Chiral Rare Earth Lewis Acids

2017 ◽  
pp. 261-298
Author(s):  
Helen C. Aspinall
Keyword(s):  
Rare Earth ◽  
Lewis Acids

Recent Applications of Rare Earth Complexes in Photoredox Catalysis for Organic Synthesis

2021 ◽  
Vol 25 ◽  
Author(s):  
Alexis Prieto ◽  
Florian Jaroschik
Keyword(s):  
Rare Earth ◽  
Lewis Acids ◽  
Rare Earth Complexes ◽  
Photoredox Catalysis ◽  
Organic Transformations ◽  
New Paradigm ◽  
Active Centers ◽  
Redox Active ◽  
Wide Range ◽  
Made In

: In recent years, photoredox catalysis has appeared as a new paradigm for forging a wide range of chemical bonds under mild conditions using abundant reagents. This approach allows many organic transformations through the generation of various radical species, enabling the valorization of non-traditional partners. A continuing interest has been devoted to the discovery of novel radical-generating procedures. Over the last ten years, strategies using rare-earth complexes as either redox-active centers or as redox-neutral Lewis acids have emerged. This review provides an overview of the recent accomplishments made in this field. It especially aims to demonstrate the utility of rare-earth complexes for ensuring photocatalytic transformations and to inspire future developments.

ChemInform Abstract: Rare-Earth Element Complexes as Water Compatible Catalysts and Lewis Acids in the Organic Synthesis

ChemInform ◽  
2010 ◽  
Vol 27 (44) ◽  
pp. no-no
Author(s):  
S. KOBAYASHI ◽  
I. HACHIYA ◽  
H. ISHITANI ◽  
M. MORIWAKI ◽  
S. NAGAYAMA
Keyword(s):  
Rare Earth ◽  
Organic Synthesis ◽  
Rare Earth Element ◽  
Lewis Acids ◽  
Earth Element

A New Glycosidation Procedure Utilizing Rare Earth Salts and Glycosyl Fluorides, with or without the Requirement of Lewis Acids

1995 ◽  
Vol 60 (1) ◽  
pp. 4-5 ◽  
Author(s):  
Shigeru Hosono ◽  
Won-Sup Kim ◽  
Hiroaki Sasai ◽  
Masakatsu Shibasaki
Keyword(s):  
Rare Earth ◽  
Lewis Acids ◽  
Rare Earth Salts

Polymerization and Chiroptical Behavior of Polymethacrylamides Bearing a Bulky Oxazoline Pendant

2014 ◽  
Vol 887-888 ◽  
pp. 688-692
Author(s):  
Zheng Fu ◽  
Hong Wei ◽  
Chao Yuan ◽  
Zhong Wen Li
Keyword(s):  
Rare Earth ◽  
Free Radical ◽  
Radical Polymerization ◽  
Lewis Acid ◽  
Rare Earth Metal ◽  
Lewis Acids ◽  
Earth Metal ◽  
Free Radical Polymerization ◽  
Optically Active ◽  
Circular Dichroïsm

The radical polymerization of optically active methacrylamide derivatives, N-[o-(4-phenyl-4,5-dihydro-1,3-oxazol-2-yl) phenymethacrylamide ((R)-PhOPMAM) and N-[o-(4-isopropyl-4,5-dihydro-1,3-oxazol-2-yl) phenymethacrylamide ((S)-PriOPMAM), were carried out under various conditions. The effect of the Lewis acid, that is, rare earth metal trifluoromethanesulfonates on the free-radical polymerization were examined under different solvents. The Lewis acids are effective in enhancing the isotacticity in the polymerization of (S)-PriOPMAM. The same phenomenon were not happened in the polymerization of (R)-PhOPMAM. The polymerization characteristics and the chiroptical behavior of the resultant polymers have been examined by using circular dichroism (CD), UVVis, and NMR spectroscopies.

Characterization of Rare-Earth Fluoride Anti-Stokes Phosphors by Scanning arid Transmission Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 142-143
Author(s):  
N. M. P. Low ◽  
L. E. Brosselard
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Elevated Temperatures ◽  
Stoichiometric Composition ◽  
Rare Earth Ions ◽  
Crystalline Solid ◽  
Precipitation Process ◽  
Rare Earth Fluoride ◽  
Earth Fluoride ◽  
Rare Earth Fluorides

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.

Study of segregation in La1.8Sr0.2CuO4 superconductor by STEM-EDS microanalysis

1987 ◽  
Vol 45 ◽  
pp. 54-55
Author(s):  
T. F. Kelly ◽  
P. J. Lee ◽  
E. E. Hellstrom ◽  
D. C. Larbalestier
Keyword(s):  
Rare Earth ◽  
High Field ◽  
Transport Current ◽  
Total Thickness ◽  
New Class ◽  
Ceramic Superconductors ◽  
Current Densities ◽  
Group Ii ◽  
Eds Microanalysis

Recently there has been much excitement over a new class of high Tc (>30 K) ceramic superconductors of the form A1-xBxCuO4-x, where A is a rare earth and B is from Group II. Unfortunately these materials have only been able to support small transport current densities 1-10 A/cm2. It is very desirable to increase these values by 2 to 3 orders of magnitude for useful high field applications. The reason for these small transport currents is as yet unknown. Evidence has, however, been presented for superconducting clusters on a 50-100 nm scale and on a 1-3 μm scale. We therefore planned a detailed TEM and STEM microanalysis study in order to see whether any evidence for the clusters could be seen.A La1.8Sr0.2Cu04 pellet was cut into 1 mm thick slices from which 3 mm discs were cut. The discs were subsequently mechanically ground to 100 μm total thickness and dimpled to 20 μm thickness at the center.

Microstructural characterization of a cast RENi5-based alloy

1993 ◽  
Vol 51 ◽  
pp. 1176-1177
Author(s):  
G. M. Micha ◽  
L. Zhang
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Microstructural Characterization ◽  
Binary Compound ◽  
Nickel Metal ◽  
Cast Material ◽  
Nickel Metal Hydride ◽  
Transmission Electron ◽  
Cast Condition

RENi5 (RE: rare earth) based alloys have been extensively evaluated for use as an electrode material for nickel-metal hydride batteries. A variety of alloys have been developed from the prototype intermetallic compound LaNi5. The use of mischmetal as a source of rare earth combined with transition metal and Al substitutions for Ni has caused the evolution of the alloy from a binary compound to one containing eight or more elements. This study evaluated the microstructural features of a complex commercial RENi5 based alloy using scanning and transmission electron microscopy.The alloy was evaluated in the as-cast condition. Its chemistry in at. pct. determined by bulk techniques was 12.1 La, 3.2 Ce, 1.5 Pr, 4.9 Nd, 50.2 Ni, 10.4 Co, 5.3 Mn and 2.0 Al. The as-cast material was of low strength, very brittle and contained a multitude of internal cracks. TEM foils could only be prepared by first embedding pieces of the alloy in epoxy.

Rare Earth Production

1952 ◽  
Vol 44 (3) ◽  
pp. 442-442
Author(s):  
Frank Spedding ◽  
Harley Wilhelm ◽  
Wayne Keller et al
Keyword(s):  
Rare Earth
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