scholarly journals Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

2018 ◽  
Author(s):  
Laura Abad Galán ◽  
Alexandre N. Sobolev ◽  
Eli Zysman-Colman ◽  
Mark Ogden ◽  
Massimiliano Massi
Keyword(s):  
Chelating Ligands ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
Claisen Condensation ◽  
X Ray ◽  
Condensation Products ◽  
Complexation Reactions ◽  
The Impact ◽  
Low Solubility

<i>β</i>-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four <i>β</i>-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by <i>in situ</i>retro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensationreaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest that using solvents of lower polarity will mimimise the impact of the retro-Claisen condensation in these complexes. <br>

scholarly journals Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

2018 ◽  
Author(s):  
Laura Abad Galán ◽  
Alexandre N. Sobolev ◽  
Eli Zysman-Colman ◽  
Mark Ogden ◽  
Massimiliano Massi
Keyword(s):  
Chelating Ligands ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
Claisen Condensation ◽  
X Ray ◽  
Condensation Products ◽  
Complexation Reactions ◽  
The Impact ◽  
Low Solubility

<i>β</i>-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four <i>β</i>-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by <i>in situ</i>retro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensationreaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest that using solvents of lower polarity will mimimise the impact of the retro-Claisen condensation in these complexes. <br>

scholarly journals Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

2018 ◽  
Author(s):  
Laura Abad Galán ◽  
Alexandre N. Sobolev ◽  
Eli Zysman-Colman ◽  
Mark Ogden ◽  
Massimiliano Massi
Keyword(s):  
Chelating Ligands ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
Claisen Condensation ◽  
X Ray ◽  
Condensation Products ◽  
Complexation Reactions ◽  
The Impact ◽  
Low Solubility

<i>β</i>-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four <i>β</i>-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by <i>in situ</i>retro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensationreaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest that using solvents of lower polarity will mimimise the impact of the retro-Claisen condensation in these complexes. <br>

scholarly journals Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

2018 ◽  
Author(s):  
Laura Abad Galán ◽  
Alexandre N. Sobolev ◽  
Eli Zysman-Colman ◽  
Mark Ogden ◽  
Massimiliano Massi
Keyword(s):  
Condensation Reaction ◽  
Chelating Ligands ◽  
X Ray Diffraction ◽  
Claisen Condensation ◽  
X Ray ◽  
Condensation Products ◽  
The Stability ◽  
Decomposition Pathway ◽  
Complexation Reactions

<i>β</i>-Triketonates have been recently used as chelating ligands for lanthanoid ions presenting unique structures varying from assemblies to polymers. Despite their novel complexation behaviour little is known about the stability of these molecules. Indeed, two examples of possible <i>in situ</i>retro-Claisen condensation reactions have been reported previously. To better understand this possible decomposition pathway, four new <i>β</i>-triketones were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media, aiming to isolate the potentially varying ligands present in solution. The X-ray diffraction studies revealed the formation of structures where one, two, or three of the molecules involved in the retro-Claisen condensation reaction were linked to the lanthanoid centres.

Unconventional Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

2018 ◽  
Author(s):  
Laura Abad Galán ◽  
Alexandre N. Sobolev ◽  
Eli Zysman-Colman ◽  
Mark Ogden ◽  
Massimiliano Massi
Keyword(s):  
Condensation Reaction ◽  
Chelating Ligands ◽  
X Ray Diffraction ◽  
Claisen Condensation ◽  
X Ray ◽  
Condensation Products ◽  
The Stability ◽  
Decomposition Pathway ◽  
Complexation Reactions

<i>β</i>-Triketonates have been recently used as chelating ligands for lanthanoid ions presenting unique structures varying from assemblies to polymers. Despite their novel complexation behaviour little is known about the stability of these molecules. Indeed, two examples of possible <i>in situ</i>retro-Claisen condensation reactions have been reported previously. To better understand this possible decomposition pathway, four new <i>β</i>-triketones were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media, aiming to isolate the potentially varying ligands present in solution. The X-ray diffraction studies revealed the formation of structures where one, two, or three of the molecules involved in the retro-Claisen condensation reaction were linked to the lanthanoid centres.

scholarly journals In Situ Observation of Stress Accumulation during Sub-Merged Arc Welding

2014 ◽  
Vol 996 ◽  
pp. 417-423 ◽  
Author(s):  
Arne Kromm ◽  
Thomas Kannengiesser
Keyword(s):  
Arc Welding ◽  
Large Scale ◽  
X Ray Diffraction ◽  
X Ray ◽  
Residual Stress State ◽  
Testing Facility ◽  
Large Scale Testing ◽  
The Impact ◽  
Stress Accumulation

Results obtained from laboratory tests mostly need to be verified under fabrication conditions in order to incorporate design specifics (joint configuration and restraint), which effect the residual stress state considerably. For this purpose, multi-pass sub merged arc welding was performed in a special large-scale testing facility. The impact of varying interpass temperatures could be proven in-situ by means of a pronounced stress accumulation during welding and subsequent heat treatment accompanied by stress determination using X-ray diffraction.

scholarly journals Dehydrogenation of Ethylene on Supported Palladium Nanoparticles: A Double View from Metal and Hydrocarbon Sides

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1643 ◽  
Author(s):  
Oleg A. Usoltsev ◽  
Anna Yu. Pnevskaya ◽  
Elizaveta G. Kamyshova ◽  
Andrei A. Tereshchenko ◽  
Alina A. Skorynina ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Palladium Nanoparticles ◽  
Pd Catalyst ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
X Ray ◽  
Ab Initio Simulations ◽  
Supported Palladium ◽  
X Ray Absorption

Adsorption of ethylene on palladium, a key step in various catalytic reactions, may result in a variety of surface-adsorbed species and formation of palladium carbides, especially under industrially relevant pressures and temperatures. Therefore, the application of both surface and bulk sensitive techniques under reaction conditions is important for a comprehensive understanding of ethylene interaction with Pd-catalyst. In this work, we apply in situ X-ray absorption spectroscopy, X-ray diffraction and infrared spectroscopy to follow the evolution of the bulk and surface structure of an industrial catalysts consisting of 2.6 nm supported palladium nanoparticles upon exposure to ethylene under atmospheric pressure at 50 °C. Experimental results were complemented by ab initio simulations of atomic structure, X-ray absorption spectra and vibrational spectra. The adsorbed ethylene was shown to dehydrogenate to C2H3, C2H2 and C2H species, and to finally decompose to palladium carbide. Thus, this study reveals the evolution pathway of ethylene on industrial Pd-catalyst under atmospheric pressure at moderate temperatures, and provides a conceptual framework for the experimental and theoretical investigation of palladium-based systems, in which both surface and bulk structures exhibit a dynamic nature under reaction conditions.

In Situ EXAFS Characterization of Nanoparticulate Catalysts

MRS Bulletin ◽  
2007 ◽  
Vol 32 (12) ◽  
pp. 1038-1043 ◽  
Author(s):  
John Evans ◽  
Anna Puig-Molina ◽  
Moniek Tromp
Keyword(s):  
Platinum Group Metal ◽  
Metal Catalysts ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
Metal Centers ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Vibrational Spectroscopies ◽  
Complementary Techniques

AbstractX-ray absorption fine structure (XAFS) spectroscopy probes the structure and electronic properties of metal centers. Because it can be applied to noncrystalline materials, it is a key technique for probing nanoparticulate materials, such as colloidal and heterogeneous metal catalysts. The high brilliance of modern synchrotron radiation x-ray sources facilitates in situ studies, which provide direct structure–function relationships with both spatial and time resolution; this is especially effective when applied in combination with complementary techniques such as x-ray diffraction, mass spectrometry, and optical or vibrational spectroscopies. Tracking the particle formation of platinum-group metal catalysts, their behavior under reaction conditions, and the distribution of sites within a catalyst bed shows that this approach is essential for understanding the chemistry of these nanoparticles. Rather than behave as monolithic entities, nanoparticulate catalysts undergo rapid structural transformations induced by the gas environment and reaction conditions, and their lifetimes as catalysts depend on the reversibility of these changes.

scholarly journals The impact of pressure on β-Cyclodextrin·acetaminophen inclusion complexes

2014 ◽  
Vol 70 (a1) ◽  
pp. C264-C264 ◽  
Author(s):  
Sofiane Saouane ◽  
Wolfgang Morgenroth ◽  
Hanns-Peter Liermann ◽  
Carsten Paulmann ◽  
Francesca Fabbiani
Keyword(s):  
High Pressure ◽  
Inclusion Complex ◽  
Aqueous Solubility ◽  
Crystal Form ◽  
Model Systems ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pharmaceutical Ingredients ◽  
The Impact

Cyclodextrins (CDs) have attracted considerable interest as model systems in supramolecular host-guest chemistry. They are described as hollow truncated cones with a hydrophilic outer surface and a nonpolar inner cavity suitable for small molecules' encapsulation.[1] By virtue of their character, CDs are used as excipients to improve the aqueous solubility of active pharmaceutical ingredients (APIs). High-pressure crystallisation techniques have been established as a suitable tool for exploring the phenomenon of polymorphism and solvate formation of pharmaceutical compounds throughout numerous examples reported in the literature.[2] Thus, exploring the inclusion-complex formation and the polymorphic behaviour of CDs with APIs at high pressure would be an interesting extension of the technique. The present work describes the attempt of an in-situ crystallisation of β-CD·acetaminophen inclusion complex and compression studies of the known β-CD·acetaminophen complex[3] in different crystallisation media at pressures up to 1.0 GPa. A new high-pressure crystal form observed at 0.8 GPa as well as unexpected results are presented herein. The crystals have been characterised by means of polarised optical microscopy, Raman spectroscopy and single-crystal X-ray diffraction using both home and synchrotron sources.

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