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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.

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This thesis details the silver(I) coordination chemistry of thirty four alkene-containing ligands. The synthesis of thirty two of these ligands is described of which fifteen are unreported compounds. The ligands were designed to fully explore the potential of the silver(I)-alkene synthon in metallosupramolecular chemistry. Five series of ligand were designed each exploring a different facet of ligand design. Three series explored different ligand cores which included benzene, naphthalene and single atoms such as carbon, oxygen and nitrogen. Another series explored ligands of higher denticity including tri-, tetra- and hexa-substituted benzenes. The last series investigated ligands with functional groups in addition to olefins, in particular, heterocyclic nitrogens. A metal-centred ligand was created from a bifunctional ligand subunit. The silver(I)-alkene synthon has been used to create a range of assemblies. Polymeric structures were favoured with a variety of one-dimensional polymers with linear, ladder, helical and necklace type structures. Two-dimensional networks were formed, with some showing porosity. Three-dimensional metallopolymers were formed, including an interpenetrated three-dimensional network. Discrete complexes are commonly of the type Ag2L2 but with the occasional formation of Ag2L. It is shown that silver(I)-alkene interactions can coexists with other stronger interactions such as silver(I)-nitrogen. The deliberate use of bifunctional ligands allowed the formation of many interesting assemblies including an Ag3L2 heterotopic helicate. A Cu(I) complex with copper(I)-alkene interactions was identified. Techniques used to characterise the ligands and complexes include NMR, mass spectrometry, elemental analysis and X-ray crystallography. The crystal structures of seven organic compounds and forty six complexes are discussed.

Thirty four silver(I) complexes of azobenzene and derivatives have been synthesised, only two of which have been previously published. The azobenzene derivatives used are 2-bromo, 3-bromo, 4-bromo, 3,4’-dibromo, 2,4’-dibromo, 3-nitro, 4-dimethylamino, 4-methoxy, 2,6-dimethyl-4’-chloro, 2,6,2’,6’-tetramethyl and 2,2’-ethyleneazobenzene. 2,2’- and 4,4’-azobispyridine were also used along with diphenyltriazine. Six different silver(I) salts were used to make the complexes; they are tetrafluoroborate, hexafluorophosphate, perchlorate, nitrate, triflate and trifluoroacetate. All of the complexes were analysed using X-ray crystallography. In the complexes with azobenzene the anion was the most crucial factor in determining the resulting structure, as five different molecular topologies were seen with each change of anion. The 2-bromoazobenzene containing complexes continue this trend giving similar topologies to the azobenzene containing complexes. Once we come to the 3-bromo and 4-bromoazobenzene, we get a different molecular topology for the hexafluorophosphate containing complexes when compared to the original azobenzene containing complex, but we see a very similar structure for the perchlorate containing complexes. This would suggest that the coordinating anions give more predictable structures than the non-coordinating anions. The trend continues with both the 3,4’-dibromo and 2,4’-dibromoazobenzene complexes with triflate being structurally similar to the previous triflate containing complexes. The trend is reinforced further with 3-nitro and 4-methoxyazobenzene showing similar structures to the previously discussed complexes. The complex containing 4-dimethylaminoazobenzene can be disregarded, as the ligand has become protonated and therefore is unlike all the previously described results. When we come to the sterically hindered ligands 2,6-dimethyl-4’-chloroazobenzene the first three complexes show the same molecular topology of a silver atom bound to two ligands with a coordinating anion, however once we come to a tridentate coordinating anion triflate a 1-D metallopolymer is observed. This breaks the trend, as the structures are similar regardless of the change in anion. A similar effect is seen in 2,6,2’,6’-tetramethylazobenzene with both structures standing alone as no complexes with a similar molecular topology were observed. This effect is again noted in the complexes containing 2,2’-ethyleneazobenzene. The complexes all form a similar structure regardless of the anion used. As expected the 2,2’- and 4,4’-azobispyridine along with diphenyltriazine do not follow the trend observed earlier with the non-sterically hindered ligands as they can coordinate through additional nitrogen atoms in the aromatic ring or in the case of diphenyltriazine an additional nitrogen atom in the triazine group.

Bacterial resistance to antibiotics has increased rapidly within recent years, and it has become a serious threat to public health. Infections caused by multi-drug resistant bacteria entail higher morbidity, mortality, and a burden to health care systems. The use of biocides, including silver compounds, may affect the resistance to both biocides and antibiotics and, thereby, can be a driving factor in this development. The aim of the following thesis was to investigate the frequency of silver resistance and the effects of silver exposure on bacterial populations being of clinical significance and from geographically different parts of the world. Furthermore, it explored the genetic background of silver resistance, and if silver could select directly or indirectly for antibiotic resistance. By a range of methods, from culture in broth to whole genome sequencing, bacterial populations from humans, birds and from the environment were characterized. The studies showed that sil genes, encoding silver resistance, occurred at a high frequency. Sil genes were found in 48 % of Enterobacter spp., in 41 % of Klebsiella spp. and in 21 % of all human Escherichia coli isolates with production of certain types of extended-spectrum beta-lactamases (CTX-M-14 and CTX-M-15). In contrast, silver resistance was not found in bird isolates or in bacterial species, such as Pseudomonas aeruginosa and Legionella spp., with wet environments as their natural habitat. One silver-resistant Enterobacter cloacae strain was isolated from a chronic leg ulcer after only three weeks of treatment with silver-based dressings. The in-vivo effects of these dressings were limited, and they failed to eradicate both Gram-positive and Gram-negative bacteria. The activity of silver nitrate in vitro was bacteriostatic on Gram-positive species such as S. aureus and bactericidal on Gram-negative species. In Enterobacteriaceae, sil genes were associated with silver resistance phenotypes in all but one case. Using whole genome sequencing, single nucleotide polymorphisms in the silS gene were discovered after silver exposure in isolates with expressed silver resistance. This resistance could co-select for resistance to beta-lactams, co-trimoxazole and gentamicin. The findings of this thesis indicate that silver exposure may cause phenotypic silver resistance, and it may reduce the susceptibility to mainly beta-lactams and select for bacteria with resistance to clinically important antibiotics.

Doctor of Philosophy (PhD) / This work involves an experimental and kinetic modelling study of the silver catalysed reaction of methanol to formaldehyde. The motivation for this was the desire to investigate the potential for Process Intensification in formaldehyde production. Formaldehyde production from methanol over silver catalyst is a fast, exothermic process where dilution is used to control heat release, and these properties are both indicators of Process Intensification potential. The process is run adiabatically and produces hydrogen (which is currently burnt). Oxygen is consumed during the reaction but is also required to activate the catalyst and is fed in understoichiometric quantities. The central overall reactions in the silver catalysed process for formaldehyde production are oxydehydrogenation CH3OH + ½ O2 -> CH2O + H2O (DH = -159kJ/mol) and dehydrogenation CH3OH <-> CH2O + H2 (DH = 84kJ/mol). When sufficient oxygen is available, formaldehyde can be further oxidised to carbon dioxide CH2O + O2 -> CO2 + H2O (DH = -519kJ/mol). Formaldehyde can decompose to carbon monoxide and hydrogen CH2O <-> CO + H2 (DH = 12.5kJ/mol). Oxidation of methanol and hydrogen also occurs and other minor products of the reaction are methyl formate, methane and formic acid. These overall reactions do not adequately describe the silver catalysed reaction mechanism. In particular, the overall dehydrogenation reaction does not include oxygen as a reactant, but it will not occur over silver that does not have active atomic oxygen species adsorbed on the surface, and these atomic oxygen species are formed from gas phase oxygen. In the absence of a complete mechanism for silver catalysed formaldehyde production, the intensification of the process was investigated using a thermodynamic model (based on the overall oxydehydrogenation and dehydrogenation reactions, not reaction kinetics). It was found that by using heat exchange (rather than heat generated from the exothermic oxydehydrogenation path) and a lower oxygen concentration in the feed stream, hydrogen selectivity could be increased while maintaining the required methanol conversion. Before this iv opportunity could be further investigated, a complete reaction mechanism that would allow the requirement of oxygen for catalyst activation to be included was required. There is agreement in the literature that two active atomic oxygen species react with methanol on silver. These are weakly bound atomic oxygen (Oa) and strongly bound atomic oxygen (Og). The location of Oa is on the surface of the silver, while the location of Og has been described as being in the silver surface (where it substitutes for silver atoms). Both species react with methanol to form formaldehyde. When the concentration of Oa is high enough, Oa will also react with formaldehyde forming carbon dioxide (while Og will not). The literature presents differing views on the extent of involvement of each atomic oxygen species in industrial formaldehyde production. There is also disagreement on the pathways for water and hydrogen formation. An extensive experimental investigation of the partial oxidation of methanol to formaldehyde was carried out using a flow reactor. The effect of temperature (250- 650°C), reactant concentration (7000-40000ppm methanol) and the feed ratio of methanol to oxygen (2.5-5.5) were studied. The extreme case of methanol reaction with Og in the absence of gas phase oxygen was also investigated. To isolate the effect of secondary reactions, the oxidation of formaldehyde, carbon monoxide and hydrogen were investigated, both in the presence and absence of silver catalyst. When methanol was exposed to silver catalyst that had been activated by being covered in Og (with this being the only source of oxygen) the catalytic nature of Og was demonstrated by the high selectivity to formaldehyde and hydrogen that was achieved (with very little carbon dioxide or water production). When gas phase oxygen was fed to the reactor along with methanol, hydrogen selectivity over silver increased up to about 40% as the concentration of reactants was increased. This result is consistent with the general rule of thumb from industrial practice that hydrogen selectivity is about 50%. When formaldehyde and oxygen were exposed to silver in the flow reactor, the only reaction products were carbon v dioxide and water and the combination of high temperature and excess oxygen was required for complete conversion of formaldehyde. A pseudo-microkinetic model (based on a Langmuir-Hinshelwood mechanism) for the partial oxidation of methanol to formaldehyde (over silver) was taken from the literature and investigated. This model predicts formaldehyde production using only Oa (no other active atomic oxygen species are included) but lacks pathways for reactions between Oa and adsorbed hydrogen or hydroxyl (so the only possible fate of adsorbed H atoms is to desorb as H2). The Oa model was combined with literature models for hydrogen desorption and the reactions involving adsorbed hydroxyl (desorption, self reaction, decomposition and reaction with adsorbed hydrogen). Comparison of this Hybrid model with experimental data showed that reactions involving Oa will predict formaldehyde formation and oxidation, but not hydrogen formation (because the rate of hydrogen desorption is too slow compared with the rate of water formation). It is concluded that any detailed model must include the reaction between methanol and Og (producing hydrogen). Although the reaction between two adsorbed OgH species has been suggested as the pathway for hydrogen formation from Og, this is not certain and so all possible reactions involving Og and hydrogen need be investigated and the appropriate pathways added to the Hybrid model. Once a complete microkinetic mechanism for the partial oxidation of methanol to formaldehyde over silver is available it can be used to further investigate the process intensification of this process. In particular, the use of staged addition of oxygen (to keep the catalyst active) combined with heat exchange (to replace the heat normally supplied by the oxydehydrogenation path) with the aim of simultaneously maximizing methanol conversion and selectivity to formaldehyde and hydrogen.

Thesis (M.S.)--Rochester Institute of Technology, 1989. / Includes bibliographical references (leaves 140-145).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 106-112).

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1908. / Mr. Hase and Mr. French both earned a Bachelor of Science degree in General Science, granted in 1908, determined from "1874-1999 MSM-UMR Alumni Directory". The entire thesis text is included in file. Typescript. Illustrated by authors. Title from title screen of thesis/dissertation PDF file (viewed March 31, 2009)