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Computational Studies of C–H/C–C Manipulation Utilizing Transition Metal Complexes
Density Functional Theory (DFT) is an effective tool for studying diverse metal systems. Presented herein are studies of a variety of metal systems, which can be applied to accomplish transformations that are currently difficult/impossible to achieve. The specific topics studied utilizing DFT include: 1) C–H bond activation via an Earth-abundant transition metal complex, 2) C–H bond deprotonation via an alkali metal superbase, 3) and amination/aziridination reactions utilizing a CuI reagent. Using DFT, the transformation to methanol (CH3OH) from methane (CH4) was examined. The transition metal systems studied for this transformation included a model FeII complex. This first-row transition metal is an economical, Earth-abundant metal. The ligand set for this transformation includes a carbonyl ligand in one set of complexes as well as a phosphite ligand in another. The 3d Fe metal shows the ability to convert alkyls/aryls to their oxidized counterpart in an energetically favorable manner. Also, “superbasic” alkali metal amides were investigated to perform C—H bond cleavage. Toluene was the substrate of interest with Cs chosen to be the metal of interest because of the highly electropositive nature of this alkali metal. These highly electrophilic Cs metal systems allow for very favorable C—H bond scission with a toluene substrate. Finally, the amination and aziridination of C–H and C=C bonds, respectively, by a CuI reagent was studied. The mechanism was investigated using DFT calculations. Presently, these mechanisms involving the use of coinage metals are debated. Our DFT simulations shed some insight into how these transformations occur and ultimately how they can be manipulated.
Computational Studies of Selected Ruthenium Catalysis Reactions.
Computational techniques were employed to investigate pathways that would improve the properties and characteristics of transition metal (i.e., ruthenium) catalysts, and to explore their mechanisms. The studied catalytic pathways are particularly relevant to catalytic hydroarylation of olefins. These processes involved the +2 to +3 oxidation of ruthenium and its effect on ruthenium-carbon bond strengths, carbon-hydrogen bond activation by 1,2-addition/reductive elimination pathways appropriate to catalytic hydrogen/deuterium exchange, and the possible intermediacy of highly coordinatively unsaturated (e.g., 14-electron) ruthenium complexes in catalysis. The calculations indicate a significant decrease in the Ru-CH3 homolytic bond dissociation enthalpy for the oxidation of TpRu(CO)(NCMe)(Me) to its RuIII cation through both reactant destabilization and product stabilization. This oxidation can thus lead to the olefin polymerization observed by Gunnoe and coworkers, since weak RuIII-C bonds would afford quick access to alkyl radical species. Calculations support the experimental proposal of a mechanism for catalytic hydrogen/deuterium exchange by a RuII-OH catalyst. Furthermore, calculational investigations reveal a probable pathway for the activation of C-H bonds that involves phosphine loss, 1,2-addition to the Ru-OH bond and then reversal of these steps with deuterium to incorporate it into the substrate. The presented results offer the indication for the net addition of aromatic C-H bonds across a RuII-OH bond in a process that although thermodynamically unfavorable is kinetically accessible. Calculations support experimental proposals as to the possibility of binding of weakly coordinating ligands such as dinitrogen, methylene chloride and fluorobenzene to the "14-electron" complex [(PCP)Ru(CO)]+ in preference to the formation of agostic Ru-H-C interactions. Reactions of [(PCP)Ru(CO)(1-ClCH2Cl)][BAr'4] with N2CHPh or phenylacetylene yielded conversions that are exothermic to both terminal carbenes and vinylidenes, respectively, and then bridging isomers of these by C-C bond formation resulting from insertion into the Ru-Cipso bond of the phenyl ring of PCP. The QM/MM and DFT calculations on full complexes …
Computational Studies of the Photophysical, Structural, and Catalytic Properties of Complex Chemical Systems
Computational chemistry employs mathematical algorithms, statistics, and large databases to integrate chemical theory with experimental observations. Computational modeling allows us to make predictions concerning molecular properties and reactivity that ultimately lead to accurate assessment of the most important fundamental properties of chemical systems. Advances in theoretical techniques and computer power have dramatically increased the usefulness and importance of computational chemistry as a complement to experimental studies. This is especially relevant to catalytic reactions of industrial importance as well as the analysis of structural properties and the resulting spectroscopic phenomena in what are often otherwise counterintuitive models. This dissertation is a representation of the research I performed during my years as a graduate student in the Chemistry Department at the University of North Texas. My research has examined novel carbenes as efficient organocatalysts, structure-based design and optimization of small molecule drugs, and surveying methods to accurately describe structure and bonding and catalytic abilities of inorganic and organometallic systems. The works presented herein have been published or are awaiting submission to peer-reviewed scientific journals. A variety of computational techniques were employed in studying metal-mediated catalysis and organocatalysis as well as the structural and photophysical properties of systems containing closed-shell transition metal ions.
Computational Study of C−H/C−C Activation and Functionalization with Nitrene, Carbene and Related Complexes
This dissertation involves inorganic/organometallic catalysis models, in particular the functionalization of carbon-hydrogen and carbon-carbon bonds. Computational methods have been utilized to better understand the factors affecting the kinetics and thermodynamics of C−H and C−C bond activation/functionalization in this dissertation. Chapter 2 investigates methane C−H activation with a diiminopyridine nitride/nitridyl complex of 3d transition metals and main group elements via three competing pathways: 1,2-addition/[2 + 2] addition, insertion and H-atom abstraction/proton coupled electron transfer. Chapter 3 investigates a transition metal catalyzed C=C bond functionalization involving C−N bond formations to synthesize aziridines from aromatic and aliphatic alkenes. The study focuses on anionic 3d transition metal (M = Mn, Fe, Co and Ni) triphenylamide-amine complexes with nitrene active intermediates for the aziridination reactions. Chapter 4 investigates a disphenoidal Ni(II) azido complex participating in intramolecular C−H functionalization and amination via a putative Ni nitridyl intermediate and a 1,2-addition/[2 + 2] addition pathway. In Chapter 5, methane oxidative addition to the Cp*ML (Cp* = η5-C5Me5; M = Co, Rh, Ir , L = CO, PMe3) motif is compared and contrasted when the classic CO and PMe3 ligands are replaced with the cyclic alkyl(amino) carbene (CAAC) as ancillary ligands.
Computational Study of Intermolecular Interactions in Complex Chemical Systems
This work discusses applications of computational simulations to a wide variety of chemical systems, to investigate intermolecular interactions to develop force field parameters and gain new insights into chemical reactivity and structure stability. First, we cover the characterization of hydrogen-bonding interactions in pyrazine tetracarboxamide complexes employing quantum topological analyses. Second we describe the use of quantum mechanical energy decomposition analysis (EDA) and non-covalent interactions (NCIs) analysis to investigate hydrogen-bonding and intermolecular interactions in a series of representative 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) ion pairs extracted from classical equilibrium and non-equilibrium molecular dynamics simulations. Thirdly, we describe the use of multipolar/polarizable AMOEBA force field to study the extraction of benzene from a gasoline model employing 1,3-dimethylimidazolium tetrafluorobrorate, [DMIM][BF4], and ethylmethylimidazolium tetrafluorobrorate, [EMIM][BF4]. Fourthly, we cover the recent improvements and new capabilities of the QM/MM code "LICHEM". Finally, we describe the use of polarizable ab initio QM/MM calculations and study the reaction mechanism of N-tert-butyloxycarbonylation of aniline in [EMIm][BF4], and ground state destabilization in uracil DNA glycosylase (UDG).
A Computational Study of Palladium (II) bis(NHC) Complexes and a Computational/Experimental Study of Gold (I) bisADC Complexes Utilizing Non-Covalent Interaction for Catalysis
Carbene ligands over these years have become a heavily utilizes and effective ligand for catalysis. The diamino carbene class of ligands are slightly less understood. The effects of bis(carbene) ligand structures of palladium (II) catalysts were investigated using the ETS-NOCV method. The results showed that the amount of π-backbonding played a major role in the rate of the reaction for these NHC complexes. The amount of pi acceptance from the ligand increased in correlation to the length of the methylene linkage in the ligand back bone resulting in increased catalytic activity. The ETS-NOCV method was used to determine the deformation densities that had a contribution to this interaction based on visual interpretation. The percent contribution of pi interactions provided a linear correlation to the natural log of the initial reaction rate, indicating that π-backbonding plays a crucial role in the overall catalytic activity of the palladium complexes. Gold (I) bis acyclic diamino carbenes (ADCs) were investigated for the possibility to be strong hydrogen bond catalysts. The ligand motif of the gold (I) bisADCs were found to be analogous thiourea compounds. Based on NBO analysis there were some improvements to hydrogen bond donicity in comparison to thioureas with the same functional group. The complexes were analyzed for hydrogen bond interactions and polarizations interactions between simple nitroolefin substrate and the catalyst using ETS-NOCV. Results showed that the compounds can form a stable hydrogen bonding system and activate the substrate. This capability is tunable by changing the electron withdrawing properties of the ligase motif, providing the idea that gold (I) bisADCs have potential to be good hydrogen bond catalysts. New thiourea-like gold (I) catalysts utilizing the acyclic diamino carbene motif that were hypothesized were synthesized using a one pot synthesis approach utilizing a metal templated synthesis method. The synthesis, characterization, and application prove …
Computational Study of Small Molecule Activation via Low-Coordinate Late First-Row Transition Metal Complexes
Methane and dinitrogen are abundant precursors to numerous valuable chemicals such as methanol and ammonia, respectively. However, given the robustness of these substrates, catalytically circumventing the high temperatures and pressures required for such transformations has been a challenging task for chemists. In this work, computational studies of various transition metal catalysts for methane C-H activation and N2 activation have been carried out. For methane C-H activation, catalysts of the form LnM=E are studied, where Ln is the supporting ligand (dihydrophosphinoethane or β-diketiminate), E the activating ligand (O, NCH3, NCF3) at which C-H activation takes place, and M the late transition metal (Fe,Co,Ni,Cu). A hydrogen atom abstraction (HAA) / radical rebound (RR) mechanism is assumed for methane functionalization (CH4 à CH3EH). Since the best energetics are found for (β-diket)Ni=O and (β-diket)Cu=O catalysts, with or without CF3 substituents around the supporting ligand periphery, complete methane-to-methanol cycles were studied for such systems, for which N2O was used as oxygen atom transfer (OAT) reagent. Both monometallic and bimetallic OAT pathways are addressed. Monometallic Fe-N2 complexes of various supporting ligands (LnFe-N2) are studied at the beginning of the N2 activation chapter, where the effect of ligand on N2 activation in end-on vs. side-on N2 isomers is discussed. For (β-diket)Fe-N2 complexes, the additional influence of diketiminate donor atom (N(H) vs. S) is briefly addressed. The remainder of the chapter expands upon the treatment of β-diketiminate complexes. First, the activation and relative stabilities of side-bound and end-bound N2 isomers in monometallic ((β-diket)M-N2) and bimetallic ((β-diket)M-N2-M(β-diket)) first row transition metal complexes are addressed. Second, the thermodynamics of H/H+/H- addition to (β-diket)Fe-bound N2, followed by subsequent H additions up to release of ammonia, is discussed, for which two mechanisms (distal and alternating) are considered. Finally, the chapter concludes with partial distal and alternating mechanisms for H addition to N2 …
A Computational Study on 18+δ Organometallics
The B3LYP density functional has been used to calculate properties of organometallic complexes of Co(CO)3 and ReBr(CO)3, with the chelating ligand 2,3-bisphosphinomaleic anhydride, in 19- and 18-electron forms. The SBKJC-21G effective core potential and associated basis set was used for metals (Co/Re) and the 6-31G* basis set was used for all other elements. The differences of bond angles, bond distances, natural atomic charges and IR vibrational frequencies were compared with the available experimental parameters. The differences between the 19- and 18-electron systems have been analyzed. The results reveal that the 19th electron is mostly distributed over the ligand of 2,3-bisphosphinomaleic anhydride, although partially localized onto the metal fragment in 1 and 2*. Two different methods, IR-frequencies and natural atomic charges, were used to determine the value of δ. Present computed values of δ are compared with available experimental values, and predictions are made for unknown complexes.
Computer Simulations of Dilute Polymer Solutions: Chain Overlaps and Entanglements
Chain conformations and the presence of chain overlaps and entanglements in dilute polymer solutions have been analyzed. The fundamental problem of existence of chain overlaps in dilute solutions is related to the drag reduction phenomenon (DR). Even though DR occurs in solutions with the concentration of only few parts per million (ppm), some theories suggest that entanglements may play an important role in DR mechanism. Brownian dynamics technique have been used to perform simulations of dilute polymer solutions at rest and under shear flow. A measure of interchain contacts and two different measures of entanglements have been devised to evaluate the structure of polymer chains in solution. Simulation results have shown that overlaps and entanglements do exist in static dilute solutions as well as in solutions under shear flow. The effect of solution concentration, shear rate and molecular mass have been examined. In agreement with the solvation theory of DR mechanism, simulation results have demonstrated the importance of polymer + polymer interactions in dilute solutions.
Conformation-Activity Studies of Pyrethroid Alcohols
The synthesis and insecticidal activity of certain alcohols (hydroxymethyldibenzofurans, hydroxymethyldibenzothiophenes and some of their ⍺-cyano derivatives), esterified with trans-chrysanthemic acid, were investigated. The preparation of these planar alcohol moieties was undertaken to study conformation-activity effects in insecticides of the pyrethroid type. The synthesis of final ester products employed two methods. One was the direct condensation of the appropriate alcohol with chrysanthemic acid chloride in the presence of pyridine. The other involved the in situ formation of the cyanohydrin from the appropriate aldehyde and subsequent condensation with chrysanthemic acid chloride in the presence of a phase transfer reagent. Insecticidal activity is to be tested at rates of 0.001, 0.01, 0.1, 10, 100, and 1000 ppm. Fenvalerate is used as the standard against Diabrotica undecimpuntata (spotted cucumber beetles).
Conformational Analogs of Some Phytoactive Compounds
In an effort to determine if there is a specific conformational structure which is most effective at the appropriate active physiological site, the synthesis of a group of sterically restricted analogs was undertaken. A portion of the polymethylene carbon skeleton of glutaric acid was replaced by selected aromatic carbons in benzenedicarboxylic acids to produce a series of ridged conformers, and the relative plant growth regulating properties of these derivatives were determined.
Conformational Analysis Using Carbon-13-Carbon-13 and Carbon-13-Hydrogen Spin-Spin Coupling Constants
This study consists of four major areas of research. First, the relationship between and was extended to Lrl nil homoallylic couplings and was used to determine the relative degree of puckering in a series of dihydroaromatic carboxylic acids. Second, the effect of coupling contributions transmitted through space were examined by theoretical calculations of the intermediate neglect of differential overlap finite perturbation theory type (INDO-FPT) including selective overlap reduction experiments to determine the sign and magnitude of the major through-space contributions and the effect of the orientation of the substituent upon the vicinal carbon3 carbon coupling. Third, the dependence of the J upon substituent orientation in norbornanes was empirically investigated by the synthesis of a series of lactones and cyclic ethers whose conformation was rigid and known. Fourth, a large number of norbornanes substituted with methyls in the 1, 3, and 7 position and a carbon-13 labeled substituent in the 2 position were synthesized and studied in order to obtain a variety of vicinal C-C couplings; all the NMR parameters for this series of compounds were determined while the carbon13 labeled substituent was varied from methyl to methylene to carbinol to aldehyde and to carboxylic acid.
Conformationally Stable Cyclohexyllithium Compounds
Organolitnium compounds have been employed in synthetic worK for many years. However only during the last decade has much progress been made in establishing the mechanistic pathways for the reactions of these compounds.
Copper (II) Complexes with Deprotonated N-(2-hydroxyethyl)ethylenediamine
This thesis reports the synthesis and characterization of two new copper(II) halide complexes with deprotonated N-(2-hydroxyethyl)ethylenediamine behaving as a bidentate. The magnetic properties of the new copper(II) complexes were studied from room temperature to liquid nitrogen temperatures. The magnetic data show that both complexes exhibit antiferromagnetic interactions with a singlet ground state and a thermally accessible triplet excited state. Magnetic data and infrared spectra indicate the complexes are halogenbridged. Deprotonation at an amine nitrogen is based on the presence of a hydroxyl stretching band in the infrared spectra. Electronic spectra and infrared spectra indicate the complexes are square planar. Elemental analyses, infrared spectra, electronic spectra, electron spin resonance spectra, and magnetic data are reported and discussed.
Copper Wire-Bonding Reliability: Mechanism and Prevention of Galvanic Aluminum Bond Pad Corrosion in Acidic Chloride Environments
With the reliability requirements of automobile microelectronics pushing towards near 0 ppb levels of failure control, halide induced corrosion issues in wire bonded devices have to be tightly controlled to achieve such a high reliability goal. With real-time corrosion monitoring, for the first time we demonstrated that the explosive H2 evolution coupled with the oxygen reduction reaction, occurring at the critical Al/Cu interfaces, is the key driving force for the observed aggressive corrosion. Several types of passivation coating on Cu wire surfaces to effectively block the cathodic H2 evolution were explored with an aim to disrupt this explosive corrosion cycle. The properties of the protective coating were evaluated using various analytical techniques. The surface coating exhibited high thermal stability up to 260 °C (evaluated using TGA analysis). A uniform, highly hydrophobic coating (surface contact angle of >130° with water), was achieved by carefully controlling CVD parameters such as time of deposition, surface control of Cu metal, amount of inhibitor compound loading, temperature of coating process etc. FTIR spectroscopy combined with corrosion screening was used to optimize the CVD passivated coating with strong chemisorption. SEM and EDX, XPS were carried out on various coated surfaces to understand the composition and selectivity of the film formed through this surface treatment. The surface selective nature of this coating (towards Cu) proved helpful in preventing potential delamination issues during epoxy molding process. The corrosion testing was carried out via HAST testing at 130°C, 2 atm pressure and 100% RH for 48 hours. Delamination analysis and continuity test showed that the inhibitor compound was able to effectively prevent the corrosion even after exposure to harsh HAST conditions.
The Correlation Between Carbon-Proton and Proton-Proton Coupling Constants
The correlation between the carbon-proton and proton-proton coupling constants have been studied in various 13 systems. Isocrotonic acid-carboxyl-3C, crotonic acid- 13 13 carboxyl-3C, and 5-norbornene-2-carboxylic acid-carboxyl-3C- 1,5,6,7,7-hexachloro were synthesized and their carbonproton coupling constants were analyzed. Nmr studies showed the magnitudes of the carbon-proton coupling constants to correlate well with analogous protonproton coupling constants, although the values of the couplings were larger than expected. The geminal olefinic couplings were considerably larger than all other couplings, but they were self-consistent. The signs of the carbon-proton coupling constants also were in agreement without exception with the signs of analogous proton-proton coupling constants.
Corrosion Inhibition with Quaternary Amines
This thesis describes experiments made to test the corrosion inhibition of quaternary amines on steel.
Corrosion Mechanism and Prevention of Wire Bonded Device in Microelectronic Manufacturing and Spectroscopic Investigation of Copper Etch Chemical Equilibria for High Density Interconnect Application
In the first part of this dissertation work, Al bond pad corrosion behavior was investigated in the presence of common industrial contaminants such as chloride (Cl-) and fluoride (F-). Al corrosion while in direct contact with Cu displayed rapid hydrogen (H2) gas evolution and dendrite propagation. In contrast, Al without bimetallic contact showed only minor surface roughening. This observed difference in the corrosion mechanism between Cl- and F- is attributed to the solubility of the corrosion products (AlCl3 vs. AlF3) formed on the Al surface. Our subsequent work explored corrosion prevention inhibition of wire-bonded devices (WBD) in the Cl- environment. Our research shows that the Al bond pad was protected against corrosion by chemically modifying the surface of the Cu wires, thereby preventing the H2 evolution. The inhibitor was observed to be highly selective, thermally stable, hydrophobic, and cost-effective, making it viable for industrial application of this coating for Al bond pad corrosion prevention. In the second part of the dissertation work, we utilized a novel approach of using ultraviolet-visible spectroscopy (UV-Vis) as a chemical-sensitive monitoring tool of the chemical environment in Cu etch bath. The UV-Vis technique illuminates the roles of H+, Cl-, Cu+, and Cu2+ to the etch bath while also providing a means to monitor the Cl- in the broad UV peak at 250 nm. The UV-Vis probe successfully demonstrated the etch rate difference between the two etch bath solutions and help in the restoration of the etching bath. Additionally, the proof-of-concept experiments (POC) to investigate UV enhanced etching for achieving anisotropic etching in PCB fabrication showed promising preliminary results with the need to develop additional etching techniques.
The Coupling Mechanism in the Organolithium-Organic Monofluoride Reaction
In this work, the principal concern will be with the coupling reaction and it is anticipated that the other reactions referred to above will be considered further when products of the RX-R'Li reactions are discussed.
Cross-Conjugation Effects on Fused β, β'–π–Extended Porphyrins
Cross-conjugation in molecules has been seen in nature for many years but was not pursued due to the difficulty of their synthesis and their lack of stability. Recently, it has become more interesting due to the rise of molecular electronics. Linear conjugation serves well as the wires to conduct electrons, but molecular electronics are made up of more than just wires. Molecules are needed that possess an on/off switch that can allow or deter conduction. Cross-conjugated systems show promise in their ability to be turned on or off from external stimuli. Pentacene quinone is a well-known cross-conjugated molecule that already shows promise in the field of molecular semiconductors. By synthetically fusing the pentacene quinone to the β, β' positions of a porphyrin, it has been shown that both the solubility and stability have been greatly improved. This has allowed us to pursue functionalization of the quinone moiety. Several new cross-conjugated pentacene quinone fused porphyrin systems were synthesized and studied. It was found that cross-conjugated platinum porphyrins show enhanced fluorescence, and phosphorescence that shifts toward the Near IR. Additionally, strong electron withdrawing groups show potential in charge transfer, and a lower HOMO to LUMO gap, while mildly withdrawing groups have a higher HOMO to LUMO gap. Furthermore, a new method to introduce halogenated methine bridges at the pentacene quinone core was developed, thus opening the doors to new polycyclic aromatic hydrocarbons to be synthesized and studied.
The Crystal and Molecular Structure of 2, 2' bipyridylglycinatochloro Copper (II) Dihydrate
The three-dimensional x-ray structure of 2,2'-bipyridylglycinatochloro copper(II) dihydrate has been fully refined to a final R factor of 0.081. The bipyridyl and glycine ligands are arranged about the central copper atom in a square planar configuration while the chlorine atom is 2.635 angstroms above this plane directly over the copper atom. This unusually long distance is explained by the positioning of a glycine group on the opposite side of the square plane, resulting in a distorted octahedral arrangement. Also, the chlorine atom is linked to three oxygen atoms via hydrogen bonding, thus stabilizing the distorted octahedral complex.
The Crystal and Molecular Structures of 8-Hydroxyquinoline-N-Oxide and 2-Hydroxymethylpyridine-N-Oxide
This dissertation looked at the crystal structure analysis of 2-hydroxymethylpyridine-N-oxide sine this compound could provide data on both substituent effects and hydrogen bonding.
The Crystal and Molecular Structures of Tri-(p-Fluorophenyl)-Amine and Tri-(p-Iodophenyl)-Amine
Because of the need for data on the geometry of nitrogen in arylamines, the determination of the crystal and molecular structures of tri-(p-fluorophenyl)-amine (TFPA) and tri-(p-iodophenyl)-amine (TIPA) was undertaken as the subject of this dissertation.
Cycloadditions of Dichloroketene
An investigation of the cycloaddition behavior of dichloroketene with various types of olefins seemed in order to determine if dichloroketene behaved similarly to dialkylketenes. It was anticipated that a study of this type would indicate the reactivity of dichloroketene to various types of olefinic compounds and thus establish if the ease of cycloaddition with dichloroketene parallels the nucleophilicity of the olefin as it does in dialkylketenes.
Cycloadditions of Ketenes with Allenes
The principle objective of this study is to conduct a definitive investigation into the cycloaddition of allenes and ketenes, with particular emphasis on halogenated ketenes.
A Dark Adaptation Study of College Men and Women
This study is the result of tests conducted to determine the adaptability of the human eye to darkness.
Denaturation, Renaturation and Other Structural Studies on Phosphoglucose Isomerases
Structural properties of phosphoglucose isomerases isolated from a variety of species have been compared by peptide fingerprinting, predicted amino acid sequence homologies and by denaturation and renaturation studies. The enzymes are more readily denatured in guanidinium chloride than in urea, and the isomerase isolated from yeast is more stable toward acid pH than the rabbit muscle enzyme. The rates of guanidinium chloride-induced denaturation are markedly increased by ionic strength and decreased by substrates, competitive inhibitors or glycerol. The enzyme can be renatured, but only in the presence of glycerol. The renaturation process is dependent on protein concentration and temperature and provides a method for the formation of mixed species heterodimers.
Deposition and Characterization of Thin Metal Oxide Heterostructures for Electronic and Magnetic Device Applications
The first study investigated the deposition and characterization of the CoO and Co3O4 phases of cobalt oxide. It was determined that both phases can be easily distinguishable by XPS, LEED and EELS and grown by only altering the oxygen partial pressure during MBE deposition. This fundamental knowledge gives a foundation for further experiments involving graphene growth on cobalt oxides. The second study focused on the layer-by-layer growth of graphene on another metal oxide, MgO. Past research gives promise of favorable interfacial interactions at the graphene/MgO interface though the exact growth mechanism is unknown. Layer by layer growth by MBE resulted in the characterization of a complex graphene oxide/buckled graphene/ graphene heterostructure confirmed by XPS, AES, LEED and EELS and supported by DFT calculations performed by the project's collaborators at the California Institute of Technology. This detailed look into graphene growth give valuable information that can be allied to graphene growth on similar oxide surfaces. The last project deviates from graphene-based studies and instead focused on interfacial interactions between two metal oxides, chrome oxide and titanium oxide. A corundum phase TiO2-x film was grown on Al2O3 via MBE and characterized using XPS, AES, LEED, and EELS. Data taken gives evidence of the presence of a two-dimensional election gas at the TiO2-x surface because of oxygen vacancies present after deposition. Deposition of chrome in UHV results in the formation of an oxidized chrome overlayer by abstraction of oxygen from the TiO2-x underlayer increasing the number of vacancies present. MOKE measurements taken by the project's collaborators at the University of Nebraska-Lincoln indicate that there is an interfacial exchange bias at the interface of the two oxides, a favorable property for magnetic device applications.
Derivatives of 1,4-Naphthoquinone and 1,4-Anthraquinone
The purpose of this investigation was the synthesis of some 1,4-naphthoquinones and 1,4-anthraquinones. It will be shown that some of these substituted quinones exhibit physiological properties.
Derivatives of Sulfonamide
This thesis describes experiments in creating derivatives of sulfonamide. The derivatives were then submitted for testing for anti-tubercular activity.
Design and Development of a Paper Spray Air Sampling Device for Use in Clinical, Defense, and Environmental Applications
Environmental monitoring is becoming increasingly important, primarily in urban areas due to the concentrated levels of human activities. The air sampling device presented is a novel method to sample air which harnesses the power of paper spray ionization paired with the intrinsic advantages of mass spectrometry such as high sensitivity, high selectivity, high throughput, and the ability to monitor multiple compounds at once.
Design and Synthesis of Gold (I) Acyclic Diamino Carbene Complexes as Metallodrugs for Cancer and for Asymmetric Catalysis
Many previous studies have demonstrated that gold compounds possess successful results in catalysis and in medicinal chemistry. The central aim of this dissertation is the design and synthesis of novel gold (I) acyclic diamino carbene complexes as a chemotherapeutic agent for triple-negative breast cancer (TNBC) and for catalysis. In this study, a series of chiral neutral and cationic gold (I) acyclic diamino carbene (ADC) complexes and neutral gold (I) bis- ADC complexes have been synthesized. As the chiral neutral gold (I) ADCs, four diastereomers of S binaphthyl L proline tertiary butyl ester gold (I) chloride, S binaphthyl D proline tertiary butyl ester gold (I) chloride, R binaphthyl L proline tertiary butyl ester gold (I) chloride, and R binaphthyl D proline tertiary butyl ester gold (I) chloride have been synthesized and characterized. Different chiral gold (I) ADC complexes with bulky chiral binaphthyl group and with different amine groups of morpholine, chiral proline methyl ester, and benzyl ester have been synthesized and characterized. After that four diastereomers of the nitrile adduct of cationic binaphthyl proline tertiary butyl ester nitrile and four diastereomers of the isonitrile versions of it have been synthesized and characterized. A series of gold (I) cationic bis ADC complexes have been synthesized and characterized. All these novel gold ADC complexes were tested for biological activity against TNBC cell line MDA-MB-231 and cationic S binaphthyl D proline ester isonitrile adduct, S binaphthyl D proline ester isonitrile adduct and R binaphthyl D proline ester isonitrile adduct gave promising inhibition rates. According to Lipinski's rule, lipophilicity determines the effectiveness of the drug absorption to the body through the lipid membrane. To determine the drug-likeness of the gold ADC complexes, log P values were calculated for some of the synthesized complexes using a modified shake flask method. Gold (I) ADC complexes have been …
Design, Synthesis and Characterization of Polymer and Protein Coated Hybrid Nanomaterials: Investigation of Prototypes for Antimicrobial and Anticancer Applications
This work involves synthesis and characterization of isotropic and anisotropic noble metal nanoparticles for applications ranging from antimicrobial uses to anticancer applications. These nanomaterials are stabilized in genuinely benign biomaterials ranging from polymers to cross linked proteins for targeted cancer treatments. The nanoparticles are found to have tunable optical properties.
Design, Synthesis and Optoelectronic Properties of Monovalent Coinage Metal-Based Functional Materials toward Potential Lighting, Display and Energy-Harvesting Devices
Groundbreaking progress in molecule-based optoelectronic devices for lighting, display and energy-harvesting technologies demands highly efficient and easily processable functional materials with tunable properties governed by their molecular/supramolecular structure variations. To date, functional coordination compounds whose function is governed by non-covalent weak forces (e.g., metallophilic, dπ-acid/dπ-base stacking, halogen/halogen and/or d/π interactions) remain limited. This is unlike the situation for metal-free organic semiconductors, as most metal complexes incorporated in optoelectronic devices have their function determined by the properties of the monomeric molecular unit (e.g., Ir(III)-phenylpyridine complexes in organic light-emitting diodes (OLEDs) and Ru(II)-polypyridyl complexes in dye-sensitized solar cells (DSSCs)). This dissertation represents comprehensive results of both experimental and theoretical studies, descriptions of synthetic methods and possible application allied to monovalent coinage metal-based functional materials. The main emphasis is given to the design and synthesis of functional materials with preset material properties such as light-emitting materials, light-harvesting materials and conducting materials. In terms of advances in fundamental scientific phenomena, the major highlight of the work in this dissertation is the discovery of closed-shell polar-covalent metal-metal bonds manifested by ligand-unassisted d10-d10 covalent bonds between Cu(I) and Au(I) coinage metals in the ground electronic state (~2.87 Å; ~45 kcal/mol). Moreover, this dissertation also reports pairwise intermolecular aurophilic interactions of 3.066 Å for an Au(I) complex, representing the shortest ever reported pairwise intermolecular aurophilic distances among all coinage metal(I) cyclic trimetallic complexes to date; crystals of this complex also exhibit gigantic luminescence thermochromism of 10,200 cm-1 (violet to red). From applications prospective, the work herein presents monovalent coinage metal-based functional optoelectronic materials such as heterobimetallic complexes with near-unity photoluminescence quantum yield, metallic or semiconducting integrated donor-acceptor stacks and a new class of Au(III)-based black absorbers with cooperative intermolecular iodophilic (I…I) interactions that sensitize the harvesting of all UV, all visible, and a broad spectrum of near-IR …
Detection of Harmful Chemicals in the Air using Portable Membrane Inlet Mass Spectrometry
Portable mass spectrometry has become an important analytical tool for chemical detection and identification outside of a lab setting. Many variations and applications have been developed to benefit various fields of science. Membrane inlet mass spectrometry is used to allow certain analytes to pass into the mass spectrometer without breaking vacuum or letting in large particulate matter. These two important analytical tools have been applied to the detection of harmful chemicals in the air. Earth-based separations and reverse gas stack modelling are useful mathematical tools that can be used to locate the source of a chemical release by back calculation. Earth-based separations studies the way different molecules will diffuse and separate through the air. Reverse gas stack modelling refers to the concentration differences of a chemical in relation to its distance from its source. These four analytical techniques can be combined to quickly and accurately locate various harmful chemical releases. The same system can be used for many applications and has been tested to detect harmful chemicals within and air-handling system. The monitoring of air-handling systems can greatly reduce the threat of harm to the building occupants by detecting hazardous chemicals and shutting off the air flow to minimize human exposure.
Detector Comparison for Simultaneous Determination of Organic Acids and Inorganic Anions
The research reported here is a study of detector systems to determine those most suited for simultaneous organic acid, inorganic anion determination. Comparisons are made on the basis of detection limits and sensitivities for conductivity, UV/Vis, photoconductivity, and derivative conductivity detection systems. The investigation was made using a constant chromatographic system with the only variable component being the detector system. Eluant optimization conditions for each detector are reported along with tables reporting detection limits and sensitivities for each detector system. Various chromatograms are also shown to provide a visual comparison between detector results.
Determination of Halogens in Organic Compounds by Using Sodium Fusion-Ion Chromatography Method
A sodium fusion-Ion chromatographic method for determination of fluorine, chlorine, bromine, and iodine in organic compounds is described. Seventeen organic halogen compounds and eleven mixtures were decomposed by Na fumes at 280-290°C for one hour or longer. The absorbing solutions were injected for ion chromatographic analysis using electrochemical and conductometric detectors. The arrangement of the apparatus includes the placement of the electrochemical and conductometric detectors. This method provides a mechanism providing for complete analysis for all four halogens in one ion chromatographic sample injection. Reproducibility is excellent and liquid sample handling is mentioned.
Determination of Nitrogen, Phosphorus, and Potassium in Various Plants
This study attempted to form some conception, through the analysis of a representative group of plants in the vicinity of Denton, of the amount of the three essential elements in the leaves as compared with the amount in the woody portions. The comparison of leaf with stem as to the quantity of nitrogen, phosphorus, and potassium is explained.
The Determination of Organic-Bound Chlorine Levels in Municipal Wastewaters After Treatment with Heavy Chlorine Doses
The development of an analytical method for the determination of total organic-bound chlorine (TOCl) produced during the chlorination of municipal wastewater effluents is presented. Sewage effluent from the Denton, Texas municipal treatment plant was chlorinated at high chlorine doses (1000 - 4000 ppm), as well as typical treatment levels. Chlororganics present in the wastewater, before and after chlorination, were concentrated by adsorption on Amberlite XAD-2 macroreticular resin, followed by elution with diethyl ether. After concentration, the extracts were analyzed for TOC1 by microcoulometry. Analysis of wastewater extracts revealed the production of substantial amounts of new chlorinated organics when effluents were treated with chlorine. The method shows good precision and estimated accuracy is favorable.
The Determination of the Constants in the System of Methyl Alcohol, Acetic Acid, and Water
The purpose of this study is to determine the specific reaction or velocity constants and the equilibrium constant in a system of methyl alcohol and acetic acid, a bimolecular reaction of the second order.
The Determination of the Constants in the System of Methyl Alcohol, Formic Acid, Methyl Formate and Water
Problems presented in this paper concern the chemical equilibrium of methyl alcohol, formic acid, and methyl formate when combined.
Determination of the Optimum Concentration of Sulfur Dioxide to be Used in Sweet Potato Dehydration
The object of this paper is to determine the optimum concentration of sulfur dioxide to be used in the commercial dehydration of the sweet potato by this process. Attention has been given to two aspects of the problem, (1) the effect of sulfur dioxide upon the extraction of water from the sweet potato by mechanical means, and (2) the effect of sulfur dioxide upon the stability of the carotene in the sweet potato over a period of several months.
A Determination of the Value of Sulphur Dioxide as a Dehydrating Agent for Sweet Potatoes
The purpose of this experiment was to determine the value of sulphur dioxide as a dehydrating agent for sweet potatoes.
Development and Testing of Gold(I) and Europium(III) Based Sensors for Environmental Applications
This dissertation focuses on the development, characterization, and analysis of luminescent materials and coatings for sensing applications, including CO2, heavy metals, and silver. Chapter 2 involves the use of a gold(I) pyrazolate trimer that is able to detect silver ions with an AgNP medium. Detection of silver is vital, because there is an influx of silver into our environment caused by the increased use of AgNP. Therefore, having a sensor that is able to differentiate between and detect only Ag ions is an important first step to solving the toxicity mystery of AgNPs. Chapter 3 focuses on the development of sensor coatings containing a Eu(III) based luminescent system for sensing dissolved CO2 without the aid of an absorption-based dye. It is well-known that monitoring CO2 levels in our environment is important since even at low concentrations it can cause adverse health effects to the human body. This work demonstrates a pH-sensitive Eu complex being used directly as a CO2 sensor without the aid of any other absorption-based dye. Chapter 4 explores the idea of developing a heavy metal sensor for lead and its ability to detect lead in wide concentration range upon changing the pH of the medium and the polymer matrix. Different heavy metals have toxicity at different concentrations, therefore, being able to change the dynamic range of the sensor is advantageous. This research is the first step towards developing a luminescent Pb sensor with a tunable dynamic range.
Development of an Optical Carbon Dioxide Sensor and Modeling of Metal-Metal Interactions for Sensor Applications
An investigation of luminescent sensing has been presented. Neutral Red, a common pH luminescent sensor, was shown to be an effective carbon dioxide sensor for the first time. Sensing experiments were performed both through fluorometric and fluorescent microscopy studies, giving rise to the possibility of carbon dioxide sensing for biological applications. Neutral Red was benchmarked against the well-established carbon dioxide sensor Pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt), HPTS. Neutral Red was shown to have improved response times and higher consistency within the sensing drift compared to HPTS. Trinuclear Au(I) complexes have previously shown to sense metal ions through changes in their luminescent properties. A computational study on d10-d10 interactions, which exist in complexes where Cu+, Ag+, and Au+ are intercalated with [Au(μ-C2,N3-ethylImidazolate)]3 in the form of both half and full sandwich adducts. Binding energies, total density plots, and Morse and Dunham analyses of potential energy surfaces are employed to better understand the metal-metal interactions and the effects of electron correlation, basis set superposition error, and dispersion of metallophilic interactions of the adduct complexes. As metal-metal interactions within these types of complexes become better understood, the tuning of trinuclear Au(I) complexes for luminescent sensing of metals becomes increasingly possible.
The Development of New Methods for the Quantitative Determinations of Bismuth and Amines
This thesis is a study of the development of new methods for the quantitative determinations of bismuth and amines.
The Development of Predictive Models for the Acid Degradation of Chrysotile Asbestos
The purpose of this study was to determine the factors affecting the acid degradation of chrysotile asbestos (Mg_3Si_2O_5(OH_4)) . Millions of tons of asbestos have found use in this country as insulative or ablative material. More than 95 percent of the asbestos in use is of the chrysotile variety. The remaining 5 percent is composed of various types of fibrous amphiboles. The inhalation of asbestos can lead to several diseases in humans. Asbestosis, lung cancer and mesothelioma are the most common afflictions associated with asbestos inhalation, and they may occur up to 40 years after the initial exposure. It has previously been reported that if more than 50 percent of the magnesium is removed from a chrysotile sample its carcinogenicity is reduced to nil. Several inorganic acids were studied to determine their ability to leach magnesium from chrysotile. It was found that the ability to leach magnesium was dependent upon the acidic anion in addition to the concentration of the acid. The ordering of the efficiency of the acids in their ability to remove magnesium from chrysotile was found to be HCl > H_2SO_4 > H_3PO_4 > HNO_3. Predictive equations were developed to allow the calculation of the amount of magnesium removed under various acid concentrations as a function of time and acid species. The effects of temperature and dissolved spectator cations upon the degradation process were also examined. There was no major effect on the amount of magnesium removed as a function of spectator cation concentration. An infrared method was also developed to allow the determination of the percent degradation of a chrysotile sample directly. The shifts in the positions of three silicate stretching peaks (1068 cm^-1, 948 cm^-1 and 715 cm^-1) and one magnesium oxygen stretching peak (415 cm"1) as a function of the percent magnesium removed were …
The Development of the Attitudes Towards Organic Chemistry Instrument
In this study, undergraduate student attitudes towards organic chemistry and the influences that shape those attitudes were explored using the Attitudes Towards Organic Chemistry Instrument (ATOC) to collect both qualitative and quantitative data. The findings from the qualitative ATOC items provide evidence that students displayed a wide range of attitudes towards organic chemistry, including positive, negative, neutral, and blended attitudes. Five major influences were shown to have shaped these attitudes including the reputation of the course, students' educators, experiences with organic chemistry, experiences with introductory chemistry, and individual experiences. Students responses longitudinally provide evidence that their influences and attitudes change over time in the course. The findings from the quantitative ATOC items provided evidence that the data generated was valid and reliable, and a relationship was found to exist between what students think and what they had heard about the course. Limitations of this investigation, as well as implications for research and practitioners, are discussed.
Diffusion Barriers/Adhesion Promoters. Surface and Interfacial Studies of Copper and Copper-Aluminum Alloys
The focus of this research is to study the interaction between copper and the diffusion barrier/adhesion promoter. The behavior of copper sputter-deposited onto sputter-cleaned tantalum nitride is investigated. The data show that copper growth on tantalum nitride proceeds with the formation of 3-D islands, indicating poor adhesion characteristics between copper and Ta0.4N. Post-annealing experiments indicate that copper will diffuse into Ta0.4N at 800 K. Although the data suggests that Ta0.4N is effective in preventing copper diffusion, copper's inability to wet Ta0.4N will render this barrier ineffective. The interaction of copper with oxidized tantalum silicon nitride (O/TaSiN) is characterized. The data indicate that initial copper depositions result in the formation a conformal ionic layer followed by Cu(0) formation in subsequent depositions. Post-deposition annealing experiments performed indicate that although diffusion does not occur for temperatures less than 800 K, copper "de-wetting" occurs for temperatures above 500 K. These results indicate that in conditions where the substrate has been oxidized facile de-wetting of copper may occur. The behavior of a sputter-deposited Cu0.6Al0.4 film with SiO2 (Cu0.6Al0.4/SiO2) is investigated. The data indicate that aluminum segregates to the SiO2 interface and becomes oxidized. For copper coverages less than ~ 0.31 ML (based on a Cu/O atomic ratio), only Cu(I) formation is observed. At higher coverages, Cu(0) is observed. These data are in contrast with the observed behavior of copper metal deposited onto SiO2 (Cu/SiO2). The data for Cu/SiO2 show that copper does not wet SiO2 and forms 3-D nuclei. Furthermore, post-annealing experiments performed on Cu0.6Al0.4/SiO2 show that neither de-wetting nor diffusion of copper occurs for temperatures up to 800 K, while Cu diffusion into SiO2 occurs ~ 600 K. These data indicate that aluminum alloyed with copper at the SiO2 interface serves as an effective adhesion promoter and thermal diffusion barrier.
Diffusion of Hydrocarbons Through Rubber Membranes
This thesis explores the seperation of isomeric paraffins in organic chemistry and how the resulting mixture of hydrocarbons might be examined.
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