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Polynuclear lanthanide complexes have attracted increasing interest in coordination and materials chemistry as they generally possess aesthetically pleasing molecular structures and display interesting properties possibly for useful chemical and materials applications. The work described herein concerned with the exploratory synthesis, structural characterization, and property investigation of a number of polynuclear lanthanide and silver complexes with selected organic ligands. Details of this thesis work are summarized in the following chapters: Chapter 1 offers a background of the research, with an emphasis on lanthanide-containing compounds and polynuclear silver complexes. Synthetic methodologies, novel structural characteristics, and interesting physical properties toward possible applications are surveyed in order to convey the justification of this thesis work. Chapter 2 describes the design and synthesis, structural characterization of a series of dinuclear lanthanide complexes with 1-(2-pyridylazo)-2-naphthol. The photophysical properties of these complexes pertinent to optical-limiting applications are evaluated. Chapter 3 details the halide-templated assembly of dodecanuclear and pentadecanuclear lanthanide hydroxide complexes featuring histidine as supporting ligand via the ligand-controlled hydrolysis. Salient structural features of these complexes are discussed. Chapter 4 reports the synthesis, structural characterization, and spectroscopic studies of the giant polynuclear lanthanide complexes containing a 60-metal cluster core when threonine was used as the supporting ligand. Carbonate has been identified as a novel anionic template in these clusters. These Ln60 cluster complexes feature a sodalite cage structure with 24 vertex-sharing cubane-like [Ln₄(μ₃-OH) ₄]⁸⁺ units. Their magnetic and optical properties are measured and discussed. Chapter 5 describes the unexpected discovery of a polynuclear silver complex with histidine, first isolated from the reaction of a halide-containing polynuclear lanthanide hydroxide complex and then rationally prepared by using silver nitrate and histidine. A series of analogous silver complexes with other amino acids have subsequently prepared and structurally characterized. Chapter 6 details two silver-amino acid helicates composed of individual helical coordination polymers. Optically pure helicates were obtained by using enantiomerically pure amino acids. While silver-glutamate possesses a double-helical structure, silver-aspartate displays an unprecedented six-strand helical structure. Chapter 7 summarizes the results presented in Chapters 2-6 and elaborates on some future research directions toward which each of these projects may be heading.

<p>Development in the field of materials science is propagated by the synthesis of polynuclear metal-containing complexes, that exhibit enhanced chemical and physical properties. This thesis describes the synthesis of new metal-containing linear polymers and dendritic molecules.</p> <p>Chapter 1 presents an overview of the field of metal-containing polymers, with particular attention to the synthesis of polymers via condensation polymerisation. This review includes the various types of metal-containing condensation polymers and the applications of these materials, where available. This discussion is followed by a brief summary of metal-containing dendrimers, which includes a concise description of their structure and applications in general.</p> <p>There are two routes to preparing metal-containing polymers. Chapter 2 describes the synthesis of three bifunctional organometallic monomers, of the general type [M]-O-{2,6-(CH2OH)2-4-CH3-C6H2}, where [M] represents the various metal-containing moieties, (&eta / 5-C5H5)(CO)2 Fe(CH2)3 (25), (&eta / 5-C5H4-CH2CH2CH2-)Re(CO)3 (26) and Fpdendr (27). These monomers were prepared using 2,6-bis(hydroxymethyl)-p-cresol as the key reagent. The monomers were used in classical polycondensation reactions with terephthaloyl chloride using ambient temperature solution techniques. This yielded new low molecular weight oligomeric polyesters, that were characterised using FTIR and 1HNMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis and sizeexclusion chromatography.</p> <p>In Chapter 3, an alternate route to metal-containing polymers is described. In this case, bifunctional organic monomers were polymerised to give preformed organic polymers. Two types of organic polymers were prepared, viz. polyesters (with pendant vinyl moieties) and polyimines (with &alpha / -diimine units along the polymer backbone). Functionalisation of these preformed organic polymers with various metal sources was attempted. Hydrozirconation reactions of the vinyl polyesters with Schwartz&rsquo / s reagent, Cp2Zr(H)Cl, were attempted and were largely unsuccessful. Competing reactions with the ester functionality prevailed, preventing the desired reaction. Reaction of the polyimines with PdCl2(COD) yielded insoluble, intractable metal-containing oligomers. Partial characterisation of the complexes is described.</p> <p>The synthesis of new poly(propylene imine) iminopyridyl metallodendrimers is described in Chapter 4. Schiff-base condensation reaction of the commercially available DAB dendrimers with 2-pyridinecarboxaldehyde, gave the dendrimers 51, 52, and 53, with four, eight and sixteen pyridylimine functionalities respectively on the periphery. Successful complexation reactions with PdCl2(COD), PtCl2(COD) and CuCl2 produced the corresponding metal-containing dendrimers, with either PdCl2 (54, 55, 56), PtCl2 (57) or CuCl2 (58) moieties bound on the periphery. The metallodendrimers were insoluble in the more common organic solvents, and were characterised by IR and 1H-NMR spectroscopy and microanalysis where possible. Dendrimers with salicylaldiminato ligands on the periphery were prepared by reacting the DAB dendrimers with salicylaldehyde. These ligands were reacted with various metal acetates in an attempt to prepare new metalcontaining salicylaldimine dendrimers. This work yielded either paramagnetic metal complexes or insoluble, intractable compounds.</p> <p>Chapter 5 describes the applications of the catalyst precursors (54, 55, 56, 57, 58), discussed in Chapter 4, in the polymerisation of ethylene and the use of complexes 54 and 55 as Heck cross-coupling catalyst precursors. The complexes all showed catalytic activity toward ethylene polymerisation. A discussion of their activity, the polyethylene molecular weight and microstructure is presented in this chapter. The precursors 54 and 55 are also effective catalysts in the Heck reactions, coupling iodobenzene with methyl acrylate, styrene and 1-octene in high conversions.</p> <p>General conclusions are given in Chapter 6.</p>

<p>Development in the field of materials science is propagated by the synthesis of polynuclear metal-containing complexes, that exhibit enhanced chemical and physical properties. This thesis describes the synthesis of new metal-containing linear polymers and dendritic molecules.</p> <p>Chapter 1 presents an overview of the field of metal-containing polymers, with particular attention to the synthesis of polymers via condensation polymerisation. This review includes the various types of metal-containing condensation polymers and the applications of these materials, where available. This discussion is followed by a brief summary of metal-containing dendrimers, which includes a concise description of their structure and applications in general.</p> <p>There are two routes to preparing metal-containing polymers. Chapter 2 describes the synthesis of three bifunctional organometallic monomers, of the general type [M]-O-{2,6-(CH2OH)2-4-CH3-C6H2}, where [M] represents the various metal-containing moieties, (&eta / 5-C5H5)(CO)2 Fe(CH2)3 (25), (&eta / 5-C5H4-CH2CH2CH2-)Re(CO)3 (26) and Fpdendr (27). These monomers were prepared using 2,6-bis(hydroxymethyl)-p-cresol as the key reagent. The monomers were used in classical polycondensation reactions with terephthaloyl chloride using ambient temperature solution techniques. This yielded new low molecular weight oligomeric polyesters, that were characterised using FTIR and 1HNMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis and sizeexclusion chromatography.</p> <p>In Chapter 3, an alternate route to metal-containing polymers is described. In this case, bifunctional organic monomers were polymerised to give preformed organic polymers. Two types of organic polymers were prepared, viz. polyesters (with pendant vinyl moieties) and polyimines (with &alpha / -diimine units along the polymer backbone). Functionalisation of these preformed organic polymers with various metal sources was attempted. Hydrozirconation reactions of the vinyl polyesters with Schwartz&rsquo / s reagent, Cp2Zr(H)Cl, were attempted and were largely unsuccessful. Competing reactions with the ester functionality prevailed, preventing the desired reaction. Reaction of the polyimines with PdCl2(COD) yielded insoluble, intractable metal-containing oligomers. Partial characterisation of the complexes is described.</p> <p>The synthesis of new poly(propylene imine) iminopyridyl metallodendrimers is described in Chapter 4. Schiff-base condensation reaction of the commercially available DAB dendrimers with 2-pyridinecarboxaldehyde, gave the dendrimers 51, 52, and 53, with four, eight and sixteen pyridylimine functionalities respectively on the periphery. Successful complexation reactions with PdCl2(COD), PtCl2(COD) and CuCl2 produced the corresponding metal-containing dendrimers, with either PdCl2 (54, 55, 56), PtCl2 (57) or CuCl2 (58) moieties bound on the periphery. The metallodendrimers were insoluble in the more common organic solvents, and were characterised by IR and 1H-NMR spectroscopy and microanalysis where possible. Dendrimers with salicylaldiminato ligands on the periphery were prepared by reacting the DAB dendrimers with salicylaldehyde. These ligands were reacted with various metal acetates in an attempt to prepare new metalcontaining salicylaldimine dendrimers. This work yielded either paramagnetic metal complexes or insoluble, intractable compounds.</p> <p>Chapter 5 describes the applications of the catalyst precursors (54, 55, 56, 57, 58), discussed in Chapter 4, in the polymerisation of ethylene and the use of complexes 54 and 55 as Heck cross-coupling catalyst precursors. The complexes all showed catalytic activity toward ethylene polymerisation. A discussion of their activity, the polyethylene molecular weight and microstructure is presented in this chapter. The precursors 54 and 55 are also effective catalysts in the Heck reactions, coupling iodobenzene with methyl acrylate, styrene and 1-octene in high conversions.</p> <p>General conclusions are given in Chapter 6.</p>

The use of gold in organic chemistry is a relatively recent occurrence. In addition to being previously considered too expensive, it was also believed to be chemically inert. Soon after the early reports indicating its rich reactivity, the number of reports on chemical transformations involving gold sky rocketed. One such report by Toste and coworkers demonstrated the intramolecular addition of silyl enol ether onto Au(I) activated alkynes, resulting in a 5-exo dig cyclization. The first part (Chapter 1) of this thesis discusses the development of a Au(I) catalyzed polycyclization reaction inspired by this transformation. The reaction demonstrated the ability of Au(I) to successfully catalyze the formation of multiple C-C bonds and resulted in the synthesis of benzothiophenes, benzofurans, carbazoles and hydrindene. With the current resurgence of photochemical transformations being reported in literature, various opportunities for the use of Au(I) complexes arose. The substantial relativistic effect observed in gold which make it a good soft Lewis acid also has a significant influence on the redox potential of this metal. Chapter 3 of this thesis discusses the development of a Au(I) photocatalyzed process which benefits from having both a strong oxidation and reduction potential for the reduction of carbon-halide bonds. Radical reductions and cyclizations were accessed with the use of polynuclear Au(I) photocatalysts. In depth analysis of catalytically active Au(I) complexes helped elucidate the mechanism by which this photochemical reaction occurs. This part (Chapter 4) also covers serendipitously discovered uncatalyzed photochemical transformations derived from our work with gold. The halogenation reaction of primary alcohols was successfully achieved and a combination of our developed methods resulted in an efficient dehydroxylation protocol.

Philosophiae Doctor - PhD / metal-containing complexes, that exhibit enhanced chemical and physical properties. This thesis describes the synthesis of new metal-containing linear polymers and dendritic molecules. Chapter 1 presents an overview of the field of metal-containing polymers, with particular attention to the synthesis of polymers via condensation polymerisation. This review includes the various types of metal-containing condensation polymers and the applications of these materials, where available. This discussion is followed by a brief summary of metal-containing dendrimers, which includes a concise description of their structure and applications in general. There are two routes to preparing metal-containing polymers. Chapter 2 describes the synthesis of three bifunctional organometallic monomers, of the general type [M]-O-{2,6-(CH2OH)2-4-CH3-C6H2}, where [M] represents the various metal-containing moieties, (η5-C5H5)(CO)2 Fe(CH2)3 (25), (η5-C5H4-CH2CH2CH2-)Re(CO)3 (26) and Fpdendr (27). These monomers were prepared using 2,6-bis(hydroxymethyl)-p-cresol as the key reagent. The monomers were used in classical polycondensation reactions with terephthaloyl chloride using ambient temperature solution techniques. This yielded new low molecular weight oligomeric polyesters, that were characterised using FTIR and 1HNMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis and sizeexclusion chromatography. In Chapter 3, an alternate route to metal-containing polymers is described. In this case, bifunctional organic monomers were polymerised to give preformed organic polymers. Two types of organic polymers were prepared, viz. polyesters (with pendant vinyl moieties) and polyimines (with α-diimine units along the polymer backbone). Functionalisation of these preformed organic polymers with various metal sources was attempted. Hydrozirconation reactions of the vinyl polyesters with Schwartz’s reagent, Cp2Zr(H)Cl, were attempted and were largely unsuccessful. Competing reactions with the ester functionality prevailed, preventing the desired reaction. Reaction of the polyimines with PdCl2(COD) yielded insoluble, intractable metal-containing oligomers. Partial characterisation of the complexes is described. The synthesis of new poly(propylene imine) iminopyridyl metallodendrimers is described in Chapter 4. Schiff-base condensation reaction of the commercially available DAB dendrimers with 2-pyridinecarboxaldehyde, gave the dendrimers 51, 52, and 53, with four, eight and sixteen pyridylimine functionalities respectively on the periphery. Successful complexation reactions with PdCl2(COD), PtCl2(COD) and CuCl2 produced the corresponding metal-containing dendrimers, with either PdCl2 (54, 55, 56), PtCl2 (57) or CuCl2 (58) moieties bound on the periphery. The metallodendrimers were insoluble in the more common organic solvents, and were characterised by IR and 1H-NMR spectroscopy and microanalysis where possible. Dendrimers with salicylaldiminato ligands on the periphery were prepared by reacting the DAB dendrimers with salicylaldehyde. These ligands were reacted with various metal acetates in an attempt to prepare new metalcontaining salicylaldimine dendrimers. This work yielded either paramagnetic metal complexes or insoluble, intractable compounds. Chapter 5 describes the applications of the catalyst precursors (54, 55, 56, 57, 58), discussed in Chapter 4, in the polymerisation of ethylene and the use of complexes 54 and 55 as Heck cross-coupling catalyst precursors. The complexes all showed catalytic activity toward ethylene polymerisation. A discussion of their activity, the polyethylene molecular weight and microstructure is presented in this chapter. The precursors 54 and 55 are also effective catalysts in the Heck reactions, coupling iodobenzene with methyl acrylate, styrene and 1-octene in high conversions. / South Africa

Important reactions are catalyzed by enzymes employing polynuclear cofactors, often characterized by weak-field ligands and transition metal ions within the sum of the van der Waals radii. While the overall stoichiometries and, in many cases, the structures, of the cofactors are known, the roles of the individual metal ions remain uncertain. Our approach is to investigate model clusters stabilized by a hexadentate, trinucleating ligand. The hexaamine ligand \((MeC (CH_2NHC_6H_4-o-NHPh)_3) (^{Ph}LH_6)\) allows facile synthesis of the clusters \((^{Ph}L)Fe_3(thf)_3\), \((^{Ph}L)Fe_3 (py)_3\), and \((^{Ph}L)Fe_3(PMe_2Ph)_3\) (thf = tetrahydrofuran, py = pyridine). The phenyl substituents on the ligand sterically prevent strong M–M bonding, but permit weaker M–M orbital interactions, with Fe–Fe distances near those found in Fe metal. The complex \((^{Ph}L)Fe_3(thf)_3\) exhibits a well-isolated S = 5 or S = 6 ground state over 5 - 300 K, as evidenced by magnetic susceptibility and reduced magnetization data. However, in the stronger-field pyridine and phosphine complexes, temperature dependent susceptibility is observed which is best modeled as a spin state transition from S = 2 to S = 4. Variable-temperature crystallography and Mössbauer spectroscopy reveal a whole-molecule, rather than site-isolated, spin transition. The all-ferrous cluster \((^{Ph}L)Fe_3(thf)_3\) can be oxidized with triphenylmethyl halides or iodine to give singly-oxidized clusters of the form \((^{Ph}L)Fe_3X(L)\) and \([(^{Ph}L)Fe_3(\mu-X)]_2 (X = Cl, Br, I; L = thf, py)\), in which one Fe–Fe distance contracts to 2.30 Å and the others lengthen to 2.6-2.7 Å. The halide and solvent ligands coordinate a unique Fe, but Mössbauer spectroscopy shows that the diiron pair bears the oxidation. Magnetic data can be modeled by considering a high-spin ferrous ion ferromagnetically coupled to an \(S = 3/2 [Fe_2]^{5+}\) unit. When \([(^{Ph}L)Fe_3(\mu-Cl)]_2\) is reacted with two or five equivalents of \(CoCl_2\) in tetrahydrofuran, the fully-substituted complexes \((^{Ph}L)Fe_2CoCl(acn)\) and \((^{Ph}L)FeCo_2Cl(acn)\) (acn = acetonitrile) can be isolated. \(^1H\) nuclear magnetic resonance shows that they are distinct species, not a mixture, and the elemental ratios are confirmed by X-ray fluorescence spectroscopy. Mössbauer spectroscopy shows that the Co preferentially substitutes into the \([M_2]^{5+}\) unit, as the ferrous site doublet is completely absent in \((^{Ph}L)FeCo_2Cl(acn)\). / Chemistry and Chemical Biology

This thesis describes a series of calix[n]arene polynuclear transition metal and lanthanide complexes. Calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition metal and lanthanide centres. Surprisingly however, with only a few exceptions, the coordination chemistry of p-tBucalix[ 4]arene (TBC[4]), p-tBu-calix[8]arene (TBC[8]) and p-tBuhomotrioxacalix[ 3]arene (TBOC[3]) with paramagnetic transition metal ions for the purpose of making and studying magnetically interesting molecules is unknown. Chapter two describes the reaction of TBC[4] with manganese salts in the presence of an appropriate base (and in some cases co-ligand) resulting in the formation of a family of calixarene-supported [MnIII 2MnII 2] clusters (1-7) that behave as Single-Molecule Magnets (SMMs). These are: [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2MeOH (1), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(H2O)2]·4MeOH·2DMF (2), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2.8MeOH (3), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(EtOH)(H2O)] (4), [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6]·2MeOH·2DMSO (5) , [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6] (6) and [MnIII 2MnII 2(OH)2(C[4])2(MeOH)6]·4MeOH (7). Variation in the alkyl groups present at the upper-rim of the cone allows for the expression of a degree of control over the self-assembly of these SMM building blocks, whilst retaining the general magnetic properties. The presence of various different ligands around the periphery of the magnetic core has some effect over the extended self-assembly of these SMMs. Chapter three describes how the combination of complementary cluster ligands; sodium phenylphosphinate and the N,O-chelate 2-(hydroxy-methyl)pyridine (hmpH) with TBC[4] results in the formation of two new calixarene-supported clusters. This being an unusual [MnIIIMnII]2 dimer of dimers [MnIIIMnII(O2P(H)Ph)(DMF)2(MeOH)2]2 (8) and a ferromagnetic [Mn5] cage that displays the characteristic bonding modes of each support [MnIII 3MnII 2(OH)2(TBC[4])2(hmp)2(DMF)6](TBC[4]-H)·xDMF ·xH2O (9). Chapter four details how using oxacalix[3]arenes can tune the nature of the metal binding site, by introduction of ≥ 1 ethereal bridge. This results in Mn(II) rather than Mn(III) bonding in the phenolic pocket, and that these components self-assemble with additional Mn(II) and Mn(III) ions to form a [Mn10] supertetrahedron with an unusual oxidation state distribution, [MnII 6MnIII 4O4(TBOC[3])4(Cl)4(DMF)3]∙3.3H2O ∙ 1.5DMF (10). Chapter five introduces a family of lanthanide complexes formed using TBC[8]. Variation in the experimental conditions employed in the reaction of TBC[8] with lanthanide salts (LnX3) provides access to Ln1, Ln2, Ln4, Ln5, Ln6, Ln7 and Ln8 complexes, [Gd(TBC[8]-2H)Cl(DMSO)4]·MeCN·H2O·(DMSO)2·hex (11), [CeIV 4(TBC[8]-6H)2(μ3- O)2(DMF)4]·(DMF)5·hex·MeCN (12), [TbIII 5(TBC[8]-5H)(μ4-O)(μ3- OH)4Cl(DMSO)8(H2O)3]Cl3·(DMSO)2(hex)2 (13), [CeIV 6(TBC[8]-6H)2(μ4-O)2(μ2-OMe)4(μ2- O)2(DMF)4]·(DMF)6·hex (14), [Dy7(TBC[8]-7H)(TBC[8]-6H)(μ4-O)2(μ3-OH)2(μ2- OH)2(DMF)9]·(DMF)3 (15) and [Gd8(TBC[8]-7H)2(μ4-CO3)2(μ5-CO3)2(μ2-HCO2)2(DMF)8] (16), with all polymetallic clusters containing the common bi-nuclear lanthanide fragment. Closer inspection of the structures of the polymetallic clusters reveals that all but one (Ln8) are in fact based on metal octahedra or the building blocks of octahedra.

Construction of polynuclear metal assemblies from discrete 0D clusters to extend 3D networks, comprised of metal ions and bridging organic/inorganic ligands has attracted immense attention, owing to their intriguing network topologies and interesting properties. Proper ligand design and the appropriate choice of the metal center are of vital importance to the design of such polynuclear assemblies. One of the various attributes of polynuclear metal assemblies is magnetism. Magnetic materials can be constructed by incorporating magnetic moment carriers such as paramagnetic metals(V, Cr, Mn, Fe, Co, Ni, Cu) in presence of bridging ligands. Though, one-atom oxo/hydroxo and two-atom cyanide bridges were of popular choices due to their short distance for transmitting strong magnetic coupling between the paramagnetic metal centers, it has been shown that, three-atom bridging ligands like carboxylate and azide (N3 ) are well-fitted moieties for this purpose since they offer a variety of magnetic interactions depending on their versatile bridging modes. It has been well known that incorporation of anionic bridging ligand in presence of azide anion is a challenging task due to the competition between the 2nd anionic ligand with azide in self-assembly process. Incorporating both azide and carboxylate functionalities, a series of polymeric complexes has been synthesized and conversion of 0D discrete clusters to extended networks with the retention of basic core by fine tuning the ligands has been achieved. Single-crystal to single-crystal transformation has received considerable attention in crystal engineering since it is difficult for crystals to retain single crystallinity after removal of the guest at high temperature. Interestingly single-crystal to single-crystal transformation was observed at high temperature for Co(II) formate-formamide complex and change in dimensionality from 3D to 0D was observed at high temperature for Cr(III) formate-formamide complex. Multiferroic materials are those where both ferroelectricity and ferromagnetism coexist in the same phase. In general the transition metal d-electrons which are essential for magnetism reduce the tendency for off-center ferroelectric distortion. First tetrazole based miltiferroic coordination polymer of Co(II) metal ion in presence of azide has been successfully synthesized whereas its analogous Mn(II) complex showed different structural topology with interesting magnetic behavior. It has been also established in the present study, the important role played by hydrazine ligand to prevent oxidation of paramagnetic Co(II) to diamagnetic Co(III) system with the formation of a metal-inorganic assembly of Co(II) which exhibited spin-canted behavior.