Physical Sciences and Mathematics Commons^™

Purification And Activity Analysis Of A Highly Active Recombinant Catalase From Psychrophilic Bacterium Psychrobacter Cryohaloentis, Andrew Stewart

Honors Program Theses

To date, the genus Psychrobacter includes 37 recognized bacterial species isolated from different sources ranging from Siberian permafrost (P. cryohalolentis) to seal feces (P. lutiphocae). Due to its diverse ecological niches, several species belonging to the genus have different enzymatic activities with potential applications in bioremediation and the food industry. In this study, a bioprospecting approach was used to perform a in depth analysis of a Psychrobacter-like bacterial strain isolated from goose feces (designated as Psychrobacter unknown). The phylogenetic analysis of 16S rRNA gene and homologous sequence studies suggest that the strain may represent a novel species of the Psychrobacter …

Synthesis, Characterization, And Kinetics Studies Of New Cobalt Complexes For The Production Of H2 In Acidic Media, Michael John Celestine

Chemistry & Biochemistry Theses & Dissertations

The kinetics and mechanism of the oxidation of [Co(dmgBF₂)₂(OH₂)₂] (where dmgBF₂ = difluoroboryldimethylglyoximato) by sodium hypochlorite (NaOCl), sodium bromate (NaBrO₃), and bromine (Br₂₎ was investigated by stopped-flow spectrophotometry at 450 nm over a wide temperature range. The pK_a1 value for [Co(dmgBF₂)₂(OH₂)₂] was calculated as 5.27 ± 0.14 at I = 0.60 (NaCl). From the variation in pH studies, the activation parameters were derived from the proposed mechanisms for NaOCl, ΔH_1*, ΔH_2*, ΔS_1*, and …

Reactions Of First-Row Transition Metal Complexes In Bis(Alkoxide) Ligand Environments With Diazoalkanes: Formation Of Carbenes Versus Reductive Coupling To Form Bridging Tetrazenes, Amanda Grass

Wayne State University Dissertations

This dissertation focuses on the design and reactions of novel late transition metal carbene complexes featuring alkoxide ligand environments. The high-valent cobalt carbene Co(OR)2(=CPh2) (OR = OCtBu2Ph), featuring short Co=C bond of 1.773(3) Å, was previously reported from the reaction of Co(OR)2(THF)2 with diphenyldiazoalkane. Magnetic and spectroscopic (EPR) studies demonstrated Co(OR)2(=CPh2) to be a low-spin S = ½ complex. Computational studies, in agreement with experimental data, suggested that the electronic structure of Co(OR)2(=CPh2) lies between intermediate spin Co(III) anti-ferromagnetically coupled to a carbene radical and a Co(IV) alkylidene. This dissertation began with investigation of this complex in carbene transfer reactivity. …

Cobalt-Catalyzed Aerobic Oxidative Cyclization Reactions Of Bisnucleophiles: New Methodologies And The Role Of Bisnucleophiles In O2 Activation, Jiaqi Liu

Graduate Theses, Dissertations, and Problem Reports

Over the past few decades, transition metals have found wide applications in the development of selective oxidative transformations mediated by molecular oxygen. Due to the benign nature of molecular oxygen as an oxidant and an increasing awareness of green chemistry practice, tremendous progress has been made towards the development of Cu-and Pd-catalyzed aerobic oxidation reactions. As a first-row transition metal alternative to copper, cobalt has been employed in aerobic catalytic transformations for its cost-efficiency and earth abundance; however, redox-active mediators such as benzoquinone (BQ), N-hydroxyphthalimide (NHPI) or salen-type ligands are usually required. To date, reactions mediated by Co/O₂ catalytic …

Activation Of Nitrite And Carbon Dioxide By Cobalt Centered Redox Active Ligand Featuring A Hemilabile Pendant Amine, Douglas F. Baumgardner

WWU Graduate School Collection

Carbon dioxide (CO₂) and bioavailable nitrogen in the form of nitrates (NO₃^-) and nitrites (NO₂^-) are serious environmental pollutants. However, without economic incentives there is little interest in remediation of these pollutants outside of laboratory scale experiments. CO₂ can be converted to carbon monoxide (CO), a valuable building block in Fischer-Tropsch sourced fuel, and NO₃^- and NO₂^- can be converted to ammonia, another important chemical building block. However, both require effective, low-cost catalysts to be financially viable options. This thesis seeks to demonstrate the conversion of CO …

Synthesis Of Magnetic Ion Doped Ii-Vi Benzenechalcogenolate Molecular Clusters, Fumitoshi Kato

Doctoral Dissertations

Diluted magnetic semiconductor quantum dots (DMS-QDs) is a class of material prepared by introducing a small percentage of magnetic impurities to impart new magneto-optical properties to the host nanocrystal (NC). Such materials are regarded as promising candidates for their potential application in spintronic devices. The overall functionality of the DMS‑QD is highly dependent on the dopant position within the host structure. A thorough understanding of the doping mechanism is, therefore, critical to gain better control over the dopant speciation in nanocrystal lattice and material properties. In this work, we utilized II‑VI molecular clusters that are analogous to bulk semiconductors as …

Cationic Cobalt (Ii) Hydroformylation, Drew Michael Hood

LSU Doctoral Dissertations

While investigating a bimetallic cobalt hydroformylation catalyst a new class of monometallic cationic cobalt (II) hydroformylation catalyst were discovered. These newly discovered catalyst proved to be very unique with high hydroformylation activity under mild conditions. The pre-catalyst were characterized using various methods including NMR, EPR, MS, and X-ray crystallography. Similarly the active catalyst was also investigated using NMR, EPR, FTIR, and X-ray crystallography. Various catalyst modifications were investigated for their effects on hydroformylation activity. Likewise various reaction parameters were probed to determine their effect on hydroformylation activity. Finally the best cationic cobalt (II) catalyst were directly compared to industry standards …

Synthesis And Applications Of Ceramic (Silicon Carbide And Silicon Nitride), Metallic (Cobalt(0)) And Polymeric (Polyurethane) Aerogels, Parwani M. Rewatkar

Doctoral Dissertations

"A new method has been demonstrated for the synthesis of monolithic ceramic and purely metallic aerogels from xerogel powder compacts, and the use of polyurethane aerogels based on cyclodextrins as efficient desiccants.

I. Highly porous ( > 80%) monolithic SiC and Si₃N₄, aerogels were prepared from compressed compacts of polyurea-crosslinked silica xerogel powders. The process is time efficient as solvent-exchange through powders is fast, and energy efficient as it bypasses drying with supercritical fluids. The final ceramic objects were chemically pure, sturdy, with compressive moduli at 37 ±7 MPa and 59 ± 7 MPa, and thermal conductivities …

Metalloglycomics: Investigating The Interactions Of Metal Complexes With Heparan Mimetics, Wyatt Johnson

Theses and Dissertations

Proteoglycans containing Heparan Sulfate (HS), a sulfated glycosaminoglycan (GAG), play a major role in the cell signaling process, interacting with many different proteins. HS is over expressed on the surface of many cancer cells. Enzymatic cleavage of HS-GAGs by heparanase causes release of angiogenic growth factors leading to tumor cell migration. Heparanase is also over-expressed in tumors with significant correlation between metastatic potential and heparanase activity. Proteoglycans and their associated enzymes are thus significant drug targets of high biological relevance.

A functional consequence of strong PPC-HS binding has been shown in proof-of-concept studies confirming inhibition of the model pentasaccharide, Fondaparinux, …

Electrodeposited Epitaxial Cobalt Oxides And Copper Metal, Caleb M. Hull

Doctoral Dissertations

"Electrochemical deposition methods are presented for the deposition of Co(OH)₂ and Cu metal. Paper I shows the deposition of β-Co(OH)₂ on Ti through electrochemical reduction of [Co(en)₃]³⁺ to [Co(en)₃]²⁺ in 2M NaOH. The catalytic properties of the deposited Co(OH)₂ towards water oxidation is found comparable to Co₃O₄, with the surface of the Co(OH)₂ converting to CoOOH during the reaction. Paper II gives the conditions suitable for epitaxial growth of Co(OH)₂ on Au(100), Au(110), and Au(111) following the same reduction mechanism as described in Paper I. …

Homo- And Heterometallic Bis(Pentafluorobenzoyl)Methanide Complexes Of Copper(Ii) And Cobalt(Ii), Janell Crowder

Legacy Theses & Dissertations (2009 - 2024)

β-Diketones are well known to form metal complexes with practically every known metal and metalloid. Metal complexes of fluorinated β-diketones generally exhibit increased volatility and thermal stability compared to the non-fluorinated analogues, and thus are used extensively in various chemical vapor deposition (CVD) processes for the deposition of metal, simple or mixed metal oxides, and fluorine-doped metal oxide thin films. Furthermore, the electron-withdrawing nature of the fluorinated ligand enhances the Lewis acidity of a coordinatively unsaturated metal center which facilitates additional coordination reactions. The physical and structural properties of fluorinated β-diketonate complexes are discussed in Chapter 1 …

Separation Of Nitrito- And Nitropentamminecobalt (Iii) Chloride By High Performance Liquid Chromatography, Tisha Hutchinson

Seton Hall University Dissertations and Theses (ETDs)

Reversed phase high performance liquid chromatography, chosen because of its ability to collect many data points over a long period of time with minimal involvement, was used to separate pentaamminenitritocobalt(III) chloride and pentaamminenitrocobalt(III) chloride. Pentaamminenitritocobalt(III) chloride was prepared, made into a concentrated solution, divided into aliquots and allowed to isomerize to pentaamminenitrocobalt(III) chloride over a period of twelve to eighteen hours. An injection was made approximately every forty-five minutes. The samples were analyzed at three wavelengths, 254 nm, 460 nm and 490 nm. The absorbance was collected and was used to determine the kinetics of the reaction.

The isomerization from …

Cobalt Mediated Oxidative Cyclizations: The Diastereoselective Synthesis Of Trans-Tetrahydrofuran Rings, Cory D.N. Palmer

Electronic Thesis and Dissertation Repository

The Mukaiyama oxidative cyclization has been a major area of study within the Pagenkopf group and within the field of THF containing natural products. This document contains a brief discussion of the major divisions of THF synthesis; S_N2, cycloadditions, and transition mediated strategies. The development of the Mukaiyama cyclization is described from the earliest applications of cobalt acac type ligand in Mukaiyama’s work to the initial discovery of the cyclization reactivity. Initial finding from the Mukaiyama group is shown, accompanied by its applications to the synthesis of mucosin, aplysiallene, and bullatacin. Previous attempts at improved catalyst design are …

Computational Studies On Mechanisms And Reactivity Of Mercury And Cobalt Organometallic Reactions, Jack Terrell Fuller

Theses and Dissertations

Density Functional Theory (DFT) is a powerful tool for treating large organometallic structures efficiently and accurately. DFT calculations on the Hg-catalyzed oxidation of methane to methyl bisulfate in sulfuric acid suggest the lowest energy pathway involves a closed-shell electrophilic C–H activation mechanism coupled with metal alkyl reductive functionalization and oxidation by SO3. Comparison to Tl, Zn, and Cd suggests that Hg is unique in its ability to catalyze this set of reaction steps. Comparison to K2S2O8 highlights the selectivity of this C–H activation reaction as opposed to radical conditions. In contrast, DFT calculations indicate that CoIII(TFA)3 oxidizes methane through a …

Synthesis And Mechanistic Investigations Of Transition Metal Complexes And Ligands For Chemotherapeutic Applications, Jimmie Lee Bullock Jr.

Chemistry & Biochemistry Theses & Dissertations

Transition metal complexes have played a critical role in antitumor therapy with many complexes incorporating platinum, ruthenium, and lanthanum having been investigated in preclinical and clinical trials. The best known transition metal therapeutic is cisplatin, which is utilized in nearly 50% of all cancer therapies, despite its significant toxic side effects. The toxic side effects of current FDA approved platinum-based chemotherapeutics are often overlooked due to the “special status” granted to these drugs due to their ability to fight, what is often considered an incurable disease with life expectancies often measured in months. Oncology drug development has therefore now focused …

Versatile Synthesis Of Transition Metal Phosphides: Emerging Front-Runners For Affordable Catalysis, April C. Mattei

Theses and Dissertations

Transition metal phosphide materials have found themselves at the forefront of research revolving around energy applications. Due to the vast range of properties possessed by marginally different phase compositions, binary and ternary metal phosphides are utilized as catalysts, semi-conductors and magnetocaloric materials along with many others. These attractive properties, which are highly phase dependent, call for a versatile and cost effective synthesis route for various phosphide materials without sacrificing properties important at the nanoscale such as particle size and morphology.

The primary focus outlined in the work of this dissertation pertains to a versatile wet chemical synthesis capable of producing …

Detection Of Iron (Iii) Using Magnetic Nanoparticles, Kaiya Hansen

Electronic Theses and Dissertations

The goal of this work was to develop an iron (III) sensor which can be mounted on buoys and gliders and automatically measure iron (III) in the ocean. The method investigated in this thesis was based on anchoring the iron (III) chelator desferrioxamine B (DFB) to magnetic particles. DFB selectively binds iron (III), resulting in a complex which produces a broad absorbance band at 430 nm. This band can be measured via UV-Vis spectroscopy (UV-Vis). However, measuring oceanic iron (III) directly in solution is difficult because the concentrations can be very low, sometimes less than 1 nM. This problem could …

Aldehydic C-H Amination Reactions Via Co(Ii)-Based Metalloradical Catalysis And Construction Of Novel Chiral Meso-Amidoporphyrin Ligands, Christopher Lee Lizardi

USF Tampa Graduate Theses and Dissertations

Medium-sized organic ring synthesis poses a seemingly insurmountable challenge, and because of this it is a field under immense investigation. Heterocyclic containing medium-sized rings are common structural motifs in nature, which has caused researchers to investigate their potential biological activity and properties as materials. This research focused on the grand challenge of medium-sized heterocyclic ring synthesis, providing the synthesis community with new tools to generate these highly evasive products, while elucidating energetic and geometric properties of one of Nature's least understood organic ring systems.

Cobalt(II)-Amidoporphyrins, [Co(D₂-Por)], are an emerging class of metalloradical catalysts (MRC) which can facilitate …

Investigation Of New Ligand Architechtures Towards Proton And Water Reduction Catalysis By Cobalt Complexes, Debashis Basu

Wayne State University Dissertations

We designed several redox-active ligand architectures to optimize and understand the redox, electronic, and catalytic properties of their respective cobalt complexes. Ligand design was varied from pentadentate donor phenolate to tetradentate acceptor oxime in order to reduce the overpotential of hydrogen generation in organic solvents. We altered the substitution, axial ligands and axial ligand substitutions to vary electronic and catalytic properties for such tetra- or pentadentate ligand systems. Knowledge of the nature of the active species for catalysis enabled us to design the pentadentate oxime ligand which exhibited rich reaction chemistry along with suitable catalytic property in organic solvent. Presence …

Co(Ii) Based Metalloradical Catalysis: Carbene And Nitrene Transfer Reactions, Joseph B. Gill

USF Tampa Graduate Theses and Dissertations

Radical chemistry has attracted a large amount of research interest over the last few decades and radical reactions have recently been recognized as powerful tools for organic synthesis. The synthetic applications of radicals have been demonstrated in many fields, including in the synthesis of complex natural products. Radical reactions have a number of inherent synthetic advantages over their ionic counterparts. For example, they typically proceed at fast reaction rates under mild and neutral conditions in a broad spectrum of solvents and show significantly greater functional group tolerance. Furthermore, radical processes have the capability of performing in a cascade fashion, allowing …

Syntheses And Structures Of Iron(Ii) And Cobalt(Ii) Complexes Of Substituted Tetra(Pyrazolyl)Lutidine Derivatives, Heidi Marie Tatlock

Master's Theses (2009 -)

Pentadentate ligands provide stability to metal complexes as well as a binding site for substrates that make them exceptionally useful for studying reactions. They have been used in biomimetic studies, water splitting, and small molecule activation studies. A series of six pentadentate ligands derived from a,a,a',a'-tetra(pyrazolyl)lutidine, pz4lut, with methyl substituents decorating the ligand periphery has been synthesized. These ligands were coordinated to FeIICl, and the electronic and structural properties of the resulting complexes were studied in order to deduce the effects of methyl substitution at the 3-, 4-, and 5-positions of the pyrazolyl groups and at the methine positions. When …

X-Ray Crystal Structures Of: [Rh2(N-{2,4,6-Ch3}C6h2)Coch3)4]•2ncc6h4 And Ba1.5[Fe(C10h13n2o7)][Co(Cn)6]•9h2o; Two Crystallographic Challenges, Kenneth K. Kpogo

Electronic Theses and Dissertations

The novel compound, [Rh₂(N-{2,4,6-CH₃}C₆H₂)COCH₃)₄] was synthesized. Crystal structures of [Rh₂(N-{2,4,6-CH₃}C₆H₂)COCH₃)₄]·2NCC₆H₅ and Ba_1.5[Fe(C₁₀H₁₃N₂O₇)][Co(CN)₆]·9H₂O were determined employing a Rigaku Mercury375R/M CCD (XtaLAB mini) diffractometer with graphite monochromated Mo-Kα radiation. For [Rh₂(N-{2,4,6-CH₃}C₆H₂)COCH₃)₄]·2NCC₆H₅, the space group was P-421c(#114) with unit cell dimensions: a =11.0169(14)Å, c =21.499(3)Å, V …

Asymmetric Nitrene Transfer Reactions With Azides Via Co(Ii)-Based Metalloradical Catalysis (Mrc), Jingran Tao

USF Tampa Graduate Theses and Dissertations

Asymmetric nitrene transfer reactions via metalloradical catalysis (MRC) with

azides has attracted research interest because of its fundamental and practical importance.

The resulting nitrogen-containing units are recurrent motifs in biologically important

molecules and can serve as versatile precursors in organic synthesis.

The [Co(D2-Por*)] have emerged as a new class of catalysts for asymmetric

aziridination and C-H amination. These metalloradical catalysts have been shown to be

highly effective for the asymmetric intermolecular aziridination of a broad scope of

substrates with different classes of azides with excellent to good enantioselectivity. The

intramolecular C-H amination utilizing various azides can allow for the construction …

Silica Polypeptide-Based Colloids: Physical Properties And Novel Materials, Cornelia Rosu

LSU Doctoral Dissertations

The investigation of polypeptide composite particles, PCPs, is described. The production of mesoporous and polycolloid architectures is also addressed. PCPs were prepared by both growing form and grafting to method. They consist of a core made of silica, silica-coated magnetite or silica-coated cobalt. Some of the particles were covalently labeled with fluorescein isothiocyanate. Several polypeptides were chosen for attachment on the core: poly(γ-stearyl-L-glutamate), PSLG, poly(Nε-carbobenzyloxy-L-lysine), PCBL and poly(o-benzyl-L-tyrosine), PBTY. Attachment of a well-characterized alkyne-end terminated PSLG and PCBL to an azide- functionalized particle yielded PCPs with a desired sparse coverage. A blend of techniques such as FTIR, XPS, TEM, HTEM, …

Coordination Chemistry Of Bis(Benzyl)Phosphinate, John S. Maass

Dissertations, Master's Theses and Master's Reports - Open

The work presented in this dissertation deals with the coordination chemistry of the bis(benzyl)phosphinate ligand with vanadium, tungsten and cobalt. The long term goal of this project was to produce and physically characterize high oxidation state transition metal oxide phosphinate compounds with potential catalytic applications.

The reaction of bis(benzyl)phosphinic acid with VO(acac)₂ in the presence of water or pyridine leads to the synthesis of trimeric vanadium(IV) clusters (V₃(µ₃-O)O₂)(µ₂-O₂P(CH₂C6H5)₂)₆(H2O) and (V₃(µ₃-O)O₂)(µ₂-O₂P(CH₂C_{6 …}

Novel Blends Of Sulfur-Tolerant Water-Gas Shift Catalysts For Biofuel Applications, Timothy Michael Roberge

USF Tampa Graduate Theses and Dissertations

As traditional sources of energy become depleted, significant research interest has gone into conversion of biomass into renewable fuels. Biomass-derived synthesis gas typically contains concentrations of approximately 30 to 600 ppm H2S in stream. H2S is a catalyst poison which adversely affects downstream processing of hydrogen for gas to liquid plants. The water-gas shift reaction is an integral part of converting CO and steam to H2 and CO2. Currently, all known water-gas shift catalysts deactivate in sulfur concentrations typical of biomass-derived synthesis gas. Novel catalysts are needed to remain active in the presence of sulfur concentrations in order to boost …

Asymmetric Intra- And Intermolecular Cyclopropanation By Co(Ii)- Based Metalloradical Catalysis, Xue Xu

USF Tampa Graduate Theses and Dissertations

Metal-catalyzed cyclopropanation of olefins with diazo reagents has attracted research interest because of its fundamental and practical importance. The resulting cyclopropyl units are recurrent motifs in biologically important molecules and can serve as versatile precursors in organic synthesis. Since they were first introduced in 2004, Co(II) complexes of D₂-symmetric chiral amidoporphyrins [Co(D₂-Por*)] have emerged as a new class of catalysts for asymmetric cyclopropanation. These metalloradical catalysts have been shown to be highly effective for asymmetric intermolecular cyclopropanation of a broad scope of substrates with different classes of carbene sources, particularly including electron-deficient olefins and acceptor/acceptor-substituted …

Design Of Colloidal Composite Catalysts For Co2 Photoreduction And For Co Oxidation, Bijith D. Mankidy

USF Tampa Graduate Theses and Dissertations

In this doctoral dissertation, novel colloidal routes were used to synthesize nanomaterials with unique features. We have studied the impact of nanoparticle size of catalyst, role of high surface area of a photocatalyst, and the effect of varying elemental composition of co-catalytic nanoparticles in combination with core-shell plasmonic nanoparticles. We have demonstrated how physical and chemical characteristics of nanomaterials with these unique features play a role in catalytic reactions, specifically the oxidation of CO and the photoreduction of CO2. The first objective of this doctoral dissertation involved the preparation of CoO nanoparticles with discrete nanoparticles sizes (1-14 nm) using a …

Synthesis And Characterization Of Catalysts For The Selective Transformation Of Biomass-Derived Materials, Isaac Tyrone Ghampson

Electronic Theses and Dissertations

The experimental work in this thesis focuses on generating catalysts for two intermediate processes related to the thermal conversion of lignocellulosic biomass: the synthesis and characterization of mesoporous silica supported cobalt catalysts for the Fischer-Tropsch reaction, and an exploration of the reactivity of bulk and supported molybdenum-based nitride catalysts for the hydrodeoxygenation (HDO) of guaiacol, a lignin model compound. The first section of the work details the synthesis of a series of silicasupported cobalt Fischer-Tropsch catalysts with pore diameters ranging from 2-23 nm. Detailed X-ray diffraction measurements were used to determine the composition and particle diameters of the metal fraction, …

Exploration Of Iron And Cobalt Core-Shell Nanoparticles Via Thermal And Microwave Polyol Synthesis, Hope M. Klukovich

Browse all Theses and Dissertations

Thermal and microwave polyol methods were investigated in the synthesis of various iron and cobalt core-shell nanoparticles. The reaction involved 1 mmol of an Fe⁺² or Co⁺² salt, bis-acetylacetanato [(Acac)2] iron (II), cobalt (Acac)2 or iron (II) acetate along with 1 mmol of a surfactant capping agent. The salt was reduced with 2 mmol of a 1,2 diol. When 1,2-hexadecanediol solid was used as a reducing agent, it was dissolved along with the metal salt and capping agent in octyl ether. When 1,2-hexanediol liquid was used as the reducing agent, it was also the solvent, and octyl ether …