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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Ion pairing effects on alkali metal alkoxide fragmentations and rearrangements in dimethyl sulphoxide

Partington, S. M. January 1986 (has links)
No description available.
2

A small molecule model for carbonic anhydrase

Greener, Bryan January 1997 (has links)
No description available.
3

Solution Studies of the Structures and Stability of Mixed Lithium Alkoxide/Alkvllithium Aggregates

DeLong, George T. (George Thomas) 12 1900 (has links)
New one- and two-dimensional NMR techniques were used to elucidate the solution structures of these complex mixtures. The system, lithium tert-butoxide/tert-butyllithium, was studied as a model system with O/Li ratios varying from 0/1 to 1/1. It was found that at low O/Li ratios, a single mixed tetrameric aggregate was formed. At higher O/Li ratios, mixed hexameric species were formed. Two other systems, lithium isopropoxide/iso-propyllithium and lithium n-propoxide/n-propyllithium were also studied at low O/Li ratios.
4

An NMR Study of 2-Ethylbutyllithium/Lithium 2-Ethyl-1-butoxide Mixed Aggregates, Lithium Hydride/Lithium 2-Ethyl-1-butoxide Mixed Aggregates, n-Pentyllithium Aggregates, and n-Pentyllithium/Lithium n-Pentoxide Mixed Aggregates

Sellers, Nicole 12 1900 (has links)
A 13C and 6Li variable temperature NMR study of 2-ethylbutyllithium/lithium 2-ethyl-1-butoxide mixed aggregates formed from reacting 2-ethyl-1-butanol with 2-ethylbutyllithium in two O/Li ratios of 0.2/1 and 0.8/1. The 0.2/1 sample resulted in two 2-ethylbutyllithium/lithium 2-ethyl-1-butoxide mixed aggregates and seven lithium hydride/lithium 2-ethyl-1-butoxide mixed aggregates. The lithium hydride mixed aggregates were also studied using selective 1H decoupling experiments. The 0.8/1 sample resulted in six 2-ethylbutyllithium/lithium 2-ethyl-1-butoxide mixed aggregates and five lithium hydride/lithium 2-ethyl-1-butoxide mixed aggregates. A low temperature 13C NMR spectroscopy study of n-pentyllithium indicated three aggregates, most likely a hexamer, an octamer, and a nonamer. A low temperature 13C NMR study of an 0.2/1 O/Li ratio sample of n-pentyllithium mixed with 1-pentanol resulted in three n-pentyllithium/lithium n-pentoxide aggregates mixed aggregates along with the three n-pentyllithium aggregates. 13C NMR data for this mixture gave inconclusive results whether or not lithium hydride/lithium alkoxide mixed aggregates were present in the sample.
5

Structural studies of titanium(IV) picolinamide alkoxide and oxide derivatives

Lord, Rianne M., Lord, S.M., Pask, C.M., McGowan, P.C. 27 April 2016 (has links)
Yes / Reactions have been carried out using the titanium(IV) precursors TiCl4 and Ti(OiPr)4, with addition of two equivalents of a functionalized picolinamide ligand. The reactions with TiCl4 led to the formation of either a mononuclear titanium species, [Ti(N,O)Cl2X2] or a dinuclear titanium species [Ti(N,O)X3]2[l- O] (X = OMe or Cl), with incorporation of one picolinamide ligand. The ligand is bound to the titanium centre as the protonated amide. The reactions with Ti(OiPr)4 resulted in the formation of mononuclear titanium bis-picolinamide species [Ti(N,O)2(OiPr)2], and also dinuclear and trinuclear products, [(N,O)Ti (OiPr)2][l-OiPr]2 and [(N,O)Ti(OiPr)2]2[l-OiPr]2[(OiPr)2Ti][l3-O] respectively. In these cases the picolinamide ligand was found to be deprotonated and bound to the titanium as the iminolate. These molecules have been characterized by X-ray crystallographic analysis and structural characteristics are discussed.
6

An NMR study of 2-ethyl-1-butyllithium and of 2-ethyl-1-butyllithium/lithium 2-ethyl-1-butoxide mixed aggregates

Ferreira, Aluisio V. C. 05 1900 (has links)
A 1H, 13C, and 6Li NMR study of 2-ethyl-1-butyllithium indicated that 2-ethyl-1-butyllithium exists only as a hexameric aggregate over the entire temperature range of 25 to - 92.1 ° C in cyclopentane. Reacting 2-ethyl-1-butyllithium with 2-ethyl-1-butanol resulted in alkyllithium/lithium alkoxide mixed aggregates, apparently of the form Ra(RO)bLia+b. A multinuclear, variable temperature NMR study of samples with O:Li ratios of 0.2 and 0.4 showed, in addition to the alkyllithium, the formation of four mixed aggregates, one of them probably an octamer. Higher O:Li ratio samples showed the formation of several other mixed aggregates. Mixing 2-ethyl-1-butyllithium with independently prepared lithium 2-ethyl-1-butoxide formed the same mixed aggregates formed by in situ synthesis of lithium alkoxide. Lithium 2-ethyl-1-butoxide also exists as aggregates in cyclopentane.
7

3d metal complexes with the perfluoro-tert-butoxide and perfluoropinacolate ligands: dioxygen reduction and intermolecular substrate oxidation

Brazeau, Sarah Elizabeth 24 April 2020 (has links)
A CuI fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2] (1), was previously shown to form a trinuclear copper–dioxygen species with a {Cu3(3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. A significantly expanded kinetic and mechanistic study of TOC4F9 formation is reported using stopped-flow spectroscopy. The TOC4F9 complex performed catalytic oxidase conversion of para-hydroquinone (H2Q) to para-benzoquinone (BQ) and hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first tri-copper species to perform tyrosinase (both monooxygenase and oxidase) chemistry. As opposed to 1, when K+ is fully encapsulated in {K(18C6)}[Cu(OC4F9)2] (4), O2 was not reduced under identical conditions. To study the effects of both alkali cation and the degree of encapsulation on reduction of O2, derivative complexes were synthesized with Na+ (16), {Na(DME)}+ (17), {Na(15C5)}+ (18), {K(15C5)}+ (19), {K(15C5)2}+ (20), Cs+ (21), {Cs(18C6)}+ (22), and {Cs(18C6)2}+ (23). Reduction of O2 was found to be encapsulation-dependent, and cation size was also determined to affect the chromophore observed. These results suggest that cation…F/O interactions between the CuI complexes assemble aggregates that are required to form reactive {Cun−O2} species. However, catalytic oxidation of H2Q to BQ and sub-stoichiometric oxidation of DBP to catecholate occurred regardless of whether a {Cun−O2} intermediate was detected, suggesting that a reactive species may self-assemble in the presence of substrate in all complex derivatives unable to reduce O2. A series of heteroleptic mixed phosphine/alkoxide 3d complexes was designed to evaluate PPh3 as a protecting group. Complexes of the form [(Ph3P)2M(OC4F9)2] (M= Fe (24), Co (25), Ni (26), Zn (27)) and [(Ph3P)2M(pinF)] (M= Co (31), Ni (32), Zn (33)) were prepared and characterized, along with related complexes with non-reactive L-donors for comparison, [(DME)Fe(OC4F9)2] (28) and [(Ph3PO)2M(OC4F9)2] (M= Fe (29), Ni (30)). Dimeric [Fe2(-O)(OPPh3)2(OC4F9)4] (36) was isolated after O2 reactivity with 24, and 28 and 29 were able to generate intermediate species capable of both oxidation of H2Q to BQ and oxygen atom transfer of thioanisole to methyl phenyl sulfoxide. The choice of fluorinated ligand influences O2 reactivity with CoII (25, 31), but not for NiII (26, 32). Related dimeric compounds [Co2(pinF)2(THF)4)] (34) and [Zn2(pinF)2(THF)2)] (35) were also isolated.
8

Chromia-Alumina Thin Films from Alkoxide Precursors : From Precursor Synthesis to Deposition and Characterisation

Elvelo, Elina January 2023 (has links)
A hetero-bimetallic alkoxide CrAl3(OiPr)12 was synthesised through metathesis of achromium(III)chloride THF complex (CrCl3 . 3 THF) and 3 KAl(OiPr)4.It was used as a single sourceprecursor to make oxide powders and films with 1:3 chromium/aluminium compositionthrough sol-gel synthesis. The final materials obtained and heat-treated samples of these wasstudied with thermogravimetric analysis (TG), X-ray diffraction (XRD) and IR spectroscopy. Itwas found that the as synthesised material was amorphous and elementally homogeneousand could be described as hydrated (oxo)-hydroxide with some loosely bonded carbonate,but no organics remaining. Above 600 oC crystallisation starts and eventually splits into twocorundum structured phases starting around 800 oC. At 1400  oC, the phases had joined backtogether in accordance with the Cr-Al-O phase diagram. Scanning Transmission ElectronMicroscopy with Electron Dispersive X-ray (STEM-EDX) tomography showed that the powderswere homogenous up to 800 oC, while after heating to 1000 oC showed chromiumenrichment in some crystals. Gracing Incidence X-ray diffraction (GI-XRD) on spin-coated filmsshowed that epitaxial growth might be achieved based on -Al2O3 (0001) substrate. The results show that the synthesis of the precursor and subsequent oxides was successful andyielded highly homogeneous gels that could be converted into oxide at ca. 600 oC andsubsequently be phase separated through spinodal decomposition at 1000 oC. The next stepwould be to try the precursor in the industrially used chemical vapour deposition (CVD)method.
9

Sol−Gel Synthesis of CMR Manganites

Pohl, Annika January 2004 (has links)
<p>The development of more advanced materials forms the basis of technological progress. One group of fascinating compounds with many potential applications in spintronic devices are the mixed-valence perovskite manganites. These have attracted considerable interest during the last decade through their very large magnetoresistance near the Curie Temperature. Although the properties of a material determinie any application, the development of reliable and flexible synthesis methods is crucial, as is the understanding of these methods. Knowledge of how different materials are formed is also of general importance in tailoring new materials. The aim of this project has therefore been not only to develop a new synthesis route, but also to understand the mechanisms involved.</p><p>This thesis describes the synthesis and characterization of a novel manganese alkoxide and its use in sol–gel processing of magnetoresistive perovskite manganites. In searching for a soluble manganese alkoxide for sol–gel processing, we found that the methoxy-ethoxide, [Mn<sub>19</sub>O<sub>12</sub>(moe)<sub>14</sub>(moeH)<sub>10</sub>]·moeH, has a high solubility in appropriate organic solvents. Being 1.65 nm across, it is one of the largest alkoxides reported; it is also of interest because of its (for oxo-alkoxides) rare planar structure. After mixing with La, Nd, Ca, Sr, and Ba methoxy-ethoxides, [Mn<sub>19</sub>O<sub>12</sub>(moe)<sub>14</sub>(moeH)<sub>10</sub>]·moeH was used in the first purely alkoxide based sol–gel processing of perovskites manganites. The phase evolution on heating xerogel powders to 1000°C was studied, and thin films were prepared by spin-coating.</p><p>It was found that the easily oxidised Mn-alkoxide facilitates the formation of high oxygen-excess modifications of the perovskites. The reactive precursor system yields fully hydrolysed gels almost without organic residues, but the gel absorbs CO<sub>2</sub> from the air, leading to carbonate formation. The carbonate decomposition is the limiting step in oxide formation. Transport measurements of La<sub>0.67</sub>Ca<sub>0.33</sub>MnO<sub>3</sub> films on LaAlO<sub>3</sub> substrate show that all-alkoxide sol–gel derived films can compete with PLD films in terms of quality of epitaxy and transport. The somewhat different behaviour of the sol–gel derived films compared to PLD films is attributed to differences in morphology and oxygen stoichiometry.</p>
10

Sol−Gel Synthesis of CMR Manganites

Pohl, Annika January 2004 (has links)
The development of more advanced materials forms the basis of technological progress. One group of fascinating compounds with many potential applications in spintronic devices are the mixed-valence perovskite manganites. These have attracted considerable interest during the last decade through their very large magnetoresistance near the Curie Temperature. Although the properties of a material determinie any application, the development of reliable and flexible synthesis methods is crucial, as is the understanding of these methods. Knowledge of how different materials are formed is also of general importance in tailoring new materials. The aim of this project has therefore been not only to develop a new synthesis route, but also to understand the mechanisms involved. This thesis describes the synthesis and characterization of a novel manganese alkoxide and its use in sol–gel processing of magnetoresistive perovskite manganites. In searching for a soluble manganese alkoxide for sol–gel processing, we found that the methoxy-ethoxide, [Mn19O12(moe)14(moeH)10]·moeH, has a high solubility in appropriate organic solvents. Being 1.65 nm across, it is one of the largest alkoxides reported; it is also of interest because of its (for oxo-alkoxides) rare planar structure. After mixing with La, Nd, Ca, Sr, and Ba methoxy-ethoxides, [Mn19O12(moe)14(moeH)10]·moeH was used in the first purely alkoxide based sol–gel processing of perovskites manganites. The phase evolution on heating xerogel powders to 1000°C was studied, and thin films were prepared by spin-coating. It was found that the easily oxidised Mn-alkoxide facilitates the formation of high oxygen-excess modifications of the perovskites. The reactive precursor system yields fully hydrolysed gels almost without organic residues, but the gel absorbs CO2 from the air, leading to carbonate formation. The carbonate decomposition is the limiting step in oxide formation. Transport measurements of La0.67Ca0.33MnO3 films on LaAlO3 substrate show that all-alkoxide sol–gel derived films can compete with PLD films in terms of quality of epitaxy and transport. The somewhat different behaviour of the sol–gel derived films compared to PLD films is attributed to differences in morphology and oxygen stoichiometry.

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