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Elucidating The Pd Active Sites Of Bimetallic Gold-Palladium Catalysts Using Chemisorption And Titration Techniques, Andrew T. Boucher

Electronic Theses and Dissertations

A bimetallic nanoparticle catalyst combines two different metals on an oxide support, which can increase the selectivity towards useful products that may be too tightly bound to a monometallic catalyst. To explore the surface properties of such a system, we made a group of four PdAu bimetallic catalysts with varying gold mass loadings to compare with a parent Pd catalyst. The parent catalyst was synthesized using ion exchange, and gold was added to this parent Pd catalyst using incipient wetness impregnation (IWI) to create four bimetallic catalysts. All catalysts were characterized using H₂ and CO chemisorption in tandem with …

Measurements Of Atmospheric Radicals, Heather L. Runberg

Electronic Theses and Dissertations

Atmospheric particulate matter (PM) is a global health concern. PM_2.5 is formed primarily through combustion processes such as automobile use and industrial activity. Natural sources of PM_2.5 result from events like volcanos and wildfires. Upon inhalation, PM_2.5 is small enough to travel deep into the lungs where it can form reactive oxygen species (ROS), such as hydroxyl radical (OH), causing oxidative damage to pulmonary tissues. PM_2.5 has been linked to cardiopulmonary diseases such as asthma, chronic obstructive pulmonary disease (COPD), and high blood pressure.

PM_2.5 is small enough to remain aloft and travel many hundreds …

The Impact Of Project-Based Learning On Students In High School Chemistry In Rural Maine, Brianna Degone

Electronic Theses and Dissertations

Project-based learning (PBL) is an instructional strategy that is promoted throughout education for its use of active learning and ability to connect to real-world applications. Studies have been conducted on PBL ranging from early elementary grades through graduate courses, however little research considers the effectiveness of PBL at the secondary science level. This thesis considers the use of PBL and describes the implementation of a PBL unit in a rural Maine 11th grade chemistry classroom. The thesis aims to better understand the impact PBL has on students’ content learning and additional skills acquired through the PBL learning process. Along with …

A Computational Approach To Predicting And Understanding New Psychoactive Substances (Nps) For Developing A Database For State And Federal Crime Laboratories, Caroline Amelia Spencer

Electronic Theses and Dissertations

The object of this dissertation was to use a computational approach to predict and understand new psychoactive substances (NPS) to develop a database for state and federal crime. The primary scope of the dissertation was to better understand the interactions that take place between new psychoactive substances and their corresponding receptors. Through analysis of the interactions between the amino acids within the receptors and the NPS an understanding into the pharmacology and toxicology of these drugs can be gained. NPS such as synthetic cannabinoids fentanyl and its analogs and kratom have become more problematic for both state and federal crime …

Groundwater Hydrogeolgy And Hydrochemistry Of Karst Springs In The Eastern Peninsula Of Fort Hood Military Installation, William Scribner Welles

Electronic Theses and Dissertations

The eastern peninsula of Fort Hood Military Installation is underlain by a complex karst spring network. These springs are a primary water source in a protected habitat for endangered songbirds, which has only recently begun to be fully investigated. These Fredericksburg Group springs express both epigenetic and hypogenetic karst signatures. The study area is part of a paleo reef trend, a hydraulically disconnected segment of the northern section of the Edwards Aquifer. This study utilized standard ion index values, repeated measures, and principal component analyses on the chemical profiles of six perennial springs to classify spring water sources and their …

Reticular Synthesis Of Metal-Organic Rotaxane Frameworks, Alexander Joseph Stirk

Electronic Theses and Dissertations

The work herein, describes the placement of mechanically interlocked molecules (MIMs) into ordered, crystalline metal-organic frameworks (MOFs) to create metal-organic rotaxane frameworks (MORFs). This placement is done through the use of the concepts of reticular synthesis, to create predictable materials based on prior known building blocks and topological nets in order to achieve robust dynamics. The concepts of MIMs, nets, reticular synthesis, robust dynamics are all discussed in detail in Chapter 1. Also outlined in Chapter 1 are six design criteria that act as a blueprint for the creation of robust dynamics using the tenants of reticular synthesis. Chapter 2 …

Steric Effects Of Alkyl Ammonium Salts On The Combustion Of Exchanged Smectite Clays, Celeste A. Keith

Electronic Theses and Dissertations

Bomb calorimetry was explored as a new method for determining the cation exchange capacity (CEC) of clays. Smectite clays were modified with several alkyl ammonium salts varying in number of carbons and the spatial orientation of the carbons about the central nitrogen atom. The clays used, standards purchased from the Source Clay Repository, have CECs of 44, 80, 88, and 120 meq/100 g. Theoretically, the combustion energy of the organo-clays should be approximately the same for each salt. Any differences in energy would be due to the different structures of the salts and how they are oriented in the interlamellar …

A Comprehensive Analysis Of Aromatic-Proton Mediated Hydrogen Bonds, Mona S. Alshamrani

Electronic Theses and Dissertations

Hydrogen bonds play critical role in folding, structure and recognition of biological macromolecules (e.g., proteins, RNA, DNA). In addition to classical hydrogen bonds (e.g., ─OH---O=, ─OH---O─, ─NH---O─ etc.), structural analysis of protein and nucleic acids, almost a decade ago, showed that hydrogen bonds (e.g., CH---O) with hydrogen atoms on aliphatic carbon atoms (hereafter, aliphatic-protons) also play very important role in the structure and function of biomolecules. Even though, protons of aromatic ring systems (hereafter, aromatic-protons) are more polar than the aliphatic-protons, systematic analysis of hydrogen bonds of aromatic-protons have not been carried out. Therefore, I carried out a systematic analysis …

Synthesis, Chemistry, Biological Evaluation And Structure-Activity Relationships Of Rac- And Chiral 6-Desmethyl-5Β –Hydroxy-D-Secoartemisinin And Analogs, Mohamed Elsideiq Jihan

Electronic Theses and Dissertations

The prevention and cure of malaria is difficult as it thrives under poor socio- and pharmacoeconomic conditions in third world, tropical and subtropical regions. It is a parasitic disease spread through the bite of an infected Anopheles mosquito. In humans, malaria can be caused by several Plasmodium species that include: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae and Plasmodium knowlesi. The natural product artemisinin is a sesquiterpene lactone with an endoperoxide bridge isolated from the Chinese annual herb qinghao (Artemisia annua L or sweet wormwood). The relatively stable endoperoxide bridge is essential for their antimalarial activity. The synthesis of …

Improvement And Development Of Analytical Forensic Methods: Arson Investigation And Drug Detection In Fingerprints And Hair, Sarah Anne Glenn

Electronic Theses and Dissertations

Forensic science is the cornerstone of criminal investigations. Due to the overexposure of forensic science in the media, the true nature of forensic science is often overlooked. Forensic science is a rigorous exacting science that applies methods developed in the wider scientific community to the analysis of evidence collected from crime scenes. As far back as the 6th century people were using forensics to solve crimes. Since then the science behind forensic science has increased exponentially with new methods being researched and developed. This research aims to address two of the larger subsections of forensic science, arson and drug detection. …

Photogenerated O-Azaxylylenes: Mechanistic Studies And Synthetic Applications, William Cole Cronk

Electronic Theses and Dissertations

This research sets out to build upon excited state o-azaxylylene cycloaddition. The mechanism behind the excitation and cycloaddition process of photogenerated o-azaxylylenes was determined experimentally. Time-correlated single-photon counting, steady-state spectroscopy, triplet quenching experiments, and quantum yield studies provided evidence suggesting that excited state intramolecular proton transfer is followed by intersystem crossing and stepwise addition to the tethered unsaturated pendant.

In keeping with the principles of diversity oriented synthesis, a modular approach was taken to gain access to a diverse array of N,O,S-Polyheterocycles which were modified postphotochemically via Suzuki coupling to yield fused biaryls. Cycloaddition products, outfitted with halogens …

Gold Nanomolecules : Developing Synthetic Protocols, Characterization And Investigation Of Ligand Effects On Structure And Properties, Praneeth Reddy Nimmala

Electronic Theses and Dissertations

The term "Nano" in chemistry refers to particles/molecules in the size range 1 to 100 nm. Gold nanoparticles were used in ancient times in making decorative glass as they produce vibrant, size dependent, colors upon interaction with light. Gold is a preferred choice of metal for the synthesis of nanoparticles mainly due to its inertness to atmospheric conditions and most chemicals. Gold thiolate nanomolecules, which is the primary focus of this dissertation research, are chemical molecules with a fixed number of gold atoms and organo-thiolate ligands. They are of the form Aux(SR)y and possess molecule-like properties as a result of …

Dopamine Transporter (Dat) And Metabotropic Glutamate Receptor 5 (Mglu5) Irreversible Probes For Identifying Anti-Psychostimulant Therapeutics, Ranganadh Velagaleti

Electronic Theses and Dissertations

Numerous behavioral studies indicate that dopamine transporter (DAT) inhibitors and metabotropic glutamate receptor 5 (mGlu5) negative allosteric modulators (NAMs) possess promising anti-addiction therapeutic properties. However, the lack of human DAT (hDAT) and mGlu5 X-ray crystal structures makes it difficult to understand how these promising anti-addiction compounds interact with their major drug targets at the molecular level. This knowledge gap represents an important problem towards rationally designing new therapeutics for numerous addiction disorders. The objective of this research was to develop irreversible chemical probes based on select DAT inhibitors and mGlu5 NAMs in order to map the corresponding binding sites and …

Multi-Configurational Investigation Of Thermolytic Pathways Of Highly Strained Ring Systems, Jeffrey Dwayne Veals

Electronic Theses and Dissertations

The isomerization pathways of model high energy structures are of interest because of their relation to high energy density fuels. Electron resonance has been found to greatly affect the relative activation barriers for several isomerization pathways, and the major goal of this research is to accurately describe its role in determining the relative barriers for strain energy release pathways. This research is centered around the potential energy surfaces (PES's) for ? bond breaking and ? bond rotation in these highly strained structures. Of particular interest was how would resonance and or electronegativity affect the allowed/disallonature of the activation barriers in …

Self-Assembly Of Squaraine Dyes, Maher A. Qaddoura

Electronic Theses and Dissertations

Squaraine dyes have been a subject of extensive investigations lately due to their wide applications in important technological fields such as bioimaging probes, bioconjucation, second generation photosensitizers for photodynamic therapy, second harmonic generating organic dyes, two-photon absorbing materials with large cross section values, and, finally, photoconducting materials in photovoltaic cells. While a large number of patents and papers has been produced regarding their applications limited work has been done concerning their thermotropic behavior, including their liquid crystalline properties, or correlation of the crystalline structure to both the solid state aggregation and their photophysical properties. In the first chapter of this …

Hydrogen Storage In Metal Fragments Grafted Silicas And Chromium Hydrazide Gels, Ahmad Hamaed

Electronic Theses and Dissertations

Hexagonally-packed mesoporous silicas (HMS) grafted with low-valent titanium, vanadium, and chromium organometallic fragments possessing oxidation states between (II) and (IV) were synthesized, tested for their hydrogen storage capacities, and characterized by XRD, nitrogen adsorption, XPS, and EA. The effects of the variation in the surface area, pore size, transition metal type, and metal oxidation state, the organometallic loading levels, as well as the ligand environment on the H2 adsorption capacity and the binding enthalpies of these systems were investigated. This study demonstrated that titanium is more effective at hydrogen binding than vanadium and chromium. HMS silica grafted with benzyl titanium …

Solid-State Nmr Spectroscopy Of Unreceptive Nuclei In Inorganic And Organic Systems, Hiyam Hamaed

Electronic Theses and Dissertations

Nuclei are termed unreceptive if they are not amenable to solid-state NMR (SSNMR) experimentation at standard magnetic field strengths due to (i) low natural abundances or dilution; (ii) low gyromagnetic ratios; (iii) inefficient longitudinal relaxation; (iv) large quadrupole moments; or (v) combinations of these factors. This thesis focuses on applying a variety of SSNMR methods to study unreceptive nuclei in a variety of systems. The first portion of this thesis focuses upon ultra-wideline (UW) SSNMR of three main group nuclei: 209Bi, 137Ba and 115In. 209Bi and 137Ba SSNMR were applied to a series of systems with important structural motifs, while …

Characterization Of Inorganic Catalysts And Materials By Solid-State Nmr, Aaron Rossini

Electronic Theses and Dissertations

This thesis demonstrates the application of solid-state nuclear magnetic resonance (SSNMR) spectroscopy to probe the structure of a variety of inorganic complexes and materials, many of which find applications in catalysis. Particular focus is given to SSNMR spectroscopy of "exotic" and unreceptive NMR nuclei. Complimentary characterization techniques such as quantum chemical calculations and X-ray diffraction experiments are also employed. The initial focus of the thesis is on the characterization of crystalline molecular metallocenes by 35Cl, 47/49Ti and 91Zr SSNMR spectroscopy. All of these nuclei are considered to be unreceptive for NMR experiments due to a combination of low natural abundance, …

Development Of Novel Dart Tofms Analytical Techniques For The Identification Of Organic Contamination On Spaceflight-Related Substrates And Aqueous Media, Kathleen Loftin

Electronic Theses and Dissertations

Organic contamination on spaceflight hardware is an ongoing concern for spaceflight safety. In addition, for the goal of analyzing for possible evidence of extra-terrestrial life, it is necessary to consider the presence of terrestrial contamination. This paper will introduce and evaluate a new method using a direct analysis real time (DART) ionization source paired with a high resolution time of flight mass spectrometer (TOFMS) for the determination of organic contamination involved in spaceflight hardware and ground support materials. This novel analytical technique has significant advantages over current methodologies. Materials analyzed in this study were historically considered as probable contaminants in …

The Influence Of Temperature And Chemical Hydrophobicity On Steady And Non-Steady State Polychlorinated Biphenyl Bioaccumulation In Temperate Fish, Michael Burtnyk

Electronic Theses and Dissertations

This thesis investigated the effects of temperature and chemical hydrophobicity on steady and non-steady state bioaccumulation of polychlorinated biphenyls over the lifetime of temperate freshwater fish. In Chapter 2, the elimination of congeners of logKow < 5.7 by yellow perch (Perca flavescens) was regulated by temperature-dependant metabolic rates. Congeners of logKow > 5.7 however, were not significantly eliminated at any temperature commonly encountered by temperate fishes. It was concluded that the bioaccumulation of congeners of logKow > 5.7 is regulated by energetically driven consumption rates. This conclusion was confirmed in Chapter 3, where it was determined that the majority of congeners of logKow > 6.8 did not achieve steady state within the lifetime of bluegill (Lepomis macrochirus) or cisco …

New Liquid Crystalline [2]Rotaxanes, Natalie Suhan

Electronic Theses and Dissertations

This thesis presents design, synthesis and characterization of a range of new liquid crystalline interlocked molecules and to study structure-property relationships between rotaxane design and mesomorphism. Chapter 1 introduces concepts of supramolecular chemistry and liquid crystals and cooperative effect between [2]rotaxane and liquid crystals towards functional molecular machines. In Chapter 2, a systematic approach to introduce liquid crystallinity into the 1,2-bis(pyridinium)ethane/DB24C8 motif is described. The chapter begins with synthesis and purification of dumbbells (without macrocycle) and [2]rotaxanes (with macrocycle) substituted with purely aliphatic extended 3,5-disubstituted stoppers with increasing alkyl chain length. Chapter continues with phase characterization and structure-property relationships between …

Synthesis And Reactivity Of Early Transition Metal "Frustrated Lewis Pairs", Ojisamola Adeseeke Labeodan

Electronic Theses and Dissertations

Our research group recently introduced the new concept of "Frustrated Lewis Pairs" (FLP) wherein sterically demanding Lewis acids and bases do not interact in the expected donor-acceptor fashion, but rather exhibit unique reactivity. To date this concept of FLPs has been limited to main group systems. In this thesis we demonstrate that Lewis acidic early metal cations can activate small molecules in the presence of sterically demanding donors to exhibit unique reactivity. The cationic Lewis acids [Cp2Zr(O't'Bu)] +, [Cp2Zr(OPh)]+, [Cp2Zr(OMes)] + and [Cp2Zr(ODipp)]+ are generated by the reaction between the neutral precursor compound and methyl abstracting reagents [Ph3C][B(C6F5)4] and B(C …

Solution Processible Aromatic Polyimides Via Diels Alder Precursor, Saral Shah

Electronic Theses and Dissertations

Aromatic polyimides are interesting materials since they possess outstanding key properties such as thermoxidative stability, high mechanical strength, high modulus, excellent electrical properties, and superior chemical resistance. However, their low solubility makes them difficult to characterize, process and obtain high molecular weight polymer. In this report, we synthesized a series of precursor polymers that contains Diels-Alder (DA) adducts of anthracene. Different dienophiles were tried. These precursor polymers are soluble in common organic solvents such as chloroform and can be easily processed to thin films. Heating the film above 215 degree induce retro-DA reaction, which generated the fully aromatic polyimides in …

Nonlinear Dynamics In Bromate-Based Chemical Oscillators, Nan Li

Electronic Theses and Dissertations

During the course of this work, I discovered that the presence of 1,4-benzoquinone not only could induce various complex behaviors but also significantly enhance the photosensitivity of the BZ system. Mechanistic study suggests that the kinetic influence of 1,4-benzoquinone mainly arises from its interaction with ferriin to form a complex. In the photo-mediated 1,4-benzoquinone-bromate oscillator, dramatic changes in the reaction behavior were achieved upon the initial presence of hydroquinone. Measurements with UV/Vis spectroscopy and MS spectrometry suggest that the formation of hydroquinone-benzoquinone dimer plays a significant kinetic role in the studied system. Further mechanistic investigations on the photo-illuminated Q-bromate reaction …

Studying The Anti-Cancer Potential Of The Natural Compound Pancratistatin., Amanda Mclachlan-Burgess

Electronic Theses and Dissertations

One of the current challenges in the fight against cancer is to find anti-cancer treatments that specifically target cancerous cells, while leaving normal cells unharmed. Apoptosis, or programmed cell death, is a non-traumatic, physiological process by which cells that are no longer needed or are potentially harmful can be removed from the system. Recently, anti-cancer research has focused on targeting the components of biochemical pathways that can induce apoptosis specifically in cancerous cells. The search for cancer-specific drugs has led some researchers to investigate the potential anti-cancer activity of natural compounds. Pancratistatin (PST) is a natural compound that was isolated …

Nickel(0) Catalyzed Carbon-Hydrogen Bond Activation: A Mechanistic Study Of The Formation Of A Nickel(I)-Nickel(I) Complex., Alana Lauren Keen

Electronic Theses and Dissertations

The first part of this thesis deals with a mechanistic investigation into the conversion of the known benzyne complex, Ni(eta2-C 6H2F2)(PEt3)2, to the novel dinuclear Ni(I)-Ni(I) complex, (PEt3)4Ni2(eta 2-C6H2-4,5-F2)2. The coupling of two molecules of Ni(eta2-C6H2F 2)(PEt3)2 does not result in the formation of (PEt3)4Ni2(eta2-C6 H2-4,5-F2)2. There is a rearrangement in the disposition of the hydrogen atoms from para disposed in Ni(eta 2-C6H2F2)(PEt3)2 to ortho disposed in (PEt3)4Ni2(eta 2-C6H2-4,5-F2)2, which was found to be the result of C-H bond activation catalyzed by Ni(0). Proposed mechanisms involving the isolated reaction intermediates Ni2(mu-eta 2:eta2-C6H2F2)(PEt 3)2 and (PEt3)2(PMe3) 2Ni2(eta2-C6H2-3,4-F 2)2 are given and …

Nonlinear Instabilities In Photochemical Oxidations Of 1,4-Cyclohexanedione And Its Derivatives., Bei Zhao

Electronic Theses and Dissertations

In the closed 1,4-cyclohexanedione(CHD) bromate oscillatory reaction, we discovered that stirring can induce transitions between simple and period-doubled oscillations. When illumination was employed to characterize the importance of micro fluctuations of concentrations, the threshold stirring rate for inducing a bifurcation was found to increase proportionally to the intensity of the applied light. Numerical simulations with an existing model illustrate that the experimental phenomena could be qualitatively reproduced by considering effects of mixing on diffusion-limited radical reactions, namely, the disproportion reaction of hydroquinone radicals. A novel light-mediated chemical oscillator, i.e. 1,4-benzoquione(Q-bromate oscillator, was uncovered and investigated systematically in a batch reactor. …

Anion Interactions Of [2]Pseudorotaxanes And [2]Rotaxanes., Iavor S. Mihalkov

Electronic Theses and Dissertations

This thesis describes studies on the interactions of anions with [2]pseudorotaxanes and [2]rotaxanes comprised of 24-membered crown ether wheels and bis(pyridinium)ethane axles which incorporate an amide anion receptor. Eight nicotinamide-based threads containing a bis(pyridinium)ethane recognition motif were synthesized. Their ability to form [2]pseudorotaxane complexes with 24-membered crown ethers was determined by 1H NMR spectroscopy. The effect of anion binding on the stability of the [2]pseudorotaxanes was investigated using 1H NMR titrations. Nine [2]rotaxanes were synthesized from the combination of three threads and three crown ethers---dibenzo-, dinaphtho-, and naphtho-24-crown-8. The selectivity of the amide receptor towards small inorganic anions---halides and dihydrogenphosphate---were …

Syntheses And Reactivities Of Improved Univalent Indium Salts., Christopher G. Andrews

Electronic Theses and Dissertations

Reported herein are the syntheses and characterizations for a number of new families of compounds containing the main group metal indium in its relatively uncommon univalent oxidation state. Starting from the known half-sandwich compound Cp*In, (Cp* = pentamethylcyclopentadienyl) it is possible to effect a clean and facile cleavage of the organic ring from the metal with the addition of a non-oxidizing Bronstead acid. Once removal of the hydrocarbon by-product is accomplished, the metal is left in a binary salt with the conjugate base of the Bronstead acid used. This protonolysis approach is a versatile method allowing for easy selection of …

Vanadium Phosphinimide Complexes For Ethylene Polymerization And The Chemistry Of Phosphinimines And Phosphine Oxides With Borane Reagents, Sarah Bess Hawkeswood

Electronic Theses and Dissertations

A reproducible and high yielding synthesis of the vanadium imide phosphinimide complexes of the general formula V(NAr)(NPR3)Cl2 (Ar = Ph, C6H3-2,6-i-Pr2; R = i-Pr, t-Bu, Ph) has been developed. These complexes upon activation by methylaluminoxane demonstrated low to moderate ethylene polymerization activities comparable to published vanadium imide complexes. The dichloride derivatives react readily with a variety of alkali metal salts and Grignard reagents to produce vanadium imide phosphinimide thiolate, alkyl, aryl, amide and alkoxide complexes. In the presence of Zn, reduction of V(NPh)(NPt-Bu3)Cl2 occurred to afford what is proposed to be a vanadium(IV) imide bridged dimeric species (V(mu-NPh)(NPt-Bu3)Cl)2. The reaction …