Chemistry Commons^™

Homopurine Guanine-Rich Sequences In Complex With N-Methyl Mesoporphyrin Ix Form Parallel G-Quadruplex Dimers And Display A Unique Symmetry Tetrad, Ming Ye , '23, Erin V. Chen , '23, S. H. Pfeil, Kailey N. Martin, Tamanaa Atrafi , '23, Sara Yun , '23, Zahara Martinez , '23, Liliya A. Yatsunyk

Chemistry & Biochemistry Faculty Works

DNA can fold into G-quadruplexes (GQs), non-canonical secondary structures formed by π-π stacking of G-tetrads. GQs are important in many biological processes, which makes them promising therapeutic targets. We identified a 42-nucleotide long, purine-only G-rich sequence from human genome, which contains eight G-stretches connected by A and AAAA loops. We divided this sequence into five unique segments, four guanine stretches each, named GA1-5. In order to investigate the role of adenines in GQ structure formation, we performed biophysical and X-ray crystallographic studies of GA1-5 and their complexes with a highly selective GQ ligand, N-methyl mesoporphyrin IX (NMM). Our data indicate …

Epitaxial Electrodeposition Of Ordered Inorganic Materials, Jay A. Switzer, Avishek Banik

Chemistry Faculty Research & Creative Works

Conspectus The quality of technological materials generally improves as the crystallographic order is increased. This is particularly true in semiconductor materials, as evidenced by the huge impact that bulk single crystals of silicon have had on electronics. Another approach to producing highly ordered materials is the epitaxial growth of crystals on a single-crystal surface that determines their orientation. Epitaxy can be used to produce films and nanostructures of materials with a level of perfection that approaches that of single crystals. It may be used to produce materials that cannot be grown as large single crystals due to either economic or …

Testing Different Approaches For The Stabilization Of Mdi: Design Of Low-Valent Molybdenum Complexes In Redox-Active Environments And Capture-Release Reactions Using N-Heterocyclic Carbenes, Asanka Indrajith Dissanayake

Wayne State University Dissertations

Methylene diphenyl diisocyanate (4,4’-MDI) is an aromatic diisocyanate, which is widely used as a monomer in the polyurethane industry. One of the main challenges with using 4,4’-MDI is its dimerization into uretdione. The polyurethane industry seeks solutions that could suppress dimerization of 4,4’-MDI and extend its shelf-life. The focus of this dissertation is on the design of chemical solutions to this problem including: (1) reversible coordination of MDI (heteroallene) to low-valent mono- or dimolybdenum complexes in redox-active ligand environment, and (2) reversible coordination of MDI with two equivalents of an appropriate N-heterocyclic carbene.

MDI (isocyanate) is a heteroallene, and heteroallenes …

Exploration And Synthesis Of Half-Heusler And Disordered Ternary Intermetallic Single Crystals, Md Fahel Bin Noor

Graduate Theses/Dissertations

Due to their distinct physical and chemical characteristics, half-Heusler compounds are intermetallic materials that have undergone substantial research. The general formula for these compounds is XYZ, where X and Y are transition metals and Z is a p-block element. Thermoelectricity is among the half-Heusler compounds' most exciting potential uses, but additional possible applications include spintronics, magnetic refrigeration, and superconductivity, among others. Recently, half-Heuslers (and Heuslers) have emerged as candidates for catalysts for hydrogenation. The CoNbSn half-Heusler compound, as well as another unique intermetallic ternary compound, the disordered Mn_4-xCr_xAl₁₁, were successfully grown as single crystals …

Computational Comparison Of Platinum, Base Metals, And Binary Intermetallic Compounds’ Efficiency In Hydrogenation Catalysis, Lauren M. Sayler

Graduate Theses/Dissertations

In the petroleum industry, platinum is used as a catalyst in hydrogenation reactions during petroleum refining. Although platinum is extremely effective as a catalyst, it is expensive. This is an investigation into platinum and what characteristics make it so efficient, with the end goal of finding intermetallic compounds composed of base metals that are as effective in hydrogenation catalysis. The metals used in this investigation are Fe, Co, Ni, Mo, and W. The research performed here is computational and used to support and direct decisions made in the laboratory. The computation is first-principle, which is accomplished using Vienna Ab initio …

S-Type Stars: Line List For The A²Π-X²Σ⁺ Band System Of Lao, P. F. Bernath, R. Dodangodage, J. Liévin

Chemistry & Biochemistry Faculty Publications

LaO bands are found in the spectra of cool S-type stars. The bands of the A²Π–X²Σ⁺ transition with v' ⩽ 3 and v'' ≤ 4 are rotationally analyzed, providing spectroscopic constants for the A²Π state. Line strengths are calculated using an ab initio transition dipole moment function, and radiative lifetimes for the A²Π state have also been computed. A line list for the A²Π–X²Σ⁺ transition of LaO is provided and can be used to determine LaO stellar abundances.

Computational Investigation Of The Ionization Potential Of Lead Sulfide Quantum Dots, Jessica Beyer

Scripps Senior Theses

The purpose of this work was to determine the impact of quantum dot size on ionization potential and to determine how the presence of carbonyl-based ligands affect the ionization potential of lead sulfide quantum dot systems. Ionization potential (IP) is defined as the energy required to remove an electron from an atom, molecule, or material. IP helps scientists determine how reactive the material of interest is, which is crucial information when manufacturing nanomaterials. Accurate quantum chemical calculations of ionization potential are challenging due to the computational cost associated with the numerical solution of the Dyson equation. In this work, the …

Multiscale Molecular Modeling Studies Of The Dynamics And Catalytic Mechanisms Of Iron(Ii)- And Zinc(Ii)-Dependent Metalloenzymes, Sodiq O. Waheed

Dissertations, Master's Theses and Master's Reports

Enzymes are biological systems that aid in specific biochemical reactions. They lower the reaction barrier, thus speeding up the reaction rate. A detailed knowledge of enzymes will not be achievable without computational modeling as it offers insight into atomistic details and catalytic species, which are crucial to designing enzyme-specific inhibitors and impossible to gain experimentally. This dissertation employs advanced multiscale computational approaches to study the dynamics and reaction mechanisms of non-heme Fe(II) and 2-oxoglutarate (2OG) dependent oxygenases, including AlkB, AlkBH2, TET2, and KDM4E, involved in DNA and histone demethylation. It also focuses on Zn(II) dependent matrix metalloproteinase-1 (MMP-1), which helps …

Functionalizing Metal-Organic Super-Containers (Moscs) For Selective Anion Recognition, Hanying Li

Dissertations and Theses

Anions are ubiquitous in Nature and play critical roles in both chemistry and biology. Biologically important molecules like enzymes, DNA, and ATP (adenosine triphosphate) are either anionic or contain negatively charged regions. Inorganic anions such as Cl- and HCO3- play essential roles in various physiological, environmental, and technological processes. Compared to cations, anions have larger ionic radii and more diffuse charge distribution, resulting in weaker electrostatic interactions. Developing synthetic receptors for controlled anion recognition is vital but poses significant challenges. Recent decades have shown remarkable progress in anion recognition, yielding diverse synthetic receptors with promising binding abilities. However, traditional approaches …

Electronic Structure And Molecular Geometries Of Metal Complexes With Dft And Multireference Method, Rina Bhowmick

Dissertations and Theses

Metal complexes are ubiquitous for their diverse applications including catalysis, sensing, medicine, and environmental applications. For effective use of metal complexes, understanding their electronic structure is essential. In most cases, molecules can be represented as a single electron configuration. However, in some cases, especially transition metal and actinide complexes, multireference electronic structures are observed. This is because the valence d (and f) orbitals in metals are often nearly degenerate, leading to close-lying energy states and the subsequently more frequent presence of multiconfigurational electronic structures. The traditional approach to modeling these systems is to use density functional theory to optimize the …

Ambient Ammonia Synthesis Via Microwave-Catalytic Materials And Plasma Chemistry, Siobhan Brown

Graduate Theses, Dissertations, and Problem Reports (ETD)

Ammonia is critical to supporting human life on earth because of its use as fertilizer. The Haber-Bosch process to produce ammonia has been practiced for over 100 years. This process operates at high pressure and temperature to overcome the thermodynamic and kinetic limitations of the ammonia synthesis reaction thus researchers have tried to overcome it for decades. At present this process represents 1% of global energy usage and 2.5% of global CO₂ emissions. The proposed chemical looping ammonia synthesis approach seeks to reduce the environmental impact of this critical process and to elucidate microwave-catalytic principles.

This research aims to …

Exploration Of Metal-Carbonyl Complexes For Decarbonylation Reactions, Rebekah C. Krupa

Graduate Theses, Dissertations, and Problem Reports (ETD)

In recent years, transition metal-mediated decarbonylation reactions have emerged as an alternative to conventional cross-coupling methods due to the advantages associated with the use of carbonyl-containing functionalities as coupling electrophiles instead of organohalides found in traditional cross-coupling reactions. This, coupled with the ubiquity of carbonyl-containing compounds in pharmaceuticals and non-biodegradable chemicals, has led to the interest in developing efficient systems for transition metal-catalyzed decarbonylation. However, these reactions are commonly limited to stoichiometric amounts of metal reagents due to the strong metal-carbonyl bond formed during transition metal-mediated decarbonylation. With the goal of gaining a better mechanistic understanding of CO dissociation in …

Water-Soluble Palladium, Copper, And Nickel Catalysts And Their Formation In Ligand-Free Suzuki-Miyaura Cross-Coupling Reactions, Priya Karna

Theses and Dissertations--Chemistry

Transition-metal catalyzed Suzuki-Miyaura (SM) cross coupling is a powerful synthetic method for constructing carbon-carbon and carbon-heteroatom bonds in designing organic compounds, agrochemicals, pharmaceuticals, and precursors for materials. However, the nature of catalysis and identity of the transition metal catalysts used in these reactions remain under debate or unknown. This dissertation reports the studies of three metals: Pd, Cu, and Ni. Pd-nanocluster catalysts and their formation in ligand-free SM reactions with Pd(II) nitrate as a precatalyst was investigated. The catalysts are water-soluble neutral Pd tetramer and trimer in their singlet electronic states as identified by UV-Vis absorption spectroscopy and are formed …

Development Of An Effective Au:Pd Bimetallic Heterogeneous Catalyst For Oxidative Lignin Depolymerization To Low Molecular Weight Aromatics, Gayan P. Karunasinghe

Theses and Dissertations--Chemistry

The principal concept behind biorefining involves the transformation of lignocellulosic biomass into valuable products and energy resources. Historically, biorefinery strategies for lignocellulosic biomass have primarily focused on improving the conversion of cellulose into ethanol, often neglecting the underutilized lignin component. Lignin consists of phenolic subunits, from which it follows that value-added products can be obtained from lignin depolymerization. Unfortunately, lignin utilization is particularly challenging due to its high structural irregularity and recalcitrance. The goal of this study was to develop an AuPd/Li-Al layered double hydroxide (LDH) bimetallic catalyst for efficient lignin depolymerization, resulting in the production of high-value aromatic compounds. …

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 …

The Design And Characterization Of Gold Nanoclusters As Elementary Building Blocks, Heather Gaebler

Theses and Dissertations (Comprehensive)

Gold nanoclusters with diameters in the quantum size regime (< ~2 nm) are promising building blocks for the design of novel nanomaterials as they exhibit unique size-dependent properties that can be altered and fine-tuned. The research outlined in this PhD thesis employs density functional theory to construct and analyze small ligand-protected cage and rod-shaped nanoclusters. Chapter 2 reports stable halide-protected gold nanocages that were engineered to have a closed-shell valence electron count of 18. This study finds that nanocages comprised of 19 and 20 gold atoms can be converted into stable magic number species containing 18 valence electrons by modifying their charged states via adsorption of halide ligands to the cage’s surface. Chapter 3 reports stable ligand-protected gold nanoclusters with a tetrahedral Au₄ core that were engineered to have a closed-shell valence electron count of 2. This study investigates the structural and electronic effects of halide and alkoxy ligands on the tetrahedral nanocluster and concludes that the results support the broader conclusion that it’s possible to fine-tune the stability and electronic properties of small gold nanoclusters using appropriate ligands. Chapter 4 reports stable gold nanorods that have diameters in the quantum regime that were constructed from elementary building blocks that contain “halide-staples”. This study presents different orientations of the “halide-staple” motifs on …

Palladium (Ii)-Catalyzed Selective Reduction Of 4’-(Phenylethynl)Acetophenone In The Presence Of A Formic Acid-Triethylamine Mixture, Suzanne Chayya, Akram Hijazi, Anis Daou, Ali Alaaeddine, Mohamad Sakr, Ghassan Younes, Mohammad El-Dakdouki

BAU Journal - Science and Technology

An efficient and straightforward palladium acetylacetonate-catalyzed hydrogen transfer of 4'- (phenylethynyl)acetophenone was developed in this study. Formic Acid was found to be the best hydrogen source in this catalytic system in the presence of triethylamine. Excellent conversions and selectivity were obtained in reducing the starting internal aromatic alkyne to either (E)-1-(4- styrylphenyl)ethanone or an interesting cyclic product, 1-(phenanthrene-3-yl)ethenone, over the ketone functional group present. Over-reduction was rarely seen. The reaction conditions were optimized in terms of the choice of the palladium catalyst, temperature, solvent, and the H-donor/base combination. Using this catalytic system, a one-step synthetic pathway of 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 …

Designing And Synthesizing A Warhead-Fragment Inhibitory Ligand For Ivyp1 Through Fragment-Based Drug Discovery, Samuel Moore

Symposium of Student Scholars

Fragment-based drug discovery (FBDD) is a powerful tool for developing anticancer and antimicrobial agents. Within this, magnetic resonance spectroscopy (NMR) provides a comprehensive qualitative and quantitative approach to screening and validating weak and robust binders with targeted proteins, making NMR among the most attractive strategies in FBDD. Inhibitor of vertebrate lysozyme (Ivyp1) of P. aeruginosa serves as an excellent target because of its active cellular location and implications in clinical prognosis for cystic fibrosis and immunocompromised patients. This study uses current NMR and biophysical techniques to develop a covalent, fragment-linked warhead inhibitor for Ivyp1 through synthetic methods, warhead linking, and …

Turning Ligands On Their Side: Computational Investigation Into The Binding Of N2o And N2 In Transition Metal Complexes, Cole Donald

Electronic Theses and Dissertations

Common greenhouse gas nitrous oxide (N₂O) is a thermodynamically potent and environmentally benign oxidant, making it a desirable target for metal center activation. Unfortunately, N₂O is a poor ligand for transition metals due to its weak sigma-donating and pi-accepting properties; as a result, few transition metal complexes capable of interacting with N₂O have been found. As the primary source of all nitrogen in organisms, abundant gas dinitrogen (N₂) is a crucially important tiny molecule and an essential part of daily existence. However, due to its inertness, it has limited practical uses in …

Computational And Experimental Investigations Of Alkali Cation Interactions At The Rutile – Water Interface, Isaac Johnston

All Dissertations

Overall, the objective of this dissertation was to investigate the degree of sorption for the alkali cations on rutile to ascertain the impact of different cation properties, such as ion size and charge density, on sorption mechanics as well as probe how the ion may alter the surface – aqueous interface. Initial molecular dynamic simulations and batch experiments showed minimal surface sorption for any alkali cation at relatively low concentrations while simultaneously suggesting the enthalpy of deprotonation shifts slightly in the presence of the alkali cations at different ionic strengths. The cations are likely causing small reorientations of the near-surface …

Synthesis And Physicochemical Characterization Of Noncentrosymmetric Quaternary Sulfides With Potential Nonlinear Optical Applications, Andrew J. Craig

Electronic Theses and Dissertations

In this work, several new quaternary sulfides were synthesized and investigated for their potential applications in optics. Chapter 1 provides an overview of nonlinear optical (NLO) materials in general, including their applications, ideal characteristics, current deficiencies, and strategies for the discovery of new candidate NLO materials, particularly those for use in the infrared (IR). Two families of compounds are investigated in this work, including Ln₃LiTS₇ (3-1-1-7) compounds and I₄-II-IV₂-VI₇ (4-1-2-7) diamond-like semiconductors (DLSs). All products were synthesized via traditional high-temperature, solid-state synthesis and their structures were solved and refined through single crystal …

Hierarchically Structured Photoelectrodes Via Atomic Layer Deposition, Justin Rowan Reed Demoulpied

Graduate Theses and Dissertations

In the search for a sustainable method to meet increasing energy needs, solar energy emerges as an underutilized, plentiful resource. Solar intermittency and requirements for transportation necessitate storing solar energy in the form of chemical bonds via artificial photosynthesis. Photoelectrochemical (PEC) water splitting generates hydrogen fuel from solar energy and water. A semiconducting material that successfully meets the complex requirements for building an industrially scalable PEC device has yet to emerge. This is leading to a reevaluation of materials previously overlooked within PEC research, mainly materials with limitations such as minimal charge carrier mobility and propensity to corrosion under illumination …

Competition Between Halogen And Chalcogen Bonding And Their Role In Probing Organic Transformations, Andrew Peloquin

All Dissertations

Halogen bonding, the attractive interaction of an electrophilic region on a halogen atom with a nucleophilic region on another atom or molecule, provides a highly directional tool in forming solid-state motifs. This interaction, along with the related chalcogen bonding interactions, forms powerful synthons, which, when combined with other typical intermolecular attractions such as hydrogen bonding, allow for the design of supramolecular structures and inputs to crystal engineering. This dissertation research serves two primary purposes: (1) to catalog halogen and chalcogen bonding interactions with various donor molecules and (2) to utilize these interactions to probe interesting organic transformations.

In order to …

Synthesis, Characterization, And Reactivity Studies Of Highly Reduced Early-Metal Complexes Supported By Imidazolin-2-Iminato Ligands, Maria Alejandra Gomez Torres

Open Access Theses & Dissertations

Our group has shown that reduction of titanium complexes supported by the sterically encumbering N-donor ligands 1,3â??bis(Dipp)imidazolinâ??2â??iminato (ImDippNâ??) and ketimine guanidinate (ketGuan = [(tBuC=N)C(NDipp)2]-) gives access to electron rich platforms featuring a metal coordinated, reduced, dearomatized arene substituent, which act as an electronic reservoir capable of facilitating multi-electron transfer chemistry driven by the rearomatization driving force. For instance, the arene-masked Ti(II) synthon (DippketGuan)(η6-ImDippN)Ti (Dipp = 2,6-iPr2C6H3) (TiDipp) is a versatile and potent one- and two-electron reductant capable of distinctive late-metal type reactivity such as transfer hydrogenation and catalytic olefin hydrogenation. Interestingly, TiDipp can mediate the reversible cleavage of thiophene and, …

Alkylthiocarbamate Metal Complexes With Antiproliferation Activity., Kritika Bajaj

Electronic Theses and Dissertations

Bis(thiosemicarbazones) (BTSCs) and their metal complexes have been extensively studied for various applications including catalysis for hydrogen evolution reactions, treatment of neurodegenerative diseases, hypoxia imaging, and a wide range of pharmacological purposes including antitumor, antiviral, antibacterial, and antifungal agents. The paramount property that makes BTSC metal complexes interesting for their use in these applications is the reduction potential of the coordinated metal, which can be selectively tuned by varying the substituents present on the ligand framework. Although the BTSCs have shown a great deal of success as potential cancer therapeutic agents, they lack selectivity towards cancer cells. For this matter, …

Dissolution And Electrochemical Recovery Of Uo2, Uo3, And U3o8 In Ionic Liquids, Katherine Iolani Thornock Luebke

UNLV Theses, Dissertations, Professional Papers, and Capstones

This research explores a novel method of increasing the solubility of uranium oxides and other actinide oxides in room temperature ionic liquids (IL) using direct dissolution. The goal is to further expand our knowledge of actinide dissolution and possible nuclear fuel cycle material applications using ionic liquids. The novelty of the methods is focused on the use of oxidizing gas generated using air passed through an ozone generator. While examples of dissolution exist in IL using acidic functionalized ionic liquids, the solubility of all possible oxide species was not demonstrated. Also, the addition of aqueous acid to IL containing actinide …

Catalytic Activity Of Tungsten-Dioxo And Tungsten-Diimido Complexes, Kayla Denike

Graduate Theses and Dissertations

Due to the significant decline in the availability of petrochemical resources and the increasing demand for the useful olefin mixtures extracted from oil, a sustainable and efficient alternative to these materials has become vital. Fortunately, renewable biomass derived materials may serve as a sustainable solution to the limited resources problem. Molecules derived from the degradation of biomasses are highly oxygenated and highly functionalized. Developing processes to efficiently defunctionalize these oxygen-rich materials will lead to potential up-conversion to carbon chemicals. Homogeneous catalytic deoxygenation processes present an opportunity to access valuable carbon commodity chemicals from biomass derived polyols. This dissertation details the …

Using An Aminimide Polymer To Extract Lithium From A Brine Solution, Austin Heidbreder, Martin Chin Ph.D.

Summer Undergraduate Research Program (SURP) Symposium

Fast lithium isolation from water partly containing lithium ions would be an improvement over the current method of obtaining lithium in lithium mining water operations. The aminimide functional group can be used to selectively bind to lithium cations to extract lithium from brine. To characterize this uptake, the concentration of water containing lithium was measured with atomic absorption spectroscopy before and after the solution has been exposed to a polymer with the aminimide functional group. Three different polymers were used: trimethyl EGDM polymer, trimethyl TMPTA polymer, and the triethyl TMPTA polymer. Of the three, the trimethyl TMPTA polymer seemed to …

Extracting Lithium Using The Steric Bulk Of An Aminimide Functional Group, Jacob Parker, Martin Chin Ph.D.

Summer Undergraduate Research Program (SURP) Symposium

An aminimide is a zwitterionic group containing a cationic nitrogen bonded to an anionic nitrogen. The goal of this project was to use the steric bulk and electronic properties of the aminimide to block other species in a brine solution such as potassium, and selectively pick up lithium. To test this, polymethacrylate beads which contain carboxyl groups were modified to the desired aminimide. Three different aminimide groups were tested, a trimethylaminimide, aminopyridiniumaminimide, and a triethylaminimide. The modified beads would be introduced to a solution containing lithium and the lithium concentration was measured before and after exposure to the beads using …