A Structural Model for the High-Valent Intermediate Q of Methane Monooxygenase from Broken-Symmetry Density Functional and Electrostatics Calculations

2002 ◽  
Vol 124 (20) ◽  
pp. 5890-5894 ◽  
Author(s):  
Timothy Lovell ◽  
Wen-Ge Han ◽  
Tiqing Liu ◽  
Louis Noodleman
Keyword(s):  
Density Functional ◽  
Structural Model ◽  
Methane Monooxygenase ◽  
Broken Symmetry ◽  
High Valent

scholarly journals Prediction of high-valent iron K-edge absorption spectra by time-dependent Density Functional Theory

2011 ◽  
Vol 40 (42) ◽  
pp. 11070 ◽  
Author(s):  
P. Chandrasekaran ◽  
S. Chantal E. Stieber ◽  
Terrence J. Collins ◽  
Lawrence Que, Jr. ◽  
Frank Neese ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Absorption Spectra ◽  
Density Functional ◽  
Time Dependent ◽  
Functional Theory ◽  
Edge Absorption ◽  
High Valent ◽  
Dependent Density

The structure and activity of potassium supported on SBA-15 molecular sieve: Density functional theory study

2014 ◽  
Vol 13 (01) ◽  
pp. 1350076 ◽  
Author(s):  
Bing Liu ◽  
Daxi Wang ◽  
Zhongxue Wang ◽  
Zhen Zhao ◽  
Yu Chen ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Lewis Acid ◽  
Molecular Sieve ◽  
Active Sites ◽  
Density Functional ◽  
Structural Model ◽  
Vibrational Frequencies ◽  
Oxygen Molecule ◽  
Lewis Base ◽  
Functional Theory

The geometries, vibrational frequencies, electronic properties and reactivity of potassium supported on SBA-15 have been theoretically investigated by the density functional theory (DFT) method. The structural model of the potassium supported on SBA-15 was constructed based on our previous work [Wang ZX, Wang DX, Zhao Z, Chen Y, Lan J, A DFT study of the structural units in SBA-15 mesoporous molecular sieve, Comput. Theor. Chem.963, 403, 2011]. This paper is the extension of our previous work. The most favored location of potassium atom was obtained by the calculation of substitution energy. The calculated vibrational frequencies of K /SBA-15 are in good agreement with the experimental results. By analyzing the properties of electronic structure, we found that the O atom of Si - O (2)- K group acts as the Lewis base center and the K atom acts as the Lewis acid center. The reactivity of K /SBA-15 was investigated by calculating the activation of oxygen molecule. The oxygen molecule can be activated by K /SBA-15 with an energy barrier of 103.2 kJ/mol. In the final state, the activated oxygen atoms become new Lewis acid centers, which are predicted to act as the active sites in the catalytic reactions. This study provides a deep insight into the properties of supported potassium catalysts and offers fundamental information for further research.

scholarly journals Use of Broken-Symmetry Density Functional Theory To Characterize the IspH Oxidized State: Implications for IspH Mechanism and Inhibition

2014 ◽  
Vol 10 (9) ◽  
pp. 3871-3884 ◽  
Author(s):  
Patrick G. Blachly ◽  
Gregory M. Sandala ◽  
Debra Ann Giammona ◽  
Tiqing Liu ◽  
Donald Bashford ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Broken Symmetry ◽  
Functional Theory

scholarly journals Mechanism and Chemoselectivity of Mn-Catalyzed Intramolecular Nitrene Transfer Reaction: C–H Amination vs. C=C Aziridination

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 292
Author(s):  
Juping Wang ◽  
Kangcheng Zheng ◽  
Ting Li ◽  
Xiaojing Zhan
Keyword(s):  
Density Functional ◽  
Structural Features ◽  
High Reactivity ◽  
Strong Electron ◽  
Functional Theory ◽  
Design Elements ◽  
Nitrene Transfer ◽  
Electrophilic Reactivity ◽  
High Valent ◽  
Orbital Character

The reactivity, mechanism and chemoselectivity of the Mn-catalyzed intramolecular C–H amination versus C=C aziridination of allylic substrate cis-4-hexenylsulfamate are investigated by BP86 density functional theory computations. Emphasis is placed on the origins of high reactivity and high chemoselectivity of Mn catalysis. The N p orbital character of frontier orbitals, a strong electron-withdrawing porphyrazine ligand and a poor π backbonding of high-valent MnIII metal to N atom lead to high electrophilic reactivity of Mn-nitrene. The calculated energy barrier of C–H amination is 9.9 kcal/mol lower than that of C=C aziridination, which indicates that Mn-based catalysis has an excellent level of chemoselectivity towards C–H amination, well consistent with the experimental the product ratio of amintion-to-aziridination I:A (i.e., (Insertion):(Aziridination)) >20:1. This extraordinary chemoselectivity towards C–H amination originates from the structural features of porphyrazine: a rigid ligand with the big π-conjugated bond. Electron-donating substituents can further increase Mn-catalyzed C–H amination reactivity. The controlling factors found in this work may be considered as design elements for an economical and environmentally friendly C–H amination system with high reactivity and high chemoselectivity.

scholarly journals Structural Refinement and Density Functional Theory Study of Synthetic Ge-Akaganéite (β-FeOOH)

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 239
Author(s):  
Donghoon Chung ◽  
Changyun Park ◽  
Woohyun Choi ◽  
Yungoo Song
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Structural Model ◽  
Dispersion Correction ◽  
Chemical Formula ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Twisted Cube

In this study, we propose a revised structural model for highly ordered synthetic Ge-akaganéite, a stable analogue of tunnel-type Fe-oxyhydroxide, based on the Rietveld refinement of synchrotron X-ray diffraction data and density functional theory with dispersion correction (DFT-D) calculations. In the proposed crystal structure of Ge-akaganéite, Ge is found not only in the tunnel sites as GeO(OH)3− tetrahedra, but also 4/5 of total Ge atoms are in the octahedral sites substituting 1/10 of Fe. In addition, the tunnel structures are stabilized by the presence of hydrogen bonds between the framework OH and Cl− species, forming a twisted cube structure and the GeO(OH)3− tetrahedra corner oxygen, forming a conjugation bond. The chemical formula of the synthetic Ge-akaganéite was determined to be (Fe7.2Ge0.8)O8.8(OH)7.2Cl0.8(Ge(OH)4)0.2.

Optimized Structures of Bimetallic Systems:  A Comparison of Full- and Broken-Symmetry Density Functional Calculations

1996 ◽  
Vol 35 (11) ◽  
pp. 3079-3080 ◽  
Author(s):  
Timothy Lovell ◽  
John E. McGrady ◽  
Robert Stranger ◽  
Stuart A. Macgregor
Keyword(s):  
Density Functional Calculations ◽  
Density Functional ◽  
Broken Symmetry ◽  
Bimetallic Systems
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