scholarly journals Recent Advances in Rare Earth Complexes Containing N-Heterocyclic Carbenes: Synthesis, Reactivity, and Applications in Polymerization

Catalysts ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 71 ◽  
Author(s):  
Yu Pan ◽  
Xinxin Jiang ◽  
Yat-Ming So ◽  
Ching Tat To ◽  
Gaohong He
Keyword(s):  
Rare Earth ◽  
Catalytic Performance ◽  
Transition Metal Catalysts ◽  
Heterocyclic Carbenes ◽  
Unique Role ◽  
Ancillary Ligands ◽  
Grubbs Catalysts ◽  
Recent Developments ◽  
Metal Catalyzed

N-heterocyclic carbenes (NHCs) are ubiquitous ancillary ligands employed in metal-catalyzed homogeneous reactions and polymerization reactions. Of significance is the use of NHCs as the supporting ligand in second- and third-generation Grubbs catalysts for their application in olefin metathesis and ring-opening metathesis polymerization. While the applications of transition metal catalysts ligated with NHCs in polymerization chemistry are well-documented, the use of analogous rare earth (Ln = Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) catalysts in this area remains under-developed, despite the unique role of rare earth elements in regio- and stereo-specific (co)polymerization reactions. By using hetero-atom-tethered chelating NHCs and, more recently, the employment of other structurally related NHCs, NHC-ligated Ln complexes have proven to be promising and fruitful catalysts for selective polymerization reactions. This review summarizes the recent developments in the coordination chemistry of Ln complexes containing NHCs and their catalytic performance in polymerization.

scholarly journals Unraveling the coordination structure-performance relationship in Pt1/Fe2O3 single-atom catalyst

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yujing Ren ◽  
Yan Tang ◽  
Leilei Zhang ◽  
Xiaoyan Liu ◽  
Lin Li ◽  
...  
Keyword(s):  
Coordination Chemistry ◽  
Homogeneous Catalysis ◽  
Catalytic Performance ◽  
Inert Atmosphere ◽  
Single Atom ◽  
Unique Role ◽  
Local Coordination ◽  
Single Atoms ◽  
Heterogeneous And Homogeneous Catalysis

Abstract Heterogeneous single-atom catalyst (SAC) opens a unique entry to establishing structure–performance relationship at the molecular level similar to that in homogeneous catalysis. The challenge lies in manipulating the coordination chemistry of single atoms without changing single-atom dispersion. Here, we develop an efficient synthetic method for SACs by using ethanediamine to chelate Pt cations and then removing the ethanediamine by a rapid thermal treatment (RTT) in inert atmosphere. The coordination chemistry of Pt single atoms on a Fe2O3 support is finely tuned by merely adjusting the RTT temperature. With the decrease in Pt-O coordination number, the oxidation state of Pt decreases, and consequently the hydrogenation activity increases to a record level without loss of chemoselectivity. The tunability of the local coordination chemistry, oxidation states of the metal, and the catalytic performance of single atoms reveals the unique role of SACs as a bridge between heterogeneous and homogeneous catalysis.

scholarly journals Non-Classical Anionic Naked N-Heterocyclic Carbenes: Fundamental Properties and Emerging Applications in Synthesis and Catalysis

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 620 ◽  
Author(s):  
Mei Leow ◽  
Curtis Ho ◽  
Michael Gardiner ◽  
Alex Bissember
Keyword(s):  
Transition Metal ◽  
Heterocyclic Carbenes ◽  
Molecular Scaffolds ◽  
Ongoing Research ◽  
Fundamental Properties ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

Ongoing research exploring the chemistry of N-heterocyclic carbenes (NHCs) has led to the development and discovery of new NHC subclasses that deviate beyond Arduengo’s prototypical N,N′-disubstituted imidazol-2-ylidene-based structures. These systems continue to enable and extend the fundamental role of NHC ligands in synthesis and catalysis. In this regard, the advent of protic NHCs has garnered particular interest. This derives in part from their applications to the selective preparation of unique molecular scaffolds and their unprecedented bifunctional reactivity, which can be exploited in transition metal-catalyzed processes. In comparison, the synthetic applications of closely related anionic naked NHCs remain rather underexplored. With this in mind, this review highlights the interesting fundamental properties of non-classical anionic naked NHCs, and focuses on their emerging applications in synthesis and catalysis.

Recent Developments in the de Novo Synthesis of Heterocycles by First-Row Transition-Metal-Catalyzed Acceptorless Dehydrogenation

2019 ◽  
Vol 23 (9) ◽  
pp. 1005-1018 ◽  
Author(s):  
V. Arun ◽  
Suman De Sarkar
Keyword(s):  
Transition Metal ◽  
De Novo ◽  
Cost Effective ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
De Novo Synthesis ◽  
Recent Developments ◽  
Key Features ◽  
Imine Compounds ◽  
Metal Catalyzed

Applications of Acceptorless Dehydrogenation (AD) process for the synthesis of important heterocycles are discussed. The key features of AD process are the generation of more reactive carbonyl/imine compounds from alcohols/amines by the release of dihydrogen as a stoichiometric byproduct. In this review, we document recent advances in this field by using first row transition metal catalysts and easily accessible coupling partners, thus offering cost-effective access to different heterocyclic rings.

Rietveld Analysis and Pair Wise Substitutional Alloys

1991 ◽  
Vol 35 (A) ◽  
pp. 63-68
Author(s):  
Wayne D. Kaplan ◽  
Giora Kimmel
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Powder Diffraction ◽  
Rietveld Analysis ◽  
Comprehensive Model ◽  
Powder Diffraction Data ◽  
Unique Role ◽  
X Ray ◽  
Substitutional Alloys

AbstractRietveld Analysis on X-Ray powder diffraction data was used to build a comprehensive model of the structures in gallmm rich R-Ga systems (R is a rare earth between La and Gd). The ability to refine occupation factors as well as atomic positions allowed for the analysis of the e solid solution, its structural relation to the ordered ∊′ phase, and the unique role of the Ga-Ga pairs in these systems.

scholarly journals Editorial: Toward Sustainable Energy: The Unique Role of Rare Earth Oxides

2019 ◽  
Vol 7 ◽  
Author(s):  
Cristina Artini ◽  
Paolo Mele ◽  
Nobuhito Imanaka
Keyword(s):  
Rare Earth ◽  
Sustainable Energy ◽  
Rare Earth Oxides ◽  
Unique Role

scholarly journals Multicomponent Reactions Involving Diazo Reagents: A 5-Year Update

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6563
Author(s):  
Olga Bakulina ◽  
Anna Inyutina ◽  
Dmitry Dar’in ◽  
Mikhail Krasavin
Keyword(s):  
Multicomponent Reactions ◽  
Diazo Compounds ◽  
Catalyst Free ◽  
Recent Developments ◽  
Diazo Reagents ◽  
Metal Catalyzed

This review summarizes recent developments in multicomponent reactions of diazo compounds. The role of diazo reagent and the type of interaction between components was analyzed to structure the discussion. In contrast to previous reviews on related topics mostly focused on metal catalyzed transformations, a substantial amount of organocatalytic or catalyst-free methodologies is covered in this work.

How do histone modifications contribute to transgenerational epigenetic inheritance in C. elegans?

2020 ◽  
Vol 48 (3) ◽  
pp. 1019-1034 ◽  
Author(s):  
Rachel M. Woodhouse ◽  
Alyson Ashe
Keyword(s):  
Histone Modifications ◽  
Molecular Mechanisms ◽  
Epigenetic Inheritance ◽  
Nematode Caenorhabditis Elegans ◽  
Histone Methyltransferases ◽  
Transgenerational Epigenetic Inheritance ◽  
C Elegans ◽  
Recent Developments ◽  
Gene Regulatory

Gene regulatory information can be inherited between generations in a phenomenon termed transgenerational epigenetic inheritance (TEI). While examples of TEI in many animals accumulate, the nematode Caenorhabditis elegans has proven particularly useful in investigating the underlying molecular mechanisms of this phenomenon. In C. elegans and other animals, the modification of histone proteins has emerged as a potential carrier and effector of transgenerational epigenetic information. In this review, we explore the contribution of histone modifications to TEI in C. elegans. We describe the role of repressive histone marks, histone methyltransferases, and associated chromatin factors in heritable gene silencing, and discuss recent developments and unanswered questions in how these factors integrate with other known TEI mechanisms. We also review the transgenerational effects of the manipulation of histone modifications on germline health and longevity.

Meiotic CENP-C is a shepherd: bridging the space between the centromere and the kinetochore in time and space

2020 ◽  
Vol 64 (2) ◽  
pp. 251-261
Author(s):  
Jessica E. Fellmeth ◽  
Kim S. McKim
Keyword(s):  
Chromosome Segregation ◽  
New Technologies ◽  
Early Prophase ◽  
Unique Role ◽  
Kinetochore Assembly ◽  
M Phase ◽  
In Vivo Analysis ◽  
Meiosis I

Abstract While many of the proteins involved in the mitotic centromere and kinetochore are conserved in meiosis, they often gain a novel function due to the unique needs of homolog segregation during meiosis I (MI). CENP-C is a critical component of the centromere for kinetochore assembly in mitosis. Recent work, however, has highlighted the unique features of meiotic CENP-C. Centromere establishment and stability require CENP-C loading at the centromere for CENP-A function. Pre-meiotic loading of proteins necessary for homolog recombination as well as cohesion also rely on CENP-C, as do the main scaffolding components of the kinetochore. Much of this work relies on new technologies that enable in vivo analysis of meiosis like never before. Here, we strive to highlight the unique role of this highly conserved centromere protein that loads on to centromeres prior to M-phase onset, but continues to perform critical functions through chromosome segregation. CENP-C is not merely a structural link between the centromere and the kinetochore, but also a functional one joining the processes of early prophase homolog synapsis to late metaphase kinetochore assembly and signaling.

142-OR: Unique Role of the a4 Component for S6-Kinase Activity in Metabolic Regulation and Anti-apoptotic Effect in Brown Adipose Tissue

Diabetes ◽  
2019 ◽  
Vol 68 (Supplement 1) ◽  
pp. 142-OR
Author(s):  
MASAJI SAKAGUCHI ◽  
SHOTA OKAGAWA ◽  
SAYAKA KITANO ◽  
TATSUYA KONDO ◽  
EIICHI ARAKI
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Metabolic Regulation ◽  
Kinase Activity ◽  
S6 Kinase ◽  
Unique Role ◽  
Brown Adipose ◽  
Apoptotic Effect

Wilfred Ethier. Modern International Economics. New York: W. W. Norton and Company. 1983. xviii + 588 pp.

1988 ◽  
Vol 27 (1) ◽  
pp. 81-83
Author(s):  
Nadeem A. Burney
Keyword(s):  
International Economic ◽  
New York ◽  
Economic Theory ◽  
International Economics ◽  
International Monetary System ◽  
International Markets ◽  
The Past ◽  
Monetary System ◽  
Recent Developments

Its been long recognized that various economies of the world are interlinked through international trade. The experience of the past several years, however, has demonstrated that this economic interdependence is far greater than was previously realized. In this context, the importance of international economic theory as an area distinct from general economics hardly needs any mentioning. What gives international economic theory this distinction is international markets for some goods and effects of national sovereignty on the character of economic activity. Wilfred Ethier's book, which incorporates recent developments in the field, is an excellent addition to textbooks on international economics for one- or twosemester undergraduate courses. The book mostly covers standard topics. A distinguishing feature of this book is its detailed analysis of the flexible exchange rates and a discussion of the various approaches used for their determination. Within each chapter, the author has extensively used facts, figures and major events to clarify the concepts in the light of the theoretical framework. The book also discusses, in a fair amount of detail, the existing international monetary system and the role of various international organizations.

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