Gaussian 09W Research Articles

Study on Photophysical Properties of N-Arylphthalamic Acid Derivative Containing 1, 2, 4-Triazole Scaffold.

A novel N-arylphthalamic acid derivative, 2-({4-[(1H-1,2,4-triazol-1-yl)methyl]phenyl}carbamoyl)benzoic acid (TMPCB) was synthesized and their absorption and emission spectra were recorded in fifteen different solvents of varying polarities at room temperature. Ground state dipole moment of the derivative was calculated experimentally by Guggenheim method and solvatochromic approach proposed by Bilot-Kawski. The singlet excited state dipole moment of TMPCB were calculated experimentally based on different approaches of solvent polarity function proposed by Lippert-Mataga, Bakhshiev, Kawskii-Chamma-Viallet, Reichardt and Bilot-Kawski. Singlet excited state dipole moment was greater than ground state dipole moment in all the approaches which could be attributed to considerable π- electron density redistribution. Multiple Linear Regression (MLR) analysis based on Kamlet-Abboud-Taft and Catalan parameters were also studied to correlate solvatochromism and influence of solvents with absorbance and emission spectra. Ground and singlet excited state optimizations of the molecule were also performed using Gaussian 09W software. HOMO-LUMO energies of the phthalamic acid derivative have been obtained using TD-DFT/PCM (B3LYP/6-31G (d, p)) computations and experimentally by using cyclic voltammetry. Mulliken charges and molecular electrostatic potential plot have also been generated from DFT calculations to identify nucleophilic and electrophilic sites of TMPCB.

Computational and experimental studies on dielectric relaxation and dipole moment of some anilines and phenol

In the present study, the dielectric relaxation behaviour of four polar molecules namely 2-Nitroaniline, 4-Bromoaniline, 4-Chloroaniline and 4-Chlorophenol were studied in dilute solutions of benzene using microwave bench at 9.59GHz frequency. The different parameters like, dielectric constant (ε′), dielectric loss (ε″), static dielectric constant (ε0) and optical permittivity (ε∞) have been determined. Further from these values, dipole moment (μ) and relaxation time (τ) were calculated for all the molecules following Gopalkrishna, microwave conductivity and the Higasi method. The dipole moment for all the molecules were also estimated theoretically from ab initio computations by using Density Functional Theory (DFT) calculations with the help of Gaussian 09W software. Dipole moments determined experimentally and through DFT computations are in good agreement with the dipole moments estimated by taking vector sum of group moments of Aniline, Nitrobenzene, Bromobenzene, Chlorobenzene and Phenol by neglecting interaction between pendant groups. The experimentally determined relaxation times were analyzed in terms of Stokes-Einstein-Debye (SED) theory and the results are compared with molecular radii estimated from DFT and Edward's atomic increment methods. Further, in order to understand the chemical stability and reactivity of all these molecules, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and HOMO-LUMO energy gap were also estimated from DFT computations. Our experimental findings suggest that, 2-Nitroaniline exhibits simple Debye type relaxation behaviour while the other three samples exhibit Higasi's distribution of relaxation times which may be due to both overall and intra-molecular rotation of the molecules. Further, the HOMO-LUMO studies revealed that, 2-Nitroaniline is more chemically reactive having least energy gap and 4-Chlorophenol is least chemically reactive having highest energy gap among the four samples.

Density functional theory studies of the uncatalysed gas-phase oxidative dehydrogenation conversion of n-hexane to hexenes

Density Functional Theory (DFT) modelling studies were conducted for the activation of n-hexane in the gas-phase under experimental conditions of 573, 673 and 773K.The aim of the study was to establish the most favourable radical mechanism for the oxidative dehydrogenation (ODH) of n-hexane to 1- and 2-hexene. Modelling of the 3-hexene pathway was omitted due to absence of this product in laboratory experiments. Computations were performed using GAUSSIAN 09W and molecular structures were drawn using the GaussView 5.0 graphics interface. The B3LYP hybrid functional and the 6-311+g(d,p) basis set were utilized for all the atoms. The most kinetically and thermodynamically favourable pathways are proposed based on the determination of the relative total energies (ΔE#, ΔE, ΔG# and ΔG) for the different reaction pathways. The initial C-H activation step is β-H abstraction from n-hexane (C6H14) by molecular oxygen (O2) to form the alkoxy (C6H13O) and hydroxyl (OH) radicals. This is proposed as the rate-determining step (RDS) with the calculated ΔE#=+42.4kcal/mol. Two propagation pathways that involve, separately, the C6H13O and OH radicals may lead to the formation of 2-hexene. In both the propagation pathways, the C6H13O and OH radicals activate further C6H14 molecules to produce C6H13OH and H2O, respectively, and the alkyl radicals (C6H13). Thereafter, one pathway involves the interaction of the C6H13 radical with further molecular O2, and leads to a second CH activation step that yields 2-hexene and the peroxy radical (OOH). The other pathway is associated with hydrogen transfer from the OOH radical to C6H13OH that is produced earlier, leading to water and the alkyl peroxy radical (C6H13OO). The C6H13OO radical undergoes intramolecular H-abstraction to yield 2-hexene and the OOH radical, and the latter disproportionate through intermediate OH radicals to produce O2 and H2O in the termination step.

QSAR analyses of Octahydroquinazolinone for insecticidal activity against spodoptera litura and its in-silico validation using molecular Docking study.

In order to establish a quantitative structure-activity relationship (QSAR) for Insecticide activity against spodoptera litura, we have, first, studied a series of 14 substituted Octahydroquinazolinone and derivatives by using Density functional theory calculations (DFT) .To get insights into the structure and property information for this series of molecules and to better understanding the relationship between structure and activity, we have used Molecular Docking method. Descriptors such as total energy, Gap energy, HOMO and LUMO energies, dipole moment (µ), electronegativity (χ), global hardness (η), softness (σ), electrophilicity index, partition coefficient, repulsion energy, ovality, log P, boiling point, cluster count and Molecular weight, provide vital information about the insecticide activity of substituted Octahydroquinazolinone, The MLR has served to select those descriptors and also to propose a quantitative model based on such calculated parameters to predict insect mortality (S. litura) by contact and feeding methods, and the % growth inhibition index against Spodoptera litura. After, we try to interpret these types of activities. The topological and the electronic descriptors were computed with ACD/ChemSketch and Gaussian 03W program, respectively.

Ab initio and QSAR study of several etoposides as anticancer drugs: Solvent effect

Quantitative structure-activity relationship (QSAR) of twenty-five different Etoposides derivatives was estimated by means of multiple linear regression (MLR), artificial neural network (ANN), simulated annealing (SA) and genetic algorithm (GA) techniques. The geometric compounds were selected as optimized samples using Gaussian 09W at B3LYP/6-31g. A high predictive ability was observed for the MLR-MLR, MLR-ANN, SA-ANN, MLR-GA and GA-ANN models, with the root mean sum square errors (RMSE) of 0.6265, 0.223, 0.195, 0.161 and 0.061 in gas phase and 0.5864, 0.226, 0.061, 0.106, and 0.0320 in the solvent phase, respectively (N = 25). The results obtained using the GA-ANN method indicated that the activity of derivatives of Etoposide depends on several parameters including Mor 14u, EEig12d, VEA1 and ICR descriptors in gas phase and RDF065p, Qxxe, ISH, RDF 050v and GATS6p descriptors in the solvent phase. Finally, the comparison of the quality of ANN with different MLR methods showed that ANN has a better predictive ability.

DFT Investigations for sensing capability of a single-walled Carbon nanotube for adsorptions H2, N2, O2 and CO molecules

Single-walled carbon nanotubes (SWCNTs) have a great deal of attention due to their unique properties. These properties of SWCNTs can be used in various devices such as nanosensors. SWCNTs nanosensors have fast response time and high sensitivity to special gas molecules which is very favorable for important applications. Recently, gas adsorption over outer surface of SWCNTs nanosensors was arguably a very interesting theoretical study. Here, the sensing capability of (6,0) SWCNTs for adsorption H2, N2, O2 and CO molecules are studied.Thegeometry optimization, electronic, thermodynamic, and vibrational properties have been investigated. All the calculations are based on the density functional theory (DFT) at the B3LYP/6-31G level through the Gaussian 09W program package. It is found that, adding these molecules to SWCNT causing a small increase in the bond lengths, and an increase in the total energy. In IR spectra, it is observed increasing the vibration modes and higher stretching vibration wave numbers of SWCNT with the studies molecules. This work confirms that (6,0) SWCNT can be used as nanosensor, and using DFT investigations, it is possible to obtain much more data to apply in medical science and industrial technologies.

Evaluation of corrosion protection of epoxy coatings on copper during exposure to an aerated 3% NaCl solution.

In this study the anticorrosion performance of a clear epoxy coating was enhanced by the incorporation of modified zinc into the polymer matrix. The structural macroscopy by X-ray diffraction (XRD). Corrosion performance of the coated copper specimens was investigated employing polarization measurements and electrochemical impedance spectroscopy (EIS) in 3% NaCl solution. Incorporation of 5 wt% zinc possessed the best corrosion performance. The electrochemical results are completely in agreement with the morphological results of the surface obtained from scanning electron microscopy (SEM). For the theoretical study, complete geometry optimization of 4, 4′- Ethylene bis (N, N diglycidylaniline) was performed using the Density Functional Theory (DFT). The Gaussian 03W software package was used in the calculations.

Growth and physical characterization of organic nonlinear optical single crystal: N,N′-diphenylguanidinium formate

A second-harmonic generation (SHG) crystal N,N′-diphenylguanidinium formate (DPGF) with good quality was successfully grown by the slow evaporation method. Single crystal X-ray diffraction study confirms that the DPGF crystallizes in orthorhombic crystal system with space group P21cn. The powder XRD pattern shows the various planes of DPGF crystal. The 1H and 13C NMR spectral studies further confirm the molecular structure of the grown crystal. The various functional groups present in the grown crystal have been identified by Fourier transform infrared spectroscopy. The UV–vis–NIR spectrum was recorded to find the optical transmittance window, lower cut off wavelength and band gap of the DPGF crystal. Photoluminescence spectrum shows broad emission peak observed at 367nm. Thermal stability of the title crystal was evaluated by thermogravimetric (TG) and differential thermal analysis. Vicker's microhardness study was carried out to reveal the mechanical properties of the grown crystal. The second harmonic conversion efficiency of DPGF crystal was 1.8 times than that of KDP crystal. Gaussian 03W program has been used to calculate the molecular orbital and first order hyperpolarizability of the molecule. The calculated first order hyperpolarizability value of DPGF is found to be 16 times greater than that of urea.

Theoretical study of the design dye-sensitivity for usage in the solar cell device

There are many applications in the polymer chemistry, pharmaceutical, agricultural and industrial fields of the thiadiazole molecule and their derivatives. Allowance of the energy gap of the polymer conjugated is an object of great interesting debit for the possible removal of a doping in the preparation of highly conductivity polymers. Thiadiazoles derivatives are structural foundation of the polymer materials. In this present work, the electronic properties of graphene nanoflakes (GNFs)-phenanthrene-1,3,4-thiadiazoles oligomers are studied and discussed. Where thiadiazoles is expanded from one to 9 unit's molecules at the structure. The energy gap, HOMO, LUMO distribution, total energy, Fermi level energy, work function, maximum wavelength absorption, vertical absorption energies, and oscillator strengths are calculated for each molecule. All calculations are carry out by usage density function theory (DFT) and depended time density function theory (TD-DFT) with the B3LYP/6-31G model in the Gaussian 09W software packages. Results show that increasing the number of monomeric units lead to great enhance in the electronic properties, which caused it decreased the band gap from 3.17eV in the system with one unit of thiadiazole just to 1.35eV in the system with 9units of thiadiazole. This case is raised the value of maximum absorption wavelengths to >500nm to give the better performance in optoelectronic and solar cell, as these structures have prime absorption bands within the solar spectrum.

QSPR and DFT Studies on the Melting Point of Carbocyclic Nitroaromatic Compounds

A quantitative structure-property relationship (QSPR) study was performed to predict the melting points of 60 carbocyclic nitroaromatic compounds using the electronic and topologic descriptors computed respectively, with ACD/ ChemSketch and Gaussian 03W programs. The structures of all 60 compounds were optimized using the hybrid density functional theory (DFT) at the B3LYP/6-31G(d) level of theory. In both approaches, 50 compounds were assigned as the training set and the rest as the test set. These compounds were analyzed by the principal components analysis (PCA) method, a descendant multiple linear regression (MLR) analyses and an artificial neural network (ANN). The robustness of the obtained models was assessed by leave-many-out cross-validation, and external validation through test set. This study shows that the PCA and MLR have served also to predict melting point and some other physicochemical properties, but when compared with the results given by the ANN (R=0.997), we realized that the predictions fulfilled by this latter were more effective and much better than other models.

Synthesis, spectroscopic investigations (FT-IR, NMR, UV–Vis, and TD-DFT), and molecular docking of (E)-1-(benzo[d][1, 3]dioxol-6-yl)-3-(6-methoxynaphthalen-2-yl)prop-2-en-1-one

The compound (E)-1-(benzo [d] [1, 3] dioxol-6-yl)-3-(6-methoxy naphthalen-2-yl) prop-2-en-1-one (AKN) was synthesized and characterized by FT-IR, NMR, and UV–Vis spectrometer. The optimized molecular geometry, bond lengths, bond angles, atomic charges, harmonic vibrational wave numbers and intensities of vibrational bonds of the title compound have been investigated by Time dependent- Density Functional Theory (TD-DFT) using a standard B3LYP method with 6–31 G (d, p) basis set available in the Gaussian 09W package. 1H and 13C NMR chemical shifts of the molecule were calculated using Gauge-independent atomic orbital method (GIAO). Experimental excitation energies of the molecules were matched with the theoretically calculated energies. The atomic charge distributions of the various atoms present in the AKN were obtained by Mulliken charge population analysis. The Molecular Electrostatic Potential (MEP) analysis reveals the sites for electrophilic attack and nucleophilic reactions in the molecule. The difference between the observed and scaled frequencies was small. The HOMO to LUMO transition implies an electron density transfer. The intramolecular contacts have been interpreted using Natural Bond Orbital (NBO) analysis. The calculation results were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. To provide information about the interactions between human cytochrome protein and the novel compound theoretically, docking studies were carried out using Schrödinger software.

Bis (3-methoxy-4-hydroxybenzaldehyde-2,4,6-trinitrophenol) organic cocrystal: Synthesis and physico-chemical properties

A 3-methoxy-4-hydroxybenzaldehyde-2,4,6-trinitrophenol (mhba-tnp) cocrystal was grown by the slow evaporation solution growth technique using ethanol as a solvent. As-grown crystals were characterized by single crystal X-ray diffraction (XRD) study and crystallized with a centrosymmetric space group. Optical properties of the grown crystal have been studied by Ultraviolet-Visible (UV-Vis) absorption spectra in the range from 200 to 800nm and the band gap energy of the crystal was obtained as 2.8eV. Fourier transform infrared (FTIR) and micro Raman spectral analyses have been carried out to confirm the functional groups present in the title compound. Differential scanning calorimetry (DSC) and polarized light thermomicroscopy (PLTM) analyses were carried out to find the melting point. In addition, the optimized geometric parameters and the molecular orbitals were calculated using density functional theory (DFT) with the help of the Gaussian 03W software.

Quantum Chemical Calculations and Molecular Docking Studies of Some NSAID Drugs (Aceclofenac, Salicylic Acid, and Piroxicam) as 1PGE Inhibitors

The molecular structure of the three compounds Aceclofenac (I), Salicylic Acid (II), and Piroxicam (III) has been determined using Gaussian 03W program with B3LYP method using 6-311++G (d,p) basis set calculations. The molecular structures were fully optimized with atomic numbering scheme adopted in the study. To understand the mode of binding and molecular interaction, the docking studies of compounds Aceclofenac (I), Salicylic Acid (II), and Piroxicam (III) have been carried out with prostaglandin H2 synthase-1 (1PGE) as target using induced fit docking. The molecular docking results show that the interactions and energy for Aceclofenac, Salicylic Acid, and Piroxicam show the best results when docked with prostaglandin H2 synthase-1 (1PGE). The hydrogen bonding interactions of compound I (Aceclofenac) are prominent with Arginine moiety, those of compound II (Salicylic Acid) are prominent with Tyrosine and Serine moieties, and compound III (Piroxicam) shows such interaction with Tyrosine and Arginine moieties. These interactions of prostaglandin H2 synthase-1 (1PGE) with substrates are responsible for governing COX-1 inhibitor potency which in turn is a direct measure of the potency of the drug.

Characterization and intramolecular bonding patterns of busulfan: Experimental and quantum chemical approach

The investigations of structural conformers, molecular interactions and vibrational characterization of pharmaceutical drug are helpful to understand their behaviour. In the present work, the 2D potential energy surface (PES) scan has been performed on the dihedral angles C6O4S1C5 and C25S22O19C16 to find the stable conformers of busulfan. In order to show the effects of long range interactions, the structures on the global minima of PES scan have been further optimized by B3LYP/6-311++G(d,p) method with and without empirical dispersion functional in Gaussian 09W package. The presence of n→σ* and σ→σ* interactions which lead to stability of the molecule have been predicted by natural bond orbital analysis. The strong and weak hydrogen bonds between the functional groups of busulfan were analyzed using quantum topological atoms in molecules analysis. In order to study the long-range forces, such as van der Waals interactions, steric effect in busulfan, the reduced density gradient as well as isosurface defining these interactions has been plotted using Multiwfn software. The spectroscopic characterization on the solid phase of busulfan has been studied by experimental FT-IR and FT-Raman spectra. From the 13C and 1H NMR spectra, the chemical shifts of individual C and H atoms of busulfan have been predicted. The maximum absorption wavelengths corresponding to the electronic transitions between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of busulfan have been found by UV–vis spectrum.

A mixed experimental and theoretical study on chelidamate copper(II) complex with 4-methylpyrimidine

A new chelidamate complex, [Cu(chel)(H2O)2(mpd)] (chel = chelidamate; mpd = 4-methylpyrimidine), has been synthesized and characterized through a combination of single crystal X-ray analysis, electron paramagnetic resonance (EPR), ultraviolet-visible (UV-vis), and fourier transform infrared spectroscopy (FT-IR). The complex has six-coordinate distorted octahedral geometry around Cu(II). The theoretical vibrational frequencies and optimized geometric parameters (bond lengths and angles) have been calculated using Density Functional Theory (DFT)/B3LYP and Hartree Fock quantum chemical methods with 6-31G(d, p) basis set by Gaussian 09W software. The EPR spectrum of the compound showed that the paramagnetic center has rhombic symmetry. The EPR studies were carried out using the following unrestricted hybrid density functionals: B3LYP, CAM-B3LYP, HSEH1PBE, WB97XD, MPW1PW91, and BPV86. The UV–vis absorption spectra have been examined in different media and compared with the calculated one using TD-DFT method by applying the polarizable continuum model. Natural bond orbital property of complex has been performed by DFT/B3LYP with 6-31G (d, p) basis set.

Theoretical calculation on a compound formed by methyl alcohol and simmondsin

Etheric oil results from the esterification reactions of oil acids with alcohols. In these reactions, one molecule water (H2O) is composed of H× protons from oil acids and OH- groups which separated from alcohol. Etheric oil is commonly used in food industry, perfume industry and medicine. From this perspective, we need to know physical properties of etheric oil as well as chemical properties. In this study, the highest occupied molecular orbital (HOMO) energies, the lowest unoccupied molecular orbital (LUMO) energies, the electronic properties (total energy, electronegativity, chemical hardness and softness), NBO analysis and thermodynamic parameters of a compound formed by methyl alcohol and simmondsin have been performed by using Gaussian 09W program. The structural and spectroscopic data of the molecule in the ground state have been calculated by using density functional method (DFT/B3LYP) with the 6-31++G(d,p) basis set.

Synthesis, spectroscopic characterization and DFT calculations on N-(Phenylsulfonyl)-l-asparagine (NPLAS): A potential nonlinear optical material

The N-(Phenylsulfonyl)-l-asparagine (NPLAS), which is a potential nonlinear optical material, was synthesized and its geometric structure was optimized to obtain its geometric parameters, vibration frequencies and electronic structures at Hartree-Fock (HF) and B3LYP level of density functional theory (DFT) with 6–311++G(d,p) basis set, using Gaussian 09W program. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the title molecule were calculated by using the gauge independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and individual gauges for atoms in molecules (IGAIM) methods and were also compared with experimental values. The electronic properties HOMO and LUMO energies were calculated and analyzed. Potential energy surface scan, natural population analysis (NPA) and Mulliken’s atomic charges were also investigated using DFT and HF models. A detailed molecular picture and intermolecular interactions arising from hyperconjugative interactions and charge delocalization of the molecule were analyzed using natural bond orbital (NBO) analysis.

Synthesis, Spectroscopic Investigation and Computational Studies of 2-Formyl-4-(Phenyldiazenyl)Phenyl Methyl Carbonate and 4-((4-Chlorophenyl)Diazenyl)-2-Formylphenyl Methyl Carbonate

Two new compounds namely 2-formyl-4-(phenyldiazenyl)phenyl methyl carbonate (FPMC) and 4-((4-chlorophenyl) diazenyl)-2-formylphenyl methyl carbonate (CFPMC) have been synthesized and have characterized using FT-IR, FT-Raman, 1H and 13C NMR techniques. Computational optimization studies have been carried out using Hatree–Fock (HF) and Density Functional Theory (DFT–B3LYP) methods with 6–31+G(d, p) basis set of Gaussian 09W software. The stable configuration of the title compounds were achieved theoretically by potential energy surface scan analysis. The complete vibrational assignments were performed on the basis of total energy distribution (TED) and natural bonding orbital (NBO) have been studied. Various parameters such as EHOMO, ELUMO,total energy, dipole moment, polarizability, first order hyperpolarizability, zero–point vibrational energy as well as thermal properties were analyzed and reported for the title compounds.

Synthesis, crystal structures, spectroscopic analysis and DFT calculations of 2-ethoxy-1-naphtaldehyde and (E)-N-((2-ethoxynaphthalen-1-yl)methylene)-3-methylaniline

(E)-N-((2-ethoxynaphthalen-1-yl)methylene)-3-methylaniline has been synthesized and characterized by using single-crystal X-ray diffraction, FT-IR, UV–Visible spectroscopy and computational methods. By using the same techniques, also for the first time, the 2-ethoxy-1-naphtaldehyde has been characterized. The molecular geometries, intra- and inter-molecular interactions of the compounds have been found by using X-ray crystallography. Characteristic infrared bands and the electronic bands have been discovered by experimental and theoretical IR and UV–Vis. spectroscopy. The geometry optimizations and the calculations of IR frequencies have been performed by using the Gaussian type orbitals at Gaussian 09W and the Slater type orbitals at ADF2009.01 software. In addition, the Fukui functions have been calculated to reveal active sites of the compounds. Furthermore, non-linear optical properties and thermodynamic correlation functions have been theoretically found for a further study of the titled compounds.

Analysis of furfural dissolved in transformer oil based on confocal laser Raman spectroscopy

Furfural (Furan-2-carbaldehyde) dissolved in transformer oil is regarded as an important mark of the thermal and mechanical degradation in oil-paper insulation. Confocal laser Raman spectroscopy (CLRS) is an effective means of detecting trace liquid and has been widely applied in many fields. Using CLRS to detect furfural concentration can overcome many disadvantages of traditional detection methods and accelerate testing. Thus, the application of CLRS in the detection of furfural concentration was investigated in this research. A structure model of a furfural molecule was constructed with Gaussian 09W software. Then, the Raman spectrum of this molecule was analyzed theoretically. Meanwhile, a set of liquid test platforms was set up based on basic CLRS principles. Subsequently, standard transformer oil samples were tested by utilizing extraction technology together with the CLRS liquid test platform. As a result, the peak at 1677 cm−1 was selected as the Raman characteristic peak. The detection limit reached 0.10 mg/L. In addition, a quantitative analysis model was constructed between the concentrations and the Raman characteristic peak areas by applying external standard method and least square method. Finally, six types of oil samples with different furfural concentrations were detected; the test results were compared with those obtained through high-performance liquid chromatography. Comparison results showed that CLRS with extraction can quantitatively and effectively detect the furfural concentration in transformer oil (with a maximum error less than 11.7%). Therefore, a new detection tool is presented for assessing the degradation of insulating papers in power transformers.