M.Sc. (Chemistry) / In this dissertation the synthesis, characterization and the application of Ag, Au and Cu dendrimer encapsulated nanoparticles (DENs) in catalysis are described. Ag, Au and Cu-DENs were synthesized using G4-G6 PAMAM-OH and G4-G6 PAMAM-NH2 dendrimers as templates as well as stabilizers. NaBH4 was used as a reducing agent for the synthesis of DENs. Binding studies were carried out in order to determine the maximum capacity of the dendrimer to which the metal ions can be added. These binding studies were performed using UV-vis spectroscopy. The synthesis of these nanoparticles (NPs) was carried out at room temperature. For the synthesis of Ag and Au-DENs with PAMAM-NH2 dendrimers, the pH of the aqueous dendrimer solution was first adjusted to acidic condition (~pH 2) using HCl before the addition of the respective metal ion precursor to the dendrimer. This is done to avoid coordination of the metal ions to the primary amine groups on the periphery of the dendrimer, which might lead to particle agglomeration. These prepared DENs were characterized by UV-vis spectroscopy and high resolution transmission (HRTEM) microscopy. The synthesized DENs were evaluated as catalysts in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. This reaction was monitored by UV-vis spectroscopy by following the absorbance at 400 nm These DENs were all found to be active catalysts for the afore-mentioned process. The rate constant for the reduction process was observed to decrease as the concentration of 4-nitrophenol increased. As the concentration of NaBH4 is increased, the rate constant was also found to increase, however this increase was only observed to a maximum concentration of NaBH4. The Au-DENs prepared using G4 PAMAM-NH2 dendrimers were subsequently immobilized onto a titania support via the sol-gel (Ti-Au-s) and wetness impregnation (Ti-Au-w) methods. The titania supported Au NPs were characterized using HRTEM, powder X-ray diffraction (PXRD), thermal gravimetric analysis (TGA), inductive coupled plasma-optical emission spectroscopy (ICP-OES) and Brunauer Emmett Teller (BET) surface area analysis. The dendrimer template was removed by calcining at 500 oC. The catalytic activity of these supported Au NPs was investigated in the oxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant. Benzaldehyde and styrene oxide were observed as the major products. The catalyst prepared by wetness impregnation method was found to give the highest styrene conversion as compared to the one prepared via sol-gel method. At 60 oC, the catalyst prepared by sol-gel method was found to selectively produce benzaldehyde while on the other hand, the catalyst prepared by wetness impregnation selectively produce styrene oxide. The highest conversion of styrene was observed at 70 oC for both catalysts. Ti-Au-w catalyst was generally found to give the highest styrene conversion.

The mono protection of 1,4,7-triazacyclononane ([9]-aneN₃) was accomplished efficiently through the formation of an orthoamide derivative. The orthoamide was used to form three mono protected derivatives of [9]-aneN₃ which contained either a formyl, methyl, or benzyl protecting group attached to one of the nitrogen donors. The macrobicyclic complexes bicycloN₅, Me-bicycloN₅, and Bz-bicycloN₅ were synthesized through the Michael addition of two functional arms to the mono protected derivatives of [9]-aneN₃ followed by a ring closure template reaction around copper with glyoxal. Incomplete reduction by BH₃ THF led to the isolation of an enamine intermediate. The solution behavior o f the Ni(II) and Ni(III) complexes of these macrobicyclic ligands is presented. The methyl and benzyl derivatives were found to have similar abilities as the parent bicycloN₅ ligand to stabilize the Ni(III) metal ion. Removal of the benzyl protecting group was achieved by reaction with formic acid in the presence of a Pd/C catalyst. Attempts to couple two mono protected nonane molecules through the addition of functional acid chloride arms under conditions of high dilution were unsuccessful. Reaction of the benzyl protected bicyclic ligand Bz-bicycloN₅ with a bridging ligand in a high dilution reaction did provide evidence for the formation of a small amount of the novel macrotricyclic ligand tricyclo[9.14.9]N₆. The Ni(II) complexes of the macrobicyclic ligands, and a series of other macrocyclic and related Ni(II) complexes having varying NiIII/II redox potentials, were used to study the quenching of the excited state of the platinum(II) dimeric complex Pt₂(pop)₄⁴− . The quenching rate constants kq were determined, and quenching of the excited state *Pt₂(pop)₄⁴− by the nickel complexes was found to proceed by reductive electron transfer. These results are discussed in terms of Marcus Theory. A plot of logkq versus the ΔG for electron transfer was found to exhibit classic Rehm- Weller behavior. The excited state potential Pt₂(pop)₄⁴⁻*/⁵- was estimated from this series of quenching reactions and a range of 1.24 to 1.34 V (vs. NHE) was identified. The photochemical and photophysical properties of the macrocyclic complex Cr([18]-aneN₆)³+ ([18]-aneN₆ = 1,4,7,10,13,16-hexaazacyclooctadecane) were investigated and compared to the properties of the photoreactive Cr(III) complex Cr(sen)³+ (sen = 4,4',4"-ethylidynetris(3-azabutan-l-amine)). The complex Cr([18]- aneN₆)³+ was found to be unreactive (Ørxn < 10⁻³) while the photoreactivity of Cr(sen)³+ was confirmed (Ørxn = 0.10). Both of these complexes have very short ambient ²E emission lifetimes and this is discussed in terms of distortions imposed on the complexes by the coordination of the ligands. Direct irradiation into the doublet excited state of Cr(sen)3⁺ at 675 nm resulted in a decrease in the quantum yield for the photoreaction of this complex from Ørxn=0.10 for quartet irradiation to Ørxn=0.08 for doublet irradiation. A model is suggested in which there are two competitive processes deactivating the doublet excited state; reverse intersystem crossing to the lowest quartet excited state and nonradiative decay back to the ground state. The temperature dependence of the ²E emission lifetime was fitted to a two-term Arrhenius function to give estimates for the pre-exponential factors and activation energies of these two deactivation processes. Values of A₁ = (1.2 ± 0.9) x 1O¹⁵ s⁻¹ and Eₐ₁ = 45 ± 1 kJ mol⁻¹,and A₂ = (5.4 ± 1.2) x 10¹¹s⁻¹ and Eₐ2 = 29 ± 1 kJ mol⁻¹ were obtained. The photostereochemistry of Cr(sen)³⁺ was investigated using a modified reversed phase HPLC technique. A total of four photoproducts were identified from the photolysis of the resolved stereoisomers of Cr(sen)³⁺ and a loss of optical activity was found to be associated with the photoreaction. These results are discussed in terms of current models for predicting photostereoreactivity of Cr(III) complexes. / Graduate

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. / The addition of cyclohexyl substituents to existing ligands was investigated for its potential use as a factor in ligand design for achieving high specificity for particular metal ions, (Abbreviation abstract) / AC 2018

Degree: Master of Science Department: Engineering / The electrochemical recovery of low concentrations ( < 200 1 l mg − ) of palladium and platinum from a selected refinery effluent was investigated. Cyclic Voltammetry (CV) provided qualitative evidence that palladium and platinum contained in an effluent with an acid chloride matrix could be deposited on a graphite cathode. Experimental techniques related to (i) the use of synthetic solutions (ii) the variation of potential scan ranges, (iii) the use of a witness ion ( + 3 Fe ), and (iv) the use of glassy carbon or platinum disc working electrodes were used to assist with the interpretation of voltammograms. Exhaustive electrolysis experiments via a graphite working electrode demonstrated the recovery of palladium and platinum in the refinery effluent to concentrations of < 1 1 l mg − . Copper present in the effluent was co-deposited with the precious metals. Exchange current densities ( o j ), electron transfer coefficients ( á), standard rate constants ( s k ) and mass transfer coefficients ( m k ) were determined for selected reduction-oxidation (redox) couples via a custom made Rotating Disc Electrode (RDE).

Degree: Master of Science Department: Science / Metal-ligand models and complex stability constants of newly synthesised chelating ligands, N,N’-bis(2-hydroxycyclopentyl)-ethylenediamine (Cyp2EN) and N,N’-bis(2-hydroxycyclohexyl)-ethylenediamine (Cy2EN), with metal ions Cd2+, Cu2+, Ni2+, Pb2+ and Zn2+ were established in this work. Stability constants were determined by Glass Electrode Potentiometry (GEP) and polarography as electrochemical techniques. A new concept, termed Virtual Potentiometry (VP), was also used for the evaluation of stability constants. In this concept, polarographic or polarographic + potentiometric data were evaluated using potentiometric computer software (ESTA). This concept assisted in obtaining a final model for Cd–Cyp2EN and Pb–Cyp2EN systems. It could refine M(HL) complex inaccessible via polarographic study of Pb–Cyp2EN system and refined the hydroxo–complex ML2(OH) that in turn was inaccessible using GEP for Cd– Cyp2EN system. For all metals studied, the complexes ML formed with the ligand Cy2EN were found more stable than the complexes ML formed with the ligand Cyp2EN. The complex M(HL) was obtained for all systems studied, but it seemed to be a minor species. The complex ML2 was obtained in different systems studied with the ligand Cy2EN while this complex was only found in Cd–Cyp2EN system. In several systems potentiometric (ESTA) and voltammetric (3D–CFC) software could not distinguish which hydroxo–complexes were present as these species were formed in the pH range where the ligand was fully deprotonated. Selectivity trends for Cyp2EN and Cy2EN were compared and related to DHEEN as a function of metal ion radius. It was observed that the large metal ions were favoured by the addition of cyclopentyl bridges in DHEEN while the small metal ions were favoured when cyclohexyl bridges were added.

No description available.

Liu, Dongmei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 263-284). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

by Tung Suet Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references. / Abstracts in English and Chinese. / Table of Contents --- p.i / Acknowledgments --- p.iv / Abstract --- p.v / Abstract (Chinese version) --- p.vii / Abbreviations --- p.ix / List of Compounds --- p.xi / Chapter Chapter1. --- synthesis and structures of iron(ii) and cobalt(ii) complexes derived from pyridine-functionalized amido ligands / Chapter 1.1 --- INTRODUCTION --- p.1 / Chapter 1.1.1 --- General Background --- p.1 / Chapter 1.1.2 --- A Brief Review on Amides of the Late Transition Metals --- p.3 / Chapter 1.2 --- OBJECTIVES OF THIS WORK --- p.5 / Chapter 1.3 --- RESULTS AND DISCUSSION --- p.7 / Chapter 1.3.1 --- Alkali Metal Derivatives of N-Silylated 2-Aminopyridines --- p.7 / Chapter 1.3.1.a. --- "Synthesis of Aminopyridines [HN(SiMe3)》(2-C5H3N-6-R)] (R=H (1a), Me (1b)) and Their Lithium Derivatives" --- p.7 / Chapter 1.3.1.b. --- Synthesis of the Potassium Derivative [{K(L1)(tmeda)}2 ] (4) --- p.8 / Chapter 1.3.1.c. --- "Physical Characterization of Compounds 2a, 3 and" --- p.4 9 / Chapter 1.3.1.d. --- Molecular Structures of Compounds 3 and4 --- p.10 / Chapter 1.3.2 --- "Synthesis, Structures and Reactivities of Iron(II) and Cobalt(II) Amides" --- p.16 / Chapter 1.3.2.a. --- Synthesis of Mononuclear Iron(II) and Cobalt(II) Diamides --- p.16 / Chapter 1.3.2.b. --- Physical Characterization of Compounds 5-8 --- p.16 / Chapter 1.3.2.C. --- Molecular Structures of Compounds 5-8 --- p.17 / Chapter 1.4 --- EXPERIMENTAL FOR CHAPTER1 --- p.28 / Chapter 1.5 --- REFERENCES FOR CHAPTER1 --- p.31 / Chapter Chapter2. --- reaction of iron(II) and cobalt(II) amides with phenolic compounds / Chapter 2.1 --- "SYTHESIS, STRUCTURES AND REACTIVITIES OF IRON(II) AND COBALT(II) BIS(ARYLOXIDE)" --- p.36 / Chapter 2.1.a. --- "Reaction of Compounds 7 and 8 with 2,2 -ethylidenebis(4,6-di-tert-butyl phenol)" --- p.36 / Chapter 2.1.b. --- "Molecular Structures, Magnetic Moments, and Reactivities of Compounds 9and10" --- p.36 / Chapter 2.2 --- A GENERAL REVIEW ON CATECHOL DIOXYGENASES --- p.44 / Chapter 2.3 --- "SYTHESIS, STRUCTURES AND REACTIVITIES OF IRON(II) AND COBALT(II) CATECHOLATES" --- p.46 / Chapter 2.3.a. --- Synthesis of Binuclear Iron(II) and Cobalt(II) Catecholates --- p.46 / Chapter 2.3.b. --- Molecular Structures of Compounds 11 and12 --- p.48 / Chapter 2.3.c. --- Reactions of Compounds 11 and 12 with Dioxygen --- p.54 / Chapter 2.3.d. --- Identification of Oxidative Cleavage Products --- p.54 / Chapter 2.4 --- EXPERIMENTAL FOR CHAPTER2 --- p.56 / Chapter 2.5 --- REFERENCES FOR CHAPTER2 --- p.59 / Chapter Chapter3. --- synthesis of late transition metal amidinates / Chapter 3.1 --- INTRODUCTION --- p.62 / Chapter 3.1.1 --- General background --- p.62 / Chapter 3.1.1.a --- Metal´ؤAmidine Bonding Modes --- p.63 / Chapter 3.1.1.b. --- Preparation of Metal Amidinates Complexes --- p.64 / Chapter 3.1.2 --- "N-Silylated Benzamidinates of Li, Na and K 一 The Starting Materials" --- p.65 / Chapter 3.1.3 --- A General Review on The Chemistry of Low-Valent Late Transition- Metal Amidinates --- p.67 / Chapter 3.2 --- OBJECTIVES OF THIS WORK --- p.72 / Chapter 3.3 --- RESULTS AND DISCUSSION --- p.73 / Chapter 3.3.1 --- Synthesis and Structures of Lithium Benzamidinates --- p.73 / Chapter 3.3.1.a. --- "Synthesis of [Li(L3)(tmeda)] (L3 = [PhC(NSiMe3){N(2,6´ؤ Me2C6H3}]) and [Li(L4)(tmeda)] (L4 = [PyC(NSiMe3){N(2,6- Me2C6H3)}]) as Ligand´ؤTransfer Reagents" --- p.73 / Chapter 3.3.1.b. --- Physical Characterization of Compounds 15 and16 --- p.74 / Chapter 3.3.1.c. --- Molecular Structures of Compounds 15 and16 --- p.75 / Chapter 3.3.2 --- "Synthesis, Structures and Reactivities of Iron(II) and Cobalt(II) Amidinates" --- p.81 / Chapter 3.3.2.a. --- Synthesis of Mononuclear Iron(II) Benzamidinates --- p.81 / Chapter 3.3.2.b. --- Synthesis of a Binuclear Cobalt(II) Benzamidinate --- p.82 / Chapter 3.3.2.c. --- Physical Characterization of Compounds 17-19 --- p.83 / Chapter 3.3.2.d. --- Molecular Structures of Compounds 17-19 --- p.84 / Chapter 3.3.2.e. --- Reaction of Compound 18 with Dioxygen --- p.94 / Chapter 3.3.2.f. --- Molecular Structure of Compound20 --- p.95 / Chapter 3.3.3 --- Synthesis and Structures of Nickel(II) and Copper(I) Benzamidinates --- p.98 / Chapter 3.3.3.a --- Synthesis of a Nickel(II) Benzamidinate --- p.98 / Chapter 3.3.3.b. --- Synthesis of a Binuclear Copper(I) Benzamidinate --- p.99 / Chapter 3.3.3.c. --- Physical Characterization of Compounds 21 and22 --- p.101 / Chapter 3.3.3.d. --- Molecular Structures of Compounds 21 and22 --- p.102 / Chapter 3.3.4 --- Synthesis and Structures of Mononuclear Zinc(II) and Cadmium(II) Amidinates --- p.107 / Chapter 3.3.4.a --- Synthesis of Mononuclear Zinc(II) and Cadmium(II) Benzamidinates --- p.107 / Chapter 3.3.4.b. --- Physical Characterization of Compounds 23 and24 --- p.107 / Chapter 3.3.4.C. --- Molecular Structures of Compounds 23 and24 --- p.108 / Chapter 3.4 --- EXPERIMENTAL FOR CHAPTER3 --- p.113 / Chapter 3.5 --- REFERENCES FOR CHAPTER3 --- p.119 / appendix1 --- p.127 / appendix2 --- p.129

and biological sources. Recent advances in decarboxylative activation has allowed for the application of these reagents as building-blocks in organic synthesis; presenting viable, green alternatives to traditional organometallic or organohalide reagents. This thesis focuses on the development of novel transition metal catalysed decarboxylations, and investigation into the mechanisms of these, and related transformations. In the first part of the thesis, an extensive overview of the latest Carboxylic acids are cheap, shelf-stable reagents readily available from several commercial and biological sources. Recent advances in decarboxylative activation has allowed for the application of these reagents as building-blocks in organic synthesis; presenting viable, green alternatives to traditional organometallic or organohalide reagents. This thesis focuses on the development of novel transition metal catalysed decarboxylations, and investigation into the mechanisms of these, and related transformations. In the first part of the thesis, an extensive overview of the latest decarboxylative methodologies is presented, with discussion of the mechanistic aspects of different metal-catalysed decarboxylations. This is followed by a mechanistic investigation into the silver-catalysed decarboxylation of benzoic acids. In this system, an ortho substituent is required to facilitate decarboxylation. Using DFT, kinetic studies and the Fujita-Nishioka LFER we were able to show that the ortho-effect is a combination of electronic and steric effects, contrary to previous reports. In the second part of the thesis a practical, mild and highly selective protocol for the mono-deuteration of a variety of (hetero)arenes is described. Ag-catalysis was shown to facilitate the deuterodecarboxylation of (hetero)aromatic carboxylic acids in D2O/DMSO. The last two parts of this thesis focus on the formation and activation of carbon-fluorine bonds. Organofluorine compounds are of great importance to the agrochemical and pharmaceutical industries; however, there are limited examples of selective C-F bond formation that do not require stoichiometric metals, harsh conditions or toxic reagents. Using transition metal catalysis, we investigated a fluorodecarboxylation methodology. Initially this was explored in aromatic systems; though no synthetically useful yields were realised. However, aliphatic carboxylic acids were successfully transformed under aqueous conditions. The developed protocol was exploited to access benzylic fluorides. Subsequently, we established unprecedented metal-free conditions to activate their C-F bonds towards nucleophilic displacement; presenting a novel, decarboxylative methodology to furnish carbon-carbon and carbon-heteroatom bonds.

An alternative approach to conventional geometric based computer aided design systems is presented. Within this new approach manufacturing modes are used as the primary input to the design process. By directly actuating a simulation of machine tools and displaying the response of the material to this machine action, manufacturing constraints are captured at the design stage. Both manufacturing and design data can be generated concurrently, leading to a reduction in prototyping development lead times. Geometric and physical models of the manufacturing process are combined through the development of an interaction rule base to form a manufacturing simulation of the bending and forming process. These interaction rules interpret interactions of the geometric models and automatically generates constraints information required by the finite element engine, which performs the physical modelling task, and allows it to be fully embedded. Design trials are presented in which designers successfully used the design by manufacturing simulation approach to design metallic fastenings significantly faster than the traditional computer aided design approach.