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Item Embargo Cu-P-Se nanoparticles: understanding the reaction pathways for the colloidal synthesis of energy conversion and storage materials(Colorado State University. Libraries, 2024) Neisius, Nathan A., author; Prieto, Amy L., advisor; Finke, Richard, committee member; Herrera-Alonso, Margarita, committee member; Paton, Robert, committee memberNanotechnology has garnered considerable interest over the last 40 years, owing to the unique, desirable properties that can be targeted through established synthetic methods for tuning the size of materials at the nanoscale. As no one single material has properties suitable for a wide range of applications, property driven synthesis has been at the forefront of the nanoparticle (NP) field. Particularly, colloidal NP syntheses provide a large synthetic landscape to explore as a result of the vast synthetic tunability to target specific parameters such as, particle size, morphology, composition, and defects. Although significant efforts have been made toward deciphering the transformation processes of unary and binary NPs, traditionally the colloidal NP field has been driven by a top-down approach, driven by trial-and-error methods, limiting the design of desired, complex materials. Thus, to further progress nanoparticle technology, understanding the underlying transformation processes occurring throughout the formation of colloidal nanoparticles is essential to develop novel materials as well as control the structure/property relationships. The copious amounts of both organic and inorganic interactions, as well as the complexity of capturing the transformation from molecular to the solid-state regime, complicates the reaction landscape for more complex, ternary phases. The purpose of the work included and explained in this dissertation is to develop stoichiometric syntheses for both Cu-P-Se ternary phases, Cu3PSe4 and Cu7PSe6, and to then understand the reaction pathways for an improved retrosynthetic analysis and enable translation of the synthetic knowledge to other systems. Cu-P-Se ternary chalcogenide NPs are of particular interest, owing to the synthetic complexity of navigating a rich phase space with thermodynamically stable binary phases close in energy to the desired ternary phases, as well as applicable structural properties for thermoelectrics, photovoltaics, and battery applications. Therefore, to contribute to the progression of the nanoparticle field the general objectives of this study are, (1) analyzing the transformation of commonly employed precursors and solvents (2) capture the influence of precursor reactivity on ternary phase formation, and (3) perform careful characterization of speciation and final nanoparticles, all of which to establish a full scope of Cu-P-Se nanoparticle formation and the impact of individual synthetic parameters on chalcogenide-based precursors. In Chapter 1, the relevant literature for the following chapters is reported and reviewed to provide the essential background information. This chapter is divided into 6 subsections; (1) Need for renewable energy and how nanoparticles provide solutions, (2) State of nanoparticle synthesis field, current limitations, and progress towards developing a better understanding of nanoparticle reaction pathways, (3) Motivation for exploring the Cu-P-Se phase space, (4) Se reactivity in NP syntheses, (5) Cu3P – the required precursor for Cu-P-Se formation, (6) Dissertation overview, publications, and presentations. The first colloidal NP synthesis report on Cu3PSe4 was developed by a previous group member, Dr. Jennifer Lee, which demonstrated that the phase purity of Cu3PSe4 requires the use of Cu3P NPs and selenium powder (Se) in ODE as precursors. Alternate reaction precursors, and therefore pathways, were disproven throughout this study, leading to the working hypothesis that the interactions of Se and ODE were a necessary step to form active species that then react with Cu3P NPs. Although frequently employed in NP research, and heavily characterized, the implications of the Se/ODE solution on Cu3PSe4 phase formation are still misunderstood. Therefore, the studies presented in Chapter 2 are aimed at probing the Cu3PSe4 reaction landscape and the findings are separated into (1) ex situ reactions that are characterized with molecular and solid-state characterization techniques to determine the implications of the solution dynamics on Cu-P-Se NP phase formation, and (2) how different Se/ODE speciation can be isolated and subsequently favor the alternate, metastable Cu-P-Se phase, Cu7PSe6. A persistent limitation to the previous study is that ODE contaminates the final products, making the findings and analysis of Se/ODE rather difficult to interpret, thus requiring a simplified, cleaner reaction to produce phase pure Cu3PSe4. For that reason, Chapter 3 shifts the direction of the Cu3PSe4 synthesis towards a more stoichiometric, atom-economical reaction by eliminating ODE as the solvent. Rather, a long-chain, aliphatic solvent, octadecane (ODA) is employed that proves to be an operationally inert solvent under the standard synthetic conditions and produces cleaner, phase pure Cu3PSe4 NPs as determined by powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). If ODA was reacting with Se0 powder, the most favorable pathway, commonly cited in literature, is the formation of H2Se and oxidized ODA (alkene). Hence, molecular characterization techniques, nuclear magnetic resonance (NMR, 1H and 13C) and fast-Fourier infrared spectroscopy (FT-IR), were utilized to demonstrate the absence of oxidized ODA species, which is consistent with Se0 preferentially reacting with Cu3P, promoting a more direct reaction pathway. Eliminating the presence of alternate, competing reaction pathways in the ODE synthesis and establishing a near-stoichiometric reaction, allows us to capture the underlying transformation process of Cu3P to Cu3PSe4. From these systematic improvements, we hypothesize that Se0 powder is dispersed in ODA, which promotes a formal eight-electron transfer between Cu3P and 4 Se0. Extracting the synthetic information from the previous chapters to target the metastable Cu-P-Se phase, Cu7PSe6, provides the framework for Chapter 4. Previous methods to isolate Cu7PSe6 are based on traditional, solid-state techniques, where the elemental precursors are ground and subsequently heated to high temperatures (>1000K). Although a colloidal or solution-based synthesis has yet to produce phase-pure Cu7PSe6 particles, attempts explained in Chapter 2 provide a basis on the phase space complexity, where the products consisted of Cu7PSe6 but with thermodynamic byproducts, Cu-Se phases and Cu3PSe4 present. Therefore, an alternate Se precursor, diphenyl diselenide (Ph2Se2), is employed to form the metastable phase, which effectively avoids Cu3PSe4 formation. Importantly, an alternate route to form Cu3PSe4 is with analogous dialkyl diselenide precursor, dibenzyl diselenide, where a key finding is the presence of amorphous phosphorus (P) on Cu1-xSe binaries at low temperatures, which then efficiently reincorporates once the desired 300 ˚C reaction temperature is reached. Thus, in Chapter 4 we investigate why Cu7PSe6 is favored with Ph2Se2 as a precursor, which is predicated on the formation of byproduct species that effectively "trap" P. A proof of concept is explored to further demonstrate the dynamics of P in solution, where the Cu-P-Se phase space can be controllably toggled across by injecting P(5+) species. A drawback for the Cu-P-Se syntheses is the lack of compositional understanding of the pre-synthesized Cu3P NPs, thus further complicating the reaction stoichiometries. Chapter 5 first investigates the previously published synthesis by Liu et al., by thoroughly characterizing the final Cu3P nanoparticles under identical reaction conditions and exploring alternate reaction stoichiometries to reduce the presence of residue precursors. From such, it is determined that the particles substantially deviate from the stoichiometric Cu3P composition, with a Cu:P ratio around 1.5:1.0. Particular focus is also placed on monitoring the degradation of a green phosphorous source, triphenyl phosphite, P(OPh)3. Although triphenyl phosphite (TPOP) has been previously used for transition metal phosphide systems, a lack of systematic investigations leads to questions on the reduction of TPOP en route to forming Cu3P, a formal P(3+) to P(3-) event. Additionally, limited characterization of the final organic byproducts in the original synthesis, begs to question what, if any, byproducts could be contaminating the Cu3P NPs. Therefore, we develop and probe stoichiometric syntheses that isolate phase pure Cu3P NPs to avoid the original 30-fold excess of P. The transformation of hexadecylamine (reductant and ligand) and TPOP were characterized with 1H and 31P NMR to evaluate the role of each en route to forming Cu3P. As this is project is still developing, the necessary future directions are given to systematically approach this problem, with an emphasis on first-step experiments and essential characterization methods to completely grasp the decomposition mechanism of TPOP. Ultimately, this has implications when systematically applying TPOP to alternate transitional metal phosphide NP syntheses, as well as developing more precise Cu-P-Se syntheses. Finally, the work presented herein is summarized in Chapter 6 along with an outlook on the project as a whole. Specifically, future directions and preliminary insight into the underlying reaction pathways and mechanism of Cu3PSe4 formation are explored. Additionally, we explore preliminary data on an analogous material Ag-P-Se, which was plagued for years by the lack of a reproducible Ag-P precursor synthesis that limited our ability to extract the synthetic intuition from the Cu-P-Se system. However, recent literature findings on a potential Ag3P precursor provides promise on synthesizing Ag-P-Se phases in the future, which is critically analyzed to ensure that any bottlenecks in future syntheses are limited. Ultimately, the work provided in the following chapters is aimed at making strides to developing a more in depth understanding of precursor interactions between transition metals and main group elements, as well as properly monitoring such reactions to extract synthetic information to analogous systems. With the knowledge gained on the presented studies, we aspire to contribute to the NP field in order to continually improve NP synthesis and therefore nanomaterials. Finally, this work is supported by NSF Macromolecular, Supramolecular, and Nanochemistry (MSN #2109141).Item Open Access Mesoscopic revelations: studying the shape of AOT reverse micelles(Colorado State University. Libraries, 2024) Gale, Christopher D., author; Levinger, Nancy E., advisor; Krummel, Amber, committee member; Prieto, Amy, committee member; Buchanan, Kristen, committee memberAerosol-OT (AOT) reverse micelles are a quintessential model system for studying nanoconfinement, creating consistent reverse micelles with a repeatable and very small size (~1-10 nm) using just 3 components. These reverse micelles have been used for studying the behavior of water and solutes in nanoconfinement, modeling the behavior of key solutes and proteins in a system more analogous to in vivo work, synthesizing nanoparticles, and even as a vehicle for suspending proteins in a low-viscosity solvent for high quality NMR experiments. Despite their usefulness, AOT reverse micelle's shape is poorly understood, but important to understanding behavior within a reverse micelle. Interfacial properties have been found to be key to many aspects of behavior within AOT reverse micelles and distance from the interface as well as the actual amount of interface present are highly dependent on shape. Therefore, the study of shape is key to a better understanding of AOT reverse micelles and behavior in nanonconfinement. In this work, I develop a series of metrics for shape--- coordinate-pair eccentricity (CPE), convexity, and the curvature distribution--- and apply them to several simulations of AOT reverse micelles. The simulations were designed to test the impact of the force field on the shape and behavior of the reverse micelles, including the first parameterization of AOT into the OPLS force field. The system was extensively checked to ensure equilibration was achieved and the system was not biased by the starting configuration. To aid in the shape analysis, I have developed a model and a formal proof to predict how the CPE changes for an arbitrary shape as it grows to model the shape behavior of general core-shell structures. Additionally, I measured the dipole moment of AOT, the rotational anisotropy decay of water, and several radial distribution functions to provide experimental verification where possible and further explore the behavior of the AOT reverse micelle system. Several key findings emerge from this work. Most notably, I find that AOT reverse micelles are significantly aspherical and non-convex over every force field tested, providing robust evidence that AOT reverse micelles are aspherical at any given moment in time. This provides strong evidence in support of the idea that experimental observations of spherical particles are the result of ensemble averaging. I also observe that the shape at the AOT/oil interface is comparatively more spherical with a "Goldilock's" value of convexity, neither too high nor too low, compared to the water/AOT interface. My model predicts that the CPE should fall with the addition of a shell, here provided by the AOT surfactant layer, suggesting this is largely the result of geometry. There is great variation between simulations and metrics in their dynamics, but in general, the shape appears to change on the order of 10 ns. This provides a useful method of deducing which values may or may not be impacted by shape, based on the time scale. For instance, it can reasonably be said that shape likely has no impact on water dynamics based on the roughly four orders of magnitude difference in the time scales of each process, which is supported by my own findings. Across all metrics studied, there are noticeable differences between simulations, but none of the differences are consistent. I believe this observation has important implications for both the behavior and simulation of AOT reverse micelles. First, this implies that the forces and interactions giving rise to different aspects of the reverse micelle are complex and largely independent, and that there is a disconnect between molecular-level measurements like radial distribution functions and and mesoscopic-level measurements like shape. Second, this implies that any simulation parameterized on one measure has no guarantee that it reproduces any other aspect of the reverse micelle accurately.Item Open Access The development of new synthetic methods and techniques using strong Brønsted bases(Colorado State University. Libraries, 2024) Hoteling, Garrett A., author; Bandar, Jeffrey, advisor; Miyake, Garret, committee member; Menoni, Carmen, committee member; Peebles, Christie, committee memberBrønsted bases are indispensable tools in synthetic chemistry and, as such, deprotonation serves as a ubiquitous mode of molecular activation. By pushing the boundaries of what is possible within the acid-base reaction paradigm, unique synthetic methods and techniques can be developed. The work described in this thesis focuses on gaining a fundamental understanding of strong-base chemistry in efforts towards the development of new base-promoted synthetic methods. Herein, Brønsted bases have been investigated in two ways; 1) the design and application of benchtop-stable precatalyst salts for valuable organic superbases; and 2) the implementation of base-promoted halogen-transfer to develop benzylic oxidative coupling reactions with alkyl (hetero)arenes. This dissertation consists of five chapters. Chapters One and Three provide background and motivation for the work disclosed in this dissertation. Chapters Two, Four and Five represent project areas I have developed with Chapter Two adapted from published work and Chapters Four and Five as drafts of unpublished work. Below is a list of the chapters including a summary of the content for each. Chapter One describes the importance of organic superbases and their relevance to the synthetic community and the Bandar Group as a whole. Presented here will be the various classes of superbases and their unique properties that distinguish them from other classes of bases. Additionally, applications and known limitations to use of these bases will be discussed here. Chapter Two describes work along with Dr. Stephen J. Sujansky on the development of benchtop-stable organic superbase salts and the method for their facile in situ activation. Here, air-sensitive organic superbases form salts when mixed with carboxylic acids that are indefinitely stable on the benchtop. When combined with an epoxide additive, the carboxylate will react to open the epoxide and generate an alkoxide that can neutralize the superbase conjugate acid. This strategy is effective at promoting catalytic Michael-type additions and polymerizations as well as stoichiometric substitution and Pd-catalyzed cross-coupling reactions. This strain-release mechanism not only provides an accessible precatalyst for air-sensitive superbases but provides a new opportunity for controlling base concentration in situ. Chapter Two describes the development of the Bandar Group’s base-promoted halogen transfer research program. The history and importance of this mechanistic platform will be discussed as well as previous reports in the area by our group. In this chapter, the mechanism of base-promoted halogen-transfer is described, which enables the exchange of weakly acidic C–H bonds for C–X bonds that can be subsequently substituted with a pronucleophile in situ. This section will also provide the necessary background and motivation for Chapters Four and Five. Chapter Four describes the development of a new method for the synthesis of benzylic amines from alkyl (hetero)arenes. The development, optimization, and scope investigation of this reaction are described herein. The results of this work represent the first general approach for benzylic C–H amination, functioning on a broad scope of alkyl (hetero)arenes and amine coupling partners. Chapter Five describes the use of base-promoted halogen-transfer to enable alkyl (hetero)arene desaturation. With ethyl- and longer alkyl-substituted arenes, after benzylic halogenation, elimination takes place in the presence of excess base, a process that is competitive iv with the substitution protocol described in Chapter Two. Here, this reactivity has been exploited to develop a general desaturation technique for alkyl (hetero)arenes. Under desaturation conditions, an amine pronucleophile can be added, at which point β-addition followed by subsequent desaturation affords the β -aryl enamine, which is a diversifiable functional handle. This chapter describes the development of desaturation, cascade enamine formation, and the modification of enamine products.Item Open Access Ring-conversion and functionalization of nitrogen-containing heterocycles(Colorado State University. Libraries, 2024) Josephitis, Celena M., author; McNally, Andrew, advisor; Bandar, Jeff, committee member; Chung, Jean, committee member; Reisfeld, Bradley, committee memberPyridines and related azines are ubiquitous in pharmaceuticals and agrochemicals development. Chemist rely on the development of new synthetic methods to modify these heterocycles. Described herein are the development of methods to functionalize azines and convert pyridines and diazines into new heterocycles. Novel hydrogenation and molecular editing strategies were designed and leveraged to accomplish this goal. Chapter one introduces the importance of pyridines and related heterocycles in pharmaceuticals as well as methods to access and functionalize these molecules. Both classical and contemporary methods for functionalization and hydrogenation of pyridines are discussed to provide context for this work. Chapter two describes a novel method to selectively reduce pyridines to dihydropyridines, tetrahydropyridines, and piperidines. This method offers a complementary alternative to current hydrogenation or reduction methods, in which the degree of saturation cannot be controlled, and applies to complex azine starting materials. Chapter three explains the importance of structure-activity relationship (SAR) studies and its implications on the drug-discovery process. It also describes classical and contemporary strategies that apply to SAR diversification including de novo heterocycle synthesis and molecular editing strategies. Finally, chapter four presents a novel method for SAR diversification of pyrimidine containing molecules using a deconstruction/reconstruction approach.Item Embargo Investigations of low-temperature reaction pathways in solid-state reactions(Colorado State University. Libraries, 2024) Tran, Gia Thinh, author; Neilson, James R., advisor; Prieto, Amy L., committee member; Sambur, Justin B., committee member; Chen, Hua, committee memberAdvances in our technology are limited by our knowledge of functional materials, and access to new, possibly better, functional materials is limited by our synthesis methods. This dissertation discusses different synthesis methods for a variety of solid state materials. At the core of this thesis are metathesis reactions i.e. double displacement reactions. Metathesis reactions allow for control over product selectivity and reaction kinetics with choice of the spectating ions. We demonstrate these characteristics with different spectating ions in metathesis and cometathesis (e.g., combining 2 halides) reactions. LaMnO3 was chosen to probe the product selectivity of anion cometathesis towards specific off-stoichiometries of LaMnO3. The metathesis reaction for BiFeO3 illustrates that prediction of thermodynamic selectivity is important, but reaction kinetics remain important as well. Kinetic studies of metathesis reactions that form YMnO3 demonstrate the importance of crystalline intermediates to modulate the reaction rates. The complexity of solid-state kinetics their kinetic regimes within a reaction can be identified through synchrotron X-ray diffraction. We attempted to synthesize LiMoO2 as precursors for the proposed phase LaMoO3. We demonstrate our considerations on the synthesis challenges and offer gained insights into alternative Mo-based systems (nitrides). Aside from metathesis reactions, we employ learned concepts to flux reactions to influence the chemical potential of N2. Synthesis of Li-Fe-O-N and Li-Mn-O-N phases was attempted under the hypothesis that alkali halide salt mixtures solubilize nitrogen and pin nitrogen's chemical potential to prevent N2 formation. Cs2SbCl6 was chosen as a single crystal target to gain clearer insights into the electronic structure. Single crystals were synthesized via hydrothermal synthesis, but preliminary conductivity measurements suggest that Cs2SbCl6 has a photoconductance below our limit detection.Item Embargo Site-selective pyridine functionalization via nucleophilic additions to activated pyridiniums(Colorado State University. Libraries, 2024) Nguyen, Hillary M. H., author; McNally, Andrew, advisor; Bandar, Jeff, committee member; Chung, Jean, committee member; Shoemaker, Mark, committee memberPyridines and diazines are important heterocycles commonly found in pharmaceuticals, agrochemicals, ligands, and various other organic molecules. Pyridines existing in these molecules usually have multiple bonds connected to them that contribute to their reactivity and characteristics. Therefore, there are ongoing efforts l to find new methods to functionalize these heterocycles. Our lab has contributed to this field by developing methods to functionalize pyridines directly from the C–H bond through phosphonium salts or Zincke imines. Chapter One gives an overview of the current methods for pyridine functionalization and their limitations. Chapter Two describes the synthesis of N-Tf Zincke imines and their use for regioselective 3-position pyridine functionalization. Bipyridines and pyridine-piperidine coupled products are accessed through this method. Chapter Three discusses using N-Tf Zincke imines to form 15N pyridines and coupled with deuteration forms higher mass isotopologues. Chapter Four describes the formation of N-alkyl pyridinium salts from N-Tf Zincke imines. This chapter focuses on optimizing the ring-opening of 2-ester pyridines and ring-closing them with amino esters to access pipecolic esters for macrocyclization. Chapter Five highlights direct nucleophile additions to the 4-position of N-Tf pyridinium salts for pyridine functionalization. 4-aminated pyridines are formed with both aliphatic amines and anilines from the C–H bond. The regioselectivity of this amination is controlled by the basicity of the reaction. In addition, 4-NH2 pyridines are achieved through this method by adding benzophenone imine, an ammonia surrogate. This reaction extends to adding in heteroatom nucleophiles including alcohols, thioesters, amides, and sulfonamides.Item Embargo Leveraging bio-based monomers, chemical recyclability, and sustainable polymerization techniques for sustainable polymer synthesis(Colorado State University. Libraries, 2024) Bernsten, Simone Noelle, author; Miyake, Garret, advisor; McNally, Andy, committee member; Reynolds, Melissa, committee member; Reisfeld, Brad, committee memberPolymeric materials have become vital to everyday life since their commercialization. Although polymers are integral to many industries and consumers, their synthesis and use brings with them a myriad of environmental concerns. Unsustainability can arise even before polymer synthesis in that many synthetic polymers are made from petroleum-derived monomers which are inherently nonrenewable. Next, many polymers are synthesized using one or more unsustainable components such as precious metals including iridium and ruthenium. Finally, at the end of a polymer's useful life, options for recycling are limited by the inability to make virgin-quality materials that can be used for the same application as the original polymer. The work described in this thesis aims to address each of these issues. The polymerizations of several bio-based monomers are described. The use of organic photoredox catalysis to enable polymerization represents sustainable synthesis of polymers. Polymers exhibiting chemical recyclability are also investigated, wherein end-of-life materials can be depolymerized and used to produce virgin- quality materials. Ultimately, this work represents a diverse array of methodologies for increasing the overall sustainability of polymeric materials.Item Embargo Charge carrier dynamics of 2-dimensional photoelectrodes probed via ultrafast spectroelectrochemistry(Colorado State University. Libraries, 2024) Austin, Rachelle, author; Sambur, Justin, advisor; Krummel, Amber, advisor; Rappe, Anthony, committee member; Prieto, Amy, committee member; McNally, Andrew, committee member; Brewer, Samuel, committee memberThe integration of hot charge carrier-based energy conversion systems with two-dimensional (2D) semiconductors holds immense promise for enhancing the efficiency of solar energy technologies and enabling novel photochemical reactions. Current approaches, however, often rely on costly multijunction architectures. In this dissertation, I present research that combines spectroelectrochemical and in-operando transient absorption spectroscopy measurements to unveil ultrafast (<50 fs) hot exciton and free charge carrier extraction in a proof-of-concept photoelectrochemical solar cell constructed from earth-abundant monolayer (ML) MoS2. Theoretical analyses of exciton states reveal enhanced electronic coupling between hot exciton states and neighboring contacts, facilitating rapid charge transfer. Additionally, I discuss insights into the physical interpretation of transient absorption (TA) spectroscopy data in 2D semiconductors, comparing historical perspectives from physical chemistry and solid-state physics literature. My perspective encompasses various physical explanations for spectral features and experimental trends, particularly focusing on the contribution of trions to TA spectra. Furthermore, I examine how different physical interpretations and data analysis procedures can yield distinct timescales and mechanisms from the same experimental results, providing a comprehensive framework for understanding charge carrier dynamics in 2D semiconductor-based optoelectronic devices.Item Open Access Understanding selectivity in organic reactions through density functional theory(Colorado State University. Libraries, 2024) de Lescure, Louis Raymond Philibert, author; Paton, Robert, advisor; McNally, Andrew, advisor; Bandar, Jeffrey, committee member; Kennan, Alan, committee member; Herrera-Alonso, Margarita, committee memberThe success of chemical reactions is often expressed through the lens of selectivity, defined as the preference for a desired reaction pathway over an undesirable one. A profound understanding of the rationale behind the selectivity of chemical reactions is crucial for the progression of synthetic methodologies in organic chemistry. Utilizing quantum chemical approximations, density functional theory (DFT) calculations offer unparalleled insights into the electronic structures and mechanisms of reactions, which can be correlated with observed empirical selectivities. This dissertation demonstrates the significant utility of DFT, in tandem with experimental evidence, in elucidating the intricate mechanisms of reactions. Chapter 1 defines the thematic and methods used throughout this thesis. Chapters 2 and 3 detail collaborative work with the McNally group at Colorado State University. Here, we developed innovative methods for the halogenation of pyridines and advanced modifications of pyrimidine rings utilizing redesigned Zincke chemistry. This chapter focuses on the factors influencing the regioselectivity of halogenation processes and provides mechanistic insights into the formation of crucial intermediates. Chapter 3 outlines a joint project with the Race group at the University of Minnesota, where we explored the homologation of benzylic carbon-bromide bonds. Our investigations centered on the ring-opening of phenonium intermediates, a critical step in determining the success of the reaction. Chapter 4 presents a collaboration with the Aggarwal group at the University of Bristol. This chapter examines the nuanced interplay between kinetic and thermodynamic factors that govern the enantioselectivity of the reaction discussed. This comprehensive study underscores the integration of theoretical and experimental approaches in advancing our understanding of complex chemical reactions.Item Embargo The design and synthesis of super reducing organic photocatalysts through mechanistic understanding with application towards unactivated arene activation(Colorado State University. Libraries, 2024) Green, Alexander Richard, author; Miyake, Garret, advisor; Paton, Robert, committee member; Bailey, Travis, committee member; Reisfeld, Brad, committee memberThe work described in this dissertation focuses on the understanding of an organic photocatalyst system through a degradation and mechanistic study, leading to development of a new class of organic photocatalyst and improved application. The design of new organic photocatalysts is crucial for eliminating the need to use rare and expensive ruthenium and iridium that have dominated the field of photoredox catalysis for the past decade. Additionally, most of the catalysts describe here-in operate through a unique two electron, one proton activation mechanism to generate a closed shell species which enables direct quenching towards unactivated arenes such as benzene, without the use of a stoichiometric amount of reductant such as solvated electrons coming from pyrophoric metals. The progress described within this dissertation provides a deeper understanding of tunable organic reductants and their function.Item Embargo Application and effects of metal-based therapeutics on cancer cell lines in tissue culture(Colorado State University. Libraries, 2024) Klugh, Kameron Leigh, author; Crans, Debbie, advisor; Paton, Robert, committee member; Menoni, Carmen, committee memberIn recent years, metal-based drugs have emerged as significant players in the field of therapeutics, leveraging the unique properties of metals to enhance medical treatments. These compounds, incorporating transition metals such as vanadium and platinum, have shown remarkable efficacy in treating various conditions, most notably cancer. The ability of such metals to form complex structures with organic molecules allows for precise targeting and modulation of biological pathways, leading to improved drug efficacy and reduced side effects. Thus, this approach has opened new avenues for designing advanced therapeutics such as vanadium(V) Schiff base catecholate complexes for the treatment of cancer. This thesis aims to explore the potential of non-innocent Schiff base vanadium(V) catecholate complexes as promising agents against glioblastoma, an aggressive form of brain cancer. Two catecholate ligands, 3,5-di-isopropyl catechol and 3,4,6-tri-isopropyl catechol, were synthesized and coordinated to both known and novel vanadium(V) Schiff base scaffolds. Upon testing on glioblastoma T98g cell lines, two of the new complexes, namely [VO(3-tBuHSHED)(TIPCAT)] and [VO(3,5-tBuHSHED)(TIPCAT)], showed remarkable antiproliferative activity. Parallelly, the manuscript delves into the therapeutic applications of platinum-based drugs and how the resistance of platinum-based chemotherapeutics remains a significant challenge. This area of the manuscript identifies the newly discovered role of long non-coding RNAs in platinum-resistance in gastrointestinal cancer treatment. The interaction of these drugs with cellular RNA, in addition to DNA, contributes to this resistance. This manuscript examines the speciation of cisplatin and oxaliplatin, their interactions with DNA and RNA, and the resulting physiological responses of long non-coding RNAs. It identifies aberrantly expressed lncRNAs in platinum-resistant gastrointestinal cancer cell lines, including those from oral cavity, esophageal, gastric, and colorectal cancers. Despite testing different cell lines, similar patterns of aberrant expression compared to normal cells suggest consistent changes in gene expression and cellular pathways. Understanding these changes may help develop new therapeutic strategies for gastrointestinal cancer patients. Together, the vanadium(V) complex investigations and the new insights into platinum-resistance underscore progress in the understanding of the molecular interactions of metal-based drugs, offering pathways to enhance their efficacy and overcome resistance in cancer therapy.Item Embargo Comparative analysis of the role of redox active molecules on bioenergetically active membranes(Colorado State University. Libraries, 2024) Dolan, Connor Cathal, author; Crans, Debbie, advisor; Kennan, Alan, committee member; Chicco, Adam, committee memberTransition metals play crucial roles in various biological processes, with vanadium and manganese being prominent examples due to their redox activity and impact on oxidative stress, mitochondrial function, and disease progression. This manuscript focuses on the role of transition metals, particularly vanadium, in biological functioning, with an emphasis on oxidative stress and mitochondria. Chapter 1 of this thesis discusses the respective role that vanadium plays on oxidative stress and how that influences biological systems. Due to its variety of speciation states and its ability to redox cycle as well as its structural and electronic properties, vanadium can affect biological systems in a variety of ways. These include the generation of reactive oxygen species, lipid peroxidation, protein inhibition, changes in membrane fluidity and potential. DNA damage and cell death. The effects that vanadium has is highly dependent on the speciation and state that they exist in. this can impact the system that is being affected and the outcome. Species such as decavanadate have a unique and profound biological effect. Changing of the species, oxidation state and complexation can alter the biological consequences associated with vanadium. Chapter 2 of this thesis explores the differences and similarities between vanadium and manganese on cardiac mitochondrial dysfunction and oxidative stress. Using varying vanadium and manganese compounds, we investigated the effects they had on isolated cardiac mitochondria using high resolution respirometry and UV-Vis spectroscopy. We found similarities between metal salts on inhibition of respiration as well as significant differences on the metals iii effect on mitochondrial swelling. We further investigated the role of transport proteins on vanadium induced swelling and found that the mitochondrial calcium uniporter played an important role in vanadium induced mitochondrial swelling. We further investigated the differences in species and oxidation state on function. We tested the difference between VV and VIV on mitochondrial swelling and found that VIV led to significantly greater swelling. We also found that there the VO(OH)3 - monomer and dimer were present in both VIV compounds and the Mn2+ ion was present in both manganese compounds. This speciation similarity between compounds may account for some of the similar effects seen within the same metal compounds as well as the differences seen when comparing manganese and vanadium together.Item Embargo Advancements in the chemical recyclability of acrylic polymers through investigation of monomer design(Colorado State University. Libraries, 2024) Gilsdorf, Reid Anthony, author; Chen, Eugene, advisor; Miyake, Garret, committee member; Shores, Matthew, committee member; Herrera-Alonso, Margarita, committee memberDepolymerization is a key avenue of state-of-the-art recycling of polymeric materials. Although many polymers have been investigated for their ability to depolymerize, a subset of polymers has been widely left out of the conversation, polyolefins, or polymers containing C-C bonds in the polymer main-chain. Acrylic polymers are an important class of polyolefins used throughout the world in a variety of applications. One of the key drawbacks of the polymer, however, is their unfavorable depolymerization conditions, requiring high temperatures in expensive reactors. Although much work has been performed on the depolymerization of the most widely used acrylic polymer, poly(methyl methacrylate) (PMMA), there have been few reports on trying to improve upon the recycling methods, such as decreasing depolymerization temperature or gaining control over the depolymerization mechanism. In this work, key mechanistic steps of acrylic polymer depolymerization are investigated to gain fundamental understanding on the limitations faced during depolymerization and try to improve upon them. When poly(α-methylene-γ-butyrolactone) (PMBL) and poly(α-methylene-γ-methyl-γ-butyrolactone) (PMMBL) were investigated, the suppression of side reactions that occurred with PMMA depolymerization were identified, attributed to the pendant lactone tethering radical species together. Employing this tethering effect, the design of new polymers with pendant lactones and lower equilibrium polymerization temperatures (ceiling temperature or TC), was carried out, overall decreasing depolymerization temperatures and improving polymer recyclability. Finally, these new polymers were incorporated into the design of copolymers with PMMA and PMMBL in order to exploit the new polymers' depolymerizability without hindering thermomechanical properties. Overall, this work has shed light onto the importance of polyolefin design in, not just thermomechanical properties, but also polymerization and depolymerization behavior which will benefit the continued development of recyclable-by-design polymers.Item Open Access Thermoplastic electrode surface modifications for use as label-free electrochemical immunosensors(Colorado State University. Libraries, 2024) Martinez, Brandaise, author; Henry, Charles S., advisor; Reynolds, Melissa, committee member; Snow, Christopher, committee member; Tobet, Stuart, committee memberPoint-of-care (POC) testing has grown in popularity in recent years, though most common lateral flow assay (LFA) techniques lack sensitivity and are not quantitative. Electrochemical sensors are a promising alternative, specifically thermoplastic electrodes (TPEs) due to their electrochemical performance and durability while remaining inexpensive. TPEs have been used for a wide variety of applications, but their use as immunosensors has been limited due to difficulty with antibody immobilization. This work seeks to explore techniques for modifying TPE surfaces for use as label-free immunosensors. Chapter 2 examines common antibody immobilization techniques applied to TPEs and determines that the standard existing protocols are lacking. Passive adsorption, EDC/NHS coupling, and chitosan films are used to attach antibodies to the surface. It was found that while each are commonly used in immunosensor fabrication, they have drawbacks that make them unsuitable for TPE immunosensors. Passive adsorption results in unstable antibody attachments leading to inconsistent sensing. EDC/NHS crosslinking is prone to side reactions and again led to inconsistencies in detection of the antigen. Chitosan films were perhaps the most promising, but they passivated the electrode to the extent that detecting the antigen was limited. Chapter 3 moves towards the development and characterization of a new TPE surface modification using aryl diazonium grafting followed by click chemistry to biotinylate electrodes for easy antibody immobilization. A variety of electrochemical techniques and surface characterizations were used to examine the stepwise modification of the TPE surface. It was shown that click chemistry can be successfully used on TPEs to attach various moieties following aryl diazonium grafting. Ethynyl ferrocene was clicked to the surface resulting in a surface coverage (ΓFc) of (1.0 ± 0.2) × 10-10 mol∙cm-2, which is comparable to literature values for similar approaches on commercial carbon electrodes. Streptavidinated antibody was successfully attached as well with a clear change in electrochemical signal upon binding. The method is expanded in Chapter 4 with the use of heterogeneous modifications with multiple functions. The monolayer contains surface bound ferrocene to aid in electron transport, long polyethylene glycol (PEG) spacers to block nonspecific adsorption, in addition to the antibody immobilization point. The modified TPEs were used to successfully detect the nucleocapsid protein of inactivated SARS-CoV-2 virus in buffer solution as a proof-of-concept without the need for a label. The LOD was approximately 6 PFU/mL which exceeds many existing POC tests for COVID-19. The work here expands on the potential applications of TPEs with increased performance and durability over other carbon electrode immunosensors. Potential future directions to expand the sensing capabilities include multiplexed sensors, alternative electrode materials, and expanding to non-antibody based systems.Item Open Access Novel polynuclear copper compounds of halides and pseudo-halides(Colorado State University. Libraries, 1987) Reibenspies, Joseph Henry, author; Anderson, Oren, advisor; Elliott, C. Michael, committee memberMixed-valence compounds (one trinuclear (4) and two polymeric (5,6)) of copper(I,II) containing bridging cyano ligands and the ligands 1 (Pre-H) and 2 (cyclops) have been synthesized and characterized by single crystal X-ray diffraction. For 4, [Cu(1)(μ-NC)]2Cu(CN) · H2O, a= 9.723(2) Å, b = 10.908(2) A, c = 16.184(3) A, ɑ = 97.82(1) ᵒ, β = 103.64(2)ᵒ, γ= 92.21(2)ᵒ. Compound 5 ([Cu(1)(μ-NC)Cu(μ-CN)]n) occurs in three structural modifications. For 5a, a= 7 .755(2) Å, b = 13.179(3) Å, c = 16.508(5) A. For 5b, a= 7.878(2) Å, b = 8.418(2) Å, c = 25.874(4) Å, ~= 94.15(2)ᵒ. For 5c, a= 8.85(1) Å, b = 20.755(8) Å, c = 23.081(8) Å. For 6, [Cu(2)(μ-NC)Cu(μ- CN)·(l/2C6H6)]n, a= 11.667(2) Å, b = 8.962(2) Å, c = 19.895(5) Å,~= 97.58(2)ᵒ. The discrete molecules of 4 contain a trigonal planar [Cu(CN)3]^2- unit, which bridges between two [Cu(l)]+ complexes through two cyano ligands. Each of the polymeric species 5a, 5b, 5c, and 6 consists of a chain of [Cu(CN)2]- units joined by bridging cyano ligands. A cyano ligand also bridges between the copper(I) atoms of the chain and [Cu(1)]+ or [Cu(2)]+ complexes. The structures of three dinuclear copper(II) complexes, in which the Cu(II) atoms are bridged by azido and hydroxo ligands and by either the phenolate oxygen atom of N6OH or N6'OH have been determined by single crystal X-ray diffraction. The compound [Cu2(μ-l,3-N3)(N6O)](ClO4)2·THF (7) crystallized in the orthorhombic space group P 212121, with a= 12.977(2) Å, b = 13.188(3) Å, c = 22.033(6) Å. The compound [Cu2(μ-1,1-N3)(N6'O)](BF4)2·THF (8) crystallized in the orthorhombic space group P21cn, with a= 10.222(2) Å, b = 16.683(4) Å, c = 23.517(7) Å. The compound [Cu2(μ- OH)(N6'O)](BF4)i · THF (9a) crystallized in the monoclinic space group ?21/n, with a= 12.457(3) Å, b = 10.222(3) Å, c = 30.397(10) Å, β= 91.63(2). In these complexes each copper(II) atom is five-coordinate and is bound to three nitrogen atoms and the bridging phenoxo oxygen atom of either N60- or N6'0-. The fifth coordination site on each copper(II) atom is occupied by an atom of the bridging azido or hydroxo ligand. A dinuclear copper(II) complex which contains a bridging iodo ligand and two [Cu(2)]+ moieties has been characterized by X-ray crystallography. [Cu2(2)2I](ClO4) · 2MeOH (10) crystallized in the monoclinic system, space group C2/c, with Z = 4 and a= 21.564(3) Å, b = 11.920(2) Å, c = 14.831(2) Å, β = 96.83(1)ᵒ. Each of the copper(II) atoms in the dimer is coordinated to four nitrogen atoms of ligand 2 and to the bridging iodo ligand. The structures of two phases of the perchlorate salt of the copper(II) complex of 1 and methanol have been characterized by X-ray crystallography. For the room temperature phase {[Cu(1)]C1O4 · 1/2 MeOH}n (11a), a= 23.018(3) Å, b = 6.903(1) Å, c = 22.511(3) Å, β= 105.48(1)ᵒ. For the low temperature phase { [Cu(l)]ClO4 · 1/2 MeOH}i ((llb), a= 6.850(2) A, b = 11.886(3) A, c = 22.303(5) A, a= 75.26(2)0 , β= 88.97(2)ᵒ, γ= 73.38(2)ᵒ. When cooled, the crystalline solid 11 undergoes a reversible structural change. 11a is polymeric in nature, with bridging between copper atoms accomplished by an oxime oxygen atom of ligand 1. 11b is best described as dimeric.Item Open Access Structural variations in metal ion complexes of the ligand EGTA⁴-(Colorado State University. Libraries, 1985) Schauer, Cynthia Karen, author; Anderson, Oren, advisor; Elliott, C. Michael, committee memberStructural studies of several metal ion complexes with the tetraanion of the octadentate ligand, H^4EGTA (3,12-bis(carboxymethyl)-6, 9-dioxa-3, 12-diazatetradecanedioic acid), as well as the structure of H^4EGTA, have been performed by single crystal X-ray diffraction. Of particular interest was the structural basis for the large preference for EGTA^4- to bind calcium ion rather than (K(CaL^2-) ~= 10^6 magnesium ion = 10^6 (K(MgL^2-)), a preference which is similar to that exhibited by intracellular calcium binding proteins. The alkaline earth compounds, Ca[Ca(EGTA)]·(22/3)H2o, Sr[Ca(EGTA)] ·6H2O, Mg[Sr(EGTA)(OH2 )]·7H2o, Mg(Ba-(EGTA)]·(8/3)H2O·(1/3) (CH3) 2CO, and (Mg2(EGTA)(OH2 )6]·5H2O, have been structurally characterized. [Ca(EGTA)]2- is eight-coordinate and utilizes the full octadentate chelating capability of the EGTA^4- ligand. The ether oxygen atoms are bound at a shorter distance than the amine nitrogen atoms. EGTA^4 - is octadentate toward both the strontium and barium ions, which are nine- and ten-coordinate, respectively. The magnesium complex is dinuclear, utilizing each end of the EGTA^4- ligand as a tridentate iminodiacetate ligand; the ether oxygen atoms are not involved in coordination to the metal ion. Structures of EGTA^4 - chelates of metal ions that are commonly used as spectroscopic probes for calcium ion binding sites have also been determined. The cadmium chelate in Sr[Cd(EGTA)]·7H2 o is eight-coordinate, li k e [Ca(EGTA)]^2 -, but the amine nitrogen atoms are bound at shorter distances than the ether oxygen atoms. The metal ions in the structures of tripositive lanthanide ion complexes, Ca[Er(EGTA)(OH2)]2·12H2O and Ca[Nd(EGTA)- (OH 2 )]2·9H2O, are nine- and ten-coordinate, respectively. To further explore coordination modes of the EGTA^4 - ligand with smaller metal ions, where the ligand is not likely to be octadentate, structures of manganese and copper complexes of were determined. Sr[Mn(EGTA)] ·7H2O is isomorphous with the cadmium compound. As a result, the Mn(II) ion is eight-coordinate. The copper complex crystallizes as a dinuclear species, [CU2(EGTA)(OH2)2] ·2H2O, in which each end of the EGTA^4- ligand binds a copper(II) ion in a tetradentate fashion; the ether oxygen atom is bound in the apical position of the square pyramidal coordination sphere.Item Open Access Characterizing the fluorescence intermittency of individual cadmium selenide/zinc sulfide quantum dot clusters with spatially correlated single molecule fluorescence spectroscopy and atomic force microscopy(Colorado State University. Libraries, 2008) Yu, Ming, author; Van Orden, Alan K., advisorIn this thesis, I describe work done to study the optical behaviors of CdSe/ZnS quantum dots, especially the fluorescence blinking behavior of small quantum dot clusters. QDs have unique optical properties that impart several key advantages over molecular dyes. However, when examined at the single-molecule level, QDs emission exhibit novel fluorescence intermittency, or "blinking," behavior. This blinking is believed to be caused by trapping and de-trapping of the photoexcited carriers, causing the QDs to fluctuate between emissive and non-emissive states. A spatially correlated single molecule fluorescence spectroscopy and atomic force microscopy (AFM) apparatus was used to carry out these studies. Single molecule spectroscopy examines the blinking behavior of individual, isolated QDs and QD clusters, while the AFM images the nanometer scale topography of the particles. When multiple isolated QDs were probed simultaneously, the fluorescence behavior was consistent with independent blinking of the individual QDs. However, when close-packed QD clusters were probed, the fluorescence intermittency became much more rapid and intense than could be explained by the summation of multiple particles blinking independently. This suggests when the small QDs aggregate together, they become electronically coupled in some way that enhances the fluorescence blinking. Subsequently, we studied variations of the emission wavelengths of isolated small QD clusters possessing the enhanced blinking behavior. The emission wavelength of the coupled enhanced blinking is red shifted relative to that of normal blinking. We propose that red-shifting in emission is one of the characteristics of electronic coupling in the QD clusters and resulted from the quantum confinement Stark effect. In the following chapters, environment and substrate dependence were also studied. Compared with ambient air, dry nitrogen decreases the population, intensity and/or durations of "on" times. Both CTAB- and Mg 2+-mica substrates quench the fluorescence of single QDs and QD clusters, which is due to the dissociation of electron hole pairs of excited QDs by the electron attractive sites in CTAB molecules and Mg2+ ions.Item Open Access Enantioselective rhodium-catalyzed [2+2+2] and [4+2+2] cycloaddition reactions of alkenyl heterocumulenes: applications to alkaloid synthesis(Colorado State University. Libraries, 2009) Yu, Robert Tzu Hsiang, author; Rovis, Tomislav, advisorAn intermolecular rhodium-catalyzed [2+2+2] cycloaddition of alkenyl isocyanates and internal alkynes has been developed. In the presence of a catalytic amount of [Rh(C2H4)2Cl]2 and P(4-MeO-C6H4)3, the cycloaddition produces substituted indolizinones and quinolizinones with newly formed sp 3-stereocenters. Depending on the alkynyl partners, a CO migration process can be involved during the cycloaddition to furnish cycloadducts possessing vinylogous amide functionality. The use of TADDOL-based phosphoramidite ligands on rhodium allows for the incorporation of terminal alkynes in a highly enantioselective [2+2+2] cycloaddition with alkenyl isocyanates. Terminal alkyl alkynes provide bicyclic lactams, while the use of aryl alkynes provides complementary access to vinylogous amides through a CO migration process. Product selectivity seems to be governed by a combination of electronic and steric factors, with smaller and/or more electron-deficient substituents favoring lactam formation. The synthetic utility is demonstrated in an expedient asymmetric total synthesis of the alkaloid (+)-lasubine II. A highly enantioselective rhodium-catalyzed [2+2+2] cycloaddition of terminal alkynes and alkenyl carbodiimides has been realized. The cycloaddition with aryl alkynes provides complementary selectivity to the reaction previously described using isocyanates. In addition, this reaction demonstrates the feasibility of olefin insertion into carbodiimide-derived metalacycles, and provides a new class of chiral bicyclic amidines as the major products. A new catalyst system has been realized. The use of chiral biphenyl-based phosphoramidite ligands on rhodium provides an efficient cycloaddition between terminal alkyl alkynes and alkenyl isocyanates. The cycloaddition proceeds through a CO migration pathway, and generates various 5-alkyl indolizinone products with high enantiomeric excess. A four-step asymmetric synthesis of indolizidine (-)-209D has been achieved. A highly enantioselective rhodium-catalyzed [4+2+2] cycloaddition of terminal alkynes and dienyl isocyanates has been developed. The cycloaddition provides a rapid entry to highly functionalized and enantioenriched bicyclic azocines. This reaction represents the first [4+2+2] cycloaddition strategy to construct nitrogen-containing eight-membered rings.Item Open Access Combinatorial discovery and optimization of novel metal oxide materials for photoelectrolysis using visible light(Colorado State University. Libraries, 2008) Woodhouse, Michael, author; Parkinson, Bruce, advisorEfficient and inexpensive production of hydrogen from water and sunlight has been the "holy grail" of photoelectrochemistry since Fujishima and Honda first demonstrated the feasibility of the process by illuminating TO2 single crystals with UV light. While it was a great proof of concept, a more suitable material will most likely be an oxide semiconductor containing multiple metals that will each contribute to the required properties of stability, light absorption, and being catalytic for hydrogen or oxygen evolution. Therefore we developed a high throughput combinatorial approach to prepare overlapping patterns of metal oxide precursors onto conducting glass substrates that can be screened for photolectrolysis activity by measuring the photocurrent generated by rasterng a laser over the materials while they are immersed in an electrolyte. A ternary oxide containing cobalt, aluminum and iron, and not previously known to be active for the photoelectrolysis of water, was identified using the combinatorial technique. The optimal composition and thickness for photoelectrochemical response of the newly identified material has been further refined using quantitative ink jet printing. Chemical analysis of bulk and thin film samples revealed that the material contains cobalt, aluminum and iron in a Co3O 4 spinel structure with Fe and Al substituted into Co sites with a nominal stoichiometry of Co3-x-yAlxFeyO4 where x and y are about 0.18 and 0.30 respectively. The material is a p-type semiconductor with an indirect band gap of around 1.5 eV, a value that is nearly ideal for the efficient single photoelectrode photoelectroylsis of water. Photoelectrochemical measurements indicate that the material has a respectable photovoltage but the photocurrent is limited by the slow kinetics for hydrogen evolution. This new cobalt iron aluminum oxide is most likely not the "holy grail" of photoelectrochemistry that we seek, but our methodology gives a rational approach for future materials discovery and optimization.Item Open Access Indirect electrochemical detection of DNA hybridization based on catalytic oxidation of cobalt(II) and concentration gradient formation in redox conducting polymers(Colorado State University. Libraries, 2008) Xue, Di, author; Elliott, C. Michael, advisorSince the new concept was introduced back in 1993, efforts to develop electrochemical methods for detecting nucleic acid hybridization (e.g., DNA) have mushroomed. Compared with nearly all other analytical techniques, electrochemical instrumentation is inexpensive, robust, and relatively simple to operate. The first part of the dissertation (Chapter 1 to Chapter 4) describes the development of a novel electrochemical DNA sensor based on catalytic oxidation of a cobalt bipyridine "mediator molecule" on an ITO electrode. Interaction of the surface bound DNA probe with the DNA target results in formation of hybrid duplex, which subsequently brings redox catalyst molecules from solution to the electrode surface. The mode of selective catalyst binding is intercalation between base pairs of ds-DNA. This surface-bound catalyst "turns on" the redox chemistry of the mediator molecule which is otherwise kinetically inert to oxidation on ITO. With this approach, we demonstrate detection of a 20-mer DNA target oligonucleotide at picomolar concentrations with outstanding signal-to-noise. The second part of our research (Chapter 5) mainly concerns redox polymer films containing permanently locked concentration gradients. Upon redox gradient formation, the conducting polymer displays interesting properties, such as solid diode behavior and electroluminescence. Previous methods explored drying and/or cooling the film to physically immobilize its gradient. Unfortunately, this preservation was temporary, and underwent degradation over time. Our work is aimed to overcome this limitation by covalently attaching counterions to the polymer backbone and thus permanently locking the redox gradients. Both parts of this dissertation utilize heteroleptic metal complexes possessing redox potentials close to zero (vs SSCE). Compounds with highly negative potentials are strongly reducing and highly positive potentials means strong oxidizing capabilities, which exerts strict requirements on supporting electrolytes and solvents, including high impurity, broad potential window as well as exclusion of environmental interference. Thus, the closer the potential to zero (vs SSCE), the more stable (electrochemically) the complex and the easier the electrochemical measurements.