A general synthesis approach in action: preparation and characterization of polyoxomolybdenum(vi) organophosphonates through oxidative Mo–Mo bond cleavage in {MoV2O4}

CrystEngComm ◽  
2012 ◽  
Vol 14 (14) ◽  
pp. 4826 ◽  
Author(s):  
Lijuan Zhang ◽  
Jingmei Sun ◽  
Yunshan Zhou ◽  
Sadaf ul Hassan ◽  
Enbo Wang ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Action Preparation ◽  
General Synthesis ◽  
Synthesis Approach

scholarly journals Unveiling the crucial intermediates in androgen production

2015 ◽  
Vol 112 (52) ◽  
pp. 15856-15861 ◽  
Author(s):  
Piotr J. Mak ◽  
Michael C. Gregory ◽  
Ilia G. Denisov ◽  
Stephen G. Sligar ◽  
James R. Kincaid
Keyword(s):  
Bond Cleavage ◽  
Nucleophilic Attack ◽  
Reaction Intermediates ◽  
Structural Determinants ◽  
Initial Product ◽  
Androgen Synthesis ◽  
Ferric Peroxo ◽  
Enzymatic Mechanisms ◽  
Primary Substrate

Ablation of androgen production through surgery is one strategy against prostate cancer, with the current focus placed on pharmaceutical intervention to restrict androgen synthesis selectively, an endeavor that could benefit from the enhanced understanding of enzymatic mechanisms that derives from characterization of key reaction intermediates. The multifunctional cytochrome P450 17A1 (CYP17A1) first catalyzes the typical hydroxylation of its primary substrate, pregnenolone (PREG) and then also orchestrates a remarkable C17–C20 bond cleavage (lyase) reaction, converting the 17-hydroxypregnenolone initial product to dehydroepiandrosterone, a process representing the first committed step in the biosynthesis of androgens. Now, we report the capture and structural characterization of intermediates produced during this lyase step: an initial peroxo-anion intermediate, poised for nucleophilic attack on the C20 position by a substrate-associated H-bond, and the crucial ferric peroxo-hemiacetal intermediate that precedes carbon–carbon (C-C) bond cleavage. These studies provide a rare glimpse at the actual structural determinants of a chemical transformation that carries profound physiological consequences.

scholarly journals Crystallization and preliminary X-ray characterization of the 2,4′-dihydroxyacetophenone dioxygenase fromAlcaligenessp. 4HAP

2014 ◽  
Vol 70 (6) ◽  
pp. 823-826 ◽  
Author(s):  
G. Beaven ◽  
A. Bowyer ◽  
P. Erskine ◽  
S. P. Wood ◽  
A. McCoy ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Formic Acid ◽  
Molecular Oxygen ◽  
Aromatic Ring ◽  
Bond Cleavage ◽  
Its Sequence ◽  
Hydroxybenzoic Acid ◽  
X Ray

The enzyme 2,4′-dihydroxyacetophenone dioxygenase (or DAD) catalyses the conversion of 2,4′-dihydroxyacetophenone to 4-hydroxybenzoic acid and formic acid with the incorporation of molecular oxygen. Whilst the vast majority of dioxygenases cleave within the aromatic ring of the substrate, DAD is very unusual in that it is involved in C—C bond cleavage in a substituent of the aromatic ring. There is evidence that the enzyme is a homotetramer of 20.3 kDa subunits each containing nonhaem iron and its sequence suggests that it belongs to the cupin family of dioxygenases. By the use of limited chymotrypsinolysis, the DAD enzyme fromAlcaligenessp. 4HAP has been crystallized in a form that diffracts synchrotron radiation to a resolution of 2.2 Å.

Synthesis and Characterization of Magnesium Vanadates as Potential Mg-ion Cathode Materials Through an Ab Initio Guided Carbothermal Reduction Approach

2021 ◽  
Author(s):  
Jeongjae Lee ◽  
Sunita Dey ◽  
Siân Dutton ◽  
Clare Grey
Keyword(s):  
Transition Metal ◽  
Ab Initio ◽  
Transition Metal Oxides ◽  
Solid State Nmr ◽  
Local Charge ◽  
Synthesis Strategy ◽  
Specific Complex ◽  
Magnesium Vanadates ◽  
Synthesis Approach

Many technologically relevant transition metal oxides for advanced energy storage and catalysis feature reduced transition metal (TM) oxides and are often nontrivial to prepare because of the need to control the reducing nature of the atmosphere in which they are synthesized. In this work, we show that an ab initio predictive synthesis strategy can be used to produce multiple gram-scale products of various MgVxOy-type phases (δ-MgV2O5, spinel MgV2O4, and MgVO3) containing V3+ or V4+ relevant for Mg-ion battery cathodes. Characterization of these phases using 25Mg solid-state NMR spectroscopy illustrates the potential of 25Mg NMR for studying reversible magnesiation and local charge distributions. Rotor-Assisted Population Transfer is used as a much needed signal-to-noise enhancement technique. The ab initio guided synthesis approach is seen as a step forward towards a predictive synthesis strategy for targeting specific complex TM oxides with variable oxidation states of technological importance.

Synthesis and Characterization of Novel AlF3 Cubes

NANO ◽  
2015 ◽  
Vol 10 (05) ◽  
pp. 1550071 ◽  
Author(s):  
Maoquan Xue ◽  
Changsheng Li
Keyword(s):  
Electron Microscopy ◽  
Synthesis And Characterization ◽  
Metal Fluoride ◽  
Controlled Synthesis ◽  
X Ray ◽  
Transmission Electron ◽  
Cubic Structure ◽  
Synthesis Approach ◽  
Scanning Electron

In this paper, regularly shaped AlF 3 particles with cubic structure were successfully synthesized via a solvothermal route. The as-prepared products were characterized by X-ray powder diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results indicated that reaction temperature and time have significant effects on the morphology of the as-prepared products. A possible formation process has also been investigated on the basis of a series of XRD and SEM studies of the product obtained at different conditions. This well-controlled synthesis approach may be extended to fabricate other metal fluoride materials.

La-Based Perovskites as Oxygen-Exchange Redox Materials for Solar Syngas Production

MRS Advances ◽  
2017 ◽  
Vol 2 (55) ◽  
pp. 3365-3370 ◽  
Author(s):  
Rahul R. Bhosale ◽  
Anand Kumar ◽  
Anchu Ashok ◽  
Parag Sutar ◽  
Gorakshnath Takalkar ◽  
...  
Keyword(s):  
Solution Combustion Synthesis ◽  
Scanning Transmission Electron Microscope ◽  
Bet Surface Area ◽  
Synthesis And Characterization ◽  
Solution Combustion ◽  
Syngas Production ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Synthesis Approach

ABSTRACTThis contribution reports the synthesis and characterization of La-based perovskites which can be used for the production of syngas via solar thermochemical splitting of H2O/CO2. The La-based perovskites were synthesized using a solution combustion synthesis approach. The derived perovskites were analyzed using powder X-ray diffractometer (PXRD), BET surface area analyzer (BET), and scanning/transmission electron microscope (SEM/TEM). The results associated with the synthesis and characterization of La-based perovskites is reported in detail.

ChemInform Abstract: First Characterization of Zirconium Enolate Radical Cations in Solution and Their Mesolytic Bond Cleavage to Zirconocene Cations.

ChemInform ◽  
2010 ◽  
Vol 29 (25) ◽  
pp. no-no
Author(s):  
M. SCHMITTEL ◽  
R. SOELLNER
Keyword(s):  
Bond Cleavage ◽  
Radical Cations

scholarly journals Synthesis and Characterization of New Diiron and Diruthenium μ-Aminocarbyne Complexes Containing Terminal S-, P- and C-Ligands

2007 ◽  
Vol 62 (3) ◽  
pp. 427-438 ◽  
Author(s):  
Vincenzo G. Albano ◽  
Luigi Busetto ◽  
Fabio Marchetti ◽  
Magda Monari ◽  
Stefano Zacchini ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Diffraction Study ◽  
Coordination Mode ◽  
Bond Cleavage ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dithiocarbamate Ligand ◽  
High Yields

The diiron aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (R = Xy1, 1a; R = Me, 1b; R = CH2Ph, 1c; Xy1 = 2,6-Me2C6H3) undergo replacement of the coordinated nitrile by halides, diethyldithiocarbamate, and dicyanomethanide to give [Fe2{μ-CN(Me) (R)}(μ-CO)(CO)(X)(Cp)2] complexes (R = Me, X = Br, 4a; R = Me, X = I, 4b; R = CH2Ph, X = Cl, 4c; R = CH2Ph, X = Br, 4d; R = CH2Ph, X = I, 4e; R = Xy1, X = SC(S)NEt2, 5a; R = Me, X = SC(S)NEt2, 5b; R = Xy1, X = CH(CN)2, 7), in good yields. The molecular structure of 5a shows an unusual η1 coordination mode of the dithiocarbamate ligand. Similarly, treatment of [M2{μ-CN(Me) (R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (M = Fe, R = Xy1, 1a; M = Fe, R = Me, 1b; M = Ru, R = Xy1, 2a; M = Ru, R = Me, 2b) with a series of phosphanes generates the cationic complexes [M2{μ- CN(Me)(R)}(μ-CO)(CO)(P)(Cp)2][SO3CF3] (M = Fe, R = Xy1, P = PPh2H, 6a; M = Fe, R = Xy1, P = PPh3, 6b; M = Fe, R = Xy1, P = PMe3, 6c; M = Fe, R = Me, P = PMe2Ph, 6d; M = Fe, R = Me, P = PPh3, 6e; M = Fe, R = Me, P = PMePh2, 6f; M = Ru, R = Xy1, P = PPh2H, 6g; M = Ru, R = Me, P = PPh2H, 6h), in high yields. The molecular structure of 6a has been elucidated by an X-ray diffraction study. The reactions of [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO)(NCR′)(Cp)2][SO3CF3] [R′ = Me, 1a; R′ = tBu, 3] with PhLi and PPh2Li yield [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(Ph)(Cp)2] (8) and [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(PPh2)(Cp)2] (9), respectively. The molecular structure of 8 has been ascertained by X-ray diffraction. Conversely, the reaction of 1a with MeLi generates the aminoalkylidene compound [Fe2{C(Me)N(Me)(Xy1)}(μ-CO)2(CO)(Cp)2] (10).Finally, the acetone complex [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(OCMe2)(Cp)2][SO3CF3] (12) reacts with lithium acetylides to give complexes [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(C≡CR)(Cp)2] (R = p-C6H4Me, 11a; R = Ph, 11b; R = SiMe3, 11c), in high yields. Filtration through alumina of a solution of 11a in CH2Cl2 results in hydration of the acetylide group and C-Si bond cleavage, affording [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO){C(O)Me}(Cp)2] (12).

Characterization of Oligosaccharides of the Lactosamine Series Derived from Keratan Sulfates by Tandem Mass Spectrometry

2000 ◽  
Vol 6 (2) ◽  
pp. 193-203 ◽  
Author(s):  
Masayuki Kubota ◽  
Keiichi Yoshida ◽  
Akira Tawada ◽  
Mamoru Ohashi
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Bond Cleavage ◽  
The Other ◽  
Negative Ion ◽  
Ring Cleavage ◽  
Tandem Mass ◽  
Fragment Ions ◽  
Glycosidic Bond Cleavage

Positive- and negative-ion fast-atom bombardment tandem mass spectrometry with collision-induced dissociation (FAB-CID-MS/MS) has been used in the characterization of di-and tetra-saccharides of the lactosamine series from keratan sulfates. FAB-CID-MS/MS of Galβ1-4GlcNAc (L1) exhibited strong fragment ions originating from ring cleavage at the reducing-terminal sugar moiety together with glycosidic bond-cleavage ions, whereas GlcNAcβ1-3Gal (K1) showed strong glycosidic bond-cleavage ions but no ring-cleavage ions. A series of ring-cleavage fragment ions was observed with members of the L-series which have free hydroxyl groups at the C1 and C3 positions. CID-MS/MS spectra of the [M + Na – SO3]+ ion ( m/z 406) from L2 and the [M + Na − 2SO3]+ ion ( m/z 406) from L4 were almost identical with the CID-MS/MS spectrum of the [M + Na]+ ion ( m/z 406) from L1, which indicated that the sugar skeletons of L2 and L4 are the same as that of L1. On the other hand, the CID-MS/MS spectrum of the [M + Na – SO3]+ ion ( m/z 508) from L4 did not resemble that of the [M + Na]+ ion ( m/z 508) from L2. The former showed peaks that were additional to the peaks in the latter. Since these extra peaks were accounted for on the basis of the structure of L3 [Galβ1(6S)-4GlcNAc, S = sulfate], the in-source loss of sulfate groups by ester exchange upon FAB ionization takes place in a dual manner; one reaction at the non-reducing terminal sugar to give L2 and the other at the reducing-terminal sugar to give L3. The CID-MS/MS spectra were characteristic for the tetrasaccharides L1-L1, L2-L2 and L4-L4 while in-source fragmentation confirms the component disaccharides of each tetrasaccharide. The structure of a tetrasaccharide trisulfate was confirmed as L2–L4 and not L4–L2 by CID-MS/MS. Negative-ion FAB-CID-MS/MS spectra of the sulfated di-and tetra-saccharides showed a pattern similar to that of the positive-ion spectra. Subtraction of the CID-MS/MS spectrum of the [M – H]− ion of L2 [Galβ1-4GlcNAc(6S)] from that of the [M – H – SO3]− ion of L4 [Gal(6S)β1-4GlcNAc(6S)] gave several specific ions whose origins were nicely explained on the basis of the structure of L3. The structure of a pentasaccharide consisting of N-acetylneuraminic acid and a tetrasaccharide trisulfate was confirmed, on the basis of FAB-CID-MS/MS, as NeuNAcα2-6L2-L4.

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