Chemistry Commons^™

Using Superatomic Clusters And Charge Transfer Ligands To Control Electronic Characteristics Of Phosphorene Nanoribbons And Phosphorene Monolayer, Ryan Lambert

Theses and Dissertations

Phosphorene is a two-dimensional electron poor p-type semiconductor with high carrier mobility and great promise for applications in electronics and optoelectronics. As the main theme in this dissertation, the following work represents different investigations of various electronic properties associated with phosphorene. Most notable are the findings on charge transfer doping with metal-chalcogenide superatoms which displays novel control of the two most important properties of a semiconductor – the band gap energy and the nature of carriers. By tuning the width of the gap and p-/n-type character of conduction, we gain control over a material’s capacity to play a certain role …

Developing Novel Femtosecond Time-Resolved Mass Spectrometry Techniques For Analysis Of Energetic Materials, Shane L. Mcpherson

Theses and Dissertations

Energetic materials and the unimolecular dissociation dynamics attributed to their initiation and subsequent bimolecular detonation have been a subject of interest for defense agencies such as the Department of Defense (DoD) for decades. The timescale in which these initial dynamics exist ranges from several picoseconds to dozens of femtoseconds, necessitating equally fast time-resolved experiments to capture and characterize these events. Our lab specializes in one such laser-based technique: femtosecond time-resolved mass spectrometry (FTRMS). FTRMS is an essentially nondiscriminatory pump-probe laser technique with nearly infinite modifications via pulse shaping, intensity, and wavelength modulation that can readily examine previously undefined dissociation pathways …

Synthesis And Characterization Of Polymer Grafted Nanoparticles, Eric Gerald Ruzicka

Theses and Dissertations

This dissertation focuses on the design, synthesis, and characterization of well controlled interfaces on nanoparticle surfaces. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize block copolymers and polymer grafted silica nanoparticles (PGNs) with precise control over molecular weight, graft density, and architectures.

In the first chapter, polymer molecular weights were determined through diffusion ordered spectroscopy NMR (DOSY NMR) as an alternative to size exclusion chromatography (SEC). Polymer standards of known molecular weight were analyzed through DOSY to obtain their respective diffusion coefficients. A calibration curve was generated correlating diffusion coefficients with polymer molecular weights. The reliability of the …

I. Preparation Of Strategic Synthetic Building Blocks For World Health Organization Essential Medicines. Ii. Applying The Principles Of Process Intensification To The Synthesis Of Fluoroquinolone Antibiotics., Jeffrey M. Noble

Theses and Dissertations

The synthesis of active pharmaceutical ingredients is often a time-consuming and expensive process. Due to the nature of pharmaceutical manufacturing, these costs are carried forward to the final purchase price by the consumer. Although there are many factors which are involved in the final costing of a pharmaceutical, the cost associated with the synthesis is the primary one which can be managed by chemists and engineers.

This work discusses the synthetic routes of four active pharmaceutical ingredients as well as the synthetic techniques and equipment used with an emphasis on how the application of specific techniques can be applied to …

Investigating The Dynamics And Fragmentation Of Nitroaromatic Radical Cations Through Femtosecond Time-Resolved Mass Spectrometry And Computational Chemistry, Hugo Andres Lopez Pena

Theses and Dissertations

Chemists have sought to control molecular dissociation with lasers for decades. Effective control of unimolecular dissociation was only achieved with the development of high-intensity ultrashort pulsed lasers and coherent control techniques that operate on timescales faster than vibrational energy redistribution. In view of this, our lab has specialized in the study of polyatomic radical cations using femtosecond time-resolved mass spectrometry (FTRMS). The interest in radical cations stems from the fact that they are highly reactive species that contribute to many physical, chemical, and biological processes. For instance, radical cations participate in shock initiation of detonated energetic materials used as explosives …

Asymmetric Cuh-Catalyzed Reductive Coupling Of Allenamides With Carbonyl Electrophiles & Development Of Nanocatalysts For Heterogeneously Catalyzed Buchwald-Hartwig Amination, Raphael K. Klake

Theses and Dissertations

Many drugs and natural products contain multiple stereogenic carbons bearing heteroatoms throughout their carbon framework. Therefore, methods that can efficiently install multiple heteroatoms on a molecule are valuable. Reductive coupling reactions have been extensively studied, and the allylation of carbonyls via the reductive coupling approach has been a key method for generating chiral tertiary and secondary allylic alcohols. This work utilizes inexpensive Cu for the asymmetric reductive coupling of allenamides with carbonyls to simultaneously install two heteroatoms (oxygen and nitrogen) on the product. These molecules have a polarity profile that make them difficult to make using traditional methods. Herein, we …

Synthesis And Application Of Redox-Active Covalent Organic Frameworks In Rechargeable Batteries, Mohammad K. Shehab

Theses and Dissertations

Synthesis and Application of Redox-Active Covalent Organic Frameworks in Rechargeable Batteries

Mohammad K. Shehab

Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States

Abstract

In recent years, lithium-ion batteries (LIBs) have been considered the dominant energy storage devices for portable electronics and electric vehicles due to their high energy density, low self-discharge rate, and long cycle life. In LIBs, the traditional positive electrodes employed are mainly derived from metal-containing inorganic compounds composed of cobalt, iron, nickel, or manganese (LiCoO₂, LiMn₂O₄, and LiFePO₄) coupled with graphite as the negative electrode. Despite …

Molecular Insights Into The Redox Of Atmospheric Mercury Through Laser Spectroscopy, Rongrong Wu Cohen

Theses and Dissertations

The widespread pollution of mercury motivates research into its atmospheric chemistry and transport. Gaseous elemental mercury (Hg(0)) dominates mercury emission to the atmosphere, but the rate of its oxidation to mercury compound (Hg(II)) plays a significant role in controlling where and when mercury deposits to ecosystems. Atomic bromine is regarded as the main oxidant for Hg(0) oxidation, known to initiate the oxidation via a two-step process in the atmosphere – formation of BrHg (R1) and subsequent reactions of BrHg with abundant free radicals Y, i.e., NO2, HOO, etc. (R2), where the reaction of BrHg +Y could also lead to the …

The Chemistry And Catalytic Activity Of Dehydrogenative Silylation And Hydroboration Of Complexes Bearing Semirigid Ligands With Group 14 Elements, Niroshani S. Abeynayake

Theses and Dissertations

Incorporation of silicon in the ligand backbone would yield electron-rich metal complexes upon coordination to transition metal complexes. The coordination chemistry of semirigid benzyl phosphines bearing a single or multiple phosphorus atoms and varying number of Si−H moieties has gained interest in recent years. This dissertation focuses on synthesizing silyl and germyl transition metal complexes of groups 9 and 10. Chapter II presents the synthesis of a family of four coordinated 14-electron rhodium complexes. The newly synthesized complexes were characterized in solution by multinuclear NMR spectroscopy and in the solid-state by single-crystal X-ray diffraction. These d⁶ complexes possess sawhorse …

Green Synthesis Of Spiro Compounds And The Phytochemical Investigation Of Diethyl Ether Fraction Of Camu-Camu (Myrciaria Dubia) Leaves, Judith Anane

Theses and Dissertations

There are a lot of lucrative plant species found in the Amazon and camu-camu (Myrciaria dubia (H.B.K.) Mc Vaugh) is distinct among them. This is due to its exceptional Vitamin C content which varies from 1600 to 6112 mg/100g of pulp. Besides the fruits which is popularly used, different parts of camu-camu plants including the stems, leaves, seeds, barks, and roots are also traditionally used in folklore practices for treating various ailments and diseases and research has showed the presence of antioxidant, antimicrobial, anticancer, anti-inflammatory agents present in these parts. In this study, the characterization of a bioactive compound, …

Dft Investigation Of Lewis Acid Assisted C-Cn Bond Activation Of Benzonitrile With [Ni(Dmpe)] Fragment, Lubna Kader

Theses and Dissertations

There has been recent interest in the field of organometallics with C—C bond activation of organic substrates that are mediated by transition metal complexes. The bond activation of C—C bonds is important, not only in organic synthesis but also in industrial processes. However, the activation of these bonds remains difficult since they are thermodynamically more stable and sterically less available to activate than the activation of the C—H bond. Most of the successful C—C cleavage uses the relief of ring strain, achievement of aromaticity, or proximity, as the driving force for the reaction.3 Another strategy is the use of a …

The Use Of Flexible Organic And Inorganic Building Blocks In Complex Metal- Organic Frameworks, Sahar Yahia Rajeh

Theses and Dissertations

Metal organic frameworks (MOFs) are new class of hybrid materials that draw the attention of scientists to discover new properties that help in many fields. The structural diversity of MOFs is accessible by incorporating different organic linkers to the same metal cluster. In this work, we reacted seven flexible organic linkers with different lengths varying from 4-carbons to 10-carbons to a copper-paddlewheel metal cluster. The flexibility of the linkers make the confirmation of MOFs a challenge, although we were able to prepare a new crystalline MOF from a 5-carbon organic linker with two different copper-clusters. Another MOF in powder form …

Synthesis Of Bioactive Heterocycles, Shaila Akter Shetu

Theses and Dissertations

The Discovery of a variety of heterocyclic drugs for the treatment of cancer and other diseases (e.g, neglected tropical diseases) is a medical breakthrough and inspiring for the research community as a whole. A wide range of natural, semi-synthetic, and synthetic anticancer drugs are synthesized using various methods. Among them, β -lactams stand out as a novel class of antibiotics that has different types of biological as well as anti-cancer properties. β -lactam has become a premier and active research subject towards the development of revolutionary anti-cancer drugs. In recent years, a large amount of investigations have been done to …

Investigating The Effects Of Ionic Liquids On Dna Gquadruplex And Protein Structure Using Molecular Dynamics Simulations, Nicholas J. Paradis

Theses and Dissertations

Nucleic acids and proteins have huge implications in biomedicine and bioengineering, however their storage instability limits their applicability and current storage protocols are expensive and globally-inaccessible. Finding an alternative biocompatible media to store nucleic acids and proteins would reduce costs and increase their applicability. Ionic liquids (ILs) are molten salt compounds that have been shown to modulate the stability and activity of nucleic acids and proteins. In this thesis, molecular modeling studies of DNA/RNA and protein structure in ILs will be discussed (Chapter 1) and this method will be used to study the IL effects on the structure on the …

Self-Assembling Porous Supramolecular Networks Capable Of Post-Synthetic Modification With A New Approach To Reticular Design With Semiconductor Potential, Steven A. Sloope

Theses and Dissertations

In past decades, research in self-assembling supramolecular frameworks have been produced with vast surface area, inherent from their porous nature. Predesigning monomers in a reticular manner allows a framework’s structure to be known before self-assembly occurs. This is very helpful since high porosity is sought after for many purposes such as hosting guests within the framework, post-synthetic modifications, sensing and detection, selective catalysis, semiconduction, etc. Methods of design usually focus on forming intrinsic porosity and unfortunately, sometimes the network formed is not as expected and porosity is lost.

In Chapter 1, we discuss novel ways of network formation, their potential …

Deciphering The Molecular Circuitry That Controls Iron Regulation In Non-Pathogenic Yeast, Debolina Hati

Theses and Dissertations

The trace metal iron is essential for the survival of almost all living organisms. It is a co-factor for many proteins involved in a variety of vital functions such as respiration, nitrogen fixation, and DNA biosynthesis, to name a few. Iron homeostasis in non-pathogenic fungi such as Schizosaccharomyces pombe has been extensively studied over the past few decades to better understand how intracellular iron is regulated under different environmental conditions. Iron regulation in S. pombe is controlled by two Fe-responsive transcriptional repressors known as Php4 and Fep1. Both rely on iron-sulfur (Fe-S) clusters as signals to balance iron acquisition, storage, …

Characterization Of The Interaction Between Grx4-Bol2 And The Iron-Responsive Transcription Factor Aft1 In Candida Glabrata, Evan A. Talib

Theses and Dissertations

Iron is an indispensable protein cofactor that plays a critical role in biological functions such as cellular respiration. However, excess iron causes cellular damage via the generation of reactive oxygen species. To obtain optimal intracellular iron levels, eukaryotic cells have developed mechanisms to tightly regulate iron levels. The molecular mechanism for iron regulation in the pathogenic yeast Candida glabrata has not yet been explored, although this yeast bears iron regulation pathways that are very similar to the model yeast Saccharomyces cerevisiae. Understanding how C. glabrata regulates iron levels is critical for the treatment of infections caused by this opportunistic …

Mechanistic Insights Into An Iron-Responsive Repressor, Fep1, From Schizosaccharomyces Pombe, Allison Nicole Kimsey

Theses and Dissertations

Iron is an essential metal cofactor required for a variety of biochemical pathways in most living organisms. In recent years, the nonpathogenic fungi Schizosaccharomyces pombe has been used to study iron regulation and uncover the molecular mechanisms for controlling intracellular iron levels. Some of these regulation pathways are conserved with those of pathogenic fungi, making these studies applicable for the future development of antifungals that target iron homeostasis. In S. pombe, the GATA-type transcriptional repressor Fep1 is responsible for repressing iron uptake genes during times of iron abundance. Previous reports have proposed that the binding of an iron-sulfur (Fe-S) …

The Optimization Of Anion Exchange Membrane Fuel Cells And Water Electrolyzers By Varying Catalyst Design And Changing Gas Inlet Composition, Jasmine D. Bohannon

Theses and Dissertations

Researchers around the globe are looking to avoid the consequences of climate change by shifting away from the burning of fossil fuels as a source of energy. While using fossil fuels have negatively affected the earth’s climate for at least the last hundred and fifty years, the introduction of renewables looks to use abundant and naturally occurring resources. Sources of renewable energy include solar power, wind power, hydropower, geothermal energy, and biomass2 . These sources work by converting the abundant source into mechanical, electrical, or chemical energy that can be used to power industrial plants or residential areas and they …

Success And Confidence In, Or Inclusive Of, Undergraduate Chemistry Students Surrounding A Collaborative Learning Intervention, Encouragement Of Metacognition, And A Multifaceted Scholarship Support Program, Maggie Erin Leake

Theses and Dissertations

Student success in chemistry has been linked to a wide range of factors. Some of these factors are familiar, easily quantified measures; colleges typically rely on factors like high school GPA and measures of aptitude to make admission decisions or set course prerequisites. Success in chemistry courses can be linked to these measures, and math aptitude scores in particular are often used as prerequisites for introductory chemistry courses. However, success in chemistry can also be affected by factors like motivation, peer interactions, sense of belonging, and metacognitive skill. Additionally, outcomes in chemistry and other STEM courses like math and physics …

Development And Characterization Of A Peanut-Shell Based Activated Carbon And The Outcomes Of A Hands-On Approach To Chemical Education, Danielle Pitre

Theses and Dissertations

Heavy metals are a recognized toxic environmental contaminant, even at very low concentrations. There have been well-known events in the last decade within the US of high amounts of lead in the drinking water supplies of cities, leading to detrimental effects within its population. Ways have been found to remove this metal, and others, from water with expensive adsorbents. The aim of the first part of this research was to create an inexpensive adsorbent from a waste material and modify it in such a way that it would be adept at removing heavy metals from water.

In Chapter I, we …

Polyaniline-Derivatives Based On Poly (Heterocyclic Diphenylamine) With Improved Electrochemical Stability And Processability, Mohammed Noifa Almtiri

Theses and Dissertations

Today, smart innovation has become an essential part of human life; thus, contemporary technologies are always looking for intelligent, responsive, and efficient materials to satisfy these demands. Consequently, synthetic "metals" or, more precisely, intrinsically conducting polymers (CPs) have begun to find a place as valuable and practical materials for a new generation of devices. Amongst all intrinsic conducting polymers, polyaniline (PANI) has attracted significant attention due to its outstanding air and moisture stability, simple preparation technique, and high electrical conductivity (chapter I).

Chapter II represents the synthesis of a new PANI derivative that contains a phenoxazine unit co-polymerized with p-phenylenediamine …

Synthesis And Processing Of Polymeric Materials For Hydrogen Storage, Dominic Adrewie

Theses and Dissertations

Hydrogen is one of the most promising alternatives and clean fuel sources, but it has faced several hurdles due to storage and transportation issues. Several methods have been proposed, developed, and are being improved. Key among these is the use of polymers as safe hydrogen storage media.

This work investigated the polymerization of methyl vinyl ketone using different concentrations 2,2’-Azobis(2-methylpropionitrile) as the initiator in a free radical polymerization mechanism. There was a subsequent analysis of the effect of the initiator concentration on the conversion rate and the molecular weight of the polymers produced with the help of Gel permeation chromatography. …

Rotational Spectroscopy Of Nonafluoro-Tert-Butyl Alcohol, Zayra Leticia Gonzalez

Theses and Dissertations

Nonafluoro-tert-butyl alcohol (NFTBA) is an alcohol being used in medicine and for the analysis of physiochemical and biological properties. Quantum chemical calculations on NFTBA were carried out using cluster computers from the Texas Advanced Computing Center (TACC) at Austin, TX. We scanned the C–C–O–H dihedral angle for 36 steps with each step at 10 degrees at the B3LYP/aug-cc-pVTZ level in order to identify the stable conformations and the energy barriers. The geometry of nonafluoro-tert-butyl was studied using MP2 and B3LYP Density Functional Theory (DFT) with an aug-cc- pVTZ basis set. The calculated rotational constants and dipole moments were used to …

Disinfection Byproducts In Wastewater, Swimming Pools, And Tea: Identification, Quantification, And Drivers Of Toxicity, Caroline O. Granger

Theses and Dissertations

Drinking water disinfection is considered one of the greatest scientific achievements of the 20th Century because it significantly reduced the number of deaths related to waterborne diseases. However, in 1974 J.J. Rook discovered that chlorine, a commonly used disinfectant, can react with natural organic matter to form disinfection byproducts (DBPs). Since then, more than 700 DBPs have been identified, with several epidemiological and toxicological studies linking DBPs to several adverse health effects such as bladder and colorectal cancer, adverse birth outcomes, and asthma. Due to their ubiquity in disinfected water and their adverse health effects, studying the formation and identifying …

Mass Spectrometric Investigation Of Removal/Transformation Of Emerging Contaminants For Safer Potable Wastewater Reuse, Kristin Cochran

Theses and Dissertations

Water scarcity is of increasing global concern as rising demand depletes current sources, so other sources such as potable wastewater reuse are being utilized. Advanced wastewater reuse removes pathogens and many contaminants, but there are concerns about resistant contaminants and the transformation products that are generated during the treatment process. This research focuses on several different contaminant classes, how well they are removed via advanced treatment processes, what transformation products arise from both advanced treatment and chlorination disinfection, and how those treated waters may impact health via toxicity and estrogen activity.

Contaminant classes considered are illicit drugs, pharmaceuticals such as …

The Development Of A Monolithic Spatial Heterodyne Spectrometer For Extreme Environments, Arelis Michelle Colόn

Theses and Dissertations

This work describes improvements to a novel instrument, the monolithic spatial heterodyne Raman spectrometer (mSHRS), which has potential to be utilized in space exploration and deep-ocean marine sensing. In previous work, the spatial heterodyne Raman spectrometer (SHRS) was demonstrated, as a small, high resolution, wide field of view spectrometer, originally developed for space applications where small size and compactness is a key consideration or where a wide field of view is advantageous, such as in remote spectroscopy. The spatial heterodyne spectrometer (SHS) was then later utilized for remote Laser-Induced Breakdown Spectroscopy (LIBS). The high throughput, high spectral resolution, and large …

Pyridyl Bis-Urea Macrocycles As Supramolecular Synthons And The Design And Synthesis Of Small Molecule Pharmaceuticals Targeting Ly6k, Devan D. Buchanan

Theses and Dissertations

Assembled pyridyl bis-urea macrocycles have been utilized as 1D supramolecular synthons to construct hierarchical assemblies. These macrocycles have both urea and pyridyl functional groups and can form non-covalent interactions with hydrogen or halogen bond donors through symmetric, ditopic acceptor motifs. Bis-urea macrocycles offer interesting capabilities as synthons to organize donors into well-defined crystal structures. In part, this is due to the urea motifs’ propensity to assemble through hydrogen bonding. New, asymmetric pyridyl macrocycles were synthesized, crystallized, and experimentally probed to determine how symmetry affects their assembly and utility as supramolecular synthons.

The Uphadhyay group identified small molecules, including NSC11150, …

Synthesis And Catalytic Behaviors Of Sub-10nm Platinum Group Metal Nanocatalysts, Zixin Wang

Theses and Dissertations

Nanoparticles of platinum group elements(Pd, Pt, Rh, Ir, Ru and Os) exhibit intriguing catalytic behaviors that are sensitively dependent upon their particle dimensions, chemical compositions, and surface structures. Platinum group elementbased nanomaterials have been widely utilized for catalyzing a series of important chemical reactions, producing over 90% of chemicals and fuels and accounting for 35% of the world's GDP globally. Reducing the overall particle sizes of the catalysts to the sub-10 nm size regime not only effectively mitigates the cost issues associated with the noble metal-based materials, but also remarkably modifies the surface atomic coordinations and the electronic band energies, …

Small Molecule Activation By Dirhenium Carbonyl Complexes, Meenal Kaushal

Theses and Dissertations

The background of small molecule activation is discussed in Chapter 1. Carbon-hydrogen (C-H) bond activation and carbon-carbon (C-C) bond formation using transition metal complexes are explained using examples from the literature. It also includes the previous work done by Dr. Adams’ lab on C-H bond activation and zwitterions in metal carbonyl complexes.

The reaction of Re₂(CO)₈(µ-C₆H₅)(µ-H) with vinyl acetate yielding three new products has been discussed in Chapter 2. One of the products Re₃(CO)₁₃(µ-η² -C₂H₃), 2.3 further reacts with I₂ resulting in …