Metal Salen Complexes in Anion Binding and Catalysis PDF Download
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Author: Eric R. Libra
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Languages : en
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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: Eric R. Libra
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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: Candace A. Zieleniuk
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Languages : en
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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: Paul Andrew Duckmanton
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 406
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Author: Paul J. Dyson
Publisher: Springer Science & Business Media
ISBN: 1402039158
Category : Science
Languages : en
Pages : 255
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Metal Catalysed Reactions in Ionic Liquids is the first non-edited book on the subject of metal catalyzed reactions in ionic liquids to cover the literature from its origins until early 2005. Following a general introduction to the field of biphasic/multiphasic catalysis, the book moves on to describe the synthesis, the functionalisation, and fundamental properties of ionic liquids relevant to catalysis. It then analyses the catalysed reactions according to their type, encompassing hydrogenation, hydroformylation, oxidation, C-C coupling reactions, metathesis, dimerisation, polymerisation and more. Trends, generalisations, advantages and disadvantages of ionic liquids for specific reaction types are also examined as well as specific processes such as supported ionic liquid phase catalysis, continuous processes using CO2 extraction and nanoparticle catalysis. Metal Catalysed Reactions in Ionic Liquids is of interest to those working in catalysis/green chemistry, in particular to advanced level undergraduate and graduate students and researchers in bi- or multiphasic catalysis using ionic liquids.
Author: Mark Stradiotto
Publisher: John Wiley & Sons
ISBN: 1118839773
Category : Science
Languages : en
Pages : 448
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The design of ancillary ligands used to modify the structural and reactivity properties of metal complexes has evolved into a rapidly expanding sub-discipline in inorganic and organometallic chemistry. Ancillary ligand design has figured directly in the discovery of new bonding motifs and stoichiometric reactivity, as well as in the development of new catalytic protocols that have had widespread positive impact on chemical synthesis on benchtop and industrial scales. Ligand Design in Metal Chemistry presents a collection of cutting-edge contributions from leaders in the field of ligand design, encompassing a broad spectrum of ancillary ligand classes and reactivity applications. Topics covered include: Key concepts in ligand design Redox non-innocent ligands Ligands for selective alkene metathesis Ligands in cross-coupling Ligand design in polymerization Ligand design in modern lanthanide chemistry Cooperative metal-ligand reactivity P,N Ligands for enantioselective hydrogenation Spiro-cyclic ligands in asymmetric catalysis This book will be a valuable reference for academic researchers and industry practitioners working in the field of ligand design, as well as those who work in the many areas in which the impact of ancillary ligand design has proven significant, for example synthetic organic chemistry, catalysis, medicinal chemistry, polymer science and materials chemistry.
Author: Khrystyna Herasymchuk
Publisher:
ISBN:
Category :
Languages : en
Pages : 207
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Transition metal complexes incorporating redox-active ligands have the potential to facilitate controlled multielectron chemistry, enabling their use in catalysis and energy storage applications. Moreover, the use of transition metal complexes containing redox-active ligands has been extended to two- (2D) and three-dimensional (3D) materials, such as supramolecular assemblies (i.e., metallacycles, molecular cages, or macrocycles) and metal-organic frameworks (MOFs) for catalytic, magnetic, electronic, and sensing applications. Salens (N2O2 bis(Schiff-base)-bis(phenolate) are an important class of redox-active ligands, and have been investigated in detail as they are able to stabilize both low and high metal oxidation states for the above-mentioned applications. The work in this thesis focuses on the synthesis and electronic structure elucidation of metal salen complexes in monomeric form, as discrete supramolecular assemblies and 3D MOFs. Structural and spectroscopic characterization of the neutral and oxidized species was completed using mass spectrometry, cyclic voltammetry, X-ray diffraction, NMR, UV-Vis-NIR, and EPR spectroscopies, as well as theoretical (DFT) calculations. Chapter 2 discusses the synthesis and electronic structure evaluation of a series of oxidized uranyl complexes, containing redox-active salen ligands with varying para-ring substituents (tBu, OMe, NMe2). Chapters 3 and 4 discuss the incorporation of a redox-active nickel salen complex equipped with pyridyl groups on the peripheral positions of the ligand framework into supramolecular structures via coordination-driven self-assembly. The self-assembly results in formation of a number of distinct metallacycles, affording di-, tetra-, and octa-ligand radical species. Finally, the design, synthesis, and incorporation of metal salen units into MOFs is discussed in Chapter 5. Preliminary assembly and oxidation experiments are presented as an opportunity to explore the redox-properties of salen complexes incorporated into a solid-state 3D framework. Overall, the work described in this thesis provides a pathway for salen ligand radical systems to be used in redox-controlled host-guest chemistry, catalysis, and sensing.
Author: Christian Bruneau
Publisher: John Wiley & Sons
ISBN: 9783527318926
Category : Science
Languages : en
Pages : 360
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Focusing on preparation and applications in synthesis and catalysis, this book finally closes a gap in the literature by summarizing this hot topic for the first time. As such, it gathers in one volume the key features of metal vinylidene and allenylidene complexes as well as reactive species and covers applications in metathesis, polymerization, molecular materials, carbon rich compounds and fine chemical production. The emphasis here is on the selective transformations of alkynes and enynes plus simple and complex molecules containing a triple C-C bond. The result is a must-have ready reference for organic, catalytic, complex, theoretical and polymer chemists, as well as those working with/on organometallics.
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: Jamie Hunt
Publisher:
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Category :
Languages : en
Pages : 0
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Author: Nathan Patmore
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Category :
Languages : en
Pages : 0
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