scholarly journals Comparative DFT Study of Phytochemical Constituents of the Fruits of Cucumis trigonus Roxb. and Cucumis sativus Linn.

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Subarayan Bothi Gopalakrishnan ◽  
Thangaraj Kalaiarasi ◽  
Ramasamy Subramanian
Keyword(s):  
Cucumis Sativus ◽  
Density Functional ◽  
Energy Gap ◽  
Effective Properties ◽  
Chemical Reactivity ◽  
Basis Set ◽  
The Density Functional Theory ◽  
Homo And Lumo ◽  
Phytochemical Constituents ◽  
Effective Drugs

The hepatoprotective active phytochemical constituents from the ethanolic extracts of the fruits of Cucumis trigonus Roxb. and Cucumis sativus Linn. were identified by GC-MS analysis. The density functional theory (DFT) of these molecules was calculated by density functional B3LYP methods using B3LYP/6-311++G(d,p) basis set. The optimized geometries of phytochemical constituents were evaluated. Physicochemical properties such as HOMO, LUMO, ionization potential, electron affinity, electronegativity, electrochemical potential, hardness, softness, electrophilicity, total energy, and dipole moment have also been recorded. These are very important parameters to understand the chemical reactivity and biological activity of the phytochemical constituents. Glycodeoxycholic acid and 2-(2-methylcyclohexylidene)-hydrazinecarboxamide were found to be effective drugs selected on the basis of their HOMO and LUMO energy gap and softness. The effective properties of these compounds may be due to the presence of amino, carbonyl, and alcohol as a functional group.

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

2020 ◽  
Vol 17 ◽  
Author(s):  
Sangeeta Srivastava ◽  
Nadeem Ahmad Ansari ◽  
Sadaf Aleem
Keyword(s):  
Gallic Acid ◽  
Density Functional ◽  
Energy Gap ◽  
Basis Set ◽  
Major Constituent ◽  
Orbital Energy ◽  
Reactivity Descriptors ◽  
Homo And Lumo ◽  
Electrophilic Reactivity ◽  
Global And Local

: 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 6-31G (d,p) basis set have been used for quantum chemical calculations. AIM (Atom in 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 gap were calculated by time dependant DFT approach using IEFPCM model. Small value for HOMO–LUMO energy gap indicated that easier charge transfer occurs within compound 4. The nucleophilic and electrophilic reactivity were 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.

SOLVENT EFFECTS ON THE ELECTRONIC STRUCTURE AND NON-LINEAR OPTICAL PROPERTIES OF PYRENE AND SOME OF ITS DERIVATIVES BASED ON DENSITY FUNCTIONAL THEORY

2021 ◽  
Vol 4 (4) ◽  
pp. 236-251
Author(s):  
A. S. Gidado ◽  
L. S. Taura ◽  
A. Musa
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Energy Gap ◽  
Chemical Reactivity ◽  
Basis Set ◽  
Lumo Energy ◽  
Functional Theory ◽  
Organic Optoelectronic ◽  
Homo Lumo

Pyrene (C16H10) is an organic semiconductor which has wide applications in the field of organic electronics suitable for the development of organic light emitting diodes (OLED) and organic photovoltaic cells (OPV). In this work, Density Functional Theory (DFT) using Becke’s three and Lee Yang Parr (B3LYP) functional with basis set 6-311++G(d, p) implemented in Gaussian 03 package was  used to compute total energy, bond parameters, HOMO-LUMO energy gap, electron affinity, ionization potential, chemical reactivity descriptors, dipole moment, isotropic polarizability (α), anisotropy of polarizability ( Δ∝) total first order hyper-polarizability () and second order hyperpolarizability (). The molecules used are pyrene, 1-chloropyrene and 4-chloropyrene  in gas phase and in five different solvents: benzene, chloroform, acetone, DMSO and water. The results obtained show that solvents and chlorination actually influenced the properties of the molecules. The isolated pyrene in acetone has the largest value of HOMO-LUMO energy gap of and is a bit closer to a previously reported experimental value of  and hence is the most stable. Thus, the pyrene molecule has more kinetic stability and can be described as low reactive molecule. The calculated dipole moments are in the order of 4-chloropyrene (1.7645 D) < 1-chloropyrene (1.9663 D) in gas phase. The anisotropy of polarizability ( for pyrene and its derivatives were found to increase with increasing polarity of the solvents.  In a nutshell, the molecules will be promising for organic optoelectronic devices based on their computed properties as reported by this work.

Density Functional Study on the Configurations of Nen (n=2~36) Clusters

2017 ◽  
Vol 727 ◽  
pp. 381-387
Author(s):  
Chang Ning Peng ◽  
Xing Rong Zheng
Keyword(s):  
Binding Energy ◽  
Density Functional ◽  
Energy Gap ◽  
Geometry Optimization ◽  
Basis Set ◽  
Functional Study ◽  
B3lyp Method ◽  
The Density Functional Theory ◽  
Quantum Chemistry Calculations ◽  
Average Bond

Based on the First-principles and the method of quantum chemistry calculations, using the B3LYP method and 6-31G basis set of the density functional theory (DFT), the configurations and binding energy of Nen (n=2~36) clusters are calculated and studied theoretically after the calculation of geometry optimization. By changing the atomic number n of the Nen (n=2~36) clusters, it obtained that the stable structures, the binding energy and HOMO - LUMO energy gap of the Nen (n=2~36) clusters under the same ideal conditions, and summarizes the change rule of the stable configurations, the binding energy and the average bond length of the Nen (n=2~36) clusters.

scholarly journals On the Use of DFT+U to Describe the Electronic Structure of TiO2 Nanoparticles: (TiO2)35 as a Case Study

2020 ◽  
Author(s):  
Angel Morales ◽  
Stephen Rhatigan ◽  
Michael Nolan ◽  
Frances Illas
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Plane Waves ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Rotationally Invariant

One of the main drawbacks in the density functional theory (DFT) formalism is the underestimation of the energy gaps in semiconducting materials. The combination of DFT with an explicit treatment of electronic correlation with a Hubbard-like model, known as DFT+<i>U</i> method, has been extensively applied to open up the energy gap in materials. Here, we introduce a systematic study where the selection of <i>U</i> parameter is analyzed considering two different basis sets: plane-waves (PWs) and numerical atomic orbitals (NAOs), together with different implementations for including <i>U</i>, to investigate the structural and electronic properties of a well-defined bipyramidal (TiO<sub>2</sub>)<sub>35 </sub>nanoparticle (NP). This study reveals, as expected, that a certain <i>U</i> value can reproduce the experimental value for the energy gap. However, there is a high dependence on the choice of basis set and, and on the +<i>U</i> parameter employed. The present study shows that the linear combination of the NAO basis functions, as implemented in FHI-aims, requires a lower <i>U</i> value than the simplified rotationally invariant approaches as implemented in VASP. Therefore, the transferability of <i>U</i> values between codes is unfeasible and not recommended, demanding initial benchmark studies for the property of interest as a reference to determine the appropriate value of <i>U</i>.

scholarly journals (E)-1-(Benzo[d][1,3]dioxol-5-yl)-3-([2,2′-bithiophen]-5-yl)prop-2-en-1-one: crystal structure, UV–Vis analysis and theoretical studies of a new π-conjugated chalcone

2019 ◽  
Vol 75 (5) ◽  
pp. 632-637
Author(s):  
Ainizatul Husna Anizaim ◽  
Muhamad Fikri Zaini ◽  
Muhammad Adlan Laruna ◽  
Ibrahim Abdul Razak ◽  
Suhana Arshad
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Weak Interactions ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Functional Theory ◽  
Compound C ◽  
Homo And Lumo ◽  
Experimental Values ◽  
Homo Lumo

In the title compound, C18H12O3S2, synthesized by the Claisen–Schmidt condensation method, the essentially planar chalcone unit adopts an s-cis configuration with respect to the carbonyl group within the ethylenic bridge. In the crystal, weak C—H...π interactions connect the molecules into zigzag chains along the b-axis direction. The molecular structure was optimized geometrically using Density Functional Theory (DFT) calculations at the B3LYP/6–311 G++(d,p) basis set level and compared with the experimental values. Molecular orbital calculations providing electron-density plots of HOMO and LUMO molecular orbitals and molecular electrostatic potentials (MEP) were also computed both with the DFT/B3LYP/6–311 G++(d,p) basis set. The experimental energy gap is 3.18 eV, whereas the theoretical HOMO–LUMO energy gap value is 2.73 eV. Hirshfeld surface analysis was used to further investigate the weak interactions present.

scholarly journals On the Use of DFT+U to Describe the Electronic Structure of TiO2 Nanoparticles: (TiO2)35 as a Case Study

2020 ◽  
Author(s):  
Angel Morales ◽  
Stephen Rhatigan ◽  
Michael Nolan ◽  
Frances Illas
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Plane Waves ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Rotationally Invariant

One of the main drawbacks in the density functional theory (DFT) formalism is the underestimation of the energy gaps in semiconducting materials. The combination of DFT with an explicit treatment of electronic correlation with a Hubbard-like model, known as DFT+<i>U</i> method, has been extensively applied to open up the energy gap in materials. Here, we introduce a systematic study where the selection of <i>U</i> parameter is analyzed considering two different basis sets: plane-waves (PWs) and numerical atomic orbitals (NAOs), together with different implementations for including <i>U</i>, to investigate the structural and electronic properties of a well-defined bipyramidal (TiO<sub>2</sub>)<sub>35 </sub>nanoparticle (NP). This study reveals, as expected, that a certain <i>U</i> value can reproduce the experimental value for the energy gap. However, there is a high dependence on the choice of basis set and, and on the +<i>U</i> parameter employed. The present study shows that the linear combination of the NAO basis functions, as implemented in FHI-aims, requires a lower <i>U</i> value than the simplified rotationally invariant approaches as implemented in VASP. Therefore, the transferability of <i>U</i> values between codes is unfeasible and not recommended, demanding initial benchmark studies for the property of interest as a reference to determine the appropriate value of <i>U</i>.

Investigating the Effect of Nitro Groups on the Electronic Properties of Phenanthrene Compound

2021 ◽  
Vol 14 (3) ◽  
pp. 221-230
Keyword(s):  
Fermi Level ◽  
Electronic Properties ◽  
Ionization Potential ◽  
Nitro Group ◽  
Density Functional ◽  
Energy Gap ◽  
Basis Set ◽  
Potential Surfaces ◽  
Homo And Lumo ◽  
Total Energies

Abstract: Theoretical study for calculating the electronic structure of phenanthrene compound and its simplest derivatives with nitro groups in different positions was performed using density functional theory (DFT) based on the hybrid function of three parameters. Lee-Yang-Parr [B3LYP] with 6-31 [d, p] basis set was used to investigate the effect of nitro groups on the electronic properties of phenanthrene compound. All calculations were obtaind by employing the used method using the Gaussian 09 package of programs. The energy gaps, total energies, the energy of HOMO and LUMO, softness, dipole moment, Fermi level, molecular symmetry, electrochemical hardness, electron density, electrostatic potential surfaces and infrared spectra were calculated. The results showed that the electronic properties of phenanthrene molecule are affected by the added nitro group. The total energy, energy gap and the HOMO and LUMO energy decreased compared with the original molecule. The ionization potential (IP), electron affinity (EA) and Fermi level (Ef) are increased compared with the original molecule. Keywords: B3LYP/DFT calculations, Phenanthrene molecule, Nitro group, Energy gap, Ionization potential.

scholarly journals Investigation of The Influence of Halogens, Cycloalkanes, Carbonyls and the Hydroxyl Groups on The Reactivity of 1, 3-Butadienes With Imine Dienophile: Insight From DFT, MEDT, and QTAIM

2021 ◽  
Author(s):  
Fredrick Asogwa ◽  
Hitler Louis ◽  
Dollars I. Kenthurky ◽  
Obieze C. Enudi
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Biological Activities ◽  
Diels Alder ◽  
Basis Set ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Free Energy Of Activation ◽  
Homo And Lumo ◽  
Gibb’S Free Energy

Abstract The presence of nitrogen atom either on the diene or the dienophile structure gives rise to aza or imino-Diels-Alder reactions (DARs). Among hetero-DARs, imino-dienophiles yields numerous functionalized compounds with numerous biological activities including but not limited to antifungal, antibacterial and enzymatic properties. Density functional theory (DFT) using the B3LYP functional at the 6-31+G (d, p) basis set along with topological studies (QTAIM) were used for the investigation of 10 different (SD1-SD10) DARs which differ in the nature of substituents groups attached to the diene molecule. The study indicates higher electron density and stronger interaction for substituted dienes with the cycloalkanes, furan, carbonyl, and -OH groups. It was observed in the HOMO-LUMO energy differences that the bulky groups; SD3, SD4, and SD6 had destabilization energy of -7.86 and 0.09, -7.88 and 0.10 and -7.50 and -0.014 eV respectively in their HOMO and LUMO levels while the halogen substituted dienes SD1, SD2, and SD5 had -8.20 and -0.32, -8.31 and -0.34 and -8.19 and -0.20 eV respectively. The study showed that synthesis of hetero-nuclear aza-cyclohexene is achieved faster with furan substituent of energy gap 7.534 eV and molecular hardness of 3.677 compared to 7.799 (SD7) -8.100 eV (SD8) and 3.899 (SD7) - 4.050 (SD8) respectively scored by other substituents noting that smaller energy gap leads to higher reactivity. HCOCH3 (SD8) retarded the rate of the reaction by about 58% (unspontaneous) following the calculated Gibb’s free energy of activation while SD6 in the ELF analysis showed complete covalent character against other cycloalkanes that showed dual characteristics of a double and single bond between N-C at their transition states.

Molecular Investigations of the Newly Synthesized Azomethines as Antioxidants: Theoretical and Experimental Studies

2019 ◽  
Vol 19 (6) ◽  
pp. 419-433 ◽  
Author(s):  
Siyamak Shahab ◽  
Masoome Sheikhi ◽  
Liudmila Filippovich ◽  
Evgenij Dikusar ◽  
Anhelina Pazniak ◽  
...  
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Experimental Studies ◽  
Antioxidant Property ◽  
Nbo Analysis ◽  
Antioxidant Potential ◽  
Functional Theory ◽  
Homo And Lumo ◽  
Intramolecular Hydrogen ◽  
Activity Mechanism

: In this study, the antioxidant property of new synthesized azomethins has been investigated as theoretical and experimental. Methods and Results: Density functional theory (DFT) was employed to investigate the Bond Dissociation Enthalpy (BDE), Mulliken Charges, NBO analysis, Ionization Potential (IP), Electron Affinities (EA), HOMO and LUMO energies, Hardness (η), Softness (S), Electronegativity (µ), Electrophilic Index (ω), Electron Donating Power (ω-), Electron Accepting Power (ω+) and Energy Gap (Eg) in order to deduce scavenging action of the two new synthesized azomethines (FD-1 and FD-2). Spin density calculations and NBO analysis were also carried out to understand the antioxidant activity mechanism. Comparison of BDE of FD-1 and FD-2 indicate the weal antioxidant potential of these structures. Conclusion: FD-1 and FD-2 have very high antioxidant potential due to the planarity and formation of intramolecular hydrogen bonds.

scholarly journals Density Functional Theory and Molecular Docking Investigations of the Chemical and Antibacterial Activities for 1-(4-Hydroxyphenyl)-3-phenylprop-2-en-1-one

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3631
Author(s):  
Ahmed M. Deghady ◽  
Rageh K. Hussein ◽  
Abdulrahman G. Alhamzani ◽  
Abeer Mera
Keyword(s):  
Density Functional Theory ◽  
Antibacterial Activity ◽  
Molecular Docking ◽  
Carbonyl Group ◽  
Active Sites ◽  
Density Functional ◽  
Chemical Reactivity ◽  
Basis Set ◽  
Molecular Docking Study ◽  
Functional Theory

The present investigation informs a descriptive study of 1-(4-Hydroxyphenyl) -3-phenylprop-2-en-1-one compound, by using density functional theory at B3LYP method with 6-311G** basis set. The oxygen atoms and π-system revealed a high chemical reactivity for the title compound as electron donor spots and active sites for an electrophilic attack. Quantum chemical parameters such as hardness (η), softness (S), electronegativity (χ), and electrophilicity (ω) were yielded as descriptors for the molecule’s chemical behavior. The optimized molecular structure was obtained, and the experimental data were matched with geometrical analysis values describing the molecule’s stable structure. The computed FT-IR and Raman vibrational frequencies were in good agreement with those observed experimentally. In a molecular docking study, the inhibitory potential of the studied molecule was evaluated against the penicillin-binding proteins of Staphylococcus aureus bacteria. The carbonyl group in the molecule was shown to play a significant role in antibacterial activity, four bonds were formed by the carbonyl group with the key protein of the bacteria (three favorable hydrogen bonds plus one van der Waals bond) out of six interactions. The strong antibacterial activity was also indicated by the calculated high binding energy (−7.40 kcal/mol).

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