scholarly journals Electronic and Structural Properties of the Double Cubane Iron-Sulfur Cluster

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 245
Author(s):  
Nadia Elghobashi-Meinhardt ◽  
Daria Tombolelli ◽  
Maria Andrea Mroginski
Keyword(s):  
Density Functional ◽  
Spin Coupling ◽  
Functional Theory ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur ◽  
Cubane Cluster ◽  
Covalently Linked ◽  
Electronic And Structural Properties ◽  
Electronic Ground ◽  
Fundamental Reference

The double-cubane cluster (DCC) refers to an [Fe8S9] iron-sulfur complex that is otherwise only known to exist in nitrogenases. Containing a bridging µ2-S ligand, the DCC in the DCC-containing protein (DCCP) is covalently linked to the protein scaffold via six coordinating cysteine residues. In this study, the nature of spin coupling and the effect of spin states on the cluster’s geometry are investigated computationally. Using density functional theory (DFT) and a broken symmetry (BS) approach to study the electronic ground state of the system, we computed the exchange interaction between the spin-coupled spins of the four FeFe dimers contained in the DCC. This treatment yields results that are in excellent agreement with both computed and experimentally determined exchange parameters for analogously coupled di-iron complexes. Hybrid quantum mechanical (QM)/molecular mechanical (MM) geometry optimizations show that cubane cluster A closest to charged amino acid side chains (Arg312, Glu140, Lys146) is less compact than cluster B, indicating that electrons of the same spin in a charged environment seek maximum separation. Overall, this study provides the community with a fundamental reference for subsequent studies of DCCP, as well as for investigations of other [Fe8S9]-containing enzymes.

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.

A Density Functional Theory Study of the Isomerization of Substituted 2and#39;-hydroxychalcones to the Corresponding Flavanones

2021 ◽  
Vol 43 (1) ◽  
pp. 25-25
Author(s):  
Said Abdelqadar Said Said Abdelqadar Said ◽  
Omar A Shareef and Abdulkhalik S Alkazzaz Omar A Shareef and Abdulkhalik S Alkazzaz
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Ring Closure ◽  
Basis Set ◽  
Functional Theory ◽  
Rate Determining Step ◽  
The Density Functional Theory ◽  
Electronic And Structural Properties ◽  
Maximum Hardness Principle

The transformation of 2and#39;-hydroxychalcones to their corresponding flavanones was studied theoretically by the use of the density functional theory (DFT) with B3-LYP/ 6-311G basis set to get important information about the role of both of electronic and structural properties in this process. The obtained energies were found to be in agreement with our previous results that obtained from HPLC studies. The estimated hardness, polarizability, and electrophilicity profiles were found to obey the maximum hardness principle (MHP), minimum polarizability principle (MPP), and the minimum electrophilicity principle (MEP) respectively. Flavanone ring closure was found to be the rate-determining step.

Hyperconjugation In Trialkylboranes Shown By Indirect Nuclear Spin-Spin Coupling Constants. Experimental Data And Density Functional Theory (Dft) Calculations

2005 ◽  
Vol 60 (3) ◽  
pp. 259-264 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Oleg L. Tok
Keyword(s):  
Experimental Data ◽  
Dft Calculations ◽  
Density Functional ◽  
Calculated Data ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Functional Theory ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
C Nmr

Trimethylborane (1), triethylborane (2), 1,3-dimethyl-1-boracyclopentane (3), 1-methyl-1- boracyclohexane (4), 9-methyl- and 9-ethyl-9-borabicyclo[3.1.1]nonane [5(Me) and 5(Et)], and 1- boraadamantane (6) were studied by 11B and 13C NMR spectroscopy with respect to coupling constants 1J(13C,11B) and 1J(13C,13C). Results of DFT calculations at the B3LYP/6-311+g(d,p) level of theory show satisfactory agreement with the experimental data. Hyperconjugation arising from C-C σ bonds adjacent to the tricoordinate boron atom is indicated, in particular for 1-boraadamantane (6), by the optimised calculated structures, and by the experimental and calculated data 1J(13C,13C). The calculated magnitude of 1J(13C,1H) for carbon atoms adjacent to boron becomes significantly smaller if the optimised structures suggest hyperconjugative effects arising from these C-H bonds

Indirect Nuclear Spin-Spin Coupling Constants 1J(17O,11B). First Observation And Calculation Using Density Functional Theory (Dft)

2006 ◽  
Vol 61 (8) ◽  
pp. 949-955 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Oleg L. Tok
Keyword(s):  
Density Functional ◽  
Reasonable Agreement ◽  
Bond Angle ◽  
Calculated Data ◽  
Molecular Structures ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Functional Theory ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Coupling constants 1J(17O,11B) of borates, borane adducts and boranes with boron-oxygen bonds have been calculated on the basis of optimised molecular structures using the B3LYP/6-311+G(d,p) level of theory. This indicates that such coupling constants can be of either sign and that their magnitudes can be rather small. Since both 11B and 17O are quadrupole nuclei, it is therefore difficult to measure representative data. In the cases of trimethoxyborane and tetraethyldiboroxanes, it proved possible to obtain experimental data 1J(17O,11B) (22 and 18 Hz) by measurement of 17O NMR spectra at high temperature (120 °C and 160 °C) respectively. The magnitude of these coupling constants is in reasonable agreement with calculated data. In the case of the diboroxane, this points towards a bond angle B-O-B more close to 180◦ than to 140°

Magnetic Properties of Hole-Doped Pyrochlore Iridate (Y1-x-yCuxCay)2Ir2O7

2019 ◽  
Vol 966 ◽  
pp. 269-276
Author(s):  
Julia Angel ◽  
Retno Asih ◽  
Hironori Nomura ◽  
Tomoya Taniguchi ◽  
Kazuyuki Matsuhira ◽  
...  
Keyword(s):  
Density Functional ◽  
Muon Spin ◽  
Quantum Critical Point ◽  
Magnetic Ordering ◽  
Photoemission Spectroscopy ◽  
Metal Insulator Transition ◽  
Functional Theory ◽  
Metal Insulator ◽  
X Ray ◽  
Electronic Ground

We report the results of studies on the electronic state of the hole-doped Y-based pyrochlore iridate, (Y1-x-yCuxCay)2Ir2O7. We carried out the resistivity, Muon Spin Relaxation (μSR), X-ray Photoemission Spectroscopy (XPS) measurements and Density Functional Theory (DFT) calculations on the non-doped (x=y=0) and doped (x=0.05, y=0.15) systems. We found in the non-doped system that the magnetic ordering of Ir spins which was accompanied by the metal-insulator transition (MIT) occurred at around 157 K and disappeared in the doped system in which MIT seems to disappear or smeared out. We suggest from the current study that a quantum critical point which shows a change in the electronic ground state from insulating to metallic to exist between those two systems.

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