This dissertation investigates the preparation and electrochemical studies on a series of novel redox active hybrid dendrimers. The author also describes cucurbit[8]uril (CB8) mediated dendrimer self-assembly and their size selection by applying external electrochemical stimulus. In addition to this, a series of redox active, carboxylic acid terminated dendrimers were deposited onto indium tin oxide (ITO) surfaces. The surface interactions between the dendrimers and the metal oxides were characterized by electrochemical, spectroscopic, and atomic force microscopic methods. Additionally, the author describes molecular recognition behavior studies between several redox active guests and cucurbit[7]uril (CB7) in non-aqueous media. Furthermore, the author also describes the preparation and electronic communication studies on a series of bisferrocenylamino triazine derivatives. Three chapters of this dissertation deal with dendrimer applications in several different topics. A general introduction to dendrimers is given in Chapter I, including a short history, dendrimer structural features, synthetic methodologies, and also including their general applications on several different topics. Chapter II describes the preparation and characterization of a series of novel redox active hybrid dendrimers. These dendrimers consist of a ferrocenylamino nucleus and two series of popular dendrons (Fréchet and Newkome type). Interestingly, the microenvironment surrounding the redox residues is finely adjustable by varying the size of these two types of dendrons. Chapter III describes the molecular recognition studies with selected redox active guests and the macrocyclic host CB7 in non-aqueous media. The extremely strong host-guest interaction between CB7 and ferrocenylmethyl-trimethylammonium (FA) in aqueous media experiences a substantial thermodynamic stability loss when transferred to non-aqueous media. In stark contrast to this, the binding behavior between CB7 and the dicationic guest methyl viologen (MV) exhibits less sensitivity to environmental variation. Furthermore, the electrochemical studies were performed under non-aqueous media. In general, host CB7 encapsulation of these redox active guests in non-aqueous media induces different electrochemical behavior compared to that of aqueous media. For instance, the cyclic voltammetric response of CB7 encapsulated FA in DMSO exhibit substantial cathodic potential shift, which is opposite to the behavior in aqueous media. Chapter IV describes CB8 mediated dendrimer self-assembly. A new series of pi-donor containing Newkome type dendrimers were synthesized. These pi-donor containing dendrimers are found to form stable ternary charge transfer complexes with another series of pi-acceptor (viologen) containing dendrimers. Furthermore, one electron reduction of the viologen residue disrupts the charge transfer complexes and leads to the assembly of viologen radical cation dimmers. And, thus, may result in substantial size selection between these two types of dendrimer assemblies. Chapter V describes the exploration of a series of redox active dendrimers bearing multiple carboxylic acids as surface anchoring groups to attach onto the optical transparent semiconductor material ITO coated glass surfaces. The dendrimer derivatized ITO slides were further prepared as working electrodes, and the subsequent electrochemical studies revealed that these dendrimers strongly adsorb onto ITO surfaces. Especially, the ITO electrodes treated with the second generation dendrimer exhibit rather stable electrochemical behavior. The surface coverages of ITO electrodes treated with dendrimers were estimated by current integration. Atomic force microscopic studies provided insights on surface topographical variation before and after the dendrimer deposition. Infrared spectroscopic studies further revealed the chemical interactions between dendrimer carboxylic acid groups and the metal oxide surfaces. Chapter VI describes the preparation of a series of triazine based bisferrocenylamino derivatives. Variable 1H-NMR and 13C-NMR spectroscopic studies clearly indicate that these bisferrocenylamino triazine derivatives exhibit rotamerization phenomena. And, the rotamer coalescence temperatures are mediated by the third substituent group. The X-ray crystallographic analyses disclose the partial double bond character between the amino nitrogen and the triazine carbon, which reveal the structural proof behind the rotamerization phenomena. Furthermore, electrochemical experiments are performed under two sets of experimental conditions. No electronic communication is observed when using the traditional tetrabultylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. In stark contrast to this, electronic communication between the bisferrocenyl residues is observed when using tetrabultylammonium tetrakis(pentafluorophenyl)borate (TBAB(C6F5)4) as supporting electrolyte. Surprisingly, the electronic communication strength can be mediated by a third substituent group. Computational studies provide insights into the molecular geometry and electronic structure of the mixed valence species. By combining the supporting electrolyte dependant electronic communication behavior, near-IR spectroscopic studies and the computational results, we conclude that, the electronic communication between the bisferrocenyl residues in these investigated triazine derivatives occurs through space metal-metal interactions.

Supercapacitors are one of the most important electrochemical energy storage and conversion devices, however low ionic conductivity of solid state polymer electrolytes and the poor accessibility of the ions to the active sites in the porous electrode will cause low performance for all-solid-state supercapacitors and will limit their application. The objective of the dissertation is to improve the performance of all-solid-state supercapactor by improving electrolyte conductivity and solving accessibility problem of the ions to the active sites. The low ionic conductivity (10-8 S/cm) of poly(ethylene oxide) (PEO) limits its application as an electrolyte. Since PEO is a semicrystal polymer and the ion conduction take place mainly in the amorphous regions of the PEO/Lithium salt complex, improvements in the percentage of amorphous phase in PEO or increasing the charge carrier concentration and mobility could increase the ionic conductivity of PEO electrolyte. Hot pressing along with the additions of different lithium salts, inorganic fillers and plasticizers were applied to improve the ionic conductivity of PEO polymer electrolytes. Four electrode methods were used to evaluate the conductivity of PEO based polymer electrolytes. Results show that adding certain lithium salts, inorganic fillers, and plasticizers could improve the ionic conductivity of PEO electrolytes up 10-4 S/cm. Further hot pressing treatment could improve the ionic conductivity of PEO electrolytes up to 10-3 S/cm. The conductivity improvement after hot pressing treatment is elucidated as that the spherulite crystal phase is convert into the fringed micelle crystal phase or the amorphous phase of PEO electrolytes. PEO electrolytes were added into active carbon as a binder and an ion conductor, so as to provide electrodes with not only ion conduction, but also the accessibility of ion to the active sites of electrodes. The NaI/I2 mediator was added to improve the conductivity of PEO electrolyte and provide pseudocapacitance for all-solid-state supercapacitors. Impedance, cyclic voltammetry, and gavalnostatic charge/discharge measurements were conducted to evaluate the electrochemical performance of PEO polymer electrolytes based all-solid-state supercapacitors. Results demonstrate that the conductivity of PEO electrolyte could be improved to 0.1 S/cm with a mediator concentration of 50wt%. A high conductivity in the PEO electrolyte with mediator is an indication of a high electron exchange rate between the mediator and mediator. The high electron exchange rates at mediator carbon interface and between mediator and mediator are essential in order to obtain a high response rate and high power. This automatically solves the accessibility problem. With the addition of NaI/I2 mediator, the specific capacitance increased more than 30 folds, specific power increased almost 20 folds, and specific energy increased around 10 folds. Further addition of filler to the electrodes along with the mediator could double the specific capacitor and specific power of the all-solid-state supercapacitor. The stability of the corresponded supercapacitor is good within 2000 cycles.

This thesis focuses on liquid redox electrolytes in dye-sensitized solar cells (DSCs). A liquid redox electrolyte, as one of the key constituents in DSCs, typically consists of a redox mediator, additives and a solvent. This thesis work concerns all these three aspects of liquid electrolytes, aiming through fundamental insights to enhance the photovoltaic performances of liquid DSCs. Initial attention has been paid to the iodine concentration effects in ionic liquid (IL)-based electrolytes. It has been revealed that the higher iodine concentration required in IL-based electrolytes can be attributed to both triiodide mobility associated with the high viscosity of the IL, and chemical availability of triiodide. The concept of incompletely solvated ionic liquids (ISILs) has been introduced as a new type of electrolyte solvent for DSCs. It has been found that the photovoltaic performance of ISIL-based electrolytes can even rival that of organic solvent-based electrolytes. And most strikingly, ISIL-based electrolytes provide highly stable DSC devices under light-soaking conditions, as a result of the substantially lower vapor pressure of the ISIL system. A significant synergistic effect has been observed when both guanidinium thiocyanate and N-methylbenzimidazole are employed together in an IL-based electrolyte, exhibiting an optimal overall conversion efficiency. Tetrathiafulvalene (TTF) has been investigated as an organic iodine-free redox couple in electrolytes for DSCs. An unexpected worse performance has been observed for the TTF system, albeit it possesses a particularly attractive positive redox potential. An organic, iodine-free thiolate/disulfide system has also been adopted as a redox couple in electrolytes for organic DSCs. An impressive efficiency of 6.0% has successfully been achieved by using this thiolate/disulfide redox couple in combination with a poly (3, 4-ethylenedioxythiophene) (PEDOT) counter electrode material under full sunlight illumination (AM 1.5G, 100 mW/cm2). Such high efficiency can even rival that of its counterpart DSC using a state-of-the-art iodine-based electrolyte in the systems studied.The cation effects of lithium, sodium and guanidinium ions in liquid electrolytes for DSCs have been scrutinized. The selection of the type of cations has been found to exert quite different impacts on the conduction band edge (CB) of the TiO2 and also on the electron recombination kinetics, therefore resulting in different photovoltaic behavior. / QC 20120124

<p>Prior studies of groundwater systems have associated increasing salinity and anoxic conditions with increasing radium (Ra) activities in water due to the decreasing effectiveness of Ra removal processes. However, the components of salinity (e.g. Ca vs. Na and SO₄^2- vs. Cl^--dominated waters), and the relative importance of salinity-sensitive vs. redox-sensitive processes for Ra mobilization, are less well understood. In this research, the response of Ra to hydrochemical change was examined using a multiple tracer approach to obtain detailed information on divalent cation and Ra mobility. A range of salinity and redox conditions was examined in five field-based studies in the United States and Morocco: (1) fresh waters in fractured crystalline rocks in the Piedmont region of North Carolina; (2) the Willcox Basin, an oxic alluvial basin-fill aquifer in southeastern Arizona; (3) the Jordan sandstone aquifer, a carbonate-cemented quartz sandstone in southeastern Minnesota; (4) an unconfined coastal aquifer undergoing salinization in the city of Agadir, Morocco; and (5) the confined, fresh to saline Cretaceous and Pliocene aquifers of the Atlantic Coastal Plain in North Carolina.</p><p> </p><p>In addition to analysis of major element concentrations, trace metal concentrations, and ²²⁴Ra, ²²⁶Ra, and ²²⁸Ra activities, complementary isotope systems were applied to gain insights on the relative stability of chemical processes that remove radium and other alkaline earth metals: (1) strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) trace divalent cation release from sources such as clay and carbonate minerals in the aquifer solids and also indicate conditions in which divalent cation release (rather than uptake) is dominant; (2) boron concentrations and isotopes (&delta;¹¹B) coincide with the opposite condition in freshening conditions of the Atlantic Coastal Plain, in which divalent cations are removed in exchange for Na; and (3) sulfur and oxygen isotopes (&delta;³⁴S, &delta;¹⁸O) of sulfate trace sulfate sources and provide information on sulfate-reducing conditions, which can inhibit barite (BaSO₄) from removing Ra by coprecipitation. In addition, other isotopic and ion measurements trace salinity sources and groundwater residence time, including &delta;²H, &delta;¹⁸O, ³H, Br^-/Cl^-, Na/Cl^-, and Ca/Na.</p><p>This dissertation documents correlations between salinity and radium in the brackish to saline North Carolina coastal plain aquifer with total dissolved solids (TDS) up to ~18,000 mg L^-1 and to some degree in the Moroccan coastal aquifer, but even the lower-salinity waters (TDS <3000 mg L^-1) exhibit a range of Ra activities spanning approximately 3 orders of magnitude. Among these low-TDS waters, the highest Ra activities were observed in the anoxic Jordan sandstone aquifer and the lowest were observed in the oxic Willcox Basin aquifer. Although the main control on radium activities in fresh groundwater is the U- and Th-series radionuclide content of the aquifer solids, important secondary controls include the stability of redox-sensitive radium adsorption sites (Mn and Fe oxides), the relative dominance of divalent vs. monovalent cations (e.g. the Ca/Na ratio), formation of the uncharged RaSO₄⁰ complex, and/or the saturation state with respect to barite. These processes interact in varied ways in the field-based studies. Increasing radium activities and decreasing ²²²Rn/²²⁶Ra ratios in the North Carolina fractured crystalline rock groundwater system are correlated with increasing Ba, Mn, and Fe concentrations and decreasing dissolved oxygen concentrations, related to weathering and/or organic carbon oxidation. Radium activities in the oxic, neutral to slightly basic Willcox Basin are very low (median ²²⁶Ra activity 2 mBq L^-1), probably due to a combination of effective Ra removal processes including adsorption to Mn and/or Fe oxides and the overall removal of divalent cations during groundwater evolution in this system. These are the same surface charge conditions that release arsenic, of regional water concern, in this pH range. Radium in Jordan aquifer groundwater is dependent on local variations in solid-phase radionuclide levels, probably hosted in the carbonate cement phase. Also, Ra is inefficiently adsorbed to the aquifer solids in the aquifer's anoxic conditions, resulting in the highest radium levels reported in this dissertation (²²⁶Ra up to 420 mBq L^-1) despite apparent barite precipitation that partially removes Ra. Radium-224 activity in the Moroccan coastal aquifer is associated with salinity, but Ra overall is apparently controlled by barite, indicated by conditions near BaSO₄ saturation. Radium activity in the saline waters of the Atlantic Coastal Plain aquifers is associated with TDS concentrations, but the cation exchange properties of the aquifer may provide a major mechanism of Ra removal in the Na-HCO₃^- and Na-Cl^- waters. Overall, the complex interaction between groundwater chemistry and Ra-removing processes implies that in waters with TDS below approximately 3,000 mg L^-1, dissolved solids concentration alone does not fully describe radium's response to hydrochemical conditions, but rather that aquifer-specific examination of Ra removal mechanisms is needed.</p> / Dissertation

Dye-sensitized solar cells (DSCs) convert sunlight to electricity at a low cost. In the DSC, a dye anchored to a mesoporous TiO2 semiconductor is responsible for capturing the sunlight. The resulting excited dye injects an electron into the conduction band of the TiO2 and is in turn regenerated by a redox mediator, normally iodide/triiodide, in a surrounding electrolyte. The success of the iodide/triiodide redox couple is mainly attributed to its slow interception of electrons at the TiO2 surface, which suppresses recombination losses in the DSC. One of the main limitations with the iodide/triiodide redox couple is, however, the large driving force needed for regeneration, which minimizes the open circuit voltage and thus the energy conversion efficiency. In this thesis, alternative redox couples to the iodide/triiodide redox couple have been investigated. These redox couples include the one-electron transition metal complexes, ferrocene and cobalt polypyridine complexes. The use of one-electron redox couples in the DSC has previously been shown to lead to poor photovoltaic performances, because of increased recombination. Cobalt redox couples were here found to give surprisingly high efficiencies in combination with the triphenylamine-based organic dye, D35. The success of the D35 dye, in combination with cobalt redox couples, was mainly attributed to the introduction of steric alkoxy chains on the dye, which supress recombination losses. By introducing steric substituents on the dye, rather than on the redox couple, mass transport limitations could in addition be avoided, which previously has been suggested to limit the performance of cobalt complexes in the DSC. The result of this study formed the basis for the world record efficiency of DSCs of 12.3 % using cobalt redox couples. Interfacial electron-transfer processes in cobalt-based DSCs were investigated to gain information of advantages and limitations using cobalt redox couples in the DSC. The redox potentials of cobalt redox couples are easily tuned by changing the coordination sphere of the complexes, and regeneration and recombination kinetics were systematically investigated by increasing the redox potential of the cobalt complexes. Our hope is that this thesis can be a guideline for future design of new redox systems in DSCs.

New ideas and solutions are necessary to face challenges in the electricity industry. The application of electricity storage systems (ESS) can improve the quality and stability of the existing electricity network. ESS can be used for peak shaving, instead of installing new generation or transmission units, renewable energy time-shift and many other services. There are few ESS technologies existing today: mechanical, electrical and electrochemical storage systems. Flow batteries are electrochemical storage systems which use electrolyte that is stored in a tank separated from the battery cell. Electrochemistry is very important to understand how a flow battery functions and how it stores electric energy. The functioning of a flow battery is based on reduction and oxidation reactions in the cell. To estimate the voltage of a cell the Nernst equation is used. It tells how the half-cell potential changes depending on the change of concentration of a substance involved in an oxidation or reduction reaction. The first flow battery was invented in the 1880’s, but was forgotten for a long time. Further development was revived in the 1950’s and 1970’s. A flow battery consists of two parallel electrodes separated by an ion exchange membrane, forming two half-cells. The electro-active materials are stored externally in an electrolyte and are introduced into the device only during operation. The vanadium redox battery (VRB) is based on the four possible oxidation states of vanadium and has a standard potential of 1.23 V. Full ionic equations of the VRB include protons, sulfuric acid and the corresponding salts. The capital cost of a VRB is approximately 426 $/kW and 100 $/kWh. Other flow batteries are polysulfide-bromine, zinc bromine, vanadium-bromine, iron-chromium, zinc-cerium, uranium, neptunium and soluble lead-acid redox flow batteries. Flow batteries have long cycle life and quick response times, but are complicated in comparison with other batteries. / Nya idéer och lösningar är nödvändiga för att möta utmaningarna i elbranschen. Användningen av elektriskt lagringssystem (ESS) kan förbättra kvalitén och stabiliteten av det nuvarande elnätet. ESS kan användas till toppbelastningsutjämning, istället för att installera nya produktions eller kraft överförnings enheter, förnybar energi tidsförskjutning och många andra tjänster. I dagsläget finns det få olika ESS: Mekaniska, elektriska och elektrokemiska lagringssystem. Flödesbatterier tillhör kategorin elektrokemiska lagringssystem som använder sig utav elektrolyt som är lagrad i en tank separerad från battericellen. För att kunna förstå hur flödesbatteriernas funktioner och på vilket sätt som dem lagrar elektriskt energi är det viktigt att kunna elektrokemi. Flödesbatteriernas funktion är baserad på reduktions och oxidations reaktioner i cellen. Nernsts ekvation används för att kunna uppskatta voltantalet i en cell. Nernsts ekvation säger hur halvcell potentialen ändras beroende av ändringen av koncentrationen av ämnet involverat i oxidations eller reduktions reaktionen. Det första flödesbatteriet uppfanns 1880-talet, men blev bortglömt under en lång tid. Vidare utveckling förnyades under 1950 och 1970-talet. Ett flödesbatteri består utav två parallella elektroder som är separerade utav ett jonbytes membran vilket formar två halvceller. Dem elektroaktiva materialen är lagrade externt i elektrolyt och är införs bara i anordningen under användning. Vanadium redox batteriet (VRB) är baserat på dem fyra möjliga oxidations tillstånden av vanadium och har en standard potential på 1.23 V. Fullt joniska ekvationer av VRB inkluderar protoner, svavelsyra och deras motsvarande salter. Kapitalkostnaden av ett VRB är ungefär 426 $/kW och 100 $/kWh. Det finna andra flödesbatterier som är polysulfide-brom, zink-brom, vanadium-brom, järn-krom, uran, neptunium och löslig blysyre redox flödesbatterier. Flödesbatterier har en lång omloppstid samt en snabb svarstid men är komplicerade jämfört med andra batterier.

<p>In this dissertation several metalloproteins, both metal transport proteins and the classic metalloprotein hemoglobin, are investigated using a variety of biophysical and electrochemical techniques. In each case, thermodynamic measurements provide insight into the role and mode of action of the metalloprotein under investigation. In Chapters 2 and 3, we focus on the thermodynamic properties of the metal while bound by the protein. In Chapter 4, we focus on the thermodynamic properties of the protein with and without the metal. In Chapter 5, we utilize both the metal and the protein as our probe.</p> <p>In Chapter 2, we probe the thermodynamic properties of the heme-bound iron to elucidate the structure-function relationships underlying two important physiological responses of hemoglobin (Hb): the Root Effect of hemoglobin from certain fish and the different nitrite reactivities of hemoglobins from clams. Hemoglobins of some fish exhibit significantly lowered oxygen affinity at low pH, allowing for proton-mediated release of O₂. This phenomenon, known as the Root Effect, serves as a proton-driven pump delivering O₂ to the swim bladders and eyes of the fish. The clam, ,<italic>L. pectinata</italic>, expresses functionally distinct Hb I that transports H₂S and Hb II that transports O₂. These two hemoglobins differ widely in their reactivity with nitrite, a reactant of great importance to the study of vasodilation in humans. The structural basis of the extreme pH-sensitivity of the Root Effect Hbs and the extreme reactivities of the <italic>Lucina Hbs</italic> with nitrite are debated. Focusing on the metal as the probe, we investigate the reduction potentials of these Hbs using spectroelectrochemistry and compare our findings with oxygen binding studies performed by our collaborators. In both cases, our data strongly suggest that steric hindrance is the determining factor governing the respective physiological response of each hemoglobin. </p> <p>In Chapter 3, we again use the metal as the probe to determine the reduction potential of titanium bound by transferrin (Tf). Tf is the human iron transport protein that can also bind titanium. To address the possible mechanisms of titanium transport through the hypothesized redox-mediated Fe₂-Tf transport pathway, a modified spectroelectrochemistry (SEC) method was developed to measure the electrochemical properties of metalloproteins with very negative potentials. However, the reduction potential of Ti₂-Tf is far too negative to access with our system. As an alternative approach, the redox properties of several model titanium and iron compounds were characterized in order to develop a linear free energy relationship (LFER) allowing us to estimate the reduction potential of Ti₂-Tf to be ca. -900 mV vs. NHE. Our results indicate that the reduction potential of Ti₂-Tf is too low to be reduced by biological reducing agents and suggest that transferrin-mediated titanium transport follows a different mechanism than iron transport.</p> <p>In Chapter 4, our focus shifts to the thermodynamic properties of the protein. Some pathogenic Gram-negative bacteria such as <italic>N. gonorrhoeae</italic> steal iron from their human host by expressing a receptor (TbpA/TbpB), which binds the human iron transport protein transferrin (Tf). Once iron crosses the outer membrane, ferric binding protein (FbpA) transports it across the periplasm to the cytosol. Focusing on the protein, we investigated the protein-protein interactions involved in this transport process and the roles that TbpA and TbpB play with the use of an H/D exchange and mass spectrometry based method termed SUPREX. We report herein the first direct measurement of periplasmic FbpA binding to the outer membrane protein TbpA and we demonstrate that both TbpA and TbpB individually can deferrate Tf without energy supplied from TonB, resulting in sequestration by apo-FbpA.</p> <p>In Chapter 5, we extend our investigation of the <italic>N. gonorrhoeae</italic> iron uptake system by using the metal as the probe in one case and the protein as the probe in another case. TbpA, the &#946;-barrel receptor protein that is required for utilization of Fe₂-Tf as an iron source, has a plug domain which we hypothesize binds iron and interacts with FbpA on the periplasmic side of the outer membrane. Utilizing SUPREX to monitor the thermodynamic properties of protein folding, we investigate 1) the possible interactions between the TbpA-plug and FbpA and 2) the ability of the TbpA-plug to bind iron. </p> <p>Focusing on the metal as the probe, we designed an experimental apparatus to investigate the possible thermodynamic effects of the TbpA/TbpB receptor on the release of iron from Tf. We report the use of a competitive iron chelator and equilibrium dialysis allows for the spectroscopic monitoring of iron release from Tf in the absence of FbpA, but in the presence of opaque bacterial membrane preparations containing the receptor.</p> / Dissertation

<p>The research presented here aims to expand our understanding of the structural factors that contribute to selectivity for iron and to iron complex stability in siderophores, as well as iron transport processes in siderophore systems. This work will also investigate the factors that contribute to therapeutic applications of chelating agents, both for chelation therapy and for antimicrobial agents.</p> <p>The thermodynamics of iron(III) binding of a number of molecules, both natural and synthetic, are determined using pH-dependent spectrophotometric titrations and potentiometric titrations . Three of the synthetic siderophore analogs studied here are a tris-hydroxypyridinone and two bis-hydroxypyridinone ligands. A determination of the solution thermodynamics of the iron(III) complex of a water-soluble analog of Brasilibactin A, a membrane-bound mycobactin-type bacterial siderophore is also presented and related to the role of mycobactins in iron uptake of mycobacteria. The thermodynamics of chelation of iron(III) by a synthetic Trojan Horse antimicrobial agent featuring a 3-hydroxy-4-pyridinone moiety were also determined. In these studies, the thermodynamic stability constants of the iron-chelator complexes are determined through a series of spectrophotometric and potentiometric titrations. Also, the redox chemistry of the iron-chelator complexes are investigated using cyclic voltammetry. The structural features that contribute to complex stability in a series of tripodal tris-hydroxamate siderophores using computational techniques is presented, and it is shown that the position of the arm of an exocyclic siderophore system can contribute to differences in complex stability, as can the orientation of the donor group.</p> <p>Kinetics studies of the iron(III) exchange reactions of some polydentate chelators are presented. The study of the kinetics of some reactions of iron complexes featuring hydroxypyridinone donor-group chelators is performed by spectrophotometric kinetics experiments. A determination of the mechanism of proton-driven complex dissociation of a bishydroxypyridinone siderophore mimic is shown. Also, the mechanism of exchange between desferrioxamine B and an iron(III)-trishydroxypyridinone complex is determined through spectrophotometric monitoring of the reaction. The ability of a bidentate hydroxypyridinone chelator to catalyze the exchange of iron(III) from desferrioxamine B to EDTA is explored and the mechanism is determined.</p> <p>Finally, an investigation into the efficacy of chelation therapy treatments to protect from metal toxicity using the nematode C. elegans as a model organism is presented. The model developed therein can also be used as a model for soil remediation of toxic metals using chelating agents.</p> / Dissertation

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