A theoretical study of ionic liquids using analytical theory and molecular dynamics simulation
Year of Dissertation:
2011
In a series of theoretical analyses and simulation studies, we explore the relationship between ionic structure and liquid dynamics in room-temperature ionic liquids (ILs).
Two Types of Protein Salt Bridges Studied by Quantum Calculation
Year of Dissertation:
2009
Abstract
Development of Highly Efficient Transition Metal-Catalyzed Addition Reactions
Year of Dissertation:
2011
Development of new and efficient reactions as powerful tools for synthetic chemistry is one of the most important tasks in modern chemistry. Transition metal-catalyzed carbon-carbon bond-forming reactions including addition reactions are some of the most powerful transformations in organic synthesis. My research is on developing highly efficient transition metal-catalyzed addition reactions as powerful tools for organic synthesis.
Electronic spectroscopy and computational studies of GSCbl, H2OCbl, and MeCbl
Year of Dissertation:
2011
In the present study we are interested in the electronic and geometric structure of GS-Cbl and the chemical nature of its Co(III)-S bond in comparison with aquo- and methyl- axial ligand bonds to Co(III) in cobalamins. We examine the structures with DFT calculations of truncated models of the entire molecule. Furthermore, we compare the electronic spectroscopy (UV-VIS and CD) of GS-Cbl(III) with H2O-Cbl(III) and CH3-Cbl(III) using both experimental spectra and TD-DFT calculated spectra.
Synthesis of C-Glycoside Analogs of the Immunostimulatory Glycosphingolipid, alfa-Galactosylceramide
Year of Dissertation:
2011
This dissertation presents the asymmetric total synthesis of immunostimulatory &alpha-C-galactosylceramide (&alpha-C-GalCer) glycolipids and D-ribo-phytosphingosine. Also included in this dissertation is an improved two-step synthetic route to primary allylic alcohols from aldehydes and verification of configurations of three contiguous stereogenic centers in the phytosphingosine backbone of &alpha-1C-GalCer, the nonisosteric analog of &alpha-C-GalCer in which the glycosidic oxygen atom linking the sugar with phytosphingosine is deleted..
Enhanced Raman Effect on MBE Grown Semiconductor Quantum Dots
Author:
Richard Livingstone
Year of Dissertation:
2010
Using Surface Enhanced Raman Spectroscopy (SERS), I observed Raman enhancements (104-105) for pyridine, 4-tertbutylpyridine and other biological molecules adsorbed on a II-VI semiconductor CdSe/ZnBeSe sample of uncapped self-assembled quantum dots produced by molecular beam epitaxy. When a monolayer of Raman active molecule is adsorbed on these structures, excitation at 488 nm produces intense Raman spectra and a very large enhancement of the a1, b1 and b2 modes. This indicates the presence of charge-transfer as a contributor to the enhancement. Furthermore, the excitation wavelength is in the vicinity of several interband transitions located both in the quantum dots and the wetting layer, and it is likely that these resonances also contribute to the enhancement factor. The observed enhancement is among the largest yet seen on semiconductor quantum dot systems and is the first obseved on MBE grown quantum dots.
DESIGN, SYNTHESIS, AND ANTI-TUMOR ACTIVITIES OF BENZOPOLYSULFANE COMPOUNDS THAT MIMICS A TUNICATE-DERIVED NATURAL PRODUCT
Author:
Adaikapillai Mahendran
Year of Dissertation:
2011
Benzopolysulfanes are untapped potential therapeutic compounds, which possess an impressive array of biological activities. By developing an entirely new class of compounds (polysulfanes) drug resistance can be evaded due to the lack of exposure of organisms to these compounds. However, polysulfanes are challenging compounds to prepare, and usually have very poor water-solubility. New synthetic methods and studies on solubility and cell-directed delivery are needed to explore the range of possibilities of this novel class of compounds. This thesis outlines (1) synthesis and biological activities of benzopolysulfane conjugates namely, PEGylated benzopoylsulfanes; and (2) mechanistic aspects on mode of introduction of sulfur atom to the catechol core;
Ultra-Large-Pore Ordered Mesoporous Organosilicas and Related Hollow Nanoparticles
Year of Dissertation:
2010
My dissertation describes the synthesis of ultra-large-pore ordered mesoporous organosilicas and related hollow nanoparticles. In the first part, we developed a versatile approach through which a series of periodic mesoporous organosilicas (PMOs) with 2-dimensional hexagonal structure and different bridging groups can be synthesized. The bridging groups are methylene (-CH2-), ethylene (-CH2CH2-), ethenylene (-CH=CH-), and phenylene (-C6H4-). For this purpose, a combination of a commercially available triblock copolymer Pluronic P123 (EO20PO70EO20) with judiciously chosen micelle swelling agent (cyclohexane, or 1,3,5-triisopropylbenzene) was used as a miceller template, and the initial step of the synthesis was performed at temperature between 10 and 18 oC, followed by hydrothermal treatment at 100-150 oC. The PMOs were characterized using small-angle X-ray scattering (SAXS), nitrogen adsorption, transmission electron microscopy, and solid-state 29Si NMR. For all PMO compositions, the formation of 2-D hexagonal structures with (100) interplanar spacing, d100, up to 21-26 nm was achieved, which is at least seven nanometers larger than d100 reported earlier for any PMO with 2-D hexagonal structure. The nominal (BJH) pore diameters up to 20-27 nm were achieved for the considered compositions of PMOs with with 2-D hexagonal ordering, while even larger pore sizes were sometimes attained for disordered or weakly ordered structures. The mesopores exhibited constrictions or narrow entrances that were widened by increasing the hydrothermal treatment temperature. The pore diameter tended to increase as an initial synthesis temperature decreased, allowing for the pore size adjustment, but the useful temperature range depended on the bridging groups. The present work suggests that the low-temperature micelle-templated synthesis with judicious selected swelling agents is a general pathway to ultra-large-pore 2-D hexagonal PMOs with both aliphatic and aromatic bridging groups.
The Development Of New Organocatalysts and New Organocatalytic Cascade Reactions
Author:
Patrick McGarraugh
Year of Dissertation:
2012
Advisor:
Stacey Brenner-Moyer
Organocatalysis is the use of small organic molecules to catalyze chemical reactions. They are generally cheaper, less toxic, and easier to handle on a laboratory and industrial scale than more traditional metal-based catalysts. This dissertation discusses the development of new organocatalysts and organocatalytic methods for the asymmetric synthesis of useful small molecules. The research conducted has specifically focused on the use of chiral diarylprolinol silyl ether organocatlysts and their ability to catalyze a variety of useful cascade reactions through iminium and enamine catalysis. Cascade reactions are useful in that a great deal of molecular complexity may be generated in a one-pot process using simple, readily available building blocks. Herein, is provided a comprehensive background on the use of diarylprolinol silyl ethers in the catalysis of iminium-initiated cascade reactions. The research conducted has focused on three main topics: 1.) The development of a novel class of bifunctional bissulfonamide organocatalysts for the asymmetric conjugate addition of dicarbonyls to nitroolefins. 2.) The use of diarylprolinol silyl ether organocatalysts to catalyze a novel Michael-Michael cascade reaction which generates fused carbocycles. 3.) The discovery and development of a novel organocascade kinetic resolution reaction using diarylprolinol silyl ether organocatalysts, which can be used for the synthesis of chiral 2,6-disubstituted tetrahydropyrans and chiral 2,5-disubstituted tetrahydrofurans.
SPECIATION OF TECHNETIUM-99 INCORPORATED INTO METAL OXIDE MATRICES: A MOLECULAR LEVEL UNDERSTANDING OF Tc-99 REDUCTION AND ITS COMPLEXATION INTO POLYOXOMETALATES
Year of Dissertation:
2009
Technetium-99 (99Tc) is a long-lived (T1/2 = 2.13 x 105 years) β-emitting (Emax = 294 KeV) radionuclide formed during the fission of 235U and fallout from nuclear weapons testing. It exists in relatively high concentrations in nuclear waste tanks, and the pertechnetate (TcO4-) anion has been shown to leach into surrounding subsurface soils and groundwaters. Due to its long half-life and the high mobility of the pertechnetate (TcO4-) anion, 99) Tc management is an issue for both waste characterization and long-term storage. A better understanding of both its extensive redox chemistry and the parameters that affect the speciation and coordination environment of Tc will promote the development of more appropriate methods for the separation of Tc from nuclear waste tanks as well as more fitting mediums for storage.