Matching Items (21)
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Description
Metal hydride materials have been intensively studied for hydrogen storage applications. In addition to potential hydrogen economy applications, metal hydrides offer a wide variety of other interesting properties. For example, hydrogen-dominant materials, which are hydrides with the highest hydrogen content for a particular metal/semimetal composition, are predicted to display high-temperature

Metal hydride materials have been intensively studied for hydrogen storage applications. In addition to potential hydrogen economy applications, metal hydrides offer a wide variety of other interesting properties. For example, hydrogen-dominant materials, which are hydrides with the highest hydrogen content for a particular metal/semimetal composition, are predicted to display high-temperature superconductivity. On the other side of the spectrum are hydrides with small amounts of hydrogen (0.1 - 1 at.%) that are investigated as viable magnetic, thermoelectric or semiconducting materials. Research of metal hydride materials is generally important to gain fundamental understanding of metal-hydrogen interactions in materials. Hydrogenation of Zintl phases, which are defined as compounds between an active metal (alkali, alkaline earth, rare earth) and a p-block metal/semimetal, were attempted by a hot sintering method utilizing an autoclave loaded with gaseous hydrogen (< 9 MPa). Hydride formation competes with oxidative decomposition of a Zintl phase. The oxidative decomposition, which leads to a mixture of binary active metal hydride and p-block element, was observed for investigated aluminum (Al) and gallium (Ga) containing Zintl phases. However, a new phase Li2Al was discovered when Zintl phase precursors were synthesized. Using the single crystal x-ray diffraction (SCXRD), the Li2Al was found to crystallize in an orthorhombic unit cell (Cmcm) with the lattice parameters a = 4.6404(8) Å, b = 9.719(2) Å, and c = 4.4764(8) Å. Increased demand for materials with improved properties necessitates the exploration of alternative synthesis methods. Conventional metal hydride synthesis methods, like ball-milling and autoclave technique, are not responding to the demands of finding new materials. A viable alternative synthesis method is the application of high pressure for the preparation of hydrogen-dominant materials. Extreme pressures in the gigapascal ranges can open access to new metal hydrides with novel structures and properties, because of the drastically increased chemical potential of hydrogen. Pressures up to 10 GPa can be easily achieved using the multi-anvil (MA) hydrogenations while maintaining sufficient sample volume for structure and property characterization. Gigapascal MA hydrogenations using ammonia borane (BH3NH3) as an internal hydrogen source were employed in the search for new hydrogen-dominant materials. Ammonia borane has high gravimetric volume of hydrogen, and additionally the thermally activated decomposition at high pressures lead to a complete hydrogen release at reasonably low temperature. These properties make ammonia borane a desired hydrogen source material. The missing member Li2PtH6 of the series of A2PtH6 compounds (A = Na to Cs) was accessed by employing MA technique. As the known heavier analogs, the Li2PtH6 also crystallizes in a cubic K2PtCl6-type structure with a cell edge length of 6.7681(3) Å. Further gigapascal hydrogenations afforded the compounds K2SiH6 and Rb2SiH6 which are isostructural to Li2PtH6. The cubic K2SiH6 and Rb2SiH6 are built from unique hypervalent SiH62- entities with the lattice parameters of 7.8425(9) and 8.1572(4) Å, respectively. Spectroscopic analysis of hexasilicides confirmed the presence of hypervalent bonding. The Si-H stretching frequencies at 1550 cm-1 appeared considerably decreased in comparison with a normal-valent (2e2c) Si-H stretching frequencies in SiH4 at around 2200 cm-1. However, the observed stretching modes in hypervalent hexasilicides were in a reasonable agreement with Ph3SiH2- (1520 cm-1) where the hydrogen has the axial (3e4c bonded) position in the trigoal bipyramidal environment.
ContributorsPuhakainen, Kati (Author) / Häussermann, Ulrich (Thesis advisor) / Seo, Dong (Thesis advisor) / Kouvetakis, John (Committee member) / Wolf, George (Committee member) / Arizona State University (Publisher)
Created2013
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Description
The overall objective of this project is to optimize the development of magnetic ferrite thin films targeted for enabling low-loss broadband communication devices, miniaturized low-microwave inductors and electromagnetic noise suppressors. The focus of this objective is to design and build a reactor and improve the spin-spray process. Each film is

The overall objective of this project is to optimize the development of magnetic ferrite thin films targeted for enabling low-loss broadband communication devices, miniaturized low-microwave inductors and electromagnetic noise suppressors. The focus of this objective is to design and build a reactor and improve the spin-spray process. Each film is then characterized and optimized to have a high permeability and high frequency in the range of 500 MHz - 3 GHz. Films produced by the µ-droplet deposition regime yields a higher Snoek's product than the continuous liquid layer regime. The highest Snoek's product occurs when it is deposited at an oxidant pH of 8.28. The Ni-Zn-Co ferrite magnetic domains were imaged using the Lorentz TEM in which multi-grain domains are experimentally observed for the first time.
ContributorsRay, Nicole M (Author) / Petuskey, William T. (Thesis advisor) / Diaz, Rodolfo E. (Committee member) / Chamberlin, Ralph V. (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Organic light emitting diodes (OLEDs) is a rapidly emerging technology based on organic thin film semiconductors. Recently, there has been substantial investment in their use in displays. In less than a decade, OLEDs have grown from a promising academic curiosity into a multi-billion dollar global industry. At the heart of

Organic light emitting diodes (OLEDs) is a rapidly emerging technology based on organic thin film semiconductors. Recently, there has been substantial investment in their use in displays. In less than a decade, OLEDs have grown from a promising academic curiosity into a multi-billion dollar global industry. At the heart of an OLED are emissive molecules that generate light in response to electrical stimulation. Ideal emitters are efficient, compatible with existing materials, long lived, and produce light predominantly at useful wavelengths. Developing an understanding of the photophysical processes that dictate the luminescent properties of emissive materials is vital to their continued development. Chapter 1 and Chapter 2 provide an introduction to the topics presented and the laboratory methods used to explore them. Chapter 3 discusses a series of tridentate platinum complexes. A synthetic method utilizing microwave irradiation was explored, as well as a study of the effects ligand structure had on the excited state properties. Results and techniques developed in this endeavor were used as a foundation for the work undertaken in later chapters. Chapter 4 introduces a series of tetradentate platinum complexes that share a phenoxy-pyridyl (popy) motif. The new molecular design improved efficiency through increased rigidity and modification of the excited state properties. This class of platinum complexes were markedly more efficient than those presented in Chapter 3, and devices employing a green emitting complex of the series achieved nearly 100% electron-to-photon conversion efficiency in an OLED device. Chapter 5 adapts the ligand structure developed in Chapter 4 to palladium. The resulting complexes exceed reported efficiencies of palladium complexes by an order of magnitude. This chapter also provides the first report of a palladium complex as an emitter in an OLED device. Chapter 6 discusses the continuation of development efforts to include carbazolyl components in the ligand. These complexes possess interesting luminescent properties including ultra-narrow emission and metal assisted delayed fluorescence (MADF) emission.
ContributorsTurner, Eric (Author) / Li, Jian (Thesis advisor) / Adams, James (Committee member) / Alford, Terry (Committee member) / Arizona State University (Publisher)
Created2014
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Description
Redox reactions are crucial to energy transduction in biology. Protein film electrochemistry (PFE) is a technique for studying redox proteins in which the protein is immobilized at an electrode surface so as to allow direct exchange of electrons. Establishing a direct electronic connection eliminates the need for redox­active mediators, thus

Redox reactions are crucial to energy transduction in biology. Protein film electrochemistry (PFE) is a technique for studying redox proteins in which the protein is immobilized at an electrode surface so as to allow direct exchange of electrons. Establishing a direct electronic connection eliminates the need for redox­active mediators, thus allowing for interrogation of the redox protein of interest. PFE has proven a versatile tool that has been used to elucidate the properties of many technologically relevant redox proteins including hydrogenases, laccases, and glucose oxidase.

This dissertation is comprised of two parts: extension of PFE to a novel electrode material and application of PFE to the investigation of a new type of hydrogenase. In the first part, mesoporous antimony-doped tin oxide (ATO) is employed for the first time as an electrode material for protein film electrochemistry. Taking advantage of the excellent optical transparency of ATO, spectroelectrochemistry of cytochrome c is demonstrated. The electrochemical and spectroscopic properties of the protein are analogous to those measured for the native protein in solution, and the immobilized protein is stable for weeks at high loadings. In the second part, PFE is used to characterize the catalytic properties of the soluble hydrogenase I from Pyrococcus furiosus (PfSHI). Since this protein is highly thermostable, the temperature dependence of catalytic properties was investigated. I show that the preference of the enzyme for reduction of protons (as opposed to oxidation of hydrogen) and the reactions with oxygen are highly dependent on temperature, and the enzyme is tolerant to oxygen during both oxidative and reductive catalysis.
ContributorsKwan, Patrick Karchung (Author) / Jones, Anne K (Thesis advisor) / Francisco, Wilson (Committee member) / Moore, Thomas (Committee member) / Arizona State University (Publisher)
Created2014
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Description
Alkali treated aluminosilicate (geopolymer) was functionalized by surfactant to increase the hydrophobicity for making Pickering emulsion for the first part of this work. In the first part of this study, alkali treated metakaolin was functionalized with cetyltrimethylammonium bromide ((C16H33)N(CH3)3Br, CTAB). The electrostatic interaction between this quaternary ammonium and the surface

Alkali treated aluminosilicate (geopolymer) was functionalized by surfactant to increase the hydrophobicity for making Pickering emulsion for the first part of this work. In the first part of this study, alkali treated metakaolin was functionalized with cetyltrimethylammonium bromide ((C16H33)N(CH3)3Br, CTAB). The electrostatic interaction between this quaternary ammonium and the surface of the aluminosilicate which has negative charge has taken place. The particles then were used to prepare Pickering emulsion. The resulting stable dispersions, obtained very fast at very simple conditions with low ratio of aluminosilicate to liquid phase. In the second part, the interaction between geopolymer and glycerol was studied to see the covalent grafting of the geopolymer for making geopolymer composite. The composite material would be the basis material to be used as support catalyst, thin coating reagent and flame retardant material and so on, Variety of techniques, Thermogravimetric (TGA), Particle-induced X-ray emission (PIXE), FTIR, Solid state NMR, Powder X-ray diffraction (PXRD), BET surface area, Elemental analysis (CHN), TEM, SEM and Optical microscopy were used to characterize the functionalized geopolymer.
ContributorsMesgar, Milad (Author) / Seo, Dong-Kuyn (Thesis advisor) / Petuskey, William (Committee member) / Gould, Ian (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Understanding the mechanisms of metalloproteins at the level necessary to engineer new functionalities is complicated by the need to parse the complex overlapping functions played by each amino acid without negatively impacting the host organism. Artificial or designed metallopeptides offer a convenient and simpler platform to explore metal-ligand interactions in

Understanding the mechanisms of metalloproteins at the level necessary to engineer new functionalities is complicated by the need to parse the complex overlapping functions played by each amino acid without negatively impacting the host organism. Artificial or designed metallopeptides offer a convenient and simpler platform to explore metal-ligand interactions in an aqueous, biologically relevant coordination context. In this dissertation, the peptide SODA (ACDLPCG), a synthetic derivative of the nickel-binding pocket of nickel superoxide dismutase, is used as a scaffold to construct a variety of novel metallopeptides and explore their reactivity. In Chapter 2, I show that SODA binds Co(II) and the resulting peptide, CoSODA, reacts with oxygen in an unexpected two step process that models the biosynthesis of Co nitrile hydratase. First, the thiolate sulfur is oxidized and then the metallocenter is oxidized to Co(III). In Chapter 3, I show that both CoSODA and CuSODA form CN- adducts. Spectroscopic investigations of these metallopeptides are compared with data from NiSODA and Ni(CN)SODA to show the remarkable geometric versatility of SODA with respect to interactions with metallocenters. In Chapter 4, exploiting the propensity of sulfur ligands to form bridging structures, NiSODA is used as a metallosynthon to direct synthesis of hetero bi- and tri-metallic peptides as models for [NiFe]-hydrogenases and the A cluster of acetyl-CoA synthase carbon monoxide dehydrogenase. Building on this synthetic strategy, in Chapter 5, I demonstrate synthesis of NiRu complexes including a Ru(bipyridine)2 moiety and characterize their photochemistry.
ContributorsDutta, Arnab (Author) / Jones, Anne K (Thesis advisor) / Moore, Ana L (Committee member) / Vermass, Willem (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Carbon lacks an extended polyanionic chemistry which appears restricted to carbides with C4-, C22-, and C34- moieties. The most common dimeric anion of carbon atoms is C22- with a triple bond between the two carbon atoms. Compounds containing the dicarbide anion can be regarded as salts of acetylene C2H2 (ethyne)

Carbon lacks an extended polyanionic chemistry which appears restricted to carbides with C4-, C22-, and C34- moieties. The most common dimeric anion of carbon atoms is C22- with a triple bond between the two carbon atoms. Compounds containing the dicarbide anion can be regarded as salts of acetylene C2H2 (ethyne) and hence are also called acetylides or ethynides. Inspired by the fact that molecular acetylene undergoes pressure induced polymerization to polyacetylene above 3.5 GPa, it is of particular interest to study the effect of pressure on the crystal structures of acetylides as well. In this work, pressure induced polymerization was attempted with two simple metal acetylides, Li2C2 and CaC2. Li2C2 and CaC2 have been synthesized by a direct reaction of the elements at 800ºC and 1200ºC, respectively. Initial high pressure investigations were performed inside Diamond anvil cell (DAC) at room temperature and in situ Raman spectroscopic measurement were carried out up to 30 GPa. Near 15 GPa, Li2C2 undergoes a transition into a high pressure acetylide phase and around 25 GPa this phase turns amorphous. CaC2 is polymorphic at ambient pressure. Monoclinic CaC2-II does not show stability at pressures above 1 GPa. Tetragonal CaC2-I is stable up to at least 12 GPa above which possibly a pressure-induced distortion occurs. At around 18 GPa, CaC2 turns amorphous. In a subsequent series of experiments both Li2C2 and CaC2 were compressed to 10 GPa in a multi anvil (MA) device and heated to temperatures between 300 and 1100oC for Li2C2, and 300°C to 900°C for CaC2. The recovered products were analyzed by PXRD and Raman spectroscopy. It has been observed that reactions at temperature higher than 900°C were very difficult to control and hitherto only short reaction times could be applied. For Li2C2, a new phase, free of starting material was found at 1100°C. Both the PXRD patterns and Raman spectra of products at 1100oC could not be matched to known forms of carbon or carbides. For CaC2 new reflections in PXRD were visible at 900ºC with the starting material phase.
ContributorsKonar, Sumit (Author) / Häussermann, Ulrich (Thesis advisor) / Seo, Dong (Thesis advisor) / Steimle, Timothy (Committee member) / Wolf, George (Committee member) / Arizona State University (Publisher)
Created2012
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Description
ABSTRACT

Transition metals have been extensively employed to address various challenges

related to catalytic organic transformations, small molecule activation, and energy storage

over the last few decades. Inspired by recent catalytic advances mediated by redox noninnocent

pyridine diimine (PDI) and α-diimine (DI) ligand supported transition metals,

our group has designed new PDI and DI ligands

ABSTRACT

Transition metals have been extensively employed to address various challenges

related to catalytic organic transformations, small molecule activation, and energy storage

over the last few decades. Inspired by recent catalytic advances mediated by redox noninnocent

pyridine diimine (PDI) and α-diimine (DI) ligand supported transition metals,

our group has designed new PDI and DI ligands by modifying the imine substituents to

feature donor atoms. My doctoral research is focused on the development of PDI and DI

ligand supported low valent first row metal complexes (Mn, Fe, Co) and their application

in bond activation reactions and the hydrofunctionalization of unsaturated bonds.

First two chapters of this dissertation are centered on the synthesis and

application of redox non-innocent ligand supported low valent iron complexes. Notably,

reduction of a DI-based iron dibromide led to the formation of a low valent iron

dinitrogen compound. This compound was found to undergo a sequential C-H and C-P

bond activation processes upon heating to form a dimeric compound. The plausible

mechanism for dimer formation is also described here.

Inspired by the excellent carbonyl hydrosilylation activity of our previously

reported Mn catalyst, (Ph2PPrPDI)Mn, attempts were made to synthesize second generation

Mn catalyst, which is described in the third chapter. Reduction of (PyEtPDI)MnCl2

furnished a deprotonated backbone methyl group containing Mn compound

[(PyEtPDEA)Mn] whereas reduction of (Ph2PEtPDI)MnCl2 produced a dimeric compound,

[(Ph2PEtPDI)Mn]2. Both compounds were characterized by NMR spectroscopy and XRD

analysis. Hydrosilylation of aldehydes and ketones have been studied using

[(PyEtPDEA)Mn] as a pre-catalyst. Similarly, 14 different aldehydes and 6 different

ii

formates were successfully hydrosilylated using [(Ph2PEtPDI)Mn]2 as a pre-catalyst.

Encouraged by the limited number of cobalt catalysts for nitrile hydroboration, we

sought to develop a cobalt catalyst that is active for hydroboration under mild conditions,

which is discussed in the last chapter. Treatment of (PyEtPDI)CoCl2 with excess NaEt3BH

furnished a diamagnetic Co(I) complex [(PyEtPDIH)Co], which exhibits a reduced imine

functionality. Having this compound characterized, a broad substrate scope for both

nitriles and imines have been investigated. The operative mechanism for nitrile

dihydroboration has been investigated based on the outcomes of a series of stoichiometric

reactions using NMR spectroscopy.
ContributorsGhosh, Chandrani (Author) / Trovitch, Ryan J. (Thesis advisor) / Seo, Don (Committee member) / Moore, Ana (Committee member) / Arizona State University (Publisher)
Created2018
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Description
New sol-gel routes based on peroxo complexes of early transition metals in a highly acidic medium were developed, to prepare metal oxide phosphates that feature structural protons. A sol-gel synthetic route was chosen because it allows atomic level mixing of precursors and lower heating temperatures, which are preferable in exploring

New sol-gel routes based on peroxo complexes of early transition metals in a highly acidic medium were developed, to prepare metal oxide phosphates that feature structural protons. A sol-gel synthetic route was chosen because it allows atomic level mixing of precursors and lower heating temperatures, which are preferable in exploring metastable phases. Titanium and molybdenum sol-gel chemistries were the focus of the initial studies and the synthesis of Ti1-xMoxP2O7 (x = 0 – 0.5) and Mo1-yTiyP2O8-y (y = 0 – 0.4) type metal oxide phosphates were explored. For the synthesis of the metal oxide phosphates, hydrogen peroxide was employed to prepare the respective precursor solutions. The peroxide ligand suppressed the immediate precipitation of metal cations in aqueous medium, by coordinating to Ti4+ and Mo6+ ions, and produced a soft wet-gel following polycondensation. Phosphoric acid was used to acidify the reaction medium and to provide protons and phosphate ions as structural components. From this synthetic route, a series of Ti1-xMoxP2O7 (x = 0 – 0.5) and Mo1-yTiyP2O8-y (y = 0 – 0.4) crystalline compounds, with various degrees of purity, were synthesized. For x = 0 and y = 0, the crystalline compounds TiP2O7 and MoP2O8 were produced, respectively, after calcining at 600 °C.

In pursuit of new metastable molybdenum oxide phosphate compounds, peroxo-molybdenum precursor mixtures with different molar ratios were treated gently by low-temperature heating. After controlled drying in a lab oven, MoO2(H2O)(HPO4) crystals were obtained as a highly crystalline pure product instead of a gel. The dissolution of MoO2(H2O)(HPO4) in water and precipitation with a CsCl solution produced a new crystalline compound with a cubic unit cell (a = 11.8(2) Å). Further studies will lead to crystal structure determination and elucidation of the aqueous chemistry of MoO2(H2O)(HPO4).
ContributorsAbeysooriya, Shanika (Author) / Seo, Dong K (Thesis advisor) / Chan, Candace K. (Committee member) / Trovitch, Ryan J (Committee member) / Arizona State University (Publisher)
Created2018
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Description
The search for highly active, inexpensive, and earth abundant replacements for existing transition metal catalysts is ongoing. Our group has utilized several redox non-innocent ligands that feature flexible arms with donor substituents. These ligands allow for coordinative flexibility about the metal centre, while the redox non-innocent core helps to overcome

The search for highly active, inexpensive, and earth abundant replacements for existing transition metal catalysts is ongoing. Our group has utilized several redox non-innocent ligands that feature flexible arms with donor substituents. These ligands allow for coordinative flexibility about the metal centre, while the redox non-innocent core helps to overcome the one electron chemistry that is prevalent in first row transition metals. This dissertation focuses on the use of Ph2PPrDI, which can adopt a κ4-configuration when bound to a metal. One reaction that is industrially useful is hydrosilylation, which allows for the preparation of silicones that are useful in the lubrication, adhesive, and cosmetics industries. Typically, this reaction relies on highly active, platinum-based catalysts. However, the high cost of this metal has inspired the search for base metal replacements. In Chapter One, an overview of existing alkene and carbonyl hydrosilylation catalysts is presented. Chapter Two focuses on exploring the reactivity of (Ph2PPrDI)Ni towards carbonyl hydrosilylation, as well as the development of the 2nd generation catalysts, (iPr2PPrDI)Ni and (tBu2PPrDI)Ni. Chapter Three presents a new C-O bond hydrosilylation reaction for the formation of silyl esters. It was found the (Ph2PPrDI)Ni is the most active catalyst in the literature for this transformation, with turnover frequencies of up to 900 h-1. Chapter Four explores the activity and selectivity of (Ph2PPrDI)Ni for alkene hydrosilylation, including the first large scope of gem-olefins for a nickel-based catalyst. Chapter Five explores the chemistry of (Ph2PPrDI)CoH, first through electronic structure determinations and crystallography, followed by an investigation of its reactivity towards alkyne hydroboration and nitrile dihydroboration. (Ph2PPrDI)CoH is the first reported cobalt nitrile dihydroboration catalyst.
ContributorsRock, Christopher L (Author) / Trovitch, Ryan J (Thesis advisor) / Kouvetakis, John (Committee member) / Pettit, George R. (Committee member) / Arizona State University (Publisher)
Created2018