scholarly journals Iron-TAML Complexes: A Computational Approach to Improving Stability

2021 ◽  
Author(s):  
◽  
Kevin Tuano
Keyword(s):  
Water Oxidation ◽  
Density Functional ◽  
Prolonged Exposure ◽  
Computational Study ◽  
Macrocyclic Ligand ◽  
Oxidation Mechanism ◽  
Nucleophilic Attack ◽  
Functional Theory ◽  
The Stability ◽  
Oxidation Chemistry

<p>Researchers at the Institute for Green Oxidation Chemistry of the Carnegie Mellon University developed a group of catalysts called tetra amido macrocyclic ligand (TAML) activators. The purpose of that research was that TAML activators would breakdown pollutants in the presence of a sacrificial oxidant. Furthermore, the catalyst was designed to decompose on a required timescale, as to not damage the environment by prolonged exposure. Since the initial designs from the 1980’s, the TAML structure has undergone significant changes to increase efficiency or selectivity. Other uses of this group of catalysts have been explored, namely, the oxidation of water to molecular oxygen.  This work presents a computational study using Density Functional Theory (DFT) which addresses the issue regarding the stability of certain iron-TAML intermediates in the water oxidation mechanism. Hence, the work seeks to explore how changing certain groups on the TAML ring can affect the stability of the reactive intermediates and the activation energy of the nucleophilic attack within the mechanism. The work highlights the importance of the fluorinated tail of the TAML structure in the accessibility of the desired transition state.</p>

scholarly journals Iron-TAML Complexes: A Computational Approach to Improving Stability

2021 ◽  
Author(s):  
◽  
Kevin Tuano
Keyword(s):  
Water Oxidation ◽  
Density Functional ◽  
Prolonged Exposure ◽  
Computational Study ◽  
Macrocyclic Ligand ◽  
Oxidation Mechanism ◽  
Nucleophilic Attack ◽  
Functional Theory ◽  
The Stability ◽  
Oxidation Chemistry

<p>Researchers at the Institute for Green Oxidation Chemistry of the Carnegie Mellon University developed a group of catalysts called tetra amido macrocyclic ligand (TAML) activators. The purpose of that research was that TAML activators would breakdown pollutants in the presence of a sacrificial oxidant. Furthermore, the catalyst was designed to decompose on a required timescale, as to not damage the environment by prolonged exposure. Since the initial designs from the 1980’s, the TAML structure has undergone significant changes to increase efficiency or selectivity. Other uses of this group of catalysts have been explored, namely, the oxidation of water to molecular oxygen.  This work presents a computational study using Density Functional Theory (DFT) which addresses the issue regarding the stability of certain iron-TAML intermediates in the water oxidation mechanism. Hence, the work seeks to explore how changing certain groups on the TAML ring can affect the stability of the reactive intermediates and the activation energy of the nucleophilic attack within the mechanism. The work highlights the importance of the fluorinated tail of the TAML structure in the accessibility of the desired transition state.</p>

Computational Study of Tetrahedral Fullerenes Containing Fused Pentagon-Triples

2021 ◽  
Vol 21 (4) ◽  
pp. 2419-2426
Author(s):  
Csaba L. Nagy ◽  
Katalin Nagy
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Chemical Shifts ◽  
Point Group ◽  
Functional Theory ◽  
Global Strain ◽  
The Stability ◽  
Global And Local ◽  
Hybrid Density Functional ◽  
Electronic And Structural Properties

Fullerenes that violate the isolated pentagon rule are too reactive and were obtained only as endoor exohedral derivatives. Density functional theory using the B3LYP hybrid density functional was applied to investigate the electronic and structural properties of the ten smallest tetrahedral (Td or T point group) fullerenes containing four directly fused pentagon-triples. The influence of nitrogen doping and exohedral hydrogenation of the four reactive sites was also analyzed. Nucleus independent chemical shifts values computed using B3LYP/6-31G(d) are used as global and local aromaticity probe. The global strain energy is evaluated in terms of the pyramidalization (POAV) angle. The results show that the stability increases with the elimination of the energetically unfavorable strain.

scholarly journals Mononuclear Cr(III), Mn (II), and Fe(III) complexes derived from new ONO symmetrical flexible hydrazone: synthesis, spectral characterization, optical band gap and DFT computational study

2019 ◽  
Vol 8 (4) ◽  
pp. 743-753
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Molecular Electrostatic Potential ◽  
Optical Band Gap ◽  
Computational Study ◽  
Atomic Charge ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Stability ◽  
Global And Local

New mononuclear Mn (II), Cr (III) and Fe (III) complexes of flexible symmetrical 2-(2-(2-hydroxy-3-methoxybenzylidene) hydrazinyl)-2-oxo-N-(pyridine-2-yl) acetamid (H4MPA) were isolated and characterized. IR spectra proved that the hydrazone coordinates as ONO dibasic or monobasic in keto and enol forms. The density functional theory (DFT) based quantum chemical calculations were accomplished at B3LYP/6-level of theory. Muilikan atomic charge in a companion with global and local reactivities and various energitic values have been calculated at the selected atoms, and the reactive sites have been assigned on the surface of the molecules through molecular electrostatic potential (MEP) map. The stability of all compounds was examined by TGA and DrTGA and the associated kinetic parameters were determined. Also, the optical band gap values were evaluated and found to be comparable with those obtained by DFT suggesting the possibility of using the title compounds in solar cells.

scholarly journals Orbital Analysis of Natural Bonds, Calculations of the Functional Theory of Density Time-Dependent and Absorption Spectral of a Series of Rhodanine Derivatives

2020 ◽  
Vol 10 (5) ◽  
pp. 453
Author(s):  
Koffi Alexis Respect Kouassi ◽  
Anoubilé Benié ◽  
Kouakou Nobel N’guessan ◽  
Mamadou Guy-Richard Koné ◽  
Adenidji Ganiyou ◽  
...  
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Dft Method ◽  
Energy Difference ◽  
Exchange Capacity ◽  
Nucleophilic Attack ◽  
Electronic Density ◽  
Functional Theory ◽  
Preferential Site ◽  
The Stability

<p>In this work, the density functional theory (DFT) method at the B3LYP/6-31 + G (d, p) level has used to determine the optimization of five rhodanine derivatives. The stability of the derivatives (7a-7e) of 5-arylidene rhodanine, the hyperconjugative interactions, the delocalization of the atomic charges was analyzed with the analysis of the Natural Bond Orbital (NBO). The electronic structures were discussed and the relocation of electronic density was determined. Molecular Electrostatic Potential (MEP), local density functional descriptors, border molecular orbitals and absorption spectrum were studied. Through the local Fukui reactivity indices, the carbon of the carbonyl group (C = O) is the preferential site of the nucleophilic attack and the sulfur atom linked to the trigonal carbon (C = S) is the preferential site of electrophile attack. Analysis of the global descriptors revealed that compound 7c is the most reactive with an energy difference between the frontier orbitals of ΔEgap = 3.305 eV. Furthermore, this compound 7c is the less stable, the softest and has the greatest electronic exchange capacity of all studied compounds. The intramolecular electronic transitions which stabilize these compounds are LP → π * for 7a and 7d and σ → σ * for 7b, 7c and 7e. The rhodanine derivatives are more reactive and more soluble in polar solvents.</p>

scholarly journals A Computational Study of AlF3 and ACF Surfaces

Inorganics ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 124 ◽  
Author(s):  
Riddhish Pandharkar ◽  
Christian Becker ◽  
Johannes Budau ◽  
Zeinab Kaawar ◽  
Beate Paulus
Keyword(s):  
Surface Properties ◽  
Density Functional ◽  
Computational Study ◽  
Equilibrium Shape ◽  
Dft Methods ◽  
Wulff Construction ◽  
Functional Theory ◽  
Metal Fluorides ◽  
Potential Equilibrium ◽  
The Stability

By applying first principles density functional theory (DFT) methods, different metal fluorides and their surfaces have been characterized. One of the most investigated metal fluorides is AlF3 in different polymorphs. Its chloride-doped analogon AlClxF3−x (ACF) has recently attracted much attention due to its application in catalysis. After presenting a summary of different first-principle studies on the bulk and surface properties of different main group fluorides, we will revisit the problem of the stability of different α -AlF3 surfaces and extend the investigation to chloride-doped counterparts to simulate the surface properties of amorphous ACF. For each material, we have considered ten different surface cuts with their respective terminations. We found that terminations of ( 01 1 ¯ 0 ) and ( 11 2 ¯ 0 ) yield the most stable surfaces for α -AlF3 and for the chlorine substituted surfaces. A potential equilibrium shape of the crystal for both α -AlF3 and ACF is visualized by a Wulff construction.

A Computational Study of Catalytic Platinum Nanoparticles With and Without OH Chemisorption During Reactions

2008 ◽  
Author(s):  
Mikhail Sekachev ◽  
Cheng-Xian Lin ◽  
Zhiyu Hu ◽  
Don Dareing
Keyword(s):  
Binding Energy ◽  
Total Energy ◽  
Platinum Nanoparticles ◽  
Cluster Size ◽  
Density Functional ◽  
Energy Gap ◽  
Computational Study ◽  
Basis Set ◽  
Functional Theory ◽  
The Stability

In this paper, various energies and geometries of pure platinum nanoparticles and those of platinum nanoparticles with adsorbed OH were investigated. Ten different platinum clusters of up to 28 atoms were studied using spin-unrestricted density functional theory (DFT) with a double numerical plus polarization basis set. Three different shapes were presented, and the effect of cluster size on binding energy, total energy, and HOMO-LUMO energy gap was investigated. The same set of calculations was performed for selected clusters with OH adsorbate on the Pt(111) surface. The results show that the stability of both the pure clusters and the clusters with adsorbed OH molecule increases with an increase of cluster size. This fact indicates that direct influence of the size of Pt cluster on the reaction rate is possible, and the understanding of how cluster size would affect binding energy is important. The effect of cluster size on total energy of molecule was shown to be a linear function independent of cluster type, as expected. We also found that optimized (stable) Pt clusters were bigger in size than that of the initial clusters, or clusters with bulk geometry.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nilanjan Roy ◽  
Sucharita Giri ◽  
Harshit ◽  
Partha P. Jana
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Structure Type ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Functional Theory ◽  
The Stability ◽  
Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

scholarly journals Computational Study of the Electron Spectra of Vapor-Phase Indole and Four Azaindoles

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1947
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Vapor Phase ◽  
Density Functional ◽  
Computational Study ◽  
Geometry Optimization ◽  
The Other ◽  
Functional Theory ◽  
Electron Spectra

After geometry optimization, the electron spectra of indole and four azaindoles are calculated by density functional theory. Available experimental photoemission and excitation data for indole and 7-azaindole are used to compare with the theoretical values. The results for the other azaindoles are presented as predictions to help the interpretation of experimental spectra when they become available.

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