scholarly journals Changes in CO2 Adsorption Affinity Related to Ni Doping in FeS Surfaces: A DFT-D3 Study

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 486
Author(s):  
Aleksandar Zivković ◽  
Michiel Somers ◽  
Eloi Camprubi ◽  
Helen E. King ◽  
Mariette Wolthers ◽  
...  
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Ni Doping ◽  
Functional Theory ◽  
Small Organic Molecules ◽  
Adsorption Affinity ◽  
The Origin Of Life ◽  
Carbon Dioxide Co2 ◽  
Partial Desorption ◽  
Good Agreement

Metal sulphides constitute cheap, naturally abundant, and environmentally friendly materials for energy storage applications and chemistry. In particular, iron (II) monosulphide (FeS, mackinawite) is a material of relevance in theories of the origin of life and for heterogenous catalytic applications in the conversion of carbon dioxide (CO2) towards small organic molecules. In natural mackinawite, Fe is often substituted by other metals, however, little is known about how such substitutions alter the chemical activity of the material. Herein, the effect of Ni doping on the structural, electronic, and catalytic properties of FeS surfaces is explored via dispersion-corrected density functional theory simulations. Substitutional Ni dopants, introduced on the Fe site, are readily incorporated into the pristine matrix of FeS, in good agreement with experimental measurements. The CO2 molecule was found to undergo deactivation and partial desorption from the doped surfaces, mainly at the Ni site when compared to undoped FeS surfaces. This behaviour is attributed to the energetically lowered d-band centre position of the doped surface, as a consequence of the increased number of paired electrons originating from the Ni dopant. The reaction and activation energies of CO2 dissociation atop the doped surfaces were found to be increased when compared to pristine surfaces, thus helping to further elucidate the role Ni could have played in the reactivity of FeS. It is expected that Ni doping in other Fe-sulphides may have a similar effect, limiting the catalytic activity of these phases when this dopant is present at their surfaces.

Green Synthesis of Triazole-Based Chemosensors and their Efficacy Towards Mercury Sensing

2020 ◽  
Vol 16 (6) ◽  
pp. 738-743 ◽  
Author(s):  
Poonam Rani ◽  
Kashmiri Lal ◽  
Vikas D. Ghule ◽  
Rahul Shrivastava
Keyword(s):  
Detection Limit ◽  
Metal Ions ◽  
Density Functional ◽  
Organic Molecules ◽  
Functional Theory ◽  
Small Organic Molecules ◽  
Industrial Activities ◽  
Binding Stoichiometry ◽  
Visible Spectra ◽  
Uv Visible

Background: The synthesis of small organic molecules based Hg2+ ions receptors have gained considerable attention because it is one of the most prevalent toxic metals which is continuously discharged into the environment by different natural and industrial activities. 1,4-Disubstituted 1,2,3-triazoles have been reported as good chemosensors for the detection of various metal ions including Hg2+ ions. Methods: The synthesis of 1,2,3-triazoles (4a-4c) was achieved by Cu(I)-catalyzed azide-alkyne cycloaddition, and their binding affinity towards various metal ions and anions were studied by UVVisible titration experiments. The perchlorate salts of metal ions and tetrabutylammonium salts of anions were utilized for the UV-Visible experiments. DFT studies were performed to understand the binding and mechanism on the sensing of 4a toward Hg2+ using the B3LYP/6-311G(d,p) method for 4a and B3LYP/LANL2DZ for 4a-Hg2+ species on the Gaussian 09W program. Results: The UV-visible experiments indicated that the compounds 4a-4c show a selective response towards Hg2+ ion in UV-Visible spectra, while other ions did not display such changes in the absorption spectra. The binding stoichiometry was evaluated by Job’s plot which indicated the 1:1 binding stoichiometry between receptors (4a-4c) and Hg2+ ion. The detection limit of 4a, 4b and 4c for the Hg2+ ions was found to be 29.1 nM, 3.5 μM and 1.34 μM, respectively. Conclusion: Some 1,2,3-triazole derivatives were synthesized (4a-4c) exhibiting high selectively and sensitivity towards Hg2+ ions in preference to other ions. Compound 4a has a low detection limit of 29.1 nM and the binding constant of 2.3×106 M-1. Similarly, 4b and 4c also showed selective sensing towards Hg2+ ions in the μM range. The observed experimental results were corroborated by density functional theory (DFT) calculations.

scholarly journals Prediction of Homolytic Bond Dissociation Enthalpies for Organic Molecules at near Chemical Accuracy with Sub-Second Computational Cost

2019 ◽  
Author(s):  
Peter St. John ◽  
Yanfei Guan ◽  
Yeonjoon Kim ◽  
Seonah Kim ◽  
Robert Paton
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Soot Formation ◽  
Chemical Reactivity ◽  
Hydrogen Abstraction ◽  
Computational Cost ◽  
Absolute Error ◽  
Functional Theory ◽  
Small Organic Molecules ◽  
Bond Dissociation

Bond dissociation enthalpies (BDEs) of organic molecules play a fundamental role in determining chemical reactivity. However, BDE computations at sufficiently high levels of quantum mechanical (QM) theory require substantial computing resources. We have therefore developed A machine-Learning derived, Fast, Accurate Bond dissociation Enthalpy Tool (ALFABET), capable of accurately predicting BDEs for organic molecules in a fraction of a second. Automated density functional theory (DFT) calculations at the M06-2X/def2-TZVP level of theory were performed for 42,577 small organic molecules, resulting in a dataset of 290,664 BDEs. A graph neural network was trained on a subset of these results, achieving a mean absolute error of 0.58 kcal/mol for the BDE values of unseen molecules. An interface for the developed prediction tool is available online at https://ml.nrel.gov/bde. The model rapidly and accurately predicts major sites of hydrogen abstraction in metabolism of drug-like molecules and determines the dominant molecular fragmentation pathways during soot formation.

scholarly journals Prediction of Homolytic Bond Dissociation Enthalpies for Organic Molecules at near Chemical Accuracy with Sub-Second Computational Cost

2019 ◽  
Author(s):  
Peter St. John ◽  
Yanfei Guan ◽  
Yeonjoon Kim ◽  
Seonah Kim ◽  
Robert Paton
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Soot Formation ◽  
Chemical Reactivity ◽  
Hydrogen Abstraction ◽  
Computational Cost ◽  
Absolute Error ◽  
Functional Theory ◽  
Small Organic Molecules ◽  
Bond Dissociation

Bond dissociation enthalpies (BDEs) of organic molecules play a fundamental role in determining chemical reactivity. However, BDE computations at sufficiently high levels of quantum mechanical (QM) theory require substantial computing resources. We have therefore developed A machine-Learning derived, Fast, Accurate Bond dissociation Enthalpy Tool (ALFABET), capable of accurately predicting BDEs for organic molecules in a fraction of a second. Automated density functional theory (DFT) calculations at the M06-2X/def2-TZVP level of theory were performed for 42,577 small organic molecules, resulting in a dataset of 290,664 BDEs. A graph neural network was trained on a subset of these results, achieving a mean absolute error of 0.58 kcal/mol for the BDE values of unseen molecules. An interface for the developed prediction tool is available online at https://ml.nrel.gov/bde. The model rapidly and accurately predicts major sites of hydrogen abstraction in metabolism of drug-like molecules and determines the dominant molecular fragmentation pathways during soot formation.

scholarly journals Prediction of Homolytic Bond Dissociation Enthalpies for Organic Molecules at near Chemical Accuracy with Sub-Second Computational Cost

2019 ◽  
Author(s):  
Peter St. John ◽  
Yanfei Guan ◽  
Yeonjoon Kim ◽  
Seonah Kim ◽  
Robert Paton
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Soot Formation ◽  
Chemical Reactivity ◽  
Hydrogen Abstraction ◽  
Computational Cost ◽  
Absolute Error ◽  
Functional Theory ◽  
Small Organic Molecules ◽  
Bond Dissociation

Bond dissociation enthalpies (BDEs) of organic molecules play a fundamental role in determining chemical reactivity. However, BDE computations at sufficiently high levels of quantum mechanical (QM) theory require substantial computing resources. We have therefore developed A machine-Learning derived, Fast, Accurate Bond dissociation Enthalpy Tool (ALFABET), capable of accurately predicting BDEs for organic molecules in a fraction of a second. Automated density functional theory (DFT) calculations at the M06-2X/def2-TZVP level of theory were performed for 42,577 small organic molecules, resulting in a dataset of 290,664 BDEs. A graph neural network was trained on a subset of these results, achieving a mean absolute error of 0.58 kcal/mol for the BDE values of unseen molecules. An interface for the developed prediction tool is available online at https://ml.nrel.gov/bde. The model rapidly and accurately predicts major sites of hydrogen abstraction in metabolism of drug-like molecules and determines the dominant molecular fragmentation pathways during soot formation.

Synthesis of New α-Amino Phosphonates Containing 3-Amino-4(3H) Quinazolinone Moiety as Anticancer and Antimicrobial Agents: DFT, NBO, and Vibrational Studies

2018 ◽  
Vol 15 (2) ◽  
pp. 286-296 ◽  
Author(s):  
Mohamed K. Awad ◽  
Mahmoud F. Abdel-Aal ◽  
Faten M. Atlam ◽  
Hend A. Hekal
Keyword(s):  
Biological Activity ◽  
Cell Line ◽  
Quantum Chemical ◽  
Density Functional ◽  
Carcinoma Cell ◽  
Liver Carcinoma ◽  
Anticancer Activities ◽  
Functional Theory ◽  
Ft Ir ◽  
Good Agreement

Aim and Objective: Synthesis of new .-aminophosphonates containing quinazoline moiety through Kabachnik-Fields reaction in the presence of copper triflate catalyst [32], followed by studying their antimicrobial activities and in vitro anticancer activities against liver carcinoma cell line (HepG2) with the hope that new anticancer agents could be developed. Also, the quantum chemical calculations are performed using density functional theory (DFT) to study the effect of the changes of molecular and electronic structures on the biological activity of the investigated compounds. Materials and Method: The structures of the synthesized compounds are confirmed by FT-IR, 1H NMR, 13C NMR, 31P NMR and MS spectral data. The synthesized compounds show significant antimicrobial and also remarkable cytotoxicity anticancer activities against liver carcinoma cell line (HepG2). Density functional theory (DFT) was performed to study the effect of the molecular and electronic structure changes on the biological activity. Results: It was found that the electronic structure of the substituents affects on the reaction yield. The electron withdrawing substituent, NO2 group 3b, on the aromatic aldehydes gave a good yield more than the electron donating substituent, OH group 3c. The electron deficient on the carbon atom of the aldehydic group may increase the interaction of the Lewis acid (Cu(OTf)2) and the Lewis base (imine nitrogen), and accordingly, facilitate the formation of imine easily, which is attacked by the nucleophilic phosphite species to give the α- aminophosphonates. Conclusion: The newly synthesized compounds exhibit a remarkable inhibition of the growth of Grampositive, Gram-negative bacteria and fungi at low concentrations. The cytotoxicity of the synthesized compounds showed a significant cytotoxicity against the liver cancer cell line (HepG 2). Also, it was shown from the quantum chemical calculations that the electron-withdrawing substituent increases the biological activity of the α-aminophosphonates more than the electron donating group which was in a good agreement with the experimental results. Also, a good agreement between the experimental FT-IR and the calculated one was found.

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

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