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Bifunctional Enamine‐Metal Lewis Acid Catalysis and α-Enaminones for Cyclization Reactions

The use of enamines continues to be an important tool in organic syntheses as both a catalyst and reactant. The addition of metal catalysts coupled with enamine catalysis has generated many reactions that normally would not occur separately. However, catalysts' incompatibility is an issue that we wish to solve allowing new chemistry to occur without hindrance. The use of enamines has continued to be a well-studied area of organic chemistry, but the field is ripe for different types of enamines to gain the spotlight. Enaminones are enamines with both nucleophilic and electrophilic properties. They allow reactions that are normally not possible with enamines to become obtainable. Chapter 1 is a brief introduction on enamines and the reason they gained so much attention. Then ends with enaminones and what makes them interesting reactants. Chapter 2 described a new synthesis for the tricyclic synthesis of chromanes using a novel bifunctional catalyst system of enamine-metal Lewis acid giving great yields (up to 87 %yield) and excellent stereoselectivity (up to 99 % ee). Chapter 3 covered new reactions for ring-open cyclopropane (up to 94% yield), tetrahydroquinolinones (up to 84% yield) and enantiospecific tetrahydroquinolinones (up to 84% yield and 97% ee) using α-enaminone and donor-acceptor …
Date: August 2022
Creator: Davis, Jacqkis
System: The UNT Digital Library

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

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 methods (ORP, specific gravity, and conductivity). Application of this UV-Vis ATR probe confirmed that two industrial etch baths, in identical working conditions, confirmed a difference in Cu2+ concentration by the difference of the near IR 860nm peak. The scope of this probe allowed chemically specific monitoring of the Cu etch bath to achieve a successful regeneration for repeated use. Interlayer dielectrics (ILDs) provide mechanical and electrical stability to the 3D electrical interconnects found in IC devices. It is particularly important that the structural support is created properly in the multilayered architecture to prevent the electrical cross signaling in short range distances. A combined multiple internal reflection and transmission FTIR has been employed for the characterization of silicon oxycarbonitride (SiOCN) films. These …
Date: August 2022
Creator: Caperton, Joshua M
System: The UNT Digital Library

Computational Investigations of Catalytic Activity by Metal-Containing Complexes

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 divalent and trivalent main group element-containing complexes as well as Group 13 dimetallene complexes were investigated with density functional theory (DFT) to identify their ability to activate C–H of hydrocarbons, including methane, by quantifying their thermodynamics and kinetics of reaction. With several substitutions to the base complex, improved catalysts were designed to decrease the energy barriers of the activations. Multiconfiguration self-consistent field methods were also employed to characterize the biradical character of these Group 13 compounds. Olefin oligomerization by zirconium boratabenzenes with various ancillary pendant groups was also investigated via DFT to identify the most ideal variations as well as the most likely reaction pathway.
Date: August 2022
Creator: Carter, Carly Catherine
System: The UNT Digital Library

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.
Date: August 2022
Creator: Collini, Melissa Anne
System: The UNT Digital Library
Earth Abundant Transition Metal Catalysts for Activation and Functionalization of Light Hydrocarbons (open access)

Earth Abundant Transition Metal Catalysts for Activation and Functionalization of Light Hydrocarbons

Light hydrocarbons activations, functionalization, and reactions have been a subjects of catalysis research for decades but dominated by the rarer and more expensive noble metals. Switching over to using the more earth abundant third row transition metals could be more economical and less toxic but come with their own challenges. Their use as catalysts with light hydrocarbons could be employed better utilize and more efficiently use our hydrocarbon resources that the world still depends on.
Date: August 2022
Creator: Grumbles, William M
System: The UNT Digital Library
Ultrafast Charge Transfer in Donor-Acceptor Push-Pull Constructs (open access)

Ultrafast Charge Transfer in Donor-Acceptor Push-Pull Constructs

Ultrafast charge and electron transfer, primary events in artificial photosynthesis, are key in solar energy harvesting. This dissertation provides insight into photo-induced charge and electron transfer in the donor and acceptor constructs built using a range of donor and acceptor entities, including transition metal dichalcogenides (TMDs, molybdenum disulfide (MoS2), and tungsten disulfide (WS2)), N-doped graphene, diketopyrrolopyrrol (DPP), boron-dipyrromethene (BODIPY), benzothiadiazole (BTD), free base and metal porphyrins, zinc phthalocyanine (ZnPc), phenothiazine (PTZ), triphenylamine (TPA), ferrocene (Fc), fullerene (C60), tetracyanobutadiene (TCBD), and dicyanoquinodimethane (DCNQ). The carefully built geometries and configurations of the donor and (D), acceptor (A), with a spacer in these constructs promote intramolecular charge transfer, and intervalence charge transfer to enhance charge and electron transfer efficiencies. Steady-state UV-visible absorption spectroscopy, fluorescence and phosphorescence spectroscopies, electrochemistry (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)), spectroelectrochemistry (absorption spectroscopy under controlled potential electrolysis), transient absorption spectroscopy, and quantum mechanical calculations (density functional theory, DFT) are used to probe ground and the excited state events as well as excited state charge separation resulting in cation and anion species. The current findings are useful for the increased reliance on renewable energy resources, especially solar energy.
Date: August 2022
Creator: Jang, Young Woo
System: The UNT Digital Library

"You get what you pay for" vs "You can alchemize": Investigating Discovery Research Experiences in Inorganic Chemistry/Chemistry Education via an Undergraduate Instructional Laboratory

Synthesis of d10 complexes of monovalent coinage metals, copper(I) and gold(I), with dithiophosphinate/diphosphine ligands -- along with their targeted characterization and screening for inorganic or organic light emitting diodes (LEDs or OLEDs, respectively) -- represents the main scope of this dissertation's scientific contribution in inorganic and materials chemistry. Photophysical studies were undertaken to quantify the phosphorescence properties of the materials in the functional forms required for LEDs or OLEDs. Computational studies were done to gain insights into the assignment of the phosphorescent emission peaks observed. The gold(I) dinuclear complexes studied would be candidates of OLED/LED devices due to room temperature phosphorescence, visible absorption/excitation bands, and low single-digit lifetimes -- which would promote higher quantum yield at higher voltages in devices with concomitant lower roll-off efficiency. The copper(I) complexes were not suited to the OLED/LED applications but can be used for thermosensing materials. Crystallographic studies were carried to elucidate coefficients of thermal expansion of the crystal unit cell for additional usage in materials applications besides optoelectronic devices. This has uncovered yet another unplanned potential application for both copper(I) and gold(I) complexes herein, as both types have been found to surpass the literature's threshold for "colossal" thermal expansion coefficients. Two other investigations …
Date: August 2022
Creator: Bodenstedt, Kurt Wallace
System: The UNT Digital Library
Theoretical Thermochemistry of Tungsten Including σ and π Bond Components (open access)

Theoretical Thermochemistry of Tungsten Including σ and π Bond Components

Computational chemistry examination of the bond dissociation enthalpies of tungsten and main group elements. Includes quantification and calibration of theoretical methods to address the question of bond strengths including component σ and π molecular bonds.
Date: August 2021
Creator: Moulder, Catherine Anne
System: The UNT Digital Library
A Combined Theoretical and Experimental Study on Deposition of Solid State Materials (open access)

A Combined Theoretical and Experimental Study on Deposition of Solid State Materials

Deposition of solid state materials span a wide variety of methods and often utilize high energy sources such as plasmas and ultra-violet light resulting in a wide variety of characteristics and applications. A fundamental understanding is essential for furthering the applications of these materials which include catalysis, molecular filtration, electronics, sensing devices, and energy storage among others. A combination of experimental and theoretical work is presented here on several materials including 2D silicates on Pd, boron oxide, and vanadium oxynitride. Silicate formation under low energy electron microscopy demonstrate film permeability to oxygen, while ab initio molecular dynamics simulations reveal the possible initial mechanisms associated with the formation of boron oxide films during atomic layer deposition. Lastly, vanadium oxynitrides have shown preferential sputtering of N over O sites and theoretical binding energies serve as a guide for assigning experimental x-ray photoelectron spectra.
Date: August 2020
Creator: Lee, Veronica
System: The UNT Digital Library

Novel Metal-Containing Nanoparticle Composites for Cancer Therapy and Imaging

With all the improvements in cancer treatments, multidrug resistance is still the major challenge in treating cancer. Cells can develop multidrug resistance (MDR) during or after treatment, which will render the cancer cells resistant not only to the chemotherapy drug being used but also to many other structurally- and mechanically-different chemotherapeutics. In the first project, the main focus was on development of drug resistant cell lines by selection with taxol. Gene changes in the L1T2 cell line after treatment with Taxol was studied. Treatment of L1T2 cells with taxol leads to changes in the expression of ABC transporter proteins, whereas the combination of Taxol with protease inhibitors leads to increased efficacy via inhibition of P-glycoprotein (P-gp). In the second project, we showed that our innovatively-designed Au-loaded poly(lactide-co-glycolic acid) nanoparticles (GPLGA NPs) are able to cross biological barriers and deliver inside the cells without being recognized by the ABC protein transporter. (We focus specifically on P-gp-mediated drug efflux in a model of HEK cell lines.) The concentration of gold was measured using inductively-coupled plasma/mass spectrometry (ICP-MS) after 6- and 24-hour treatment of GPLGA NPs, which did not show significant increase of gold inside the cells in presence of the P-gp inhibitor …
Date: August 2020
Creator: Nasiri, Nooshin Mirza
System: The UNT Digital Library
Synthesis, Characterization, and Reactivity of Prochiral Ruthenium Clusters and Bimetallic Rhenium Complexes with an Unsymmetrical Diphosphine and Hard-Soft Donor Ligands (open access)

Synthesis, Characterization, and Reactivity of Prochiral Ruthenium Clusters and Bimetallic Rhenium Complexes with an Unsymmetrical Diphosphine and Hard-Soft Donor Ligands

The reaction of [BrRe(CO)₄]₂ with 2-(diphenylphosphino)pyridine (PN) and 6-(diphenylphosphino)-2-formylpyridine (PON) was investigated. The reactions were regiospecific and exclusively produced the phosphorus-coordinated products, BrRe(CO)₄(κᵖ-PN) and BrRe(CO)₄(κᴾ-PON). The kinetics for the chelate ring closure (κᴾ→ κᴾᴺ) in BrRe(CO)₄(κᴾ-PN) were confirmed to occur by dissociative CO loss. The reaction of [BrRe(CO)₄]₂ with 2-(diphenylphosphino)pyridine (PN) was modeled computationally by DFT calculations. The preferred reaction pathway for the substitution reaction was determined to occur by direct attack of the pnictogen donor on the dimer and formation of the κᴺ isomer as the kinetic substitution product occurs. The κᴺ kinetic product then rapidly isomerizes to the κᴾ thermodynamic product by way of a reversible ligand dissociation. Treatment of the tetrahedral cluster H₂Ru₃(CO)₃(μ₃-S) (1) with 2-(diphenylphosphino)thioanisole (PS) furnishes the cluster H₂Ru₃(CO)₇(κ²-PS)(μ₃-S) (2). Cluster 2, which exhibits a chelated thiophosphine ligand (κ²-PS), exists as a pair of diastereomers with Keq = 1.55 at 298 K that differ in their disposition of ligands at the Ru(CO)(κ²-PS) center. The PS ligand occupies the equatorial sites (Peq, Seq) in the kinetic isomer and axial and equatorial sites (Pax, Seq) in the thermodynamically favored species. The reversible first-order kinetics to equilibrium have been measured experimentally by NMR spectroscopy and HPLC over the …
Date: August 2019
Creator: Mayberry, Darrell D.
System: The UNT Digital Library
Applications of Metallic Clusters and Nanoparticles via Soft Landing Ion Mobility, from Reduced to Ambient Pressures (open access)

Applications of Metallic Clusters and Nanoparticles via Soft Landing Ion Mobility, from Reduced to Ambient Pressures

Nanoparticles, simple yet groundbreaking objects have led to the discovery of invaluable information due to their physiological, chemical, and physical properties, have become a hot topic in various fields of study including but not limited to chemistry, biology, and physics. In the work presented here, demonstrations of various applications of chemical free nanoparticles are explored, from the determination of a non-invasive method for the study of the exposome via using soft-landing ion mobility (SLIM) deposited nanoparticles as a matrix-assisted laser desorption/ionization (MALDI-MS) matrix replacement, to the direct SLIM-exposure of nanoparticles onto living organisms. While there is plenty of published work in soft-landing at operating pressures of 1 Torr, the work presented here shows how this technology can be operated at the less common ambient pressure. The ease of construction of this instrument allows for various modifications to be performed for a wide array of applications, furthermore the flexibility in metallic sample, operating pressure, and deposition time only open doors to many other future applications. The work presented will also show that our ambient SLIM system is also able to be operated for toxicological studies, as the operation at ambient pressure opens the door to new applications where vacuum conditions are …
Date: August 2018
Creator: Aguilar Ayala, Roberto
System: The UNT Digital Library
Detection of Harmful Chemicals in the Air using Portable Membrane Inlet Mass Spectrometry (open access)

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 …
Date: August 2018
Creator: Kretsch, Amanda Renee
System: The UNT Digital Library
High-Energy, Long-Lived Charge-Separated States via Molecular Engineering of Triplet State Donor-Acceptor Systems (open access)

High-Energy, Long-Lived Charge-Separated States via Molecular Engineering of Triplet State Donor-Acceptor Systems

Molecular engineering of donor-acceptor dyads and multimodular systems to control the yield and lifetime of charge separation is one of the key goals of artificial photosynthesis for harvesting sustainably solar energy. The design of the donor-acceptor systems mimic a part of green plants and bacterial photosynthetic processes. The photochemical events in natural photosynthesis involve the capturing and funneling of solar energy by a group of well-organized chromophores referred to as an ‘antenna' system causing an electron transfer into the ‘reaction center,' where an electron transfer processes occur resulting a long-lived charge separated state. Over the last two to three decades, many efforts have been directed by the scientific community designing of multi-modular systems that are capable of capturing most of the useful sunlight and generating charge separated states of prolonged lifetimes with adequate amounts of energy. In this dissertation, we report on the design and synthesis of donor–acceptor conjugates with the goal of modulating the yield and lifetime of their charge separated states and hence, improving the conversion of light energy into chemical potential. In simple donor-acceptor systems, generally, the energy and electron transfer events originate from the singlet excited state of the donor or acceptor and can store the …
Date: August 2018
Creator: Obondi, Christopher O
System: The UNT Digital Library
Optoelectronically Active Metal-Inorganic Frameworks and Supramolecular Extended Solids (open access)

Optoelectronically Active Metal-Inorganic Frameworks and Supramolecular Extended Solids

Metal-organic frameworks (MOFs) have been intensely researched over the past 20 years. In this dissertation, metal-inorganic frameworks (MIFs), a new class of porous and nonporous materials using inorganic complexes as linkers, in lieu of traditional organic linkers in MOFs is reported. Besides novel MIF regimes, the previously described fluorous MOF "FMOF-1", is re-categorized herein as "F-MIF1". F-MIF-1 is comprised of [Ag4Tz6]2- (Tz = 3,5-bis-trifluoromethyl-1,2,4-triazolate) inorganic clusters connected by 3-coordinate Ag+ metal centers. Chapter 2 describes isosteric heat of adsorption studies of F-MIF1 for CO2 at near ambient temperatures, suggesting promise for carbon capture and storage. We then successfully exchanged some of these Ag(I) centers with Au(I) to form an isostructural Au/F-MIF1. Other, nonporous MIFs have been synthesized using Ag2Tz2 clusters with bridging diamine linkers 4,4'-bipyridine, pyrazine, and a Pt(II) complex containing two oppositely-situated non-coordinating pyridines. This strategy attained luminescent products better-positioned for photonic devices than porous materials due to greater exciton density. Chapter 3 overviews work using an entirely inorganic luminescent complex, [Pt2(P2O5)4]4- (a.k.a. "PtPOP") to form new carbon-free MIFs. PtPOP is highly luminescent in solution, but as a solid shows poor quantum yield (QY ~0.02) and poor stability under ambient conditions. By complexing PtPOP to various metals, we have …
Date: August 2018
Creator: Ivy, Joshua F.
System: The UNT Digital Library
Teaching First-Semester General Chemistry Using 3D Video Games following an Atoms First Approach to Chemistry (open access)

Teaching First-Semester General Chemistry Using 3D Video Games following an Atoms First Approach to Chemistry

The unified learning model (ULM) focuses on students' engagement, motivation, prior knowledge, and working memory. This study employs the use of video games to assess students' learning through a 3D chemistry gaming environment. In this human-subjects research, students carried out missions and applied reasoning to solve problems appropriate for general chemistry content. For learning to occur, students must be engaged and motivated as stated in the ULM. Learning cannot necessarily be accomplished by experience alone, and critical thinking is required to turn the experience into learning. The interpretation of educational theory applied to video games and this proposed study are discussed. A moderately positive correlation was found between exam score and study time (playing the game). Essentially the more time spent playing the game or an online activity the higher the exam scores. There was an alpha level less than 0.05 (p < 0.05) between the experimental group and non-traditional group (no game or online activity). Supporting that there was a statistically significant difference between groups, the null hypothesis was accepted between the game and online activity. Furthermore, as stated under the ULM, engagement is necessary for optimal learning.
Date: August 2018
Creator: Jenkins, Dave A
System: The UNT Digital Library
Ultrafast Photoinduced Energy and Electron Transfer Studies in Closely Bound Molecular and Nanocarbon Donor-Acceptor Systems (open access)

Ultrafast Photoinduced Energy and Electron Transfer Studies in Closely Bound Molecular and Nanocarbon Donor-Acceptor Systems

As part of the study, photosynthetic system constructs based on BF2-chelated dipyrromethene (BODIPY), BF2-chelated azadipyrromethene (AzaBODIPY), porphyrin, phthalocyanine, oxasmaragdyrin, polythiophene, fullerene (C60), single-walled carbon nanotube and graphene are investigated. Antenna systems of BODIPY dyads and oligomers having BODIPY as an excitation energy donor connected to different acceptors including BODIPY, azaBODIPY, oxasmaragdyrin and aluminum porphyrin are studied. Different synthetic methodologies are used to afford donor-acceptor systems either directly linked with no spacer or with short spacers of varying length and orientation. The effect of donor orientation, donor optical gap as well as nature of donor-acceptor coupling on the donor-acceptor spectral overlap and hence the rate of excitation energy transfer is investigated. In all these systems, an ultrafast energy transfer followed by electron transfer is observed. In particular, in a directly connected BODIPY-azaBODIPY dyad an unusually ultrafast energy transfer (~ 150−200 f) via Förster mechanism is observed. The observation of energy transfer via Förster instead of Dexter mechanism in such closely coupled donor-acceptor systems shows the balance between spatial and electronic coupling achieved in the donor-acceptor system. Moreover, in donor-acceptor systems involving semiconducting 1D and 2D materials, covalently functionalized single-walled carbon nanotubes via charge stabilizing (TPA)3ZnP and noncovalently hybridized exfoliated graphene via …
Date: August 2018
Creator: Gobeze, Habtom Berhane
System: The UNT Digital Library
Utilizing Rapid Mass Spectrometry Techniques to Profile Illicit Drugs from Start to Finish (open access)

Utilizing Rapid Mass Spectrometry Techniques to Profile Illicit Drugs from Start to Finish

The increasingly complex world of illicit chemistry has created a need for rapid, selective means of determining the threat posed by new drugs as they are encountered by law enforcement personnel. To streamline this process, the entirety of the problem, from the production of illicit drugs all the way to the final analysis have been investigated. A series of N-alkylated phenethylamine analogues were synthesized in a shotgun method and subjected to direct-infusion analysis. A range of products were detected without the need for time-consuming purification steps, which was extended to novel pharmacological and receptor-binding assays where mass spectrometry is used as a detector. This direct-infusion technique was also applied to studies of methamphetamine and fentanyl production to preemptively determine improvements to common reaction conditions and explore the origins of common impurities. The ability to utilize these rapid techniques directly from the fume hood has also been critically reviewed to highlight gaps in current research and opportunities for improvement. When combined, these studies seek to provide a means for rapid, simplified analysis of illicit drugs to improve the quality of data and dramatically increase throughput.
Date: August 2018
Creator: McBride, Ethan
System: The UNT Digital Library
Application of UV-Vis Spectroscopy to the Monitoring, Characterization and Analysis of Chemical Equilibria of Copper Etching Baths (open access)

Application of UV-Vis Spectroscopy to the Monitoring, Characterization and Analysis of Chemical Equilibria of Copper Etching Baths

The continuously increasing demand for innovation in the miniaturization of microelectronics has driven the need for ever more precise fabrication strategies for device packaging, especially for printed circuit boards (PCBs). Subtractive copper etching is a fundamental step in the fabrication process, requiring very precise control of etch rate and etch factor. Changes in the etching chemical equilibrium have significant effects on etching behavior, and CuCl2 / HCl etching baths are typically monitored with several parameters including oxidation-reduction potential, conductivity, and specific gravity. However, the etch rate and etch factor can be difficult to control even under strict engineering controls of those monitoring parameters. The mechanism of acidic cupric chloride etching, regeneration and recovery is complex, and the current monitoring strategies can have difficulty controlling the interlocking chemical equilibria. A complimentary tool, thin-film UV-Vis spectroscopy, can be utilized to improve the current monitoring strategies, as UV-Vis is capable of identifying and predicting etching behavior that the current standard methodologies have difficulty predicting. Furthermore, as a chemically-sensitive probe, UV-Vis can investigate the complex changes to the chemical equilibrium and speciation of the etch bath, and can contribute overall to significant improvements in the control of the copper etching system in order to …
Date: August 2017
Creator: Lambert, Alexander S.
System: The UNT Digital Library
Design, Synthesis and Optoelectronic Properties of Monovalent Coinage Metal-Based Functional Materials toward Potential Lighting, Display and Energy-Harvesting Devices (open access)

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 …
Date: August 2017
Creator: Ghimire, Mukunda Mani
System: The UNT Digital Library
Electrochemical Deposition of Nickel Nanocomposites in Acidic Solution for Increased Corrosion Resistance (open access)

Electrochemical Deposition of Nickel Nanocomposites in Acidic Solution for Increased Corrosion Resistance

The optimal conditions for deposition of nickel coating and Ni-layered double hydroxide metal matrix composite coatings onto stainless steel discs in a modified all-sulfate solutions have been examined. Nickel films provide good general corrosion resistance and mechanical properties as a protective layer on many metallic substrates. In recent years, there has been interest in incorporation nano-dimensional ceramic materials, such as montemorillonite, into the metal matrices to improve upon the corrosion and mechanical properties. Layered double hydroxides have been used as corrosion enhancer in polymer coatings by increasing mechanical strength and lowering the corrosion rate but until now, have not been incorporated in a metal matrix by any means. Layered double hydroxides can be easily synthesized in a variety of elemental compositions and sizes but typically require the use of non-polar solvents to delaminate into nanodimensional colloidal suspensions. The synthesis of a Zn-Al LDH has been studied and characterized. The effects of the non-polar solvents dimethylformamide and n-butanol on the deposition and corrosion resistance of nickel coatings from a borate electrolyte bath have been studied, a nickel-LDH nanocomposite coating has been synthesized by electrochemical deposition and the corrosion resistance has been studied. Results indicate an improvement in corrosion resistance for the …
Date: August 2017
Creator: Daugherty, Ryan E.
System: The UNT Digital Library
Kinetic Study of the Reactions of Chlorine Atoms with Fluoromethane and Fluoromethane-d3 in the Gas Phase (open access)

Kinetic Study of the Reactions of Chlorine Atoms with Fluoromethane and Fluoromethane-d3 in the Gas Phase

The kinetics of the gas-phase reactions of chlorine atoms with fluoromethane (CH3F) and fluoromethane-d3(CD3F) were tested experimentally. The relative rate method was applied by using CH4 as the reference compound for fluoromethane (CH3F) and CH4 and CH3F as the reference compound for fluoromethane-d3(CD3F). The rate constants for H-abstraction from CH3F and D-abstraction from CD3F were measured at room temperature and a total pressure of 920 Torr using Ar as a diluent. The rate constants are described by the expressions: kH= (3.50±0.52) x 10-13 cm3 molecule-1 s-1 and kD=(5.0±0.51) x 10-14 cm3 molecule-1 s-1. The kinetic isotope effect, equal to the ratio kH/kD, was found to be 7.0±1.2 at room temperature.
Date: August 2017
Creator: Shao, Kejun
System: The UNT Digital Library
MBE Growth and Characterization of Graphene on Well-Defined Cobalt Oxide Surfaces: Graphene Spintronics without Spin Injection (open access)

MBE Growth and Characterization of Graphene on Well-Defined Cobalt Oxide Surfaces: Graphene Spintronics without Spin Injection

The direct growth of graphene by scalable methods on magnetic insulators is important for industrial development of graphene-based spintronic devices, and a route towards substrate-induced spin polarization in graphene without spin injection. X-ray photoelectron spectroscopy (XPS), low energy electron diffraction LEED, electron energy loss spectroscopy (EELS) and Auger electron spectroscopy (AES) demonstrate the growth of Co3O4(111) and CoO(111) to thicknesses greater than 100 Å on Ru(0001) surfaces, by molecular beam epitaxy (MBE). The results obtained show that the formation of the different cobalt oxide phases is O2 partial pressure dependent under same temperature and vacuum conditions and that the films are stoichiometric. Electrical I-V measurement of the Co3O4(111) show characteristic hysteresis indicative of resistive switching and thus suitable for advanced device applications. In addition, the growth of Co0.5Fe0.5O(111) was also achieved by MBE and these films were observed to be OH-stabilized. C MBE yielded azimuthally oriented few layer graphene on the OH-terminated CoO(111), Co0.5Fe0.5O(111) and Co3O4(111). AES confirms the growth of (111)-ordered sp2 C layers. EELS data demonstrate significant graphene-to-oxide charge transfer with Raman spectroscopy showing the formation of a graphene-oxide buffer layer, in excellent agreement with previous theoretical predictions. XPS data show the formation of C-O covalent bonding between …
Date: August 2017
Creator: Olanipekun, Opeyemi B
System: The UNT Digital Library
Microwave-Assisted Synthesis and Photophysical Properties of Poly-Imine Ambipolar Ligands and Their Rhenium(I) Carbonyl Complexes (open access)

Microwave-Assisted Synthesis and Photophysical Properties of Poly-Imine Ambipolar Ligands and Their Rhenium(I) Carbonyl Complexes

The phenomenon luminescence rigidochromism has been reported since the 1970s in tricarbonyldiimine complexes with a general formula [R(CO)3LX] using conventional unipolar diimine ligands such as 2,2;-bipyridine or 1,10-phenanthroline as L, and halogens or simple solvents as X. As a major part of this dissertation, microwave-assisted synthesis, purification, characterization and detailed photoluminescence studies of the complex fac-[ReCl(CO)3L], 1, where L = 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl]-N,N-diethylbenzenamine are reported. The employment of microwaves in the preparation of 1 decreased the reaction time from 48 to 2 hours compared to the conventional reflux method. Stoichiometry variations allows for selective preparation of either a mononuclear, 1, or binuclear, fac-[Re2Cl2(CO)6], 2, complex. The photophysical properties of 1 were analyzed finding that it possesses significant luminescence rigidochromism. The steady state photoluminescence emission spectra of 1 in solution shift from 550 nm in frozen media to 610 nm when the matrix becomes fluid. Moreover, a very sensitive emission spectral analysis of 0.1 K temperatures steps shows a smooth transition through the glass transition temperature of the solvent host. Furthermore, synthetic modifications to L have attained a family of ambipolar compounds that have tunable photophysical, thermophysical and other material properties that render them promising candidates for potential applications in organic electronics and/or …
Date: August 2017
Creator: Salazar Garza, Gustavo Adolfo
System: The UNT Digital Library