UTSA Electronic Theses and Dissertations
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This collection contains electronic UTSA theses and dissertations (ETDs), primarily from 2005 to present. The collection is not comprehensive; search the UTSA Library Catalog for a complete list of UTSA theses and dissertations.
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Browsing UTSA Electronic Theses and Dissertations by Department "Chemistry"
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Item A tandem Mannich-Michael reaction catalyzed by modularly designed organocatalysts(2014) Algheribe, ShathaA diastereodivergent tandem Mannich-Michael reaction between an α-imino ester with 7-oxo-5-enals was achieved by using modularly designed organocatalyst (MDOs), which were self-assembled from in situ in the reaction media from á-amino acids and cinchona alkaloid derivatives. The tandem Mannich-Michael reaction generated substituted pipecolic acid derivatives. Using pseudo-diastereomeric and pseudo-enantiomeric MDOs, two diastereomers of the tandem Mannich-Michael reaction products as well as their enantiomers may be obtained in good yields, high diastereomeric ratios, and excellent ee values. The all cis -diastereomer of the tandem Mannich-Michael reaction product also undergo further cyclization under the reaction conditions to give azabicyclo[2.2.2]octanes.Item Advancing analytical chemistry through research and education(2011) Haby, GabrielleCountless hours and resources have been devoted to finding ways to make new technologies, established methods more efficient, and testing methods more portable. Similarly, there is much importance placed on finding ways to help students and future researchers excel academically. This thesis is a hybrid of two separate projects. The first takes a closer look into finding ways to reduce the effects of Joule heating in PDMS microchips. The second project examines the effect of incorporating structured group work into Analytical Chemistry at The University of Texas at San Antonio.Item Advancing sample preparation, separation, and detection methods in capillary electrophoresis for the analysis of biologically active compounds(2012) Felhofer, Jessica LeeCapillary electrophoresis (CE) is a versatile analytical technique with a range of separation modes and detection options. Despite many advantages, its limits of detection must be improved for this relatively young separation technique to gain widespread use. Additionally, although the flexibility of CE is a great advantage, the optimization of so many separation parameters can be time-consuming and labor-intensive. The objectives of the projects in this Dissertation are to improve sensitivity and selectivity in the analysis of biologically active and environmentally relevant compounds and to efficiently optimize CE separation parameters. This Dissertation includes a description of three distinct projects. The first project shows that multivariate chemometric techniques are ideal for efficient optimization of separation conditions in CE. The second project demonstrates the importance of rational design of enzyme-modified electrodes for sensitive biosensors. Finally, the third project demonstrates the advantages of a preconcentration and derivatization method that will improve the limits of detection of primary amines. These contributions are important to the long-term goal of developing novel strategies to detect biologically active compounds. The projects also have a significant impact in the field of analytical chemistry, as they contribute to the general advancement of CE as a standard analytical technique.Item Adventures in Catalysis: Development of Transition Metal-Catalyzed Reactions for C-X Bond Formations and High-Resolution Mass Spectrometry Tools for Probing Catalytic Reaction Mechanisms(2024) Silva Villatoro, Roberto NapoleonThe dissertation contained herein will chronical the development of new Pd- and Ni-catalyzed C-X bond forming reactions and the initial development of a new direct-injection high-resolution mass spectrometry (DI-HRMS) tool for detecting organometallic complexes in cross-coupling reactions at synthetically relevant concentrations. Chapter 2 focuses on the development of a Pd-catalyzed, chemoselective O-selective benzylation of 2-quinolinones and 2-pyridones. These classes of N,O-heterocycles are deemed ambident nucleophiles, i.e. they have 2 nucleophilic sites on the same molecule. Though N-alkylation is well established, selective O-alkylation has been largely dependent on the use of stoichiometric Ag salts. In collaboration with the Chemical Process Development team at Bristol Myers Squibb (BMS), we have developed a novel Pd-catalyzed system capable of selectively alkylating the oxygen atom of 2-quinolinone using benzyl bromides as the electrophilic partner. Mechanistic experiments identified a surprising Xantphos mono-oxide Pd(II) η1-benzyl complex as the resting state of our catalyst and responsible for such high chemoselectivity. Expansion of this chemistry to 2-pyridone, a related heterocycle, has proven a much larger task than initially thought. Through optimization, new biphasic reaction conditions have been identified as a promising alternative to achieve a similar chemoselectivity as was observed with 2-quinolinones. Further mechanistic experiments have begun to probe the C-O bond forming step. Chapter 3 stemmed from a curiosity from the work in Chapter 1. The Xantphos mono-oxide Pd(II) η1-benzyl complex was first identified through DI-HRMS. Without this piece of data, the discovery of this intermediate would have been greatly hindered. Given the capabilities of high-resolution mass spectrometers to detect compounds even at low concentrations, we set out to explore other canonical Pd-catalyzed cross-coupling reactions in a similar manner. So far we have explored both Sonogashira reactions and C-O coupling reactions. We have successfully detected multiple on-cycle complexes as well as some surprising off-cycle species. Current works are focused on exploring several protocols for Heck reactions and Buchwald-Hartwig aminations so explore the effects of different conditions on the detectable species. Chapter 4 follows a second collaboration with the Chemical Process Development team at Bristol Myers Squibb. Though Ni-catalyzed C-N coupling has been studied for decades, their applicability to a broad range of substrate classes and large scale reactions has left much to be desired. Using the power of HTE at BMS, we set out to establish a Ni catalyst to unify the reactivity and substrate scopes of previous incarnations while making dramatic improvements to functional group tolerability and scalability. Herein, we have demonstrated a Ni-catalyzed system capable of the C-N coupling of aryl chlorides with anilines and aliphatic amines under markedly milder conditions to those previously reported. We have demonstrated the unique reactivity of our Ni-catalyzed system and are currently pursuing expanding the electrophile scope.Item Alzheimer's Disease: Developing a Mechanistic View via Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry(2017) Kelley, Andrea ReneeAlzheimer’s disease (AD) is a progressive neurodegenerative disorder that has a complex and highly debated etiology. AD pathogenesis theories vary widely between individuals and disciplines. Some prefer the amyloid cascade hypothesis, which asserts that the generation of amyloid-beta (Aβ) -rich senile plaques (SPs) by β-secretase generated mutations of the amyloid precursor protein (APP) are the primary cause of neuronal death and dysfunction leading to dementia. Others gravitate toward the more broad oxidative stress and inflammation hypotheses. To combat this diverseness, analytical and biochemical methods are employed to enhance understanding of the latent mechanisms involved in the disease onset and progression. Mass spectrometry-based molecular composition analysis is of particular significance for use in neurodegenerative disease research. The research presented in this dissertation utilizes novel MALDI-TOF MS developments and sample preparation methods for identifying biological compounds indicative of AD from human post-mortem intact tissue sections, and isolated SPs, and their application in imaging mass spectrometry (IMS). A novel laser-induced in-source decay (ISD) fragmentation method by MALDI-TOF MS is described for the identification of Aβ in complex biological systems. Additionally, bottom-up and top-down proteomics are utilized to develop a thorough survey of the components co-isolated within SPs, including but not limited to Aβ-related peptides, as part of the plaque isolation procedure. Relative magnitude of protein expression is determined by applied MALDI methods. All mass spectrometry methods and sample preparation techniques introduced herein allow for the simplified, yet thorough, analysis of AD- affiliated proteins and peptides. The identities of the proteins found to exist within SPs using the described methods, pave the way for novel AD research in relation to potential molecular targets for future disease therapies.Item An Ab Initio quantum chemical study of cyclic carbon clusters carbon-8 and carbon-10 and their dianionic forms encapsulating a platinum atom(2012) Dee, Douglas MartinAb Initio quantum mechanical computations at the configuration interaction (CI) level including single and double excitations are performed on C8, C10, Pt@C8 and Pt@C10 both neutral and ionic forms. This work reports the effect of Pt encapsulation in these clusters, in terms of binding affinities and geometries. The Pt@C8 and Pt@C10 clusters have binding affinities of 5900 kJ/mol and 7900 kJ/mol, respectively. Pt encapsulation only occurs for dianionic carbon clusters.Item An Extraordinary Journey with Tert-butyl Nitrite and Diazo Compounds: from Nitrile Oxides to N-heterocycles(2022) De Angelis, LucaTerminal diazo compounds undergo smooth nitrosyl exchange with TBN to furnish nitrile oxides in situ after the loss of molecular nitrogen. Nitrile oxides are very useful reactive synthetic dipoles that dimerize to form furoxans or undergoes [3+2]-cycloaddition with alkenes or alkynes to generate isoxazoles and isoxazolines, respectively, in high yields. A different outcome was observed when vinyldiazo compounds and TBN were used. With these diazo compounds the nitrosonium ion intermediate did not undergo loss of dinitrogen, but instead underwent an intramolecular [5+1]-cycloaddition with the diazonium functionality to form 1,2,3-triazine 1-oxides in high yield. Thermal experiments revealed that the triazine 1-oxides are converted to isoxazoles with loss of dinitrogen in high yields. A new method for the synthesis of 5-alkyl and 5-aryl 1,2,3-triazine compounds was developed through the deoxygenation of triazine 1-oxides with trialkyl phosphites under moderate mild conditions. Based on previously report on the inverse electron demand Diels-Alder (IEDD) on symmetrical 1,2,3-triazine, the reaction occurs through a nucleophilic attack either at 4- or 6-position of the triazine core. Our triazine and triazine 1-oxide allow to differentiate those positions. In particular, the site of addition in triazines 1-oxide is the same that for 1,2,3-triazine in IEDD cycloadditions, and its mechanism occurs by C or N addition at 6-position followed by N2O/N2 elimination and cyclization pathways, but triazine 1-oxide exhibited an enhanced rate of product formation. In the triazine 1-oxide core the site of addition is reversed when TMSN3 was applied, which occurred at 4-position to form enoxime. The hydride from NaBH4 undergoes nucleophilic addition at 6-position on both triazine and triazine 1-oxide to obtain α-amino acid ester and 3,6-dihydro triazine 1-oxide, respectively. Reserve selectivity was observed when Hantzsch ester was used, and the hydride underwent selective nucleophilic addition at 4-position only on the 1,2,3-triazine-1-oxide to form enoxime in high yield and dr ratio. Alkoxides chosen as O-nucleophiles preferred the addition at the 4-position of triazine 1-oxide to obtain an oxime as one single geometrical isomer in high yield. Alternative sites of addition were observed on triazine and triazine 1-oxide when thiolate was used as a nucleophile. The site of nucleophilic addition with PhS- is at 6-position of the triazine, while it is at 4-position of the triazine 1-oxide. In the course of the latter investigations, we discovered that 1,2,3-triazine 1-oxides having an alkyl group containing a C-H bond at the 5-position undergo base promoted rearrangement to vinyldiazo oxime compounds that greatly expands access to diverse vinyldiazoacetates. A different reaction with TBN was observed with enoldiazoacetates. No loss of dinitrogen nor intramolecular cycloaddition was observed. Instead, the equivalent nitrosonium ion intermediate after silyl group-transfer generated unique compounds with 1,2,3,4-oxidized centers having vicinal 1-ester-2-diazo-3-keto-4-oxime functionalities. The treatment diazo oxime compounds with a dirhodium catalyst and water produced α-hydroxy carbonyl derivatives which are rapidly air oxidized to 1-ester-2,3-diketo-4-oxime compounds.Item An In-Depth Look at the Pyrophoric Properties of Chemical Weapon Agents and Their Simulants in a Pool Fire Environment(2018) Kidwell, TimothyChemical weapon agents (CWA) in foreign enemy territory represent a threat to local and global stability. An effective long-range destruction method of CWA has yet to be established. In this paper the pool fire properties of CWA (Mustard, Sarin, VX) simulants (2-chloroethyl ethyl sulfide, diisopropyl methyl phosphonate, and triethyl phosphate) were observed and extrapolated to their CWA counterparts in an effort to develop an effective method of destruction. Two pool fire apparatus were constructed. From those apparati it was discovered only 2-chloroethyl ethyl sulfide combusts under our conditions. Triethyl phosphate was combustible under extreme conditions while diisopropyl methyl phosphate could not sustain combustion once ignited. Using the work previously done by Blinov, Khudiakov, and Hottel several small scale steady volume pool fires of 2-chloroethyl ethyl sulfide and methanol were completed. The work was accomplished in hopes of establishing a Blinov-Khudiakov pool fire curve model that can predict simulant fires to help model large scale CWA pool fires.Item An Investigation of the Energy Levels of the Pt2+ Ion Using Multi-Reference Spin-Orbit Configuration Interaction Theory(2022) Belmares, Jacob GrayThis project sought to obtain more info for NIST's Atomic Spectra Database (ASD) by generating energies of the Pt2+ ion, whose current data is sparse. We used the COLUMBUS suite of codes to perform this task and calculated the energy levels and transition moments of Pt2+ under various symmetries using multi-reference spin-orbit configuration interaction calculations.Item Application of Organic Synthesis to Study Bioactive Natural Products from Artemisia annua: Dihydroartemisinic Acid to Artemisinin Mechanism and Arteannuin B Mode of Action(2024) Varela, KaitlynArtemisia annua (A. annua, qing hao, sweet wormwood) is a leafy plant that is traditionally used as an herbal medicine. A. annua is harvested to extract the anti-malarial compound, artemisinin, as well as other bioactive natural products from its leaves. Due to its wide range of applicability to human health, research surrounding the bioactive natural products produced by A. annua are ongoing to best replicate and utilize medicinal compounds isolated from the plant. Artemisinin, arteannuin B, artemisinic acid, and dihydroartemisinic acid are among several major sesquiterpenoids within the plant that are known for their therapeutic value. The biosynthesis of artemisinin within A. annua is highly controversial, with scientific evidence supporting a spontaneous, non-enzymatic process, as well as an enzymatic process. This research aims to investigate the spontaneous, non-enzymatic conversion of dihydroartemisinic acid to artemisinin using mechanistic studies. Deuterated isotopologues of dihydroartemisinic acid were synthesized to develop a thorough mechanistic understanding using mass spectrometry and calculated kinetic isotope effects. The role of the monoalkene in dihydroartemisinic acid was studied to determine whether a desaturated dihydroartemisinic acid analog would undergo endoperoxide formation. Finally, the natural product arteannuin B (isolated from A. annua) was used in adduction and inhibition studies on two cysteine proteases to determine its viability as a cysteine protease inhibitor and its mode of action. Through these experiments, this research aims to apply organic synthesis to study bioactive natural products from Artemisia annua.Item Assessment of Alpha-amino-beta-carboxymuconate-εpsilon-semialdehyde Decarboxylase (ACMSD) Inhibitors(2022) Udokwu, ChinedumThe biodegradation of tryptophan in the kynurenine pathway provides quinolinic acid (QUIN), the precursor for the de novo synthesis of NAD+. This occurs through, α-amino-β-carboxymuconate-ε-semialdehyde (ACMS) which, nonenzymatically decays to form QUIN. ACMSD catalyzes the breakdown of ACMSD to 2-AMS. By inhibiting the α‑amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD), more ACMS cyclizes to form QUIN which increases NAD+ levels. In this study, diflunisal derivatives were used to assess the inhibition of ACMSD. Some of these derivatives were shown to have stronger inhibitions than diflunisal. The crystal structure of ACMSD in complex with the inhibition compounds showed similar binding modes with diflunisal but different second ring positioning. In this study, two diflunisal derivatives showed half-maximal inhibitory concentration (IC50) values lower than KURA-ACMSD 17 (KA17), a previous diflunisal derivative with an IC50 values of 1.32 ± 0.07 μM. The two compounds, PA-62 and PA-67 had IC50 values of 1.29 ± 0.17 μM and 0.66 ± 0.11 μM against the human ACMSD respectively. This was the first sub micromolar concentration from the diflunisal derivatives. This shows that the diflunisal derivatives can be improved upon to create a more potent inhibitor. The crystal structures of ACMSD in complex of with the diflunisal inhibitors were determined through X-ray crystallography using a bacterial version of the enzyme that had been previously demonstrated to share a similar active site architecture with the human ACMSD. This provided a foundation for understanding the inhibitory mechanism at the molecular level.Item Cocrystallization of thioamide and bipyridine-type molecules(2008) Ellis, Carol A.Cocrystallization experiments conducted between thiocarbamide derivatives, (E)-O-alkyl N-aryl-thiocarbamide, of the general formula ROC(=S)N(H)R', for R = Me, Et and iPr and R' = Ph and C6H4NO2-4 containing an active pharmaceutical ingredient (API), i.e., -C(=S)-N(H)-, and bipyridine-type molecules, e.g., 4,4'-bipyridine, trans-1,2-bis(4-pyridyl)ethene and 1,2-bis(4-pyridyl)ethane, showed the formation of stable binary 2:1 cocrystals, e.g., {[ROC(=S)N(H)R']2(bipyridine-type molecule)}. Novel species were formed by grinding and solvent drop grinding methods, and characterized by X-ray powder diffraction methods. Five 2:1 cocrystals were isolated as single crystals by slow evaporation methods and subjected to full characterization by spectroscopic and X-ray crystallographic methods. This study shows that the eight-membered {...H-N-C=S}2 homosynthon found in the parent thiocarbamides is readily disrupted in the presence of bipyridine-type molecules to enable the formation of the stable heterosynthon, {N...H-N}.Item Computational Studies of the Formation of Imidazo[1,2-α]Pyridines Catalyzed by a Copper-Based Metal-Organic Framework(2022) Garza-Herrera, Efrain SebastianThe purpose of this project is to corroborate a plausible reaction mechanism that was proposed for the synthesis of imidazo[1,2-α]pyridines catalyzed by the Cu(BDC) (BDC = 1,4-benzenedicarboxylate) metal-organic framework (MOF) by generating approximate reaction profiles for the uncatalyzed and catalyzed reaction pathways. Geometry optimization calculations for the intermediates were performed using the B3LYP functional, 6-311G** (H, C, N, O atoms) basis set, and the LANL2TZ(f) (Cu atoms) effective core potential (ECP) and basis set combination. The energy differences of the intermediates were calculated, with and without the presence of the catalyst, and relative energy diagrams were generated. The presence of the MOF catalyst lowered the relative energies of key intermediates in the reaction pathway by a substantial amount. The stabilization of these key intermediates approximately quantifies the viability of the reaction pathway in the proposed mechanism.Item Confocal Microscope Studies of Polycyclic Aromatic Hydrocarbons and Semiconductor Single Nanoparticles(2023) Yu, ZiqiWith the rapid development of fluorescence microscopy, one could obtain an in-depth investigation of conjugated material morphology and photophysical properties in a solid state. The trimeric perfluoro-ortho-phenylene mercury compound (Hg3) and polycyclic aromatic hydrocarbon (PAH) derivatives show unique supramolecular interactions in solution and solid-state. Inspired by the previous work of Gabbai and coworkers, we found that the addition of Hg3 to alkyl-substituted derivatives of hexa-peri-hexabenzocoronene (HBC) solution leads to a noticeable red-shifting of the maximum absorbance of the HBC chromophore and a dramatic decrease in HBC luminescence as well as an appearance of phosphorescence from the Hg triad (c.a. 577 and 625 nm), which is consistent with the formation of aggregates. In transient absorption spectroscopy, the HBC-Hg3 complex reveals the triplet localizes on the HBC chromophore. A confocal laser scanning microscope is used to characterize the morphology and lifetime distributions of the HBC-Hg3 aggregates. Inorganic perovskite materials have recently attracted enormous attention because of their high absorption coefficients and facile solution processability. However, the charge transfer (CT) efficiency between light harvesters and hole/electron transporting materials is vital in improving the power conversion efficiency of perovskite photovoltaic devices. To further understand the interfacial dynamic process and quenching mechanism, a deeper investigation and further study of the electron transfer reaction between the excited perovskite nanocrystals and electron acceptors at the single-particle level is required. From the dynamical and statistical study, we found that by adding a quencher, the single nanocrystals are prone to localized at the off state, corresponding to a lower lifetime. Furthermore, single nanoparticle studies reveal how the trap state concentrations control the perovskite exciton dynamics and the fluorescence quenching limited by the nonradiative photoionization process.Item Design and Characterization of Functional Metal-Organic Frameworks for CO2/CH4 and C2H2/CH4 Separation(2017) Alduhaish, Osamah M.Metal Organic Frameworks (MOFs) compared to traditional porous materials, such as zeolites, and active carbons, are the recent class of crystalline porous materials with many special properties, including high surface areas and large internal pore volumes which result in maximum gas-adsorption capacity at high pressure. MOFs can be assembled from a diverse set of organic linkers and metal ions, which can expose selectivity for particular gases and other analytes. The coordination obtained from organic linkers can provide more flexibility in the final framework structure compared to other robust materials based on pure inorganic composition such as zeolites. This flexibility enables a dynamic behavior in porous coordination network and thus facilitates structural modification without loss of structural integrity. The development of MOFs for gas separation, several factors (porosity and rigidity of the framework and controlling pore size, and thermal stability) play roles. This dissertation work deals with the development of new strategies towards interpenetration control and tunability of pores to enhance the selectivity of both CO2 and C2H2 impurity removal from CH4, and other hydrocarbon mixtures resulting from industrial processes. In this study, critical to the design process, polyhedron-based metal-organic frameworks were used to direct self-assembly of unique MOF structures. Furthermore, mixed ligand tactics along with hetero-functional and multi-carboxylate ligands were applied as a different source of MOF versatility. The investigation of these materials reveals different crystal sutures having a unique selectivity for CO2 and C2H2 over CH4 during the gas separation, particularly at room temperature.Item Design, synthesis and polymerization of highly branched pseudodendrimers through tandem reactions and kinetics measurements of pseudodendrimeric polymerization(2008) Wang, JunyanDendritic polymers exhibit some unique properties which clearly distinguish them from other polymers. Their fascinating structural features have made them one of the best candidates for nanotechnology applications. The synthesis of dendrimers involves multi-step procedures including protective group technology. This results in high cost and accessibility only in small quantities. Hyperbranched polymers can be prepared in one-pot polymerization of ABn monomers, however, a competitive reaction between the formations of linear chains and branching occurs, and consequently the structure is imperfect and the control over layers or generations vanishes. Pseudodendrimers are intermediate polymers between hyperbranched polymers and dendrimers. Similar to dendrimers, they are also fully branched structures. But they are not perfectly symmetric, like hyperbranched polymers. Pseudodendrimers may serve as potential replacements for dendrimers. We have developed a single-reaction synthesis of pseudodendrimers. The overall goals of this project are to optimize the synthesis of pseudodendrimers, measure the kinetics of pseudodendrimer polymerization, show that pseudodendrimers have similar properties to dendrimers. The careful design of an ABB' monomer leads to higher branching by virtue of a tandem reaction that increases the reactivity of linear units during polymerization. Our work has shown that 6-amino-3-bromophthalide leads to a highly branched polymer via bromohydrin decomposition during polymerization, giving polymers of Mn of 3000 and a polydispersity index of 1.03. Our findings indicate a degree of branching of 0.84, suggesting the polymerization is a single-reaction synthesis of a pseudodendrimer. Polymerization of analogous polymers confirms our proposed intermediate. The kinetics of the model reactions show that the reaction is first order in benzylamine. We determined that the energy of activation (Ea) for the first addition reaction is 8.9 kcal mol-1 and Ea for the second addition reaction is 6.6 kcal mol-1. These data imply that dimer formation step is the rate limiting step of the two-to-one addition reaction. The reaction rate of linear units (product are dendritic units), kt, is about 30 times faster than the reaction rate of terminal units (product are linear units), kd. These differences of reactivity satisfy our designed requirements for the 3-bromophthalide-based ABB' monomer, will lead to enhanced DB, and consequently form pseudodendrimers on polymerization.Item Design, synthesis, and gas separation of metal-organic frameworks(2014) Alawisi, HussahMetal-organic frameworks (MOFs), also known as porous coordination polymers (CPs), are a new class of crystalline and porous materials in which metal ions or clusters (usually transition metals) work as nodes and link by a variety of organic compounds as bridging ligands which work as linkers. Due to the wide variety of organic and inorganic components which are the basic unit to build MOFs, there is the opportunity to synthesize a number of MOF crystals that have a variety of structures with exceptional properties and can be applied in important applications. Gas sorption is one of the applications of MOFs, and is potentially useful in gas storage and separation. We have discovered two new microporous MOFs, which is UTSA-72 and UTSA-73. UTSA-72 was synthesized by mixing Zn(II) ions with (H4PTTB), which is tetracarboxylates multi-donate organic linker to form two-dimensional MOF. The X-ray crystal structure of UTSA-72 showed that UTSA-72 has the formula [Zn2 (PTTB)(DMF) 2]n.(DMF) n; in addition, X-ray illustrate that UTSA-72 has a small pore size. The measurements of the surface area for the UTSA-72 confirmed that this MOF has permanent porosity. As a result of this porosity, this MOF has the ability to be highly selective toward small gas molecules. The activated UTSA-72a exhibits moderately high selective gas separation for C2 H2 /CH4, CO2 /CH4, and CO2 /N2 at room temperature. In addition, we have presented another new microporous MOF which is UTSA-73. This MOF was synthesized by mixing Zn(II) ions with (H4 BPTT), which is tetracarboxylates multi-donate organic linker, to form two-dimensional MOF. The crystallographic data show that this MOF is in the space group (P21/n); moreover, the two zinc atoms are five coordinated, in which four of them are from the organic ligand, and the fifth is from the DMF. Furthermore, we studied the gas sorption for this MOF as an application, and it showed that The activated UTSA-73a exhibits permanent porosity and moderately high selectivities for CO2 /N2 and CO2 /CH4 gas separations at room temperature because of the small pores within the framework.Item Developing Functional Mimics of Active Sites of Metalloenzymes Involved in Carbohydrate Binding and Transformation(2018) Stewart, Christopher DavidCarbohydrates comprise the most abundant class of organic molecules in the biosphere and find crucial roles in a vast number of biological functions. Despite their overwhelming importance, the study of metalloenzymes involved in carbohydrate metabolism such as Xylose/Glucose isomerase (XGI) using synthetic models remains largely unexplored. Towards the goal of expanding the scientific knowledge surrounding the interaction and reactivity of carbohydrates with metal complexes, new biologically relevant transition metal complexes as carbohydrate binding models have been synthesized and fully characterized using several techniques including single crystal X-ray crystallography. Several new ligands were developed to provide a coordination environment around the metal centers very similar to those found in the active site of metalloenzymes. Nearly all of the metal complexes of these new ligands were found to be soluble in common polar solvents including water. The binding of substrates such as D-mannose, D-glucose, D-xylose and xylitol with the water-soluble complexes in different reaction conditions were investigated. The metal complexes showed coordination ability towards the applied substrates. Even in the presence of stoichiometric excess of the substrates, the complexes form only 1:1 (complex/substrate) molar ratio species in solution. Apparent binding constants, pKapp, values between the complexes and the substrates were determined and specific mode of substrate binding has been proposed. Syntheses, characterizations and detailed substrate binding study using spectroscopic techniques and single crystal X-ray diffraction are reported.Item Development and characterization of novel substrates for biosensing applications(2016) Evans, ElizabethThe research plan herein described integrates the rational design, development, optimization, and application of novel biosensors to contribute to the scientific community. Specifically, the projects focuses on two main factors including being cost-effective when compared to bulky and expensive benchtop instruments and having improved analytical performance over other related biosensors. In accordance, paper analytical devices were thoroughly investigated. Microfluidic paper-based analytical devices (µPADs) are a rather new analytical tool, being in existence for less than a decade. Utilizing a paper platform, µPADs are inexpensive, portable, require small sample volumes, and are user-friendly. The research plan consists of three projects with a common theme of utilizing a paper substrate. The first section of the research strategy focuses on selecting the optimal paper type to fabricate µPADs. Next, nanotechnology was incorporated into µPADs to improve the analytical performance in the detection of three clinically-relevant analytes. After successfully exploring colorimetric detection on paper devices, the focus was then moved to a more advantageous detection method. A novel multilayer paper device was designed and optimized for the electrochemical detection of different clinically-relevant analytes. The research portfolio closes with a promising four-zone electrochemical paper-on-paper device that can be multiplexed for simultaneous detection of different analytes simply by the flip of a switch.Item Development of Functional Metal-organic Frameworks with Microposrosity for Selective Gas Separation(2022) Shi, YanshuAmong industrially important gas separations, carbon dioxide removal from pre-combustion and post-combustion processes and industrial paraffin/olefin separation are two essential parts, which are critical for reduction of carbon emissions and manufacturing of many chemicals, fuels, and materials. Conventional gas separation is carried out through liquid extraction or cryogenic distillation, which is both energy-intensive and costly. Adsorptive gas separation is a more energy efficient and economical technique. Recently, the development of CO2-selective adsorbents has shown promising application in hydrocarbon purification and CO2/N2 separations. Traditional adsorbents traditionally suffer from unsatisfactory uptake and poor selectivity for adsorptive gas separation in practice. In this regard, the development of next-generation adsorbents should be capable of realizing high selectivity and large uptake amount (working capacity) for advanced gas separation. The recent development of metal-organic frameworks (MOFs), constructed from the coordination of metal centers and organic linkers, have demonstrated great potentials as selective gas adsorbents. The construction of MOFs is rich in diverse compositions, designable structures, and tunable pore engineering. These properties render MOFs as excellent materials for gas storage and separation applications. MOFs can differentiate certain components like olefin or CO2 from other gas components, such as nitrogen and methane. Up to now, more than 100,000 MOFs have been reported, but only a small portion of MOFs can realize molecular sieving gas separation for adsorptive techniques. In this dissertation, several MOFs have been studied for highly selective CO2 capture: 1) partially desolvated Cu-F-pymo for selective adsorption of CO2 over C2H2; 2) fully activated Cu-F-pymo for size-sieving separation of CO2 from CH4 and N2; 3) a zirconium-based low-cost MOF of Zr-FA for molecular sieving CO2 Separation. Two MOF adsorbents are also developed for ethylene purification from ethane: 1) an ethylene-selective UTSA-280 was prepared from mechanochemical synthesis with high sieving selectivity of C2H4 from C2H6. 2) An ethane-selective Sc-abtc for functional sites favored C2H6 Adsorption over C2H4. These microporous metal−organic framework (MOF) materials have been proposed to systematically study their potential applications in gas adsorption and separation.