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Author: Candace A. Zieleniuk
Publisher:
ISBN:
Category :
Languages : en
Pages :
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ABSTRACT: Of all the substrates and cofactors involved in biological processes, it is estimated that 70-75% of the species are negatively charged. Since anionic species are essential for life, their presence or imperfect regulation can be either beneficial or harmful to living organisms. Despite the importance of anions in nature, the recognition of anions by synthetic hosts has been largely unexplored. A series of tripodal triphenoxymethane salens were synthesized and then used to chelate lanthanides and transition metals with 3oxidation states. The metal chelation facilitates the formation of well-defined binding pockets containing six O-H moieties of varying sizes depending upon the chelated metal ion. The same approach was also used to produce large macrocyclic urea-based salen ligands and the corresponding metal complexes as well as mixed O-H/N-H metal salens. Both the O-H and N-H based complexes were treated with the tetrabutylammonium salts of a wide range of anion and then studied for their anion binding capabilities. Chiral metal salen molecules have also been used extensively to perform asymmetric catalysis. A series of chiral BINAM triphenoxymethane based salen ligands were produced and used to synthesize extremely bulky chiral dinuclear catalysts. These catalysts were found to facilitate the asymmetric addition of ZnEt2 to benzaldehyde giving a secondary alcohol. In addition, the chiral BINAM catalysts can also produce quantitative amounts of cyclic carbonates through a cycloaddition reaction of CO2 to epoxides. The synthesis of the metal salen complexes and the results of the anion binding and catalytic studies are presented herein.
Author: Candace A. Zieleniuk
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
ABSTRACT: Of all the substrates and cofactors involved in biological processes, it is estimated that 70-75% of the species are negatively charged. Since anionic species are essential for life, their presence or imperfect regulation can be either beneficial or harmful to living organisms. Despite the importance of anions in nature, the recognition of anions by synthetic hosts has been largely unexplored. A series of tripodal triphenoxymethane salens were synthesized and then used to chelate lanthanides and transition metals with 3oxidation states. The metal chelation facilitates the formation of well-defined binding pockets containing six O-H moieties of varying sizes depending upon the chelated metal ion. The same approach was also used to produce large macrocyclic urea-based salen ligands and the corresponding metal complexes as well as mixed O-H/N-H metal salens. Both the O-H and N-H based complexes were treated with the tetrabutylammonium salts of a wide range of anion and then studied for their anion binding capabilities. Chiral metal salen molecules have also been used extensively to perform asymmetric catalysis. A series of chiral BINAM triphenoxymethane based salen ligands were produced and used to synthesize extremely bulky chiral dinuclear catalysts. These catalysts were found to facilitate the asymmetric addition of ZnEt2 to benzaldehyde giving a secondary alcohol. In addition, the chiral BINAM catalysts can also produce quantitative amounts of cyclic carbonates through a cycloaddition reaction of CO2 to epoxides. The synthesis of the metal salen complexes and the results of the anion binding and catalytic studies are presented herein.
Author: Eric R. Libra
Publisher:
ISBN:
Category :
Languages : en
Pages :
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ABSTRACT: Most forms of life require the recognition and transportation of anions. There have been numerous efforts to develop synthetic receptor systems that are both efficient and selective for the coordination of anions. Nature often employs the use of OH groups for anion coordination, yet this binding mode is one that has not been explored in the area of synthetic anion receptor design. A series of substituted metal salen compounds have been developed that show a high affinity for the coordination of anions. The rigid metal salen macrocycle can orientate four phenol groups into a tetrahedral array that tightly and selectively binds fluoride through four strong OH-F hydrogen bonding interactions. The size of the anion binding cavity can be regulated by the incorporation of different metal centers, enabling the properties of the system to be modified. Metals also offer convenient pathways to report the binding event via spectral changes from the strong metal to ligand charge transfer transitions, making these receptors anion sensors. Not only can the metal salen system organize groups for anion binding, they can also be used as chiral catalysts. The synthesis of a rigid and sterically bulky metal salen complex has been undertaken for the use as an asymmetric catalyst to promote organic transformations.
Author: Paul Andrew Duckmanton
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 406
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Author: A. Pullman
Publisher: Springer Science & Business Media
ISBN: 9401763925
Category : Science
Languages : en
Pages : 397
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Book Description
The 9th Jerusalem Symposium was dedicated to the memory of Professor Ernst David Bergmann. An imposing and deeply moving memorial session, chaired by Professor Ephraim Katzir, the President of the State of IsƯ rael and a close friend of Professor Bergmann preceded the Symposium itself. During this session, Professor Bergmann's personality, scienƯ tific achievements and contributions to the development of his country were described and praised, besides President Katzir, by Professor A. Dvoretzky, President of the Israel Academy of Sciences and Humanities, Professor D. Ginsburg, Dean of the Israel Institute of Technology in Haifa and the author of these lines. May I just quote short extracts from these speeches. President Katzir: "As we open this ninth in the series of symposia initiated in 1967, it is difficult for me as, I am sure, for many of Ernst Bergmann's friends, co-workers and students, to be here without him. He was not only a great scientist and a beloved teacher, he was one of the most important founders of science in this country. To him we owe many institutes and the establishment here of many branches of science." Professor Dvoretzky: "Ernst Bergmann's greatness did not stem from one component overshadowing all the others. It was a multifaceted greatƯ ness consisting of the harmonious co~lescing of seemingly contrasting entities into a wonderful unity "
Author: Smita S. Patil
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The helix is an important chiral motif in nature, there is increasing development in field of helical transition metal complexes and related supramolecular structures. Hence, the goals of this work are to apply the principles of helicity in order to produce metal complexes with predictable molecular shapes and to study their properties as asymmetric catalysts. Computational studies suggest that the (1R,2R)-cyclobutyldiamine unit can produce highly twisted salen complexes with a large energy barrier between the M and P helical forms. To test this prediction, the tartrate salt of (1R,2R)-cyclobutyldiamine was synthesized and condensed with a series of saliclaldehydes to produce novel salen ligands. The salicylaldehydes chosen have extended phenanthryl or benz[a]anthryl sidearms to encourage formation of helical coordination complexes. These ligands were metallated with zinc, iron and manganese salts to produce salen metal complexes which were characterized by NMR analysis, high-resolution mass spectrometry, and IR spectroscopy. A second ligand type, neutral bis(pyridine-imine) has also been synthesized from (1R,2R)-cyclobutyldiamine and quinolylaldehydes. The synthesis of bis(pyridine-imine) ligands was conducted using greener method, solvent assisted grinding. These ligands, in-situ with nickel metal salts, showed good catalytic activity for asymmetric Diels-Alder reactions. The third ligand type studied was chiral acid-functionalized Schiff-base ligands. These were synthesized by the condensation of 3-formyl-5-methyl salicylic acid and (1R,2R)-cyclobutyldiamine. With this type of ligand, there is possibility of producing both mono and dinuclear metal complexes. In our studies, we were only able to synthesize mononuclear complexs. These were tested as catalysts for asymmetric direct Mannich-type reaction, but were found to be ineffective.
Author: N. Russo
Publisher: Springer Science & Business Media
ISBN: 9400901550
Category : Science
Languages : en
Pages : 557
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Book Description
Metal-Ligand Interactions - Structure and Reactivity emphasizes the experimental determination of structure and dynamics, supported by the theoretical and computational approaches needed to establish the concepts and guide the experiments. Leading experts present masterly surveys of: clusters, inorganic complexes, surfaces, catalysis, ab initio theory, density functional theory,semiempirical methods, and dynamics. Besides the presentations of the fields of study themselves, the papers also bring out those aspects that impinge on, or could benefit from, progress in other disciplines. Refined in the fire of an interactive and stimulating conference, the papers presented here represent the state of the art of current research.
Author: Lutz H. Gade
Publisher: Springer Science & Business Media
ISBN: 3540344748
Category : Science
Languages : en
Pages : 197
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Book Description
This book provides a comprehensive summary and critical overview of a topic in organometallic chemistry. Research in this rapidly developing transdisciplinary field is having profound influence on other areas of scientific investigation, ranging from catalytic organic synthesis to biology, medicine and material science. The book is complemented by a review of metallodendritic exoreptors for the redox recognition of oxo-anions and halides.
Author: Jian Zhou
Publisher: John Wiley & Sons
ISBN: 1118071867
Category : Science
Languages : en
Pages : 712
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Book Description
This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis. • Helps organic chemists perform more efficient catalysis with step-by-step methods • Overviews new concepts and progress for greener and economic catalytic reactions • Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions • Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 512
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A group of ligands were designed based on a minimalist reduction of the structure of metalloproteins. It was thought that a modular design with facile synthesis could lead to a new family of privileged ligands. Towards this goal a series of tri-, tetra, and penta-dentate ligands were synthesized. The ligands had a common chiral core based on inexpensive amino acid starting materials. A modular diamine backbone was adjusted to control the size, bite angle and electronic nature of the binding pocket. The ligands were capped with Schiff base imines to provide an initial binding point for the metal and to create steric bulk at one face of the complex. The tetra-dentate ligands were shown to efficiently bind zinc(II), copper((II), nickel(II), and palladium(II). In the case of the penta-dentate ligands the series was extended to cobalt(II), manganese(II) and iron(II). The tri-dentate ligands did not form isolated metal complexes. The structures of these complexes were confirmed by NMR, ESR and X-ray crystallography. The chiral copper complexes were applied to a model asymmetric acylation reaction. The results were disappointing as the reactions showed no stereoselectivity.
Author: Takashiro Akitsu
Publisher: Elsevier
ISBN: 0128232722
Category : Science
Languages : en
Pages : 280
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Book Description
Computational and Data-Driven Chemistry Using Artificial Intelligence: Volume 1: Fundamentals, Methods and Applications highlights fundamental knowledge and current developments in the field, giving readers insight into how these tools can be harnessed to enhance their own work. Offering the ability to process large or complex data-sets, compare molecular characteristics and behaviors, and help researchers design or identify new structures, Artificial Intelligence (AI) holds huge potential to revolutionize the future of chemistry. Volume 1 explores the fundamental knowledge and current methods being used to apply AI across a whole host of chemistry applications. Drawing on the knowledge of its expert team of global contributors, the book offers fascinating insight into this rapidly developing field and serves as a great resource for all those interested in exploring the opportunities afforded by the intersection of chemistry and AI in their own work. Part 1 provides foundational information on AI in chemistry, with an introduction to the field and guidance on database usage and statistical analysis to help support newcomers to the field. Part 2 then goes on to discuss approaches currently used to address problems in broad areas such as computational and theoretical chemistry; materials, synthetic and medicinal chemistry; crystallography, analytical chemistry, and spectroscopy. Finally, potential future trends in the field are discussed. Provides an accessible introduction to the current state and future possibilities for AI in chemistry Explores how computational chemistry methods and approaches can both enhance and be enhanced by AI Highlights the interdisciplinary and broad applicability of AI tools across a wide range of chemistry fields
