Quantum mechanical and spectroscopic (FT-IR, FT-Raman,1H,13C NMR, UV-Vis) studies, NBO, NLO, HOMO, LUMO and Fukui function analysis of 5-Methoxy-1H-benzo[d]imidazole-2(3H)-thione by DFT studies

The role of biochemical and biophysical properties, molecular docking and dynamics studies on azelastine

The structure of the 4-(4-chlorobenzyl)-2-(1-methylazepan-4-yl) phthalazin-1(2H)-one (IA) was optimized through computational study. The optimized structure revealed that the bond length between atoms C3 and C5 was the longest at 1.54 Å, while the bond between atoms C10 and H31 had the lowest length at about 1.01 Å, respectively. The natural bond orbital (NBO) analysis indicates that the bonding π(C3-C20) to anti-bonding π∗(N2-C3) interaction exhibits the most significant stabilization energy of about 253.59 kcal/mol. Due to the solvent's influence, the gas phase MEP value and HOMO-LUMO band gap value are lower, when compared to solvents. A localized bond pair that undergoes movement between two atoms, and a bond pair that undergoes movement between two different pairs of atoms are identified by electron localized function (ELF), localized orbital locator (LOL), and average localized ionization energy (ALIE) studies, respectively. The electron density and thermodynamic properties were determined using Gaussian software. This study examined various parameters such as non-linear optical (NLO), molecular electrostatic potential (MEP), UV-vis, and HOMO-LUMO in different solvents. Further, the biological activity of the IA compound was studied using molecular docking and dynamics on the target Mycobacterium tuberculosis ArgF (7NOR) protein, which showed favorable protein-ligand interaction energy.

Synthesis, Structural Characterization, Hirshfeld Surface Analysis, and Evaluation of Nonlinear Optical Properties of Novel Cocrystal of Acridine with 2,4-Dihydroxybenzaldehyde

A cocrystal of acridine with 2,4-dihydroxybenzaldehyde (2:1 stoichiometric ratio) was synthesized, spectrally and structurally characterized using TG, DSC, ATR-FTIR and Single-Crystal XRD methods and Hirshfeld surface analysis, and its nonlinear optical properties were investigated by DFT at the B3LYP/6-311++Glevel. The obtained compound crystallizes in the noncentrosymmetric P21 monoclinic space group, with two molecules of acridine and one molecule of 2,4-dihydroxybenzaldehyde in the asymmetric unit. The strong O(aldehyde)-H⋯N(acridine) and weak C(aldehyde)-H⋯O(aldehyde) and C(aldehyde)-H⋯O(aldehyde) hydrogen bonds, as well as π(acridine)-π(acridine) and C(acridine)-H⋯π(aldehyde) interactions, are present in the crystal lattice of the title compound. The calculated energy gap (ΔE) between the HOMO-LUMO surfaces shows charge transfer interactions due to the π-π* transitions among the molecules. The calculated first and second hyperpolarizability values indicate that obtained cocrystal is a promising candidate for nonlinear optical applications.

Synthesis of indano[60]fullerene thioketone and its application in organic solar cells

Evaporable indano[60]fullerene ketone (FIDO) was converted to indano[60]fullerene thioketone (FIDS) in high yield by using Lawesson's reagent. Three compounds with different substituents in para position were successfully converted to the corresponding thioketones, showing that the reaction tolerates compounds with electron-donating and electron-withdrawing substituents. Computational studies with density functional theory revealed the unique vibrations of the thioketone group in FIDS. The molecular structure of FIDS was confirmed by single-crystal X-ray analysis. Bulk heterojunction organic solar cells using three evaporable fullerene derivatives (FIDO, FIDS, C60) as electron-acceptors were compared, and the open-circuit voltage with FIDS was 0.16 V higher than that with C60.

13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion

Benzimidazole is an important heterocyclic fragment, present in many biologically active compounds with a great variety of therapeutic purposes. Most of the benzimidazole activities are explained through the existence of 1,3-tautomeric equilibrium. As the binding affinity of each tautomer to a protein target depends on an established bioactive conformation, the effect of tautomers on the ligand protein binding mechanism is determinant. In this work, we searched and analyzed a series of reported ¹³C-NMR spectra of benzazoles and benzazolidine-2-thiones with the purpose of estimating their tautomeric equilibrium. Herein, several approaches to determine this problem are presented, which makes it a good initial introduction to the non-expert reader. This chemical shift difference and C4/C7 signals of benzimidazolidine-2-thione and 1-methyl-2-thiomethylbenzimidazole as references were used in this work to quantitatively calculate, in solution, the pyrrole–pyridine tautomeric ratio in equilibrium. The analysis will help researchers to correctly assign the chemical shifts of benzimidazoles and to calculate their intracyclic or exocyclic tautomeric ratio as well as mesomeric proportion in benzimidazoles.

Structural and Vibrational Investigation of Benzil-(1,2-Diphenylethane-1,2-Dione): Experimental and Theoretical Studies

Single crystals of benzil commonly known as 1,2-diphenylethane-1,2-dione are grown by the slow evaporation method at room temperature. Gaussian 09 program is applied for theoretical calculations with B3LYP/6-311++G(d,p) basis set. The structure is optimized, and the energy, structural parameters, vibrational frequencies, IR, and Raman intensities are determined. Complete natural bonding orbital (NBO) analysis is carried out to analyze the intramolecular electronic interactions and their stabilization energies. From the second-order perturbation theory analysis of the benzil molecule, it is observed that there exists a hyperconjugative intramolecular stabilization energy between 17.45 and 22.76 KJmol-1. HOMO-LUMO analysis has been performed to identify the charges transferred within the molecule. The energy gap is calculated to be 2.919 eV and thus establishes the soft nature of the molecule. The molecular electrostatic potential (MEP) of the grown crystal was analyzed using the B3LYP method with 6-311++G(d,p) basis set. First-order hyperpolarizability calculations reveal the nonlinear optical microscopic behavior of the benzil molecule with nonzero values. The total value of the first-order hyperpolarizability ( ${\beta }_{\text{tot}}$ ) is of the order of $41.5246\times {10}^{-31}\text{esu}$ , which is found to be 11.135 times that of urea. Hence, benzil can be referred to as a good material for nonlinear optical applications.

Food Xanthan Polysaccharide Sulfation Process with Sulfamic Acid

Xanthan is an important polysaccharide with many beneficial properties. Sulfated xanthan derivatives have anticoagulant and antithrombotic activity. This work proposes a new method for the synthesis of xanthan sulfates using sulfamic acid. Various N-substituted ureas have been investigated as process activators. It was found that urea has the greatest activating ability. BBD of xanthan sulfation process with sulfamic acid in 1,4-dioxane has been carried out. It was shown that the optimal conditions for the sulfation of xanthan (13.1 wt% sulfur content) are: the amount of sulfating complex per 1 g of xanthan is 3.5 mmol, temperature 90 °C, duration 2.3 h. Sulfated xanthan with the maximum sulfur content was analyzed by physicochemical methods. Thus, in the FTIR spectrum of xanthan sulfate, in comparison with the initial xanthanum, absorption bands appear at 1247 cm-1, which corresponds to the vibrations of the sulfate group. It was shown by GPC chromatography that the starting xanthan gum has a bimodal molecular weight distribution of particles, including a high molecular weight fraction with Mw > 1000 kDa and an LMW fraction with Mw < 600 kDa. It was found that the Mw of sulfated xanthan gum has a lower value (~612 kDa) in comparison with the original xanthan gum, and a narrower molecular weight distribution and is characterized by lower PD values. It was shown by thermal analysis that the main decomposition of xanthan sulfate, in contrast to the initial xanthan, occurs in two stages. The DTG curve has two pronounced peaks, with maxima at 226 and 286 °C.

Tuning the Computational Evaluation of Spectroscopic, ELF, LOL, NCI analysis and Molecular Docking of Novel Anti COVID-19 Molecule 4-Dimethylamino Pyridinium 3, 5-Dichlorosalicylate

In this work novel antiviral compound 4-(Dimethylamino) Pyridinium 3, 5-dichlorosalicylate was synthesized and characterized by UV-vis, FT-IR, FT-Raman, 1H NMR and 13C NMR spectra. Quantum chemical computations were carried out by Density functional theory methods at B3LYP level. Electronic stability of the compound arising from hyper conjugative interactions and charge delocalization is investigated using natural bond orbital analysis. Assignments of vibrational spectra have been carried out with the aid of Normal coordinate analysis following the SQMFF methodology. TD-DFT approach was applied to assign the electronic transition observed in UV visible spectrum measured experimentally. Frontier molecular orbital energy gap affirms the bioactivity of the molecule and NCI analysis gives information about inter and intra non covalent interactions. ESP recognises the nucleophilic and electrophilic regions of molecule and the chemical implication of molecule was explained using ELF, LOL. The reactive sites of the compound were studied from the Fukui function calculations and chemical descriptors define the reactivity of the molecule. Molecular docking done with SARS and MERS proteins endorses the bioactivity of molecule and drug likeness factors were calculated to comprehend the biological assets of DADS.

Experimental and theoretical spectroscopic (FT-IR, FT-Raman, UV-VIS) analysis, natural bonding orbitals and molecular docking studies on 2-bromo-6-methoxynaphthalene: A potential anti-cancer drug

The vibrational, electronic and charge transfer studies on 2-bromo-6-methoxynaphthalene (2BMN) were done using DFT method with B3LYP/6-311++G(d,p) theory using GAUSSIAN 09W software. Theoretical and experimental investigations on FT-IR and FT Raman were executed on 2BMN. The calculated vibrational wavenumbers were scaled using suitable scaling factors and vibrational assignments were done to all modes of vibrations using Potential Energy Distribution (PED). Frontier Molecular Orbitals were calculated using TD-DFT method and the HOMO-LUMO energy gap was also obtained. Other electronic properties and global parameters for 2BMN were found using the HOMO-LUMO energy values. An energy gap of 4.208 eV shows the stability of the molecule. The reactive sites were predicted using Molecular Electrostatic Potential (MEP), Electron Localization Function (ELF) and Fukui calculations. Hence all electrophilic sites and nucleophilic areas of the molecule were determined. The delocalization of electron density was studied using NBO calculations. The intramolecular transitions and stability of structure were explained using in detail using the former. As the compound satisfies drug-like properties and has a softness value (indicating its less toxic nature), it may be used as a pharmaceutical product. Molecular docking studies were made and the protein-ligand binding properties were discussed. It was found out that title compound exhibits anti-cancer activities. The low binding energy predicts that the compound may be modified as a drug for treating Cancer.

Speculative assessment, molecular composition, PDOS, topology exploration (ELF, LOL, RDG), ligand-protein interactions, on 5-bromo-3-nitropyridine-2-carbonitrile

Computational calculations of 5-bromo-3-nitropyridine-2-carbonitrile (5B3N2C) on molecular structure and on energy are implemented using the 6-311++G(d,p) basis set by DFT/B3LYP method. The UV-Vis spectrum of 5B3N2C was obtained by TD-DFT with chloroform as a solvent. The analysis of molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) were used to evaluate, the entire electron density and organic reactive sites of 5B3N2C. The electron-hole conversions were conjointly deliberated. Donor-acceptor interactions (NBO) analysis examines the intra-and intermolecular charge transfer, hyper conjugate interaction of the compound. The orbital molecular contributions are evaluated by density of states (DOS and PDOS). To discern the reactivity of the molecule, topology analyses were done. The biological prominence of the 5B3N2C molecule was investigated in a pertinent study of molecular docking with target protein 3CEJ exhibiting the centromere associated protein inhibitor property. Molecular Dynamics simulations were done to assess the stability of the complex. 5B3N2C physiochemical parameters were also compared to those of widely viable medications Ispinesib and Lonafarnib.

Single-crystal X-ray structural characterization, Hirshfeld surface analysis, electronic properties, NBO, and NLO calculations and vibrational analysis of the monomeric and dimeric forms of 5-nitro-2-oxindole

The information of interactions is given by RDG versus sign(λ₂)ρ product of the sign of the second largest eigenvalue of electron density Hessian matrix and electron density) investigated by RDG surface analysis.

Synthesis, characterization and biological investigations of potentially bioactive heterocyclic compounds containing 4-hydroxy coumarin

In this paper, we have reported the synthesis of a series of heterocyclic azo dyes containing 4-hydroxy coumarin by diazo-coupling reaction. The structural aspect of the newly synthesized compounds was accomplished by various physico-chemical techniques like UV-Visible, FT-IR, NMR, and mass spectrometry. The computational calculations and geometrical optimization of the newly synthesized azo dyes were investigated by using Gaussian software with the help of Density functional theory (DFT)/B3LYP method using 6-31G(d,p) basis set at gaseous phase. Also, the quantum chemical parameters were evaluated to understand the structural activity concept of the dyes. The pharmacological efficacy of the azo dyes was investigated by antimicrobial, antitubercular, DNA cleavage and in silico molecular docking studies. All the newly synthesized compounds were able to exhibit significant inhibitory activity against tested microbes. Further, the in silico molecular docking showed effective binding properties of the compounds against RpsA target receptor.

Molecular docking, quantum chemical computational and vibrational studies on bicyclic heterocycle "6-nitro-2,3-dihydro-1,4-benzodioxine": Anti-cancer agent

The heterocyclic aromatic compounds are primarily used to make pharmaceutical and agrochemicals. In addition, these compounds can be chosen as antioxidants, corrosion inhibitors, electro and opto-electronic devices, polymer material, dye stuff, developers, etc. On the account of this, the heterocyclic aromatic 6-nitro-2,3-dihydro-1,4-benzodioxine (6N3DB) was chosen and the structure is optimized to predict the important properties of it. The structural parameters such as bond length and bond angle have been obtained by DFT/B3LYP/6-311++G(d,p) basis set to know the geometry and orientation of 6N3DB. The molecule has been characterized by FT-IR and FT-Raman spectroscopic techniques to predict the functional groups, vibrational modes and aromatic nature of 6N3DB. The chemical shifts of ¹H and ¹³C have been obtained experimentally and compared with the theoretical data. The parameters such as the band gap between HOMO-LUMO orbitals, λ_max, and electron transition probability in frontier orbitals have been estimated to know the NLO and corrosion inhibition activity. HOMO-LUMO orbital diagram has been obtained for different energy levels and their band gap energies have been compared with UV-vis band gap values. The chemical significance of the molecule has been explained using ELF, LOL, and RDG. The binding energy and intermolecular energy values indicate that the title compound possesses anti-cancer property through hydrolase inhibition activity.

Quantum chemical determination of molecular geometries and spectral investigation of 4-ethoxy-2, 3-difluoro benzamide

The present work reports the application of density functional theory (DFT) at B3LYP with various basis sets which provide the relationship between the structural and spectral properties of 4-ethoxy-2, 3-difluoro benzamide (4EDFB). A Complete vibrational analysis has been performed at the density functional theory (DFT) method with various basis sets in the ground state. The results of vibrational wave numbers are in good agreement with the experimental spectra (Infrared and Raman). Energy gap of the molecule is evaluated using frontier molecular orbital energies (HOMO-LUMO). The frontier energy gap value reveals the chemical reactivity and intermolecular charge transfer occur within the molecule. Global chemical descriptors provide the local and global softness and local reactivity parameters used to identify the nucleophilic and electrophilic behavior of a specific site within the compound. The dimer structure is performed to evaluate the intermolecular hydrogen bond (O-H-O). The title molecule is capable of receiving second harmonic generation (SHG) is due to high value of hyperpolarizability indicates the NLO activity of the molecule. Apart from NLO entities, aromaticity and the molecular electrostatic potential surface (MEP) explain the hydrogen bonding and provide the reactive behavior of the molecule. The Mulliken population analysis leads to redistribution of electron density in the ring.

Experimental and theoretical studies of Schiff bases as corrosion inhibitors

Background

Relatively inexpensive, stable Schiff bases, namely 3-((4-hydroxybenzylidene)amino)-2-methylquinazolin-4(3H)-one (BZ3) and 3-((4-(dimethylamino)benzylidene)amino)-2-methylquinazolin-4(3H)-one (BZ4), were employed as highly efficient inhibitors of mild steel corrosion by corrosive acid.

Findings

The inhibition efficiencies were estimated based on weight loss method. Moreover, scanning electron microscopy was used to investigate the inhibition mechanism. The synthesized Schiff bases were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and micro-elemental analysis. The inhibition efficiency depends on three factors: the amount of nitrogen in the inhibitor, the inhibitor concentration and the inhibitor molecular weight.

Conclusions

Inhibition efficiencies of 96 and 92% were achieved with BZ4 and BZ3, respectively, at the maximum tested concentration. Density functional theory calculations of BZ3 and BZ4 were performed to compare the effects of hydroxyl and N,N-dimethylamino substituents on the inhibition efficiency, providing insight for designing new molecular structures that exhibit enhanced inhibition efficiencies.

An investigation of the olive phenols activity as a natural medicine

The natural antioxidants of olive oil have phenolic structure and their activities are related to the formation of stable derivatives. In this study, the single components of the phenolic fraction of olive oil (1,4-hydroquinone, Semiquinone and 1,4-benzoquinone) have been studied as theoretical by using DFT (Density functional Theory). The behaviors of phenolic compounds of olive against to the alkyl peroxy radicals were investigated. Our data show that 1,4-benzoquinone is the best electron transfer agent in primary metabolic processes to human life. The frontier orbital gap, namely HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gap is the smallest for 1,4-benzoquinone. Hence, it is more stable than the others in blood. The natural phenolic compound’s mechanism of many plants can be explained by using DFT method without consuming time and money. In this study, we have indicated the behaviors of natural antioxidants of olive oil’s single components phenolic structure in blood phase.