scholarly journals Theoretical Study on Electronic Structural Properties of Catalytically Reactive Metalloporphyrin Intermediates

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 224 ◽  
Author(s):  
Meijuan Cao ◽  
Aijing Gao ◽  
Yuanyuan Liu ◽  
Yang Zhou ◽  
Zhicheng Sun ◽  
...  
Keyword(s):  
Structural Properties ◽  
Density Functional ◽  
Structural Changes ◽  
Ground States ◽  
Density Functional Theory Method ◽  
Decisive Role ◽  
Chemical Oxidation ◽  
Relative Energy ◽  
Central Metal ◽  
Metal Porphyrin

Metalloporphyrins have attracted great attention in the potential application of biomimetic catalysis. Especially, they were widely investigated as green catalysts in the chemical oxidation of various hydrocarbons through the catalytic activation of molecular oxygen. The structural properties of active central metal ions were reported to play a decisive role in catalytic activity. However, those delicate structural changes are difficult to be experimentally captured or elucidated in detail. Herein, we explored the electronic structural properties of metalloporphyrins (metal porphyrin (PMII, PMIIICl)) and their corresponding catalytically active intermediates (metal(III)-peroxo(PMIII-O2), metal(III)-hydroperoxo(PMIII-OH), and metal(IV)-oxo(PMIV=O), (M=Fe, Mn, and Co)) through the density functional theory method. The ground states of these intermediates were determined based on the assessment of relative energy and the corresponding geometric structures of ground states also further confirmed the stability of energy. Furthermore, our analyses of Mulliken charges and frontier molecular orbitals revealed the potential catalytic behavior of reactive metalloporphyrin intermediates.

scholarly journals SIMULASI PERUBAHAN DENSITAS MUATAN ADSORPSI ATOM HIDROGEN-GRAFENA DENGAN TEORI FUNGSI KERAPATAN

2018 ◽  
Vol 3 (2) ◽  
pp. 179-184
Author(s):  
Albert Zicko Johannes
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Charge Density ◽  
Density Functional ◽  
Structural Changes ◽  
Density Functional Theory Method ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Center Position

Abstrak Peristiwa adsorpsi atom Hidrogen pada Grafena menyebabkan terjadinya perubahan struktur Grafena. Perubahan ini mempengaruhi keadaan densitas muatan Grafena. Pada simulasi ini posisi atom Hidrogen pada permukaan lembaran Grafena divariasikan, yaitu pada posisi tepat di atas atom Karbon (Top), posisi di tengah antara dua atom Karbon (Bridge), dan posisi pusat struktur heksagonal (Hollow). Simulasi dilakukan dengan metode Teori Fungsi Kerapatan dengan model Grafena ukuran 2x2. Hasil yang diperoleh menunjukkan adsorpsi atom Hidrogen memilih posisi Top sebagai yang paling stabil dibandingkan dengan posisi Bridge dan Hollow. Hasil dari posisi Top menunjukkan elektron dari atom Hidrogen digunakan mengikat Grafena dengan energi ikat sebesar -1.7 eV. Perubahan densitas muatan menunjukkan terjadinya perpindahan elektron menuju Grafena disertai transformasi isosurface yang unik untuk setiap posisi atom Hidrogen dengan perubahan terbesar terjadi pada posisi Top.  Kata kunci: Densitas muatan, Grafena, Adsorpsi, Teori Fungsi Kerapatan  Abstract [Title: The Simulation of Charge Density Diffrential for Hydrogen Atom - Graphene Adsorption with Density Functional Theory] Hydrogen atom adsorption on Graphene cause structural changes. This change affect Graphene charge density. In this simulation the position of Hydrogen atom on the surface of Graphene sheet are varied out, which is on the position directly above the Carbon atom (Top), the position on the middle between two Carbon atoms (Bridge), and the center position of the hexagonal structure (Hollow). The simulation is done by the Density Functional Theory method with a 2x2 size Graphene model. The results obtained showed that Hydrogen atom adsorption chose the Top position as the most balanced compared with the position of Bridge and Hollow. The results from the Top position indicate that electrons from Hydrogen atom are used to bind the Graphene with binding energy of -1.7 eV. The charge density differential indicate the occurrence of electron transfer towards Graphene accompanied by a transformation of the isosurface that are unique for each Hydrogen atom positions with the biggest change is shown in the Top position.  Keywords: Charge Density, Graphene, Adsorption, Density Functional Theory

scholarly journals Structural Properties and Reactive Site Selectivity of Some Transition Metal Complexes of 2,2′(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(phenylmethan-1-yl-1-ylidene)dibenzoic Acid: DFT, Conceptual DFT, QTAIM, and MEP Studies

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Fritzgerald Kogge Bine ◽  
Nyiang Kennet Nkungli ◽  
Tasheh Stanley Numbonui ◽  
Julius Numbonui Ghogomu
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Structural Properties ◽  
Transition Metal Complexes ◽  
Metal Ion ◽  
Density Functional ◽  
Conceptual Dft ◽  
Distorted Octahedral Geometry ◽  
Chemical Hardness ◽  
Central Metal

Herein is presented a density functional theory (DFT) study of reactivity and structural properties of transition metal complexes of the Schiff base ligand 2,2′(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(phenylmethan-1-yl-1-ylidene)dibenzoic acid (hereafter denoted EDA2BB) with Cu(II), Mn(II), Ni(II), and Co(II). The quantum theory of atoms-in-molecules (QTAIM), conceptual DFT, natural population analysis (NPA), and molecular electrostatic potential (MEP) methods have been used. Results have revealed a distorted octahedral geometry around the central metal ion in each gas phase complex. In the DMSO solvent, a general axial elongation of metal-oxygen bonds involving ancillary water ligands has been observed, suggestive of loosely bound water molecules to the central metal ion that may be acting as solvent molecules. Weak, medium, and strong intramolecular hydrogen bonds along with hydrogen-hydrogen and van der Waals interactions have been elucidated in the complexes investigated via geometric and QTAIM analyses. From the chemical hardness values, the complex [Co(EDA2BB)(OH2)2] is the hardest, while [Cu(EDA2BB)(OH2)2] is the softest. Based on the global electrophilicity index, the complexes [Ni(EDA2BB)(OH2)2] and [Cu(EDA2BB)(OH2)2] are the strongest and weakest electrophiles, respectively, among the complexes studied. In conclusion, the reactivity of the complexes is improved vis-à-vis the ligand, and stable geometries of the complexes are identified, alongside their prominent electrophilic and nucleophilic sites.

scholarly journals SIMULASI PERUBAHAN DENSITAS MUATAN ADSORPSI ATOM HIDROGEN-GRAFENA DENGAN TEORI FUNGSI KERAPATAN

2018 ◽  
Vol 3 (3) ◽  
pp. 179-184
Author(s):  
Albert Zicko Johannes
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Charge Density ◽  
Density Functional ◽  
Structural Changes ◽  
Density Functional Theory Method ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Center Position

Abstrak Peristiwa adsorpsi atom Hidrogen pada Grafena menyebabkan terjadinya perubahan struktur Grafena. Perubahan ini mempengaruhi keadaan densitas muatan Grafena. Pada simulasi ini posisi atom Hidrogen pada permukaan lembaran Grafena divariasikan, yaitu pada posisi tepat di atas atom Karbon (Top), posisi di tengah antara dua atom Karbon (Bridge), dan posisi pusat struktur heksagonal (Hollow). Simulasi dilakukan dengan metode Teori Fungsi Kerapatan dengan model Grafena ukuran 2x2. Hasil yang diperoleh menunjukkan adsorpsi atom Hidrogen memilih posisi Top sebagai yang paling stabil dibandingkan dengan posisi Bridge dan Hollow. Hasil dari posisi Top menunjukkan elektron dari atom Hidrogen digunakan mengikat Grafena dengan energi ikat sebesar -1.7 eV. Perubahan densitas muatan menunjukkan terjadinya perpindahan elektron menuju Grafena disertai transformasi isosurface yang unik untuk setiap posisi atom Hidrogen dengan perubahan terbesar terjadi pada posisi Top.  Kata kunci: Densitas muatan, Grafena, Adsorpsi, Teori Fungsi Kerapatan  Abstract [Title: The Simulation of Charge Density Diffrential for Hydrogen Atom - Graphene Adsorption with Density Functional Theory] Hydrogen atom adsorption on Graphene cause structural changes. This change affect Graphene charge density. In this simulation the position of Hydrogen atom on the surface of Graphene sheet are varied out, which is on the position directly above the Carbon atom (Top), the position on the middle between two Carbon atoms (Bridge), and the center position of the hexagonal structure (Hollow). The simulation is done by the Density Functional Theory method with a 2x2 size Graphene model. The results obtained showed that Hydrogen atom adsorption chose the Top position as the most balanced compared with the position of Bridge and Hollow. The results from the Top position indicate that electrons from Hydrogen atom are used to bind the Graphene with binding energy of -1.7 eV. The charge density differential indicate the occurrence of electron transfer towards Graphene accompanied by a transformation of the isosurface that are unique for each Hydrogen atom positions with the biggest change is shown in the Top position.  Keywords: Charge Density, Graphene, Adsorption, Density Functional Theory

scholarly journals CHEMICAL DEGRADATION OF NAFION MEMBRANES UNDER PEMFC AS INVESTIGATED BY DFT METHOD

2020 ◽  
Vol 21 (2) ◽  
pp. 49
Author(s):  
Rochmad K Sanjaya ◽  
Juliandri Juliandri ◽  
Iman Rahayu ◽  
Nurul Ismillayli ◽  
Dhony Hermanto
Keyword(s):  
Density Functional ◽  
Main Chain ◽  
Density Functional Theory Method ◽  
Dft Method ◽  
Degradation Process ◽  
Relative Energy ◽  
Chemical Degradation ◽  
Energy Value ◽  
Nafion Membranes ◽  
Final Group

CHEMICAL DEGRADATION OF NAFION MEMBRANES UNDER PEMFC AS INVESTIGATED BY DFT METHOD. An exsitu method has been developed to performance of Nafion's membrane in PEMFC (Proton Electrolyt Membrane Fuel Cells), caused by the chemical degradation of ·OH and ∙H radicals. The change of the chemical structure occurring during the degradation were primarily calculated of the relative energy of reactions by DFT (Density Functional Theory) method approach in the Gaussian software. This study aims to determine whether DFT method with functional B3LYP, PBEPBE, and B3PW91 and base sets 6-311++G can be used in determining the relative energy of a reaction and knowing the difference in role between ·OH and ∙H in the degradation process of the main chain Nafion with the final group are -CF2H, -CF=CF2 and -COOH. The three functionalities applied showed that the ·OH radical has more role than the ∙H radical in the degradation process of the Nafion main chain. In the -CF2H group was shown the relative energy value of reaction 2 is lower than reaction 5, in the -CF=CF2 group was shown the relative energy value of reaction 8* is lower than reaction 11 and in the -COOH group the relative energ value of reaction 14 is lower than reaction 16. By knowing the relative energy of the Nafion main chain degradation reaction with a certain final group and the role of certain radical compounds in the degradation process, the DFT method with functional B3LYP, PBEPBE and B3PW91 and base sets 6-311++G can recommend various modifications of the Nafion as a fuel cell membrane, particularly in increasing of membrane performance.

Decomposition of Ge2H6 on the Si(100)(2 × 1) Surface

2003 ◽  
Vol 10 (04) ◽  
pp. 577-583
Author(s):  
Şenay Katırcıoğlu
Keyword(s):  
Density Functional ◽  
Surface Coverage ◽  
High Surface ◽  
Geometry Optimization ◽  
Density Functional Theory Method ◽  
Relative Energy ◽  
Theory Method ◽  
Functional Theory ◽  
Adsorption Models ◽  
The Density Functional Theory

The decomposition of Ge 2 H 6 on Si(100)(2 × 1) was investigated on different adsorption models of fragments using the density functional theory method. The most probable adsorption models of fragments for low and high surface coverage of Ge 2 H 6 have been obtained by geometry optimization and single value relative energy calculations. It has been found that, Ge 2 H 4 makes a bridge between the adjacent surface dimers, Ge 2 H 5–H is bound to the same dimer bond with an unbroken Ge–Ge bond in Ge 2 H 6, and two GeH 3 sticks to the same surface dimer bond by a broken Ge–Ge bond in Ge 2 H 6. The parallel dimer bond structure of Si(100) was conserved in these models after geometry optimization.

scholarly journals Improvement of the Force Field for β-d-Glucose with Machine Learning

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6691
Author(s):  
Makoto Ikejo ◽  
Hirofumi Watanabe ◽  
Kohei Shimamura ◽  
Shigenori Tanaka
Keyword(s):  
Machine Learning ◽  
Force Field ◽  
Density Functional ◽  
Md Simulation ◽  
Structural Changes ◽  
Atomic Charge ◽  
Relative Energy ◽  
Machine Learning Techniques ◽  
Biomolecular Systems ◽  
Wide Range

While the construction of a dependable force field for performing classical molecular dynamics (MD) simulation is crucial for elucidating the structure and function of biomolecular systems, the attempts to do this for glycans are relatively sparse compared to those for proteins and nucleic acids. Currently, the use of GLYCAM06 force field is the most popular, but there have been a number of concerns about its accuracy in the systematic description of structural changes. In the present work, we focus on the improvement of the GLYCAM06 force field for β-d-glucose, a simple and the most abundant monosaccharide molecule, with the aid of machine learning techniques implemented with the TensorFlow library. Following the pre-sampling over a wide range of configuration space generated by MD simulation, the atomic charge and dihedral angle parameters in the GLYCAM06 force field were re-optimized to accurately reproduce the relative energies of β-d-glucose obtained by the density functional theory (DFT) calculations according to the structural changes. The validation for the newly proposed force-field parameters was then carried out by verifying that the relative energy errors compared to the DFT value were significantly reduced and that some inconsistencies with experimental (e.g., NMR) results observed in the GLYCAM06 force field were resolved relevantly.

A Solvent Free Synthetic Route for Cerium(IV) Metal-Organic Frame-works with UiO-66 Architecture and Their Photocatalytic Application

2019 ◽  
Author(s):  
Matteo Campanelli ◽  
Tiziana Del Giacco ◽  
Filippo De Angelis ◽  
Edoardo Mosconi ◽  
Marco Taddei ◽  
...  
Keyword(s):  
Density Functional ◽  
Chemical Oxidation ◽  
Solvent Free ◽  
Cerium Ammonium Nitrate ◽  
Benzylic Alcohols ◽  
Near Ultraviolet ◽  
Photocatalytic Application ◽  
Activity Density ◽  
Ultraviolet Light Irradiation ◽  
Metal Organic

<div> <p>A novel solvent-free synthesis for Ce-UiO-66 metal-organic frameworks (MOFs) is presented. The MOFs are obtained by simply grinding the reagents, cerium ammonium nitrate (CAN) and the carboxylic linkers, in a mortar for few minutes with the addition of a small amount of acetic acid (AcOH) as modulator (1.75 eq, o.1 ml). The slurry is then transferred into a 1 ml vial and heated at 120°C for 1 day. The MOFs have been characterized for their composition, crystallinity and porosity and employed as heterogenous catalysts for the photo-oxidation reaction of substituted benzylic alcohols to benzaldaldehydes under near ultraviolet light irradiation. The catalytic performances, such as yield, conversion and kinetics, exceed those of similar systems studied by chemical oxidation and using Ce-MOF as catalyst. Moreover, the MOFs were found to be reusable up to three cycles without loss of activity. Density functional theory (DFT) calculations gave an estimation of the band-gap shift due to the different nature of the linkers used and provide useful information on the catalytic activity experimentally observed.</p> </div>

scholarly journals Defect Processes in Halogen Doped SnO2

2021 ◽  
Vol 11 (2) ◽  
pp. 551
Author(s):  
Petros-Panagis Filippatos ◽  
Nikolaos Kelaidis ◽  
Maria Vasilopoulou ◽  
Dimitris Davazoglou ◽  
Alexander Chroneos
Keyword(s):  
Electronic Properties ◽  
Tin Oxide ◽  
Density Functional ◽  
Structural Changes ◽  
High Dielectric Constant ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Optical And Electronic Properties ◽  
High Dielectric ◽  
Gap States

In the present study, we performed density functional theory calculations (DFT) to investigate structural changes and their impact on the electronic properties in halogen (F, Cl, Br, and I) doped tin oxide (SnO2). We performed calculations for atoms intercalated either at interstitial or substitutional positions and then calculated the electronic structure and the optical properties of the doped SnO2. In all cases, a reduction in the bandgap value was evident, while gap states were also formed. Furthermore, when we insert these dopants in interstitial and substitutional positions, they all constitute a single acceptor and donor, respectively. This can also be seen in the density of states through the formation of gap states just above the valence band or below the conduction band, respectively. These gap states may contribute to significant changes in the optical and electronic properties of SnO2, thus affecting the metal oxide’s suitability for photovoltaics and photocatalytic devices. In particular, we found that iodine (I) doping of SnO2 induces a high dielectric constant while also reducing the oxide’s bandgap, making it more efficient for light-harvesting applications.

scholarly journals Understanding the reaction mechanism of the regioselective piperidinolysis of aryl 1-(2,4-dinitronaphthyl) ethers in DMSO: Kinetic and DFT studies

2021 ◽  
Vol 46 ◽  
pp. 146867832110274
Author(s):  
Yasmen M Moghazy ◽  
Nagwa MM Hamada ◽  
Magda F Fathalla ◽  
Yasser R Elmarassi ◽  
Ezzat A Hamed ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Density Functional ◽  
Function Analysis ◽  
Density Functional Theory Method ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Nucleophilic Attack ◽  
Common Mechanism ◽  
Slow Step ◽  
Rate Determining Step

Reactions of aryl 1-(2,4-dinitronaphthyl) ethers with piperidine in dimethyl sulfoxide at 25oC resulted in substitution of the aryloxy group at the ipso carbon atom. The reaction was measured spectrophotochemically and the kinetic studies suggested that the titled reaction is accurately third order. The mechanism is began by fast nucleophilic attack of piperidine on C1 to form zwitterion intermediate (I) followed by deprotonation of zwitterion intermediate (I) to the Meisenheimer ion (II) in a slow step, that is, SB catalysis. The regular variation of activation parameters suggested that the reaction proceeded through a common mechanism. The Hammett equation using reaction constant σo values and Brønsted coefficient value showed that the reaction is poorly dependent on aryloxy substituent and the reaction was significantly associative and Meisenheimer intermediate-like. The mechanism of piperidinolysis has been theoretically investigated using density functional theory method using B3LYP/6-311G(d,p) computational level. The combination between experimental and computational studies predicts what mechanism is followed either through uncatalyzed or catalyzed reaction pathways, that is, SB and SB-GA. The global parameters of the reactants, the proposed activated complexes, and the local Fukui function analysis explained that C1 carbon atom is the most electrophilic center of ether. Also, kinetics and theoretical calculation of activation energies indicated that the mechanism of the piperidinolysis passed through a two-step mechanism and the proton transfer process was the rate determining step.

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