentioned two-dimensional nanosheets (NSs) such as have enjoyed the interest of many research groups and scientists. Within this piece of research, the electronic and structural attributes of pure Gr (PGr), pure BC3 (PBC3) and their in-plane heterostructures were investigated by employing the DFT along with the density functionals B3LYP and WB97XD. The results demonstrated that by increasing the concentration of the B-C, there was a gradual increase in the bandgap. Also, the structural stability of the NSs was good and the cohesive energy was favourable. In addition, the adhesion attributes of these NSs were investigated towards two toxic gasses, namely CO and SO2. Amongst the heterostructures, after exposure to CO and SO2, the adhesion energy of GBC3I was greater, which was approximately −0.487 eV and −0.229 eV, respectively. Following the adhesion of SO2 onto the surface of the NSs, apart from the PGr, there was a significant change in their electronic attributes such as conductance, workfunction, Fermi level, the LUMO, the HOMO and the bandgap. However, following the adhesion of CO, the above-mentioned attributed remained almost the same. Based on the NBO and Mulliken charge analysis, there was a charge transport from the gasses to the NSs. Despite the fact that the adhesion energies for CO were relative higher than the adhesion energies for SO2for the NSs, the analysis of the MEP maps, the charge transport and the electronic attributes demonstrated that the NSs can be used as promising nanosensors for the detection of SO2 rather than CO.

Insights into the electronic structure and interaction energies of 4-ethoxy-N-(4-ethoxy-2-hydoxybenzylidene)benzohydrazide

The molecule 4-ethoxy-N-(4-ethoxy-2-hydroxybenzylidene)benzohydrazide (4EHB) is characterized by a rigid aroylhydrazone core, acting as a mesogenic unit, and a flexible chain at its terminal end. The aroylhydrazone core comprises two aromatic rings linked by connecting groups, resulting in moderate size and elongation of the molecule. Variations in the positions and orientations of elongated molecules give rise to different mesogenic phases such as Nematic, Smectic, and Hexatic Smectic. The mesogenic behavior of aroylhydrazone-based materials is governed by various non-covalent interactions. In this study, molecular geometry optimization, analysis of HOMO-LUMO orbitals, and MEP surfaces of individual and pairs of 4EHB molecules were conducted using the Density functional B3LYP technique with the basis set 6-31G**. Intermolecular interaction energies between pairs of 4EHB molecules are evaluated using the technique M06-2X/6-311G** in stacking, terminal, and side-to-side (in-plane) configurations. Basis set superposition error (BSSE) is corrected using counterpoise method and interaction energy(I.E.) is decomposed in different components using SAPT0 method at level 6-311G**, which provided insights into the mesogenic behavior of the system.

Improvement power conversion efficiency in graphene quantum dot by functionalization and heteroatom doping used in solar cell

First-principles density functional theory (DFT) was adopted for investigating the influence of adatoms (S, Si, Al) upon the graphene quantum dot functionalized with the carboxyl group (CO2H-GQD) in order to find novel materials due to unique optical (redshift) and electronic (lower bandgap) properties for utilization in quantum dot solar cells (QDSCs). For the sake of examining the alteration in the electronic attributes due to the insertion of adatoms, the bandgaps, the LUMO and the HOMO were examined using the density functional B3LYP and the basis set 6-31G. For the sake of examining the charge separation and electron injection in the un-doped and doped CO2H-GQD, we scrutinized the charge transport, molecular electrostatic potential (MESP) and the binding mechanism. The optical attributes demonstrated a broad spectrum in the visible range favorable towards harvesting solar light. We also investigated the parameters of solar cells such as efficiency (η), short circuit current density (Jsc), fill factor (FF), open circuit voltage (Voc) in order for the sake of examining the use of adatom-doped CO2H-GQD in QDSCs. There was an increase in the efficiency of S-doped, Si-doped, and Al-doped CO2H-GQD. Doping the CO2H-GQD led to the maximum efficiency since electron donating nature was more, thereby injecting more electrons in the surface of TiO2. The results demonstrated that such GQD-based sensitizers can be used effectively in QDSCs.

Structure, dissociation pathways and thermochemistry of some nitrogen-containing astrophysical molecules: a theoretical study

The structure, relative energies, dissociation pathways and thermochemistry of acetonitrile (CH3CN or methyl cyanide), acrylonitrile (CH2CHCN or vinyl cyanide), propionitrile (CH3CH2CN or ethyl cyanide) and their stable isomers have been studied in detail using density functional B3LYP, B3PW91 and ab initio MP2, QCISD and CCSD(T) methods. Several space missions have already confirmed the abundance of these molecules in different interstellar mediums (ISMs). The existence of related radicals, atoms and molecules are also confirmed using various IR-spectrometric techniques and that may be evolved in solar irradiation in the cold dark core TMC-1 or massive star-forming regions such as Sagittarius B2 or Oion-KL. Possible ways of fragmentation of ground state CH3NC, CH2CHNC and CH3CH2NC through different dissociation channels and their link to other isomers have been considered to justify the presence of such observed radicals in the interstellar cloud. Cyanide(-C≡N), iso-cyanide (-N = C) and imine (-C = N-H) isomeric forms have been considered here and out of these, cyanide isomers are more stable species compared to its iso-nitrile and imine form. Favourable product molecules, such as CH2 radical, C2H2, C2H4 and HCN/HNC, are considered in the dissociation channels.

Synthesis, crystal structure, DFT, vibrational properties, Hirshfeld surface and antitumor activity studies of a new compound 2-(2-chloro-6-(m-tolyl)imidazo[1,2-a]pyridin-3-yl)-N,N-diethylacetamide

Imidazo[1,2-a]pyridine derivatives are a kind of fused heterocyclic substances, which play an important role in the chemical field and have been proved to be the core fragments of various drug molecules. In this study, a new title compound was finally synthesized by cyclization, substitution, Suzuki coupling, hydrolysis and condensation. And the crystal of the title compound was obtained by single crystal culture. The structure of 2-(2-chloro-6-(m-tolyl)imidazo[1,2-a]pyridin-3-yl)-N,N-diethylacetamide was confirmed by 1H NMR, 13C NMR, FT-IR and single crystal X-ray diffraction. In addition, the title compound was theoretically calculated at the level of 6–311+G (2d, p) based on density functional method B3LYP, and the molecular structure optimized by DFT was consistent with the results obtained by X-ray diffraction. By calculating the Hirschfield surfaces and 2D fingerprints of molecules, the interactions between molecules can be visually revealed based on the size and color of the spots near the atoms. In addition, according to the characteristic vibration absorption band, the vibration of the title compound is reliably attributed. Furthermore, MEP, RDG, and ELF analyses were conducted to characterize the reaction sites susceptible to electrophilic and nucleophilic attacks. FMOs was used to evaluate the stability of the molecular structure. Finally, the results of the determination of biological activity showed that the compound exhibited significant inhibitory activity against HCT116 cancer cell.

THE ROLE OF QUANTUM CHEMICAL CALCULATIONS IN CATALYSIS: A REVIEW

The article talks about the high role of quantum chemical research methods in such a promising direction as the catalytic oxidation of saturated hydrocarbons, especially in the study of transition states of molecules. Theoretical analysis is based on research in catalysis and computational chemistry. Computational chemistry is an effective tool that allows one to calculate the structure and physical properties of catalysts, as well as the structure and energy of the activated complex. In this review, special attention is paid to identifying a sufficiently accurate and, at the same time, less energy-consuming method for determining the structure of the transition state. The most popular methods of quantum chemical calculations are presented, among which a special role is given to density functional theory (DFT), functionals B3LYP, OLYP, PBE and basis sets 6-31G, LANL2DZ. The use of machine learning by some authors, along with quantum chemical computing, to identify catalysts for activation and functionalization of C-H bonds has been mentioned. The advantages and disadvantages of computational chemistry for heterogeneous catalysis are discussed. The results of studies of catalysts predicated on transition metal complexes are summarized. It is underlined that nanocomposites based on transition metals attract the attention of researchers due to their d-orbitals, which are responsible for the reactivity when activating C-H bonds. The review also indicates plans for conducting quantum chemical calculations to study the catalytic processes of selective oxidation of n-alkanes using tran-sition metal nanocomposites as catalysts. This review will be useful for future applications of computational chemistry methods for the development of new catalysts and the study of chemical reaction mechanisms

The Contribution of Cornelian Cherry (Cornus mas L.) Alcoholic Beverages on the Sensory, Nutritional and Anti-Nutritional Characteristics—In Vitro and In Silico Approaches

Food producers have focused on novel and attractive raw materials with functional properties. Cornelian cherry (Cornus mas L.) fruits contain numerous compounds that may be beneficial for health. Objective: This study aimed to compare and assess the physicochemical properties and amygdalin levels in brandy and liquor prepared from frozen cornelian cherry fruits. Density functional theory-based B3LYP functionals were used to analyze the spectral and optical properties of amygdalin. The contents of the compounds and volatile products of amygdalin decay were found in two spirituose beverages of Cornus mas, using HPLC and GC-MS. Significant differences in their physicochemical properties were detected between the samples. Alcoholic beverages based on cornelian cherry fruits were rich in a wide range of functional ingredients with a low concentration of amygdalin. In silico analysis showed that orbital density diffusion has a major effect on the physical properties of amygdalin, while differences between the polarities of water and ethanol had no noticeable effect on the spectral properties of the compound. Cornelian cherry-based alcoholic drinks might be interesting functional products with rich aromatic bouquets. The amygdalin concentration is low enough to pose no toxicological threat, but rather shapes the tastory bouquet of the products. Levels of amygdalin may be controlled using the same analytical methods for solutions with different ethanol–water ratios.

DFT study, and natural bond orbital (NBO) population analysis of 2-(2-Hydroxyphenyl)-1-azaazulene tautomers and their mercapto analouges

Theoretical research on the keto-enol tautomerization of 2-(2-Hydroxyphenyl)-1-aza azulene (2HPhAZ) and its thiol-thione (2MPhAZ) analouge has been performed using the density functional B3LYP method with the 6–311 + + G(2d,2p) basis set in gas and ethanol phases. The findings of the MO computation on the energy scale and the prediction of the frontier molecular orbital (FMO) energies demonstrate that the tautomeric structures exist in a static mixture in the ground state, with the enol and thiol structure being more stable than the keto and thione structures in gas phase. The ethanol solvent causes some reordering of the relative stability of 2HPhAZ and 2MPhAZ conformers. The geometries created at the B3LYP/6–311 + + G(2d,2p) level of theory were used for NBO analysis. In the tautomerization of 2HPhAZ and its mercapto analogue 2-(2-Mercaptophenyl)-1-azaazulene (2MPhAZ), it has been found that the O(S)-C sigma bond is weak due to nO(S)—> σ*C25-O26(S26) and nO(S)—> σ*C15-N16 delocalization. It is also noted that the resulting p character of the corresponding oxygen (sulfur) natural hybrid orbital (NHO) of σO(S)-C bond orbital is related to the decreased occupancy of the localized σO(S)-C orbital in the idealized Lewis structure or the increased occupancy of σ*O(S)-C of the non-Lewis orbital and their subsequent impact on molecular stability and geometry (bond lengths) in gas phase and ethanol. Additionally, the energy of charge transfer decreases as the potential rotamers' Hammett constants (R1–R3 for O(S) atoms) increase. The partial charge distribution on the skeleton atoms demonstrates that the intra- and intermolecular interactions can be significantly influenced by the electrostatic attraction or repulsion between atoms. Lastly, the currently applied NBO-based HB strength indicator enables a fair prediction of the frequency of the proton donor NH stretching mode, but this simple picture is hidden by abundant hype conjugative effects.

Exploration of 4-Chloro-3-nitrocoumarin: Spectroscopic Analysis, DFT Insights, Molecular Docking, Assessments of Antibacterial and In Vitro Anticancer Activities as a Potent Bioactive Agent

The detailed theoretical and experimental (FT-IR, FT-Raman, UV-visible) spectroscopy analyses of the 4-Chloro-3-nitrocoumarin (CNC) molecule were carried out. The CNC compound's pharmacological properties were also investigated utilizing antibacterial and anticancer activity investigations. Initially, the CNC molecule was optimized by the density functional theory B3LYP method with a cc-pVTZ basis set using the Gaussian 09W program. The optimized molecular structure provides the harmonic vibrational frequencies of the CNC molecule. The observed and computed vibrational wavenumbers were assigned and found to be well correlated. UV-Vis absorption spectrum analysis indicates that the molecule contains π→π* electronic transition. Frontier molecular orbitals (FMOs) analysis indicates that the LUMO of CNC molecule is mainly located over the nitro group, it indicates that the nitro group is particularly prone to accepting electrons from other molecules and participate in chemical reactions where acts as an electrophile. Mulliken atomic charge distribution analysis further confirms the FMOs results. The antibacterial test results validate that the CNC molecule exhibits a stronger inhibitory effect on Staphylococcus aureus compared to the other tested bacteria. In vitro anticancer cytotoxicity analysis clearly evidences that the CNC compound inhibits the growth of HeLa cervical cancer cell lines more than A549 lung cancer cell lines. In silico molecular docking study further validates that the CNC molecule inhibits the function of the p38a Mitogen-activated protein kinase 14, which has been associated with cervical cancer. As a result, the present study paves the way for the development of new drugs to treat cervical cancer.
 Keywords: 4-Chloro-3-nitrocoumarin; DFT; FT-IR; FT-Raman; Anticancer; Molecular docking; Cervical cancer drug.

Theoretical Study of the Photophysical and Photochemical Properties of 1H‐Benzimidazole and 2‐Ethyl‐7‐nitro‐5‐Substituted 1H‐Benzimidazoles

AbstractTheoretical study of the photophysical/photochemical properties of 1H‐benzimidazole and its derivatives was carried out using APFD, B3LYP, CAM‐B3LYP and PBE0 density functionals with 6‐311+G(2d,p) basis set. The effects of ethanol, 1,4‐dioxane, acetonitrile and water was investigated by means of Integral Equation Formalism of the Polarizable Continuum Model (IEPCM) in the framework of Self‐Consistent Reaction Field (SCRF). The results obtained show that S2 state of the 1H‐benzimidazole molecule is more acidic than the S0 state as the N5−H11 bond length increased to ~ 1.01 Å. At B3LYP/6‐311+G(2d,p) level of theory, the excitation energy of 1H‐bensimidazole molecule in ethanol from S0 to the S2 state was calculated to be 273 nm (4.54 eV). The electronic energy for this transition was calculated to be 0.131 a.u. and observed to occur between π→π* orbitals. Calculations with the PBE0, APFD and B3LYP functionals reproduced the experimental dipole moment in 1,4‐dioxane, with values of 4.09, 4.09 and 4.07 Debye respectively. However, the dipole moments of the 2‐ethyl‐7‐nitro‐5‐substituted‐1H‐benzimidazoles were calculated to be higher for electron donating groups (EDGs) than those bearing electron withdrawing groups (EWGs). In addition, the molecular polarizability was observed to increase with decreasing energy gap. Local excitation (LE) and charge‐transfer (CT) were observed to mediate the mechanisms of electronic excitation in 2‐ethyl‐7‐nitro‐5‐substituted‐1H‐benzimidazoles.

Spectroscopic Characterization, Quantum Chemical, Molecular Docking, Antibacterial and Anticancer Studies on Ethyl Coumarin-3-Carboxylate: an Antibacterial and Lung Cancer Agent

The detailed theoretical and experimental (FT-IR, FT-Raman, UV-visible) spectroscopy analyses of the Ethyl Coumarin-3-Carboxylate (ECC) molecule were carried out. The ECC compound’s pharmacological properties were also investigated, utilizing antibacterial and anticancer activity investigations. Initially, the ECC molecule was optimized by the density functional theory B3LYP method with a 6-311 G++ (d,p) basis set using the Gaussian 09 W program. The optimized molecular structure provides the harmonic vibrational frequencies of the ECC molecule. The observed and computed vibrational wavenumbers were assigned and found to be well correlated. UV-Vis absorption spectrum analysis indicates that the molecule contains π →π* and n → π* electronic transitions. The Frontier molecular orbital analysis confirmed the molecular reactivity and bioactivity of ECC, while the Mulliken atomic charge distribution analysis pinpointed the molecule’s reactive sites. Antibacterial testing demonstrated the ECC compound’s inhibitory effect on various bacterial strains, with a particular impact on Klebsiella pneumonia. In vitro, anticancer assessments showcased ECC's stronger inhibitory effects on A549 lung cancer cell lines compared to HeLa cervical cancer cell lines. Additionally, in silico molecular docking investigations provided further validation that the ECC compound can inhibit the function of the epidermal growth factor receptor, a factor associated with lung cancer. As a result, this study lays the foundation for the development of novel drugs for lung cancer treatment.

Mechanical quantum analysis on the role of transition metals on the delivery of metformin anticancer drug by the boron phosphide nanotube

We scrutinized the impact of doping of X atoms (X = Fe, Co, Ni, Cu, and Zn) on the metformin (MF) drug delivery performance of a BP nanotube (BPNT) using density functional B3LYP calculations. The pristine BPNT was not ideal for the drug delivery of MF because of a weak interaction between the drug and nanotube. Doping of the Zn, Cu, Ni, Co, and Fe into the BPNT surface raised the adsorption energy of MF from −5.3 to –29.1, −28.7, −29.8, −32.1, and −26.9 kcal/mol, respectively, demonstrating that the sensitiveness of the metal-doped BPNT increased after increasing the radius atomic of metals. Ultimately, there was an increase in the adhesion performance and capacity of the MF after X (especially Co atom) doping, making the nanotube suitable for MF drug delivery. The mechanism of MF reaction with the BPNT changed from covalent bonding in the natural environment to hydrogen bonding in the cancerous cells with high acidity.

Spectral Elucidations and Molecular Docking Analysis of Hydrogen Bonded Coordination Metal Complex Cadmium Nicotinate Using DFT Method

The geometry optimization, natural bond orbital analysis, and vibrational analysis of Cadmium Nicotinate (CdN) were performed using the density functional B3LYP level with a LANL2DZ basis set. Transfer of electrons from the lone pair oxygen in COO− to the antibonding orbital of the O-H bond results in the formation of hydrogen bonds, which results in the most interesting biological properties, according to natural bond orbital analysis. The red shift in wavenumber has been confirmed by intramolecular O-H…O hydrogen bonding interactions and the water group coordinated to the central metal cadmium via oxygen atoms. UV spectral analysis, on the other hand, reveals the n→π* transition due to its strong peak in absorption spectra, demonstrating its biological activity. The MEP and Fukui Functions are used to represent the molecule’s reactive region, which remains more electrophilic around the oxygen atoms. DOS spectral analysis is used to investigate the molecular orbital contributions. The Electron Localization Function (ELF) and the Local orbital locator (LOL) were used to conduct topological studies on CdN. To investigate distinct covalent and non-covalent interactions, Hirshfeld surface analysis and reduced density gradient analysis were used. Molecular docking studies were used to investigate ligand-protein interactions and ADME parameter analysis and the Lipinski rule for the CdN molecule confirmed that the compound has good drug-like properties and could be developed as an antifungal drug in the future.

First-principles density functional theoretical study on the structures, reactivity and spectroscopic properties of (NH) and (OH) Tautomer's of 4-(methylsulfanyl)-3[(1Z)-1-(2-phenylhydrazinylidene) ethyl] quinoline-2(1H)-one

The tautomerizations mechanism of 4-(methylsulfanyl)-3[(1Z)-1-(2-phenylhydrazinylidene) ethyl] quinoline-2(1H)-one were inspected in the gas phase and ethanol using density function theory (DFT) M06-2X and B3LYP methods. Thermo-kinetic features of different conversion processes were estimated in temperature range 273–333 K using the Transition state theory (TST) accompanied with one dimensional Eckert tunneling correction (1D-Eck). Acidity and basicity were computed as well, and the computational results were compared against the experimental ones. Additionally, NMR, global descriptors, Fukui functions, NBO charges, and electrostatic potential (ESP) were discussed. From thermodynamics analysis, the keto form of 4-(methylsulfanyl)-3-[(1Z)-1-(2 phenylhydrazinylidene) quinoline-2(1H)-one is the most stable form in the gas phase and ethanol and the barrier heights required for tautomerization process were found to be high in the gas phase and ethanol ~ 38.80 and 37.35 kcal/mol, respectively. DFT methods were used for UV–Vis electronic spectra simulation and the time-dependent density functional theory solvation model (TDDFT-SMD) in acetonitrile compounds.

Theoretical Study of the Catalytic Mechanism of the Cu-Only Superoxide Dismutase.

The catalytic mechanisms for the wild-type and the mutated Cu-only superoxide dismutase were studied using the hybrid density functional B3LYP and a quantum chemical cluster approach. Optimal protonation states of the active site were examined for each stage of the catalytic cycle. For both the reductive and the oxidative half-reactions, the arrival of the substrate was found to be accompanied by a charge-compensating H+ with exergonicities of -15.4 kcal·mol and -4.7 kcal·mol, respectively. The second-sphere Glu-110 and first-sphere His-93 were suggested to be the transient protonation site for the reductive and the oxidative half-reactions, respectively, which collaborates with the hydrogen bonding water chain to position the substrate near the redox-active copper center. For the reductive half-reaction, the rate-limiting step was found to be the inner-sphere electron transfer from the partially coordinated to CuII with a barrier of 8.1 kcal·mol. The formed O2 is released from the active site with an exergonicity of -14.9 kcal·mol. For the oxidative half-reaction, the inner-sphere electron transfer from CuI to the partially coordinated was found to be accompanied by the proton transfer from the protonated His-93 and barrierless. The rate-limiting step was found to be the second proton transfer from the protonated Glu-110 to with a barrier of 7.3 kcal·mol. The barriers are reasonably consistent with experimental activities, and a proton-transfer rate-limiting step in the oxidative half-reaction could explain the experimentally observed pH-dependence. For the E110Q CuSOD, Asp-113 was suggested to be likely to serve as the transient protonation site in the reductive half-reaction. The rate-limiting barriers were found to be 8.0 and 8.6 kcal·mol, respectively, which could explain the slightly lower performance of E110X mutants. The results were found to be stable, with respect to the percentage of exact exchange in B3LYP.

The gas-phase structure determination of α-pinene oxide: An endo-cyclic epoxide of atmospheric interest.

The gas-phase rotational spectra of α-pinene oxide have been recorded using a chirped-pulse Fourier transform microwave spectrometer in the 6-18GHz frequency range. The parent species and all heavy atom isotopologues (13C and 18O) have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and the effective (r0) structures of the most stable conformer of α-pinene oxide. Calculations using the density functional theories B3LYP, M06-2X, and MN15-L and the abinitio method MP2 level of theory were carried out to check their performance against experimental results. The structure of the heavy atom's skeleton of α-pinene oxide has been compared to that of α-pinene and has shown that epoxidation does not overly affect the structure of the bicycle, validating its robustness. Furthermore, the structural features have been compared to those of other bicyclic molecules, such as nopinone and β-pinene.

DFT calculations on three 2,3‐dihydrobenzofuran linked chalcones: Structural, HOMO‐LUMO and spectroscopic (UV‐Vis and IR) interpretation

AbstractThree chalcones with a 2,3‐dihydrobenzofuran linkage were analyzed by applying the density functional theory (DFT) and B3LYP approach with the 6‐311G(d,p) basis set in this report. Spectroscopic and theoretical analyses were used to examine the structures of these three chalcones. The chalcone molecules' HOMO‐LUMO energy was determined. Chemical reactivity parameters and molecular electrostatic surface potential (MESP) plots were obtained to gain useful insight into the distribution of charge density. The HOMO–LUMO gap of all three chalcones were calculated and discussed. The (E)‐3‐(2,3‐dihydrobenzofuran‐5‐yl)‐1‐phenylprop‐2‐en‐1‐one (DBPP) is discussed in detailed for the theoretical and experimental correlation. The captodative phenomenon appears to be the most polar molecule, with a dipole moment of 8.53 Debye. The decreased bandgap indicates that charge transfer occurs within the DBNPP molecule. When the solvent polarity is changed to DCM and DMSO from the gas phase, there is an event of a hyperchromic shift. The C19 carbon atom has the highest negative atomic charge while C21 is the carbon with the largest positive charge. From the MESP plots, we can conclude that the most electropositive region is located over the hydrogen atoms of the five‐membered ring, and the electronegative region is located over the oxygen atoms. Time‐dependent density functional theory (TD‐DFT) using B3LYP functional with 6‐311G(d,p) as basis set were used for the electronic absorption study in gas phase, dichloromethane and dimethyl sulfoxide. The UV‐Vis absorption peaks and fundamental vibrational wavenumbers were calculated and a good agreement between observed and theoretical results has been achieved.

Common Reactivity and Properties of Heme Peroxidases: A DFT Study of Their Origin

Electronic structure calculations using the density-functional theory (DFT) have been performed to analyse the effect of water molecules and protonation on the heme group of peroxidases in different redox (ferric, ferrous, compounds I and II) and spin states. Shared geometries, spectroscopic properties at the Soret region, and the thermodynamics of peroxidases are discussed. B3LYP and M06-2X density functionals with different basis sets were employed on a common molecular model of the active site (Fe-centred porphine and proximal imidazole). Computed Gibbs free energies indicate that the corresponding aquo complexes are not thermodynamically stable, supporting the five-coordinate Fe(III) centre in native ferric peroxidases, with a water molecule located at a non-bonding distance. Protonation of the ferryl oxygen of compound II is discussed in terms of thermodynamics, Fe-O bond distances, and redox properties. It is demonstrated that this protonation is necessary to account for the experimental data, and computed Gibbs free energies reveal pKa values of compound II about 8.5-9.0. Computation indicates that the general oxidative properties of peroxidase intermediates, as well as their reactivity towards water and protons and Soret bands, are mainly controlled by the iron porphyrin and its proximal histidine ligand.

In silico screening of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate and some of its derivatives for their NLO activities using DFT.

The nonlinear optical (NLO) properties of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate (EMAB) and some of its derivatives are investigated herein using the density functional theory (DFT) and time-dependent (TD)-DFT methods. The density functionals B3LYP, CAM-B3LYP, M06-2X and ωB97XD, and basis sets 6-31 + G**, 6-311 + + G** and Def2-TZVPP have been used. From the results, EMAB and its substituted derivatives studied are promising candidates for NLO materials. In all cases, the static first and second hyperpolarizabilities (31.7-86.5 × 10-30 and 84.4-273 × 10-36 electrostatic units (esu), respectively) and the frequency-dependent NLO properties are found to be significantly larger (about 43-103 and 28-76 times greater) than those of the NLO prototypical molecule, para-nitroaniline. Furthermore, the maximum absorption wavelengths of the molecules fall within the UV region of the electromagnetic spectrum. Relative to EMAB, the derivatives have shown improved transparency-nonlinearity trade-offs. Natural bond orbital (NBO) and density of states (DOS) analyses herein revealed effective charge transfer within the molecules studied, especially those with stronger electron donors than that in EMAB (methoxy group). Among the molecules studied, the derivative obtained by substituting EMAB's methoxy group with the pyrrolyl group was found to exhibit the best NLO properties. Conclusively, the NLO activities of EMAB can be significantly improved through the substitution of its methoxy group with stronger electron donors.