UNT Theses and Dissertations - 272 Matching Results

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Characterization of Low Barrier Hydrogen Bonds in Enzyme Catalysis: an Ab Initio and DFT Investigation

Description: Hartree-Fock, Moller-Plesset, and density functional theory calculations have been carried out using 6-31+G(d), 6-31+G(d,p) and 6-31++G(d,p) basis sets to study the properties of low-barrier or short-strong hydrogen bonds (SSHB) and their potential role in enzyme-catalyzed reactions that involve proton abstraction from a weak carbon-acid by a weak base. Formic acid/formate anion, enol/enolate and other complexes have been chosen to simulate a SSHB system. These complexes have been calculated to… more
Date: August 1999
Creator: Pan, Yongping
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Chemical Equilibria in Binary Solvents

Description: Dissertation research involves development of Mobile Order Theory thermodynamic models to mathematically describe and predict the solubility, spectral properties, protonation equilibrium constants and two-phase partitioning behavior of solutes dissolved in binary solvent mixtures of analytical importance. Information gained provide a better understanding of solute-solvent and solvent-solvent interactions at the molecular level, which will facilitate the development of better chemical separation… more
Date: August 1997
Creator: McHale, Mary E. R.
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Chemically Optimized Cu Etch Bath Systems for High-Density Interconnects and the FTIR Operando Exploration of the Nitrogen Reduction Reaction on a Vanadium Oxynitride Electrocatalyst

Description: Printed circuit board manufacturing involves subtractive copper (Cu) etching where fine features are developed with a specific spatial resolution and etch profile of the Cu interconnects. A UV-Vis ATR metrology, to characterize the chemical transitions, has been developed to monitor the state of the bath by an in-situ measurement. This method provides a direct correlation of the Cu etch bath and was able to predict a 35% lower etch rate that was not predicted by the three current monitoring met… more
This item is restricted from view until September 1, 2027.
Date: August 2022
Creator: Caperton, Joshua M
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Chromatographic and Spectroscopic Studies on Aquatic Fulvic Acid

Description: High Performance Liquid Chromatography (HPLC) was used to investigate the utility of this technique for the analytical and preparative separation of components of aquatic fulvic acids (FA). Three modes of HPLC namely adsorption, anion exchange and reversed phase were evaluated. Aquatic fulvic acids were either extracted from surface water and sediment samples collected from the Southwest of the U.S., or were provided in a high purity form from the USGS. On the adsorption mode, a major fraction… more
Date: August 1986
Creator: Chang, David Juan-Yuan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Cleaner Futures: Covalent Organic Frameworks for Sustainable Degradation of Lignocellulosic Materials

Description: As countries pledge their commitment to a net-zero future, much of the previously forgotten climate change research were revitalized by efforts from both governmental and private sectors. In particular, the utilization of lignocellulosic materials saw a special spotlight in research interest for its abundance and its carbon removal capability during photosynthesis. The initial effort in mimicking enzymatic active sites of β-glucosidase will be explored. The crystalline covalent organic framewor… more
This item is restricted from view until June 1, 2028.
Date: May 2023
Creator: Lan, Pui Ching
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Combined Electrochemistry and Spectroscopy of Complexes and Supramolecules containing Bipyridyl and Other Azabiphenyl Building Blocks

Description: A group of azabiphenyl complexes and supramolecules, and their reduced and oxidized forms when possible, were characterized by cyclic voltammetry and electronic absorption spectroscopy. The oxidized and reduced species, if sufficiently stable, were further generated electrochemically inside a specially designed quartz cell with optically transparent electrode, so that the spectra of the electrochemically generated species could be taken in situ. Assignments were proposed for both parent and pro… more
Date: August 1995
Creator: Yang, Lei
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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A Comprehensive Investigation of Photoinduced Electron Transfer and Charge Transfer Mechanisms in Push-Pull Donor-Acceptor Systems: Implications for Energy Harvesting Applications

Description: Donor-acceptor systems exhibit distinctive attributes rendering them highly promising for the emulation of natural photosynthesis and the efficient capture of solar energy. This dissertation is primarily devoted to the investigation of these unique features within diverse donor-acceptor system typologies, encompassing categories such as closely covalently linked, push-pull, supramolecular, and multi-modular donor- acceptor conjugates. The research encompasses an examination of photosynthetic an… more
Date: December 2023
Creator: Alsaleh, Ajyal Zaki
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational and Experimental Studies of the Photoluminescence, Reactivity and Structural Properties of d10 and d8 Metal Complexes

Description: Computational chemistry has gained interest as a characterization tool to predict photoluminescence, reactivity and structural properties of organic and transition metal complexes. With the rise of methods including relativity, these studies have been expanded to the accurate modeling of luminescence spectra of complexes with considerable spin-orbit splitting due to heavy metal centers as well as the reaction pathways for these complexes to produce natural products such as hydrogen gas. These a… more
Date: May 2019
Creator: Otten, Brooke Michelle
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Computational Development of Trimetallic Cyclotrimers for Gas-Filtration Applications through Non-Covalent Interactions

Description: Photophysical properties of an array of various polyaromatic hydrocarbons were benchmarked with B3LYP, M06 and B97D methods coupled with Pople and CEP-31G(d) basis sets. Results from the benchmark show the importance of diffuse basis sets when modeling the electronic properties of highly conjugated systems and provide qualitative reliable accuracy with certain levels of theory. B97D and M06 are applied to modeling pyrene adducts governed by non-covalent interactions in both gaseous and condense… more
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Date: December 2019
Creator: Williams, Christopher M.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational Investigation of DNA Repair Enzymes: Determination and Characterization of Cancer Biomarkers and Structural Features

Description: Genomic integrity is important for living cells' correct functioning and propagation. Deoxyribonucleic acid as a molecule is a subject to chemical reactions with agents that can come from environment as well as from internal metabolism processes. These reactions can induce damage to DNA and thus compromise the genetic information, and result in disease and death of an organism. To mitigate the damage to DNA, cells have evolved to have multiple DNA repair pathways. Presented here is a computat… more
Date: May 2018
Creator: Silvestrov, Pavel
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Computational Investigations of Catalytic Activity by Metal-Containing Complexes

Description: This dissertation delves into the catalytic activity of multiple metal-containing complexes with an emphasis on the activation of C–H bonds in small molecules and olefin oligomerization. The research contained in these works employs computational methodologies to better understand the thermodynamics and kinetics of the reactions. Computations can be used to quickly identify novel models and find ideal substitutions for improved catalyst design. Within this dissertation, multiple molecules of di… more
Date: August 2022
Creator: Carter, Carly Catherine
Item Type: Refine your search to only Thesis or Dissertation
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Computational Modeling of Cancer-Related Mutations in DNA Repair Enzymes Using Molecular Dynamics and Quantum Mechanics/Molecular Mechanics

Description: This dissertation details the use of computational methods to understand the effect that cancer-related mutations have on proteins that complex with nucleic acids. Firstly, we perform molecular dynamics (MD) simulations of various mutations in DNA polymerase κ (pol κ). Through an experimental collaboration, we classify the mutations as more or less active than the wild type complex, depending upon the incoming nucleotide triphosphate. From these classifications we use quantum mechanics/molecula… more
Date: May 2022
Creator: Leddin, Emmett Michael
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational Simulations of Cancer and Disease-Related Enzymatic Systems Using Molecular Dynamics and Combined Quantum Methods

Description: This work discusses applications of computational simulations to enzymatic systems with a particular focus on the effects of various small perturbations on cancer and disease-related systems. First, we cover the development of carbohydrate-based PET imaging ligands for Galectin-3, which is a protein overexpressed in pancreatic cancer tumors. We uncover several structural features for the ligands that can be used to improve their binding and efficacy. Second, we discuss the AlkB family of enzym… more
Date: May 2018
Creator: Walker, Alice Rachel
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Computational Studies of C-H Bond Activation and Ethylene Polymerization Using Transition Metal Complexes

Description: This work discusses the C-H bond activation by transition metal complexes using various computational methods. First, we performed a DFT study of oxidative addition of methane to Ta(OC2H4)3A (where A may act as an ancillary ligand) to understand how A may affect the propensity of the complex to undergo oxidative addition. Among the A groups studied, they can be a Lewis acid (B or Al), a saturated, electron-precise moiety (CH or SiH), a σ-donor (N), or a σ-donor/π-acid (P). By varying A, we seek… more
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Date: May 2019
Creator: Parveen, Riffat
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Computational Studies of Catalysis Mediated by Transition Metal Complexes

Description: Computational methods were employed to investigate catalytic processes. First, DFT calculations predicted the important geometry metrics of a copper–nitrene complex. MCSCF calculations supported the open-shell singlet state as the ground state of a monomeric copper nitrene, which was consistent with the diamagnetic character deduced from experimental observations. The calculations predicted an elusive terminal copper nitrene intermediate. Second, DFT methods were carried out to investigate the … more
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Date: May 2019
Creator: Jiang, Quan
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Computational Studies of C–H/C–C Manipulation Utilizing Transition Metal Complexes

Description: 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. Us… more
Date: May 2015
Creator: Pardue, Daniel B.
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Partner: UNT Libraries
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Computational Studies of Selected Ruthenium Catalysis Reactions.

Description: 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 … more
Date: December 2007
Creator: Barakat, Khaldoon A.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational Studies of the Photophysical, Structural, and Catalytic Properties of Complex Chemical Systems

Description: 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 … more
Date: May 2021
Creator: Melancon, Kortney
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Partner: UNT Libraries
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Computational Study of C−H/C−C Activation and Functionalization with Nitrene, Carbene and Related Complexes

Description: 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 … more
Date: December 2020
Creator: Sun, Zhicheng
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Partner: UNT Libraries
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Computational Study of Intermolecular Interactions in Complex Chemical Systems

Description: 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-covalen… more
Date: May 2020
Creator: Vazquez Montelongo, Erik Antonio
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Partner: UNT Libraries

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

Description: 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 th… more
This item is restricted from view until August 1, 2025.
Date: July 2023
Creator: Tiemann, Matthew Austin
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational Study of Small Molecule Activation via Low-Coordinate Late First-Row Transition Metal Complexes

Description: 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 th… more
Date: May 2010
Creator: Pierpont, Aaron
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Partner: UNT Libraries
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Computer Simulations of Dilute Polymer Solutions: Chain Overlaps and Entanglements

Description: 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 dilu… more
Date: August 1996
Creator: Drewniak, Marta
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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