Inorganic Chemistry Commons^™

Calcium Bistriflimide-Mediated Sulfur(Vi)–Fluoride Exchange (Sufex): Mechanistic Insights Toward Instigating Catalysis, Brian Han, Samuel R. Khasnavis, Matthew Nwerem, Michael Bertagna, Nicholas D. Ball, O. Maduka Ogba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

We report a mechanistic investigation of calcium bistriflimide-mediated sulfur(VI)–fluoride exchange (SuFEx) between sulfonyl fluorides and amines. We determine the likely pre-activation resting state─a calcium bistriflimide complex with ligated amines─thus allowing for corroborated calculation of the SuFEx activation barrier at ∼21 kcal/mol, compared to 21.5 ± 0.14 kcal/mol derived via kinetics experiments. Transition state analysis revealed: (1) a two-point calcium-substrate contact that activates the sulfur(VI) center and stabilizes the leaving fluoride and (2) a 1,4-diazabicyclo[2.2.2]octane additive that provides Brønsted-base activation of the nucleophilic amine. Stable Ca–F complexes upon sulfonamide formation are likely contributors to inhibited catalytic turnover, and a proof-of-principle redesign …

Calcium Bistriflimide-Mediated Sulfur (Vi)–Fluoride Exchange (Sufex): Mechanistic Insights Toward Instigating Catalysis, Nicholas Ball, Brian Han, Samuel R. Khasnavis, Matthew Nwerem, Michael Bertagna, O Maduka Ogba

Pomona Faculty Publications and Research

We report a mechanistic investigation of calcium bistriflimide-mediated sulfur(VI)–fluoride exchange (SuFEx) between sulfonyl fluorides and amines. We determine the likely pre-activation resting state─a calcium bistriflimide complex with ligated amines─thus allowing for corroborated calculation of the SuFEx activation barrier at ∼21 kcal/mol, compared to 21.5 ± 0.14 kcal/mol derived via kinetics experiments. Transition state analysis revealed: (1) a two-point calcium-substrate contact that activates the sulfur(VI) center and stabilizes the leaving fluoride and (2) a 1,4-diazabicyclo[2.2.2]octane additive that provides Brønsted-base activation of the nucleophilic amine. Stable Ca–F complexes upon sulfonamide formation are likely contributors to inhibited catalytic turnover, and a proof-of-principle redesign …

Cysteine Metallochemistry And Metal Binding: Quantification Of The Thermodynamic Foundations Of Cellular Homeostasis, Matthew R. Mehlenbacher

Dartmouth College Ph.D Dissertations

Metals are required for life. Many metalloproteins contain cysteine in their metal-binding site (MBS) and cysteines are unique in that they are reactive, and strongly bind certain metals, which aid in metal selectivity and specificity. Using isothermal titration calorimetry (ITC), the thermodynamic foundation for metal binding, cellular protection, and transcriptional regulation, which all utilize cysteines in their MBS, are quantified.

In bacteria there are metalloprotein pathways that actively uptake mercury, which are regulated by the metalloregulatory protein MerR. MerR de-represses the transcription of these mer proteins in a metal-dependent manner. Using ITC, the thermodynamic foundation of the negative allosteric coupling …

C-H On The Oxo Ferryl Wheel: Comparison Of Pyridine And Imidazole-Substituted Ligands For C-H Activation And Functionalization, Elizabeth Milem

Electronic Theses and Dissertations

The selective and efficient transformation of hydrocarbon feedstocks is of high value for industry and research. While Shilov-type organometallic methods have facilitated this goal, systems designed after nature’s use of cheap and abundant iron-based enzymes are desired for wider-scale applications. This work establishes hydrocarbon oxidation efficiency of synthetic pyridine-based ligands (BPMEN, BPMPN) compared to commercially available TPA with in situ generated catalysts. Literature studies of traditionally synthesized BPMEN systems and initial in situ studies offered evidence for enhanced reactivity (TON) as compared to TPA. Expansion to a propyl backbone to produce BPMPN tested the increased chelate ring size’s impact on …

Analysis Of The Light Responsive Azobenzene Peptide Nucleic Acid Duplexes, Kat Nguyen

Honors College Theses

Peptide nucleic acids (PNAs) are oligonucleotide analogues in which the sugar-phosphate backbone has been replaced by a pseudopeptide skeleton. Since PNAs use the natural nucleobases (Adenine, Thymine, Cytosine, Uracil, and Guanine) found in either DNA and/or RNA, they are able to hybridize according to Watson-Crick base-pairing to form duplexes. PNA is a promising therapeutic agent because they can function as antigene or antisense chemical agents. To further enhance their utility, we aim to incorporate a photoswitchable moiety using azobenzene. Here, we report the results of the synthesis and purification of a photoswitchable 11 mer PNA along with initial characterization efforts.

Light Harvesting And Electrically Conducting Metal-Organic Frameworks, Monica Gordillo Varela

All Dissertations

Composed of metal clusters nodes and organic linkers, metal-organic frameworks (MOFs) have emerged as versatile platforms with unparalleled chemical and structural tunability, synthetic facility, permanent porosity, and size-selective guest encapsulation capability. These features make them potential candidates for a variety of applications such as gas storage,drug delivery, catalysis,and sensing. In recent years, the introduction of redox- and photoactive components have yielded stimuli-responsive electronic and photonic MOFs and expanded their utility in molecular electronics and energy storage devices/technologies.

Chapter one describes the light-harvesting ability of a porphyrin-based MOF. Herein, we have demonstrated spontaneous solvothermal growth of [100]-oriented uniform pillared-porphyrin framework-11 (PPF-11) …

Understanding Interfacial Reactions Initiating On Electrode Materials For Energy Storage Technologies, Jingnan Li

Graduate Theses and Dissertations

Since the first generation of lithium-ion batteries featured lithium cobalt oxide cathode and carbon anode commercialized in the 1990s, the high-capacity materials with lower cost are in demand to further increase the battery energy density. Lithium metal and silicon anode are promising high-capacity anode materials to achieve next-generation lithium batteries. However, both the materials actively react in electrolytes and suffer from dramatic volume change. Therefore, a reliable passivation layer at the electrolyte/electrode interphase (i.e., solid electrolyte interphase, or “SEI”) is required to support the long-term cycling of both materials. Cetrimonium hydro fluoride (CTAHF2) has been proposed and synthesized as an …

Structural, Charge Transport, Gas Sensing, Magnetic, Pseudocapacitive, And Electrocatalytic Properties Of Perovskite Oxides., Surendra Bahadur Karki

Electronic Theses and Dissertations

Perovskites are functional materials with the general formula ABO₃ (A = alkali, alkaline earth or lanthanoid cations and B = transition metal or main group cations). These materials are marked by a variety of crystal structures and interesting properties such as colossal magnetoresistance, ferroelectricity, multiferroicity, superconductivity, pseudocapacitance, gas sensing, charge transport, and electrocatalytic properties. The formula of perovskite can be written as AA’BB’O₆, when there is ordering between two cations over A and B-sites. Such compounds are called double perovskite oxides. Some amount of oxygen could be lost from crystal structure without decomposition of the phase. Such …

Revisiting The Chemistry Of Uranium And Rhenium Fluorides: Implication To Fuel Cycle And Nuclear Forensics Science, James Amos-Aimé Louis-Jean

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fluorine plays a major role in the nuclear industry where F2(g) and HF(g) are critical to the preparation of UF6 and UF4. These materials are prepared for uranium enrichment to increase the isotopic concentration of 235U. During separation efforts, the isotope 99Tc (a high yield fission product, 6.1% from 235U) is extracted along with uranium and can be converted to binary technetium fluorides (i.e., TcF4, TcF6) during re-enrichment of used uranium material. This provides a route for 99Tc to reenter the reactor environment and affect the nuclear properties of fuel pellets made with reprocessed uranium. The objective of this work …

Synthesis Of Inorganic-Organic Perovskite Hybrid Materials Via A Microwave Assisted Method, Anamika Poduval

LSU New Orleans Theses and Dissertations

The research presented here focusses on fabrication of organic modified inorganic two-dimensional and three-dimensional materials via microwave assisted methods. These hybrid materials are of importance due to their capacity to incorporate the characteristics of both organic and inorganic components. Microwave methods have been utilized to expedite the topochemical modification of layered perovskites. In one set of studies, microwave assisted grafting reactions were performed on layered perovskite (HLaNb₂O₇) materials with a series of hydroxy carboxylic acids. The reactivities of these organic compounds with the layered perovskites and the influence of precursor, temperature and time are demonstrated. The …

Synthesis And Characterization Of Organometallic Complexes For Biological Imaging, Emily Stumbo

Honors Theses

Luminescent transition metal complexes are of interest for biological imaging applications due to their unique photophysical properties including large Stokes shift, long fluorescence lifetimes, and tunable emission. Altering ligand structure is a useful way to manipulate the charge transfer (CT) and mixed character states that give these complexes their photophysical properties. A series of organometallic complexes containing ligands with externally facing nitrogens has been prepared and synthesized. Complexes of the form Pt (II)(tbbpy)(C2-py), Re(CO)3(N^N), Ir(C^N)2(N^N), and Ir(C^N)2(N^O) have been studied for their potential application as biological imaging agents. The goal of this project is to compare the properties of these …

Valorization Of Biopolymers And Biomass To Produce Materials For A More Circular Economy, Moira Lauer

All Dissertations

With a globally increasing population and largely unchecked consumption of raw materials, human society is on track for devastating consequences. Two industries responsible for utilizing massive amounts of raw materials and generating equally gargantuan quantities of waste are the packaging and infrastructure sectors. In 2017 in Europe, for example, packaging reached a record 173 kg of packaging waste per capita. One of the largest packaging consumers is the food industry, in which 40% of packaging is made of petroleum-derived single-use plastic, leading to a massive carbon imbalance. “The Built Environment,” on the other hand, is responsible for about 50% of …

Rational Design Of Composite Nanomaterials For Water Treatment Applications, Mariana Marcos-Hernandez

Open Access Theses & Dissertations

Water quantity and quality have been affected in communities all around the world due to population growth, pollution, changes in land use, and climate change. In order to cope with existing and anticipated water demands and shortages, the use of treated or reclaimed water is an ongoing alternative that has helped communities all over the world address this problem. The adaptation of nanotechnology to traditional water and wastewater treatment processes offers new opportunities in technological developments. Unique size-dependent properties such as: high surface to mass ratio, high reactivity, high sorption capacities, fast dissolution, superparamagnetism, among others, provide high-tech efficient materials …

Colloidal Monolayers For Concentration Light In Ultra-Thin Semiconductor Layers, Rachel Cherry

Graduate Theses and Dissertations

Thin film semiconductors are used as photoconductive absorber layers for the development of broadband terahertz generation. Using a femtosecond laser pulse, the generation of a transient increase in the conductivity occurs by photoexciting conduction band electrons in the semiconductor. These thermalize through the emission of terahertz radiation. The route to terahertz generation is not particularly efficient as significant losses come from the absorption in the substrate that is beneath the photoconductive antenna layer. This work explores the application of hexagonally close-packed monolayers of chemically synthesized nanospheres as a potential light concentration method for ultra-thin films of GaAs and black phosphorus …

A Performance Evaluation Of Architectural Coatings To Preserve Aerosol Paint On Concrete, Riley Morris

All Theses

The growing movement of assigning cultural and heritage value to graffiti and street art is one without a preservation solution to ensure the longevity of these works in-situ in an outdoor environment. The goal of this thesis was to provide a comprehensive evaluation of six architectural topcoats’ performance when applied as a conservation treatment to outdoor aerosol graffiti and street art on concrete substrate. An artist’s quality, durable, color-fast spray-paint was applied to twenty-eight concrete test panels to mimic the application of graffiti or street art. Six topcoats, Prosoco SC-1, Prosoco Gloss n’ Guard WB, Keim Faceal Oleo HD®, Keim …

Synthesis And Characterization Of Silver Thione Complexes, Audrey V. Lawrence

Honors Theses

Coordination polymers are repeating units of a coordination complex that have applications as catalysts, conductors, and magnets. In this work, silver (I) was the metal of choice because it behaves similarly to copper (I), which has been studied much more extensively and thione ligands were chosen due to their potential for forming coordination polymers. These coordination complexes with silver were synthesized by combining silver nitrate with thioacetamide, N,N'-diphenylthiourea, and 2-mercapto-1-methylimidazole. These complexes were characterized via IR spectroscopy, elemental analysis, and X-ray crystallography. Silver thioacetamide was determined to form a coordination complex through the sulfur to form a trigonal crystal lattice …

Synthesis, Characterization And Activity Of Palladium Catalysts On The Dual Support Of Cerium And Aluminum Oxides, Jihyeon Park

Theses and Dissertations

The effects of sequence of impregnation (Pd on cerium oxides -alumina and cerium oxides on Pd-alumina) and calcination temperature (500 ℃ and 850 ℃) on the catalytic oxidation of methane under lean conditions were investigated. The catalysts were prepared by a combination of impregnation, slurry and vortexing methods. The catalysts had 4.7 wt.% Pd and 10.7 wt.% Ce based on inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. The catalysts were characterized by pulse chemisorption, temperature programmed reduction (TPD), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS). The activity of the catalysts for methane combustion was measured in …

Synthesis And Characterization Of Redox-Active Multidentate Ligands For Catalytic C-H Bond Oxidation And Carbon Dioxide Reduction, Caroline Hodge

Honors Theses

This thesis focuses on two research projects. The first project reported in Chapter 1 involves the synthesis and application of a tetradentate ligand (2-(1,1-di(pyridin-2-yl)ethyl)-1,10-phenanthroline, PhenPY2Me) that is metalated with iron to give a catalyst capable of carbon-hydrogen (C-H) bond oxidation. C-H bond oxidation provides a method that may allow some transformations in organic syntheses to be streamlined. The mononuclear iron complex supported by PhenPY2Me was found to dimerize in the presence of O₂ in a non-coordinating solvent. These iron complexes and a previously reported system were assessed and compared in C-H bond oxidation with model substrates using the sacrificial …

Towards Asymmetric Mannich Reactions And Alkylation Of Indoles, Bianco Bicalho

Honors Theses

In the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,6-lutidine, acylated thiones undergo Aldol and Mannich reactions with aldehydes and nitrones to yield complex nitrogen-containing compounds. The use of a chiral metal-ligand complex is hypothesized to accelerate the reaction and increase stereochemical control during product formation. N-Alkylindoles undergo Friedel-Crafts alkylation with acetates in the presence of TMSOTf and 2,6-lutidine to produce 3-alkyl indoles. Varying Substitution on the indole at the 5 position and removal of the alkyl group from the 1 position both show continued reactivity at the 3 position even in the presence of TMSOTf.

Corrosion Prevention Of Aluminum Alloy, Andrea Brenner

Symposium of Student Scholars

Aluminum alloy (Al-alloy) is a widely used metal in construction, aerospace, aviation, and other necessary fields due to its lightweight and tweakable properties. However, corrosion is inevitable on metals and alloys, and that causes millions of dollars of revenue loss every year. Therefore, we propose to research fabricating coating to prevent corrosion on Al-alloy. This study uses an iron-based metal-organic framework (MOF) and polyurethane (PU) based composite coating to prevent corrosion on the Al-alloy. The makeup of the composite material is changed by varying the percentage of MOF. In addition, a binder is also used to enhance the homogenization between …