scholarly journals Structural Characterization of Octahedral Sheet in Dioctahedral Smectites by Thermal Analysis

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 347
Author(s):  
Xiaoli Wang ◽  
Yan Li ◽  
Hejing Wang
Keyword(s):  
Thermal Analysis ◽  
Structural Characterization ◽  
Iron Content ◽  
Octahedral Sheet ◽  
Wide Range ◽  
Cis And Trans ◽  
Octahedral Cations ◽  
Derivative Thermogravimetry ◽  
Main Factor

The structures of octahedral sheets of dioctahedral phyllosilicates show cis-vacant (cv) and trans-vacant (tv) configurations due to the different distributions of the octahedral cations over cis- and trans-sites. On the basis of the different dehydroxylation temperatures, a thermal analysis is an effective method used to identify the cv and tv configurations of an octahedral sheet in dioctahedral smectites. The proportions of cv and tv configurations were determined by fitting the derivative thermogravimetry (DTG) curves. A wide range of cv and tv proportions were detected in the samples. The dehydroxylation temperatures of samples consisting of cv configuration are about 150 to 200 °C higher than those consisting of tv configurations. The samples were classified as tv varieties when octahedral Fe3+ > 0.46 mol/FU, and the pure tv dioctahedral smectites were found when Fe3+ > 1.8 mol/FU. A clear linear relationship was found between the content of octahedral Fe3+ and Al3+ and the proportion of cv and tv configurations. The substitution of Al3+ by Fe3+ in the octahedral sheets is the main factor for the formation of tv varieties. There was no relationship detected between the layer charge density, octahedral Mg2+ content, and the proportion of tv and cv. The present results indicate that the iron content has a significant effect on the structure of the octahedral sheet.

scholarly journals Solid-State NMR Techniques for the Structural Characterization of Cyclic Aggregates Based on Borane–Phosphane Frustrated Lewis Pairs

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1400 ◽  
Author(s):  
Robert Knitsch ◽  
Melanie Brinkkötter ◽  
Thomas Wiegand ◽  
Gerald Kehr ◽  
Gerhard Erker ◽  
...  
Keyword(s):  
Solid State ◽  
Structural Characterization ◽  
Solid State Nmr ◽  
Magic Angle ◽  
Frustrated Lewis Pairs ◽  
Wide Range ◽  
Nmr Techniques ◽  
Nmr Methods ◽  
Lewis Pairs

Modern solid-state NMR techniques offer a wide range of opportunities for the structural characterization of frustrated Lewis pairs (FLPs), their aggregates, and the products of cooperative addition reactions at their two Lewis centers. This information is extremely valuable for materials that elude structural characterization by X-ray diffraction because of their nanocrystalline or amorphous character, (pseudo-)polymorphism, or other types of disordering phenomena inherent in the solid state. Aside from simple chemical shift measurements using single-pulse or cross-polarization/magic-angle spinning NMR detection techniques, the availability of advanced multidimensional and double-resonance NMR methods greatly deepened the informational content of these experiments. In particular, methods quantifying the magnetic dipole–dipole interaction strengths and indirect spin–spin interactions prove useful for the measurement of intermolecular association, connectivity, assessment of FLP–ligand distributions, and the stereochemistry of adducts. The present review illustrates several important solid-state NMR methods with some insightful applications to open questions in FLP chemistry, with a particular focus on supramolecular associates.

scholarly journals Transition metal complexes with thiosemicarbazide-based ligands. Part 60. Reactions of copper(II) bromide with pyridoxal S-methylisothiosemicarbazone (PLITSC). Crystal structure of [Cu(PLITSC−H)H2O]Br•H2O

2014 ◽  
Vol 79 (3) ◽  
pp. 291-302 ◽  
Author(s):  
Vukadin Leovac ◽  
Ljiljana Vojinovic-Jesic ◽  
Sonja Ivkovic ◽  
Marko Rodic ◽  
Ljiljana Jovanovic ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thermal Analysis ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Elemental Analysis ◽  
Structural Characterization ◽  
Electronic Spectra ◽  
Square Planar

The synthesis and structural characterization of a square-planar copper(II) complex with pyridoxal S-methylisothiosemicarbazone (PLITSC) of the formula [Cu(PLITSC?H)H2O]Br?H2O (1) as the first Cu(II) complex with monoanionic form of this ligand were described. Complex 1 together with two previously synthesized complexes [Cu(PLITSC)Br2] (2) and [Cu(PLITSC)Br(MeOH)]Br (3) were characterized by elemental analysis, IR and electronic spectra and also by the methods of thermal analysis, conductometry and magnetochemistry.

scholarly journals Inside Cover: Synthesis and Structural Characterization of Homochiral Homo-oligomers of Parent cis- and trans-Furanoid-β-Amino Acids (Chem. Eur. J. 46/2011)

2011 ◽  
Vol 17 (46) ◽  
pp. 12834-12834
Author(s):  
Sunil K. Pandey ◽  
Ganesh F. Jogdand ◽  
João C. A. Oliveira ◽  
Ricardo A. Mata ◽  
Pattuparambil R. Rajamohanan ◽  
...  
Keyword(s):  
Amino Acids ◽  
Structural Characterization ◽  
Cis And Trans

Synthesis and Structural Characterization of Homochiral Homo-Oligomers of cis-γ-Methoxy-Substituted cis- and trans-Furanoid-β-Amino Acids

2012 ◽  
Vol 2012 (13) ◽  
pp. 2656-2663 ◽  
Author(s):  
Awadut G. Giri ◽  
Ganesh F. Jogdand ◽  
Pattuparampil R. Rajamohanan ◽  
Sunil K. Pandey ◽  
Chepuri V. Ramana
Keyword(s):  
Amino Acids ◽  
Structural Characterization ◽  
Cis And Trans

scholarly journals Kinetic and Structural Characterization of the First B3 Metallo-β-Lactamase with an Active Site Glutamic Acid

2021 ◽  
Author(s):  
Liam A. Wilson ◽  
Esmée G. Knaven ◽  
Marc T. Morris ◽  
Marcelo Monteiro Pedroso ◽  
Christopher J. Schofield ◽  
...  
Keyword(s):  
Glutamic Acid ◽  
Structural Characterization ◽  
Active Site ◽  
Structural Diversity ◽  
Kinetic Properties ◽  
Design Studies ◽  
Degrading Bacterium ◽  
Active Site Motif ◽  
Wide Range

The structural diversity in metallo-β-lactamases (MBLs), especially in the vicinity of the active site, has been a major hurdle in the development of clinically effective inhibitors. Representatives from three variants of the B3 MBL subclass, containing either the canonical HHH/DHH active site motif (present in the majority of MBLs in this subclass) or the QHH/DHH (B3-Q) or HRH/DQK (B3-RQK) variations were reported previously. Here, we describe the structure and kinetic properties of the first example (SIE-1) of a fourth variant containing the EHH/DHH active site motif (B3-E). SIE-1 was identified in the hexachlorocyclohexane-degrading bacterium Sphingobium indicum , and kinetic analyses demonstrate that although it is active against a wide range of antibiotics its efficiency is lower than that of other B3 MBLs, but with improved efficiency towards cephalosporins relative to other β-lactam substrates. The overall fold of SIE-1 is characteristic of the MBLs; the notable variation is observed in the Zn1 site due to the replacement of the canonical His116 by a glutamate. The unusual preference of SIE-1 for cephalosporins and its occurrence in a widespread environmental organism suggests scope for increased MBL-mediated β-lactam resistance. It is thus relevant to include SIE-1 into MBL inhibitor design studies to widen the therapeutic scope of much needed anti-resistance drugs.

Structural Characterization of MCM-41 over a Wide Range of Length Scales

Langmuir ◽  
1999 ◽  
Vol 15 (8) ◽  
pp. 2809-2816 ◽  
Author(s):  
C. G. Sonwane ◽  
S. K. Bhatia
Keyword(s):  
Structural Characterization ◽  
Length Scales ◽  
Wide Range ◽  
Mcm 41

Thermal analysis and structural characterization of copper(II) complexes with salicyladehydes

2014 ◽  
Vol 120 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Ariadni Zianna ◽  
Konstantinos Chrissafis ◽  
Antonis Hatzidimitriou ◽  
Maria Lalia-Kantouri
Keyword(s):  
Thermal Analysis ◽  
Structural Characterization
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