Magnetism and structure of a novel trinuclear cluster compound of divalent copper

1969 ◽  
Vol 22 (12) ◽  
pp. 2527 ◽  
Author(s):  
R Beckett ◽  
R Colton ◽  
BF Hoskins ◽  
RL Martin ◽  
DG Vince
Keyword(s):  
Structural Data ◽  
Hydroxyl Group ◽  
Cluster Compound ◽  
X Ray Diffraction ◽  
Trinuclear Cluster ◽  
Metal Atoms ◽  
Doublet Ground State ◽  
Molecular Orbital Analysis ◽  
Orbital Analysis ◽  
Unusual Type

The magnetic properties of a series of salts of the type [Cu3L3OH]2+ (where HL is pyridine-2-aldehyde oxime and L is the deprotonated ligand) have been examined. All of the compounds showed a magnetic moment of 1.00 B.M. per copper atom over a wide temperature range which suggests that the cation contains a trinuclear cluster of interacting copper atoms. The crystal structure of Cu3L3OH(SO4),xH2O has been determined by single- crystal X-ray diffraction techniques and confirms that the complex does indeed contain an unusual type of trinuclear cluster of metal atoms. The three copper atoms form an equilateral triangle and the sulphato group exhibits a highly novel ?tripod? bridging function to the Cu3 triangle. On the other side of the triangle, the hydroxyl group also bridges to all the metal atoms. A qualitative molecular orbital analysis not only suggests that the hydroxyl group is involved in four-centre bonding with the Cu3 triads, but also highlights its role in reducing the spin of the trimer so that only a doublet ground state is populated between 80-300�K. However, the alternative super-exchange mechanism cannot be ruled out by the magnetic and structural data.

Synthese und Molekülstruktur der dreikernigen Cluster-Verbindung (η5C5Me5)IrFe2(CO)9 / Synthesis and Molecular Structure of the Trinuclear Cluster Compound (η5-C5Me5)IrFe2(CO)9

1981 ◽  
Vol 36 (9) ◽  
pp. 1053-1059 ◽  
Author(s):  
Ernst Guggolz ◽  
Manfred L. Ziegler ◽  
Willibald Kalcher ◽  
Johann Plank ◽  
Doris Riedel ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Cluster Compound ◽  
The Novel ◽  
X Ray Diffraction ◽  
Sandwich Complex ◽  
X Ray ◽  
Trinuclear Cluster ◽  
Half Sandwich

Abstract Reaction of triirondodecacarbonyl (1) with the dinuclear chloroiridium complex [(η5 -C5Me5)Ir(μ-Cl)Cl]2 (2) in benzene at 50 °C yields the novel mixed iron iridium cluster of composition (η5 -C5Me5)IrFe2(CO)9 (8) the molecular structure of which has been established by X-ray diffraction methods. The mononuclear half-sandwich complex (η5 -C5Me5)Ir(CO)2 (4) present in the reaction mixture was found to represent the immediate precursor of the cluster compound 8.

Li4Ru2OCl10·10H2O: crystal structure, magnetic properties and bonding interactions in ruthenium-oxo complexes

2020 ◽  
Vol 76 (5) ◽  
pp. 884-891
Author(s):  
Ranuri S Dissanayaka Mudiyanselage ◽  
Madalynn Marshall ◽  
Tai Kong ◽  
Weiwei Xie
Keyword(s):  
Crystal Structure ◽  
Magnetic Measurements ◽  
Theoretical Calculations ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Triclinic Structure ◽  
Molecular Orbital Analysis ◽  
Low Symmetry ◽  
Orbital Analysis

The results of the structural determination, magnetic characterization, and theoretical calculations of a new ruthenium-oxo complex, Li4[Ru2OCl10]·10H2O, are presented. Single crystals were grown using solvent methods and the crystal structure was characterized by single crystal X-ray diffraction. Li4[Ru2OCl10]·10H2O crystallizes into a low-symmetry triclinic structure (P 1) due to the much smaller Li+ cation compared to K+ cation in the tetragonal complex K4[Ru2OCl10]·H2O. The X-ray photoelectron spectra confirm only the single valent Ru4+ in Li4[Ru2OCl10]·10H2O even though two distinct Ru sites exist in the crystal structure. Magnetic measurements reveal the diamagnetic property of Li4[Ru2OCl10]·10H2O with unpaired electrons existing on Ru4+. Furthermore, the molecular orbital analysis matches well with the observed UV and magnetic measurements.

X-ray molecular orbital analysis. I. Quantum mechanical and crystallographic framework

2018 ◽  
Vol 74 (4) ◽  
pp. 345-356 ◽  
Author(s):  
Kiyoaki Tanaka
Keyword(s):  
Least Squares ◽  
Molecular Orbital ◽  
Molecular Orbitals ◽  
Basis Functions ◽  
X Ray Diffraction ◽  
Covalent Bonds ◽  
X Ray ◽  
Structure Factors ◽  
Molecular Orbital Analysis ◽  
Orbital Analysis

Molecular orbitals were obtained by X-ray molecular orbital analysis (XMO). The initial molecular orbitals (MOs) of the refinement were calculated by the ab initio self-consistent field (SCF) MO method. Well tempered basis functions were selected since they do not produce cusps at the atomic positions on the residual density maps. X-ray structure factors calculated from the MOs were fitted to observed structure factors by the least-squares method, keeping the orthonormal relationship between MOs. However, the MO coefficients correlate severely with each other, since basis functions are composed of similar Gaussian-type orbitals. Therefore, a method of selecting variables which do not correlate severely with each other in the least-squares refinement was devised. MOs were refined together with the other crystallographic parameters, although the refinement with the atomic positional parameters requires a lot of calculation time. The XMO method was applied to diformohydrazide, (NHCHO)2, without using polarization functions, and the electron-density distributions, including the maxima on the covalent bonds, were represented well. Therefore, from the viewpoint of X-ray diffraction, it is concluded that the MOs averaged by thermal vibrations of the atoms were obtained successfully by XMO analysis. The method of XMO analysis, combined with X-ray atomic orbital (AO) analysis, in principle enables one to obtain MOs or AOs without phase factors from X-ray diffraction experiments on most compounds from organic to rare earth compounds.

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

Effect of the intramolecular hydrogen bond in the active metabolite analogs of leflunomide for blocking the Plasmodium falciparum dihydroorotate dehydrogenase enzyme: QTAIM, NBO, and docking study

2020 ◽  
Vol 16 ◽  
Author(s):  
Reihaneh Heidarian ◽  
Mansoureh Zahedi-Tabrizi
Keyword(s):  
Hydrogen Bond ◽  
Plasmodium Falciparum ◽  
Molecular Orbital ◽  
Intramolecular Hydrogen Bond ◽  
Active Metabolite ◽  
Chemical Hardness ◽  
Dihydroorotate Dehydrogenase ◽  
Molecular Orbital Analysis ◽  
Intramolecular Hydrogen ◽  
Orbital Analysis

: Leflunomide (LFM) and its active metabolite, teriflunomide (TFM), have drawn a lot of attention for their anticancer activities, treatment of rheumatoid arthritis and malaria due to their capability to inhibit dihydroorotate dehydrogenase (DHODH) and Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) enzyme. In this investigation, the strength of intramolecular hydrogen bond (IHB) in five analogs of TFM (ATFM) has been analyzed employing density functional theory (DFT) using B3LYP/6-311++G (d, p) level and molecular orbital analysis in the gas phase and water solution. A detailed electronic structure study has been performed using the quantum theory of atoms in molecules (QTAIM) and the hydrogen bond energies (EHB) of stable conformer obtained in the range of 76-97 kJ/mol, as a medium hydrogen bond. The effect of substitution on the IHB nature has been studied by natural bond orbital analysis (NBO). 1H NMR calculations show an upward trend in the proton chemical shift of the enolic proton in the chelated ring (14.5 to 15.7ppm) by increasing the IHB strength. All the calculations confirmed the strongest IHB in 5-F-ATFM and the weakest IHB in 2-F-ATFM. Molecular orbital analysis, including the HOMO-LUMO gap and chemical hardness, was performed to compare the reactivity of inhibitors. Finally, molecular docking analysis was carried out to identify the potency of inhibition of these compounds against PfDHODH enzyme.

Compressibility of β-As4S4: an in situ high-pressure single-crystal X-ray study

2012 ◽  
Vol 76 (4) ◽  
pp. 963-973 ◽  
Author(s):  
G. O. Lepore ◽  
T. Boffa Ballaran ◽  
F. Nestola ◽  
L. Bindi ◽  
D. Pasqual ◽  
...  
Keyword(s):  
Pressure Range ◽  
Substantial Reduction ◽  
Structural Data ◽  
Unit Cell ◽  
Van Der Waals Interactions ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Intermolecular Distances

AbstractAmbient temperature X-ray diffraction data were collected at different pressures from two crystals of β-As4S4, which were made by heating realgar under vacuum at 295ºC for 24 h. These data were used to calculate the unit-cell parameters at pressures up to 6.86 GPa. Above 2.86 GPa, it was only possible to make an approximate measurement of the unit-cell parameters. As expected for a crystal structure that contains molecular units held together by weak van der Waals interactions, β-As4S4 has an exceptionally high compressibility. The compressibility data were fitted to a third-order Birch–Murnaghan equation of state with a resulting volume V0 = 808.2(2) Å3, bulk modulus K0 = 10.9(2) GPa and K' = 8.9(3). These values are extremely close to those reported for the low-temperature polymorph of As4S4, realgar, which contains the same As4S4 cage-molecule. Structural analysis showed that the unit-cell contraction is due mainly to the reduction in intermolecular distances, which causes a substantial reduction in the unit-cell volume (∼21% at 6.86 GPa). The cage-like As4S4 molecules are only slightly affected. No phase transitions occur in the pressure range investigated.Micro-Raman spectra, collected across the entire pressure range, show that the peaks associated with As–As stretching have the greatest pressure dependence; the S–As–S bending frequency and the As–S stretching have a much weaker dependence or no variation at all as the pressure increases; this is in excellent agreement with the structural data.

scholarly journals Purification, crystallization and preliminary X-ray diffraction analysis of a hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase (HCT) fromCoffea canephorainvolved in chlorogenic acid biosynthesis

2012 ◽  
Vol 68 (7) ◽  
pp. 824-828 ◽  
Author(s):  
Laura A. Lallemand ◽  
James G. McCarthy ◽  
Sean McSweeney ◽  
Andrew A. McCarthy
Keyword(s):  
Structural Data ◽  
Coffea Canephora ◽  
Molecular Replacement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Key Enzyme ◽  
Substrate Specifities ◽  
Drop Technique ◽  
Better Than

Chlorogenic acids (CGAs) are a group of soluble phenolic compounds that are produced by a variety of plants, includingCoffea canephora(robusta coffee). The last step in CGA biosynthesis is generally catalysed by a specific hydroxycinnamoyl-CoA quinate hydroxycinnamoyltransferase (HQT), but it can also be catalysed by the more widely distributed hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase (HCT). Here, the cloning and overexpression of HCT fromC. canephorainEscherichia colias well as its purification and crystallization are presented. Crystals were obtained by the sitting-drop technique at 293 K and X-ray diffraction data were collected on the microfocus beamline ID23-2 at the ESRF. The HCT crystals diffracted to better than 3.0 Å resolution, belonged to space groupP42212 with unit-cell parametersa=b= 116.1,c= 158.9 Å and contained two molecules in the asymmetric unit. The structure was solved by molecular replacement and is currently under refinement. Such structural data are needed to decipher the molecular basis of the substrate specifities of this key enzyme, which belongs to the large plant acyl-CoA-dependent BAHD acyltransferase superfamily.

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