Porphyrin and Redox Active Ligands-based Metal Complexes - Studies on Electrocatalytic Activity and Electronic Structure of Redox-active Compounds PDF Download
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Author: Shubhadeep Chandra
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Shubhadeep Chandra
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Linus Kai Ho Chiang
Publisher:
ISBN:
Category :
Languages : en
Pages : 187
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In this thesis a number of projects involving the design and characterization of complexes bearing redox active ligands are described. Focusing on the phenolate containing ligands, the properties and electronic structure of their corresponding metal complexes were studied by a series of experimental (i.e. electrochemistry, UV-Vis-NIR, EPR, rR etc.) and theoretical (DFT) methods. Specifically, the redox processes of these metal complexes were tuned by varying the para-ring substituents. In one study, nickel-salen (salen is a common abbreviation for N2O2 bis-Schiff-base bis-phenolate ligands) complexes were investigated, where the oxidation potentials of the ligand were predictably decreased as the electron donating ability of the para-ring substituents was increased (NMe2 > OMe > tBu > CF3). Interestingly, the oxidation of these geometrically-symmetric complexes afforded an asymmetric electronic structure in a number of cases, in which the ligand radical was localized on one phenolate rather than delocalized across the ligand framework. This difference in electronic structure was found to be dependent on the electron donating ability of the substituents; a delocalized ligand radical was observed for electron-withdrawing substituents and a localized ligand radical for strongly donating substituents. These studies highlight that para-ring substituents can be used to tune the electronic structure (metal vs. ligand based, localized vs. delocalized radical character) of metallosalen complexes. To evaluate if this electronic tuning can be applied to the metal center, a series of cobalt complexes of these salen ligands were prepared. Indeed, the electronic properties of the metal center were also significantly affected by para-ring substitution. These cobalt-salen complexes were tested as catalysts in organometallic radical-mediated polymerizations, where the most electron rich complexes displayed the best conversion rates. With a firm understanding of the role that the para-ring substituent can play in influencing the electronic structure and reactivity of metallosalen complexes in catalysis, two novel iron complexes, which contain a number of redox active phenolate fragments, were prepared. In addition, these iron-complexes feature a chiral bipyrrolidine backbone. Ligands with this chiral diamine backbone bind metals ions diastereoselectively owing to its increased rigidity, which is critical to stereoselectivity in catalysis. A symmetric (with two phenolates) ligand was prepared by reported methods, and a novel route to synthesize an asymmetric ligand (one phenolate and one pyridine) from symmetric starting materials was established. The neutral iron-complexes were found to be high spin (S = 5/2), and can undergo ligand based oxidation to form an antiferromagnetically-coupled (Stotal = 2) species. The results presented will serve as the basis for catalyst development using complexes of similar ligands.
Author: Mark Stradiotto
Publisher: John Wiley & Sons
ISBN: 1118839811
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: Seth N. Brown
Publisher: Wiley
ISBN: 9781118646854
Category : Science
Languages : en
Pages : 368
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Book Description
This book presents a comprehensive introduction to the unique and fundamental features of redox-active ligands, the preparation and characterization of their coordination complexes, and finally the importance of this class of molecules to biology, catalysis and materials. The book aims to provide a broadly accessible introduction to the particular features and opportunities unique to redox-active ligands. It begins with an introduction to the intellectual challenges posed by redox-active ligands and descriptions of the types of ligands and complexes in which ligand-centered redox activity are commonly observed. Following this, the book is divided into two sections as follows: The first section focuses on electronic structure and bonding, which has historically dominated this field and continues to be actively researched. The spectroscopic and other physical measurements that have been used to elucidate the electronic structure of these compounds are described. The interplay between synthesis, bonding models, and physical measurements has often been critical in shaping our understanding of these compounds. This interplay is illustrated by a number of case studies. The second section focuses on the use of redox-active complexes in stoichiometric and catalytic reactions. The scope of known reactions is presented, including examples from bioinorganic chemistry (both enzymes and model compounds). Where possible, the significance of the redox-active ligand is discussed, with an eye both to summarizing existing knowledge and pointing out possibilities for future research. This book explains the underpinnings of physical and theoretical techniques of redox-active ligands, providing up to date information on definitions, scope and applications for research scientists and graduate students working in organic and inorganic chemistry, organometallics and coordination chemistry.
Author:
Publisher:
ISBN:
Category : Medicine
Languages : en
Pages : 852
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Author: Edwin Wing Yip Wong
Publisher:
ISBN:
Category : Ligands
Languages : en
Pages : 0
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The structural and electronic properties of metal complexes with isoindoline-based redox-active ligands and the ability of these ligands to stabilize unusual oxidation states was investigated. Two types of redox-active ligands were examined: phthalocyanines (Pc) and bis(2-pyridylimino)isoindolines also known as lobsterates (Lb). In contrast to the ancillary or spectator ligands more commonly used in coordination chemistry, redox-active ligands can exist in a range of oxidation states. Additionally, the chemical inertness of the Pc ligand could be used to develop new catalysts where the Pc ligand can stabilize a highly reactive metal centre and also act as an electron reservoir in a catalytic cycle. With this in mind, the reduction of trichloro(phthalocyanato)niobium(V) was performed with various reducing agents in order to study the bond activating ability of the reduced species and to determine the crystal structure of the reduced products. C-O bond activation of ether-type solvents suggests that the Pc ligand is able to withstand bond activation from a highly reduced niobium centre while, at the same time, allowing the niobium centre to activate the C-O bonds of the solvent. NbPc complexes containing Pc(4- ) ligands were structurally characterized. A reduced MgPc complex containing a Pc(3- ) ligand was also structurally characterized. A report of gold(II) Pc and the ability of Pc to stabilize gold in an unusual, paramagnetic +2 oxidation state was re-investigated. Attempts to synthesize soluble versions of AuPc as well as the original AuPc did not produce the desired gold(II) products and only diamagnetic gold(III) Pcs were obtained. An unprecedented, ring- contracted gold(III) Pc analogue was discovered and structurally characterized in the process of these studies. A series of three new 5,6-substituted Lb ligands were synthesized and the redox properties of these ligands in copper(II) acetate complexes were evaluated using cyclic voltammetry. The reductions of the copper acetate Lb complexes were not chemically reversible. The 2,6-diisopropylphenoxy-substituted Lb copper acetate complexes formed acetate-bridged 1-D chains. Superconducting quantum interference device magnetometry suggests that the Cu centres are very weakly antiferromagnetically coupled.
Author: Yiming Leng
Publisher: OAE Publishing Inc.
ISBN:
Category : Science
Languages : en
Pages : 12
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Covalent organic polymers (COPs), as emerging porous materials with well-defined architectures and high hydrothermal stability, have attracted extensive attention in the field of electrocatalysis. Herein, we report a rational design method for preparing oxygen reduction reaction electrocatalysts with the assistance of a predesigned macrocyclic COP model molecular. With the predesigned nitrogen position and structural features in macrocyclic chain-like COP-based materials, the obtained COPMCT-Co-900 catalyst provided excellent oxygen reduction performance, where the half-wave potential (E1/2) reaches 0.85 V (vs. RHE), comparable to commercial Pt/C. We also extended the strategy to similar macrocycle COPs and Fe-based and Ni-based metal sources and studied the oxygen reduction reaction performance of corresponding catalysts, proving the universality of the method. Interestingly, we assemble COPMCT-Co-900 catalyst as air electrode catalyst of the self-made rechargeable zinc-air flow batteries, which exhibit outstanding power density (155.6 mW·cm-2) and long cycle life (90 h, 270 cycles at 10 mA·cm-2). Our studies provide a new method for the development of high-performance oxygen electrodes applied in zinc-air flow battery devices.
Author:
Publisher:
ISBN:
Category : Measurement
Languages : en
Pages : 690
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![Synthesis, Structural and Electronic Properties, and Reactivity of Group 5 Metal Complexes Incorporating the Redox-active [ONO] Ligand Platform PDF](https://books.google.com/books/content/images/frontcover/-nL-oAEACAAJ?fife=w80-h100)
Author: Steven Paul Hananouchi
Publisher:
ISBN: 9781303814730
Category :
Languages : en
Pages : 67
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This thesis describes the synthesis, electronic and structural properties, and reactivity of Group 5 metal complexes incorporating the [ONO] ligand platform. A study of the electronic and structural properties of the Group 5 metal complexes incorporating the [ONO] ligand is performed. Once the electronic properties of the complexes are known, the reactivity of the complexes is compared. Chapter 1 describes a brief history of redox-active ligands. The previously published results of redox-active ligands acting as an electron source are discussed. In Chapter 2, the synthesis and electronic and structural properties of metal dichlorides and trichlorides of Group 5 metal complexes incorporating the [ONO] ligand and comparing the metal-ligand cooperativity are performed. In Chapter 3, the synthesis and reactivity of [ONO]NbMe2 and the reactivity of reduced species of [ONO]V(L)n are discussed.
Author: Khrystyna Herasymchuk
Publisher:
ISBN:
Category :
Languages : en
Pages : 207
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Book Description
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.
