Browsing by Author "Edmond F. Bowden, Committee Member"

Now showing 1 - 18 of 18

Activation of Carbon-Hydrogen Bonds Mediated by Ru(II) Complexes
(2007-05-01) Pittard, Karl A.; David A. Shultz, Committee Member; James D. Martin, Committee Member; Edmond F. Bowden, Committee Member; T. Brent Gunnoe, Committee Chair
The RuII complex TpRu(CO)(NCMe)Me (Tp = hydridotris(pyrazolyl)borate) initiates carbon-hydrogen bond activation at the 2-position of furan and thiophene to produce methane and TpRu(CO)(NCMe)Ar (Ar = 2-furyl or 2-thienyl). Solid-state structures have been determined for TpRu(CO)(NCMe)(2-thienyl) and [TpRu(CO)(-C,S-thienyl)]2. The complex TpRu(CO)(NCMe)(2-furyl) serves as a catalyst for the formation of 2-ethylfuran from ethylene and furan. Similar catalytic reactivity was observed with TpRu(CO)(NCMe)(2-thienyl) for the production of 2-ethylthiophene. Density functional theory (DFT) calculations of the C-H activation of furan by {(TAB)Ru(CO)Me} (TAB = tris(azo)borate) indicate that the C-H activation sequence does not proceed through a RuIV oxidative addition intermediate. The reaction of TpRu(CO)(NCMe)Me and pyrrole forms TpRu(CO){ 2-N,N-(H)N=C(Me)(NC4H3)}. The formation of complex TpRu(CO){2-N,N-(H)N=C(Me)(NC4H3)} involves the cleavage of the N-H bond and 2-position C-H bond of pyrrole as well as a C-C bond forming step between pyrrole and the acetonitrile ligand of {TpRu(CO)(NCMe)}. Mechanistic studies indicate that the most likely reaction pathway involves initial metal-mediated N-H activation of pyrrole to produce TpRu(CO)(NCMe)(N-pyrrolyl) followed by C-C bond formation and proton transfer. Complex TpRu(CO)(NCMe)(N-pyrrolyl) has been independently prepared. At elevated temperatures, TpRu(CO)(NCMe)(N-pyrrolyl) converts to TpRu(CO){2-N,N-(H)N=C(Me)(NC4H3)}. Single crystal X-ray analysis has been achieved for TpRu(CO)(NCMe)(N-pyrrolyl), [TpRu(CO)(NCMe)(1-O-OC4H8) and TpRu(CO){2-N,N-(H)N=C(Me)(NC4H3)}. Computational studies support the suggested selectivity for initial N-H bond cleavage in preference to C-H bond activation. Rational design for a more electron-poor hydroarylation catalyst was discussed. Synthesis of Mp (Mp = tris(pyrazolyl)methane) complexes of the type [MpRu(PPh3)(CO)H]BAr'4, [MpRu(PPh3)(CO)Cl]BAr'4, [MpRu(PPh3)(PMe3)Cl]Cl, [MpRu(PPh3)(PMe3)Cl]BAr'4, [MpRu(PPh3)2Cl]BAr'4, [MpRu(PPh3){P(OMe)3}Cl]Cl, [MpRu(PPh3)(NCMe)Cl]BAr'4, [MpRu(PPh3)(NCMe)Cl]BAr'4 and [MpRu(PPh3)(CO)Cl]BAr'4 accomplished. A single-crystal X-ray diffraction study was carried out on the complex [MpRu(PPh3)(PMe3)Cl]Cl. [MpRu(PPh3)2Me]BAr'4 was prepared and examined by Cyclic Voltammetry (CV) where the E1/2 = 1.19 V. C-H activation was observed when [MpRu(PPh3)2Me]BAr'4 was heated in neat C6D6. Orthometalation appears to dominate reactivity via intramolecular C-H activation of a PPh3 ligand, however CH3D was produced at elevated temperatures. A series of Ep (Ep = tris(pyrazolyl)ethane) complexes of the type MpRu(Cl)2PR3 (R = Ph, OMe, or Me) were also synthesized. The [EpRu(PPh3)(NCMe)(Cl)]Cl and [EpRu(PPh3)(PMe3)(Cl)]Cl complexes were observed spectroscopically as intermediates in these syntheses. Improved synthesis of [MpRu(PPh3)2Cl]Cl was also accomplished by improving the yield by 23%, over the previously reported yield of 53%.
Design and Delivery of Water Soluble Gold Nanoparticles Containing Mixed Monolayers of Thiolated Polyethylene Glycol and Peptides to HeLa Cells
(2005-07-07) Coleman, Donna Marie; Edmond F. Bowden, Committee Member; Daniel L. Feldheim, Committee Chair; Tatyana I Smirnova, Committee Member
Drug delivery has become a major area of research interest today, particularly in cancer research. Many of the current cancer treatments have many undesirable side effects on patients leaving them weak and susceptible to other illness. Targeted drug delivery at the molecular level has many positive applications. First one could target a cancer therapeutic drug directly to the site of infection and reduce the many side effects associated with cancer therapy. Also less medication would be needed also reducing some of the side effects associated with current cancer therapeutics. Many researchers have turned their attention to nanotechnology as a way to address such cancer drug delivery issues. This thesis presents the design of a two-phase type water-soluble gold nanoparticle. The gold nanoparticle is passivated with a peptide sequence that has known cell-penetrating abilities. The thiolated polyethylene glycol imparts stability to the gold nanoparticle enabling it to stay in a stable state and remain functional in high salt concentrations such as inside of a human body. Presented in this thesis is data to confirm the preliminary results of a two-phase type gold nanoparticle passivated with thiolated polyethylene glycol and Arginine9, which could facilitate travel into the cytosol and nuclear regions of a HeLa cell. This type of delivery system has the potential of a possible future drug delivery vector.
Development and Characterization of an Atmospheric Pressure Ionization Source Matrix-Assisted Laser Desorption Electrospray Ionization Coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry for Analysis of Biological Macromolecules
(2009-07-16) Sampson, Jason Scott; Jorge A. Piedrahita, Committee Member; Edmond F. Bowden, Committee Member; Kenneth W. Hanck, Committee Member; David C. Muddiman, Committee Chair
The field of mass spectrometry has grown tremendously over the past few decades due in large part to the continued application to new and interesting areas of exploration. The advent of soft ionization sources such as electrospray ionization and matrix-assisted laser desorption/ionization have dramatically increased the capabilities of mass spectrometry and increased the amount of information derived from biological samples. As a result, there has been tremendous growth in the development of new ionization source technology in recent years. One of the main driving forces behind the development of new ionization technology is for the reduction of sample preparation required prior to analysis, yielding high throughput sample analysis. Demonstrated herein is the development and characterization of an atmospheric pressure ionization source called matrix-assisted laser desorption electrospray ionization (MALDESI). MALDESI is a hybrid combination of MALDI and ESI which utilizes laser desorption with electrospray postionization for the generation of multiply-charged ions. Multiply-charged ions are of particular importance when using Fourier transform mass spectrometry, due to the increase in resolving power and mass accuracy with increasing charge on the molecule. Top-down characterization of intact polypeptides is demonstrated as well as high mass accuracy utilizing internal calibration. A newly designed highly robust and versatile atmospheric pressure ionization platform is developed and described in detail. Solid- and liquid state analysis of three out of the four classes of biological molecules is demonstrated utilizing the newly developed versatile ionization platform. MALDESI utilizing ultraviolet and infrared laser desorption is demonstrated at various wavelengths (UV, 337 nm and 349 nm and IR, 2.94 Ã‚Âµm and 10.6 Ã‚Âµm) with and without ESI postionization for the generation of multiply-charged ions. The characteristics of liquid-state samples are described as a macroscopic electrospray droplet and characterized. MALDESI direct analysis is demonstrated and applications for high throughput analysis of complex samples are described.
Drug Partitioning and Solvation Environments in Lipid Bilayers
(2004-12-09) Carrozzino, Jennifer Marie; Edmond F. Bowden, Committee Member; Morteza G. Khaledi, Committee Chair; Charles B. Boss, Committee Member; Daniel L. Feldheim, Committee Member
The main goal of this research project was to investigate various factors influencing solute partitioning and solvation in lipid bilayer membranes using liposomes as biomembrane models and applying a combination of spectroscopic and capillary electrophoresis techniques. The first area of investigation involved using a series of polarity sensitive solvatochromic indicators to probe the dipolarity of various phospholipid and synthetic surfactant vesicles. A homologous series of probes of varying hydrophobicity allowed a systematic probing of the dipolarity in the interfacial region of the vesicles and resulted in very specific polarity information for various regions or microenvironments depending on the probes positions. This dipolarity was examined in terms of vesicle size and composition, in addition to indicator partitioning behavior. To develop Liposome Electrokinetic Chromatography (LEKC) as a method for rapidly determining liposome - water distribution coefficients, the effects of various parameters on the retention of basic drugs in liposomes were examined. This included characterizing the electrostatics of interactions between charged drugs and charged lipid membranes by examining the effect of membrane and buffer compositions. Additionally, LEKC was used to determine the effect of pH on the partitioning of basic drugs into liposomes composed of lipids which mimic the composition of natural cell membranes. Drug partitioning as a function of pH is examined in detail in terms of the fractions of charged and neutral drug forms in the aqueous and lipid phases. An increase in pH results in a smaller degree of ionization of the basic drugs and consequently leads to a lower degree of interaction with the negatively charged membranes. Finally, LEKC retention was used in QSAR studies for the evaluation of membrane permeability and intestinal absorption. LEKC retention factor data was correlated with human oral absorption in comparison with other methods such as octanol - water partitioning, total number of hydrogen bonding groups, and polar surface area. LEKC retention data was also related to Caco-2, MDCK, and human jejunal permeability in comparison with the standard model, octanol - water partitioning.
Exploring Fundamental Aspects of Proteomic Measurements: Increasing Mass Measurement Accuracy, Streamlining Absolute Quantification, and Increasing Electrospray Response
(2009-05-08) Williams, Dennis Keith Jr.; Kenneth W. Hanck, Committee Member; Edmond F. Bowden, Committee Member; David C. Muddiman, Committee Chair; Lin He, Committee Member
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers unparalleled performance in terms of resolving power and mass measurement accuracy. In order to realize the highest achievable mass measurement accuracy for a given FT-ICR MS system, frequency shifts due to space-charge effects must be accounted for via external or internal calibration methods. Herein, a dual electrospray ionization source was coupled to a hybrid quadrupole Fourier transform ion cyclotron resonance mass spectrometer and utilized to incorporate internal calibrant to yield high mass measurement accuracy results. Frequency shifts from space-charge effects were also counteracted by accounting for total ion population and relative ion population on a MALDI-FT-ICR MS and a hybrid LTQ-FT-ICR MS equipped with automatic gain control. This was achieved through the use of multiple linear regression and artificial neural networks. These experiments resulted in mean mass measurement accuracies in the parts-per-billion range. C-reactive protein (CRP) is an important clinical marker for inflammation, atherosclerosis, and has also been observed to be upregulated in patients with epithelial ovarian cancer (EOC). This dissertation contains results from a protein cleavage isotope dilution mass spectrometry method developed for the absolute quantification of CRP from human plasma. A total of 110 human plasma samples were analyzed including 54 samples from patients with EOC. The results were compared to a CLIA certified ELISA test which showed high correlation but different absolute values, which suggested different reference ranges for different analytical techniques. In addition, a correlation was observed between the stage of diagnosis of cancer and CRP concentrations. Chemical tags have long been utilized with mass spectrometry for a multitude of purposes, extending the effectiveness of the measurements dramatically. Electrospray ionization has been shown to preferentially ionize more hydrophobic species. Four new iodoacetamide derivatives, which react with the amino acid cysteine, were reacted with three peptides to determine their ability to increase electrospray response. This resulted in increases up to 2000-fold compared to alkylation of peptides with iodoacetamide. The combination of these results will aid future studies to identify and quantify proteins and peptides which contain cysteine and can be expanded to all peptides using amine-specific chemistry.
Fundamental Study and Method Development for Surface-based Laser Desorption Ionization Imaging Mass Spectrometry
(2010-05-01) Liu, Qiang; David C. Muddiman, Committee Member; Edmond F. Bowden, Committee Member; Lin He, Committee Chair; Morteza G. Khaledi, Committee Member
By providing both the chemical identity and the spatial organization of each component in biological samples, Imaging Mass Spectrometry (IMS) becomes an emerging tool in clinic and pharmacological study. Most work in IMS has been focused on protein and peptide mapping in biological samples to take advantage of effective analyte ionization in MALDI-MS, and also partially due to the limitation of MALDI-MS in small molecule detection. The focus of my research is to develop novel tools to image spatial distribution of small molecules in biological samples. A surface-based mass spectrometric imaging method, i.e. Desorption/Ionization on Silicon (DIOS), was used for biological surface analysis in the concept-proof investigation. More over, possible proton transferring pathways and impact of local chemical environment have been systematically investigated in the fundamental understanding of ionization mechanism of SALDI-MS. Based on the finding on the SALDI mechanism, a hybrid ionization approach, ME-SALDI has been developed by combing the strength of the conventional MALDI matrix and SALDI, where the improved detection sensitivity with reduced matrix-analyte interference and the improved imaging capability through analysis of mouse brain and heart sections has been demonstrated. In addition, the impact of vacuum stability of matrix in ME-SALDI-IMS applications has been examined. A solvent free, homogenous and reproducible sublimation method has been developed for ionic matrix in ME-SALDI, by which improved vacuum stability and MS detection have been achieved. Furthermore, a new generation of meso-porous oxide substrate was developed as a novel ME-SALDI substrate with a superior storage stability, extended detectable mass range and robust substrate preparation.
The Interaction of Boronic Acid Based Self-Assembled Monolayers as a Potential Glucose Sensor
(2005-08-02) Allen, Angela M.; Christopher Gorman, Committee Chair; Charles B. Boss, Committee Member; Edmond F. Bowden, Committee Member; Kenneth W. Hanck, Committee Member
Recognition of sugars such as glucose with phenylboronic acid–terminated self assembled monolayers (SAMs) was the basis for the designing and fabricating a biosensor. Self-assembled monolayers were formed on gold surfaces as shown by infrared spectroscopy. The continuous, repeatable increase of the electrochemical impedance as the concentration of glucose was increased gave indication of binding. This binding could be attributed to the precedent formation of relatively stable esters between phenylboronic acids and sugars. This impedance change upon binding between glucose and a phenylboronic acid-terminated SAM showed promise in the development of a glucose biosensor.
Multifunctional Heterometallic Oxide and Oxyfluoride Hybrid Solids
(2009-12-02) Lin, Haisheng; Lin He, Committee Member; Edmond F. Bowden, Committee Member; Mike H. Whangbo, Committee Member; Paul A. Maggard, Committee Chair
Heterometallic-oxide and oxyfluoride/organics are hybrids containing both organic ligands and inorganic metal-oxide/oxyfluoride components. These interesting types of materials are beginning to receive widespread attention because of their potential to express, within the same material, both the robustness and physical properties of inorganic components in conjunction with the versatility and chemical flexibility of organic ligands. My research efforts within this area have focused on the synthesis and design of new heterometallic hybrids which possess varied novel structures, and new investigations of their optical and phtocatalystic properties. Metal oxide systems were selected that contain an early transition-metal (i.e. V, Nb, Mo, W, Re) with a d0 electron configuration and a late transition-metal (i.e. Ag, Cu) with a d10 electron configuration. Organic ligands used in the reactions were chosen to possess different charges and sizes, and that would preferentially coordinate to the late transition metals that form part of the metal-oxide. The target of my work has been to investigate the hydrothermal syntheses of novel heterometallic hybrids and to explore the use of organic ligands in modifying and controlling the formation of resultant structures of metal oxides. The first section covers a new series of Ag/Cu-containing heterometallic-oxides/organics, with 0-1D, 2D layer, 3D pillar-layered or multi-fold interpenetrating structures through molecular-level interactions, and that have led to new insights regarding the range of optical bandgap absorption in compounds with d0/d10 transition metals. The latter aspect is analyzed with regard to its use in designing future photocatalytic materials. The syntheses, properties, and potential applications of these new materials are presented and analyzed herein, and especially, for the first known series of photocatalytically active silver-vanadate hybrids evaluated. The second section is focused on the synthesis and probing of the structures of new heterometallic-oxyfluoride/organics containing symmetric and/or asymmetric early transition metal (V, Nb, Mo, W) oxyfluorides anions. Their optical properties were studied as a function of small molecule absorptions. An understanding of the structure-properties relationships is used for further design and synthesis new visible-light photocatalytic materials.
Nanoparticle-based Delivery Vectors:Design, Preparation, Characterization, Cellular Internalization and Nuclear targeting
(2008-08-03) Liu, Yanli; Daniel L. Feldheim, Committee Chair; Lin He, Committee Member; Christian Melander, Committee Member; Edmond F. Bowden, Committee Member
New Software for Chemistry Applications: Algorithms and Experiment Planners for Automated Chemistry, and an Interactive Program for Use in Photochemistry (PhotochemCAD)
(2004-11-15) Dixon, James M.; Edmond F. Bowden, Committee Member; Jonathan S. Lindsey, Committee Chair; Kenneth W. Hanck, Committee Member; Charles B. Boss, Committee Member
This dissertation is based on convergent projects that focus on helping integrate the use of computers in the chemical field. Project 1 entails development of experiment planners for automated chemistry workstations. The power of parallel workstations has become evident in their pervasive application in high-throughput screening and combinatorial chemistry. Adaptive systems make decisions automatically based on data collected from ongoing experiments. Early adaptive systems performed reactions serially and were quickly eclipsed by workstations capable of performing parallel operations but without decision-making capabilities (i.e., open-loop). Great effort has been put into developing software for automated workstations that enables parallel, adaptive experimentation. A suite of algorithms that accompany an experiment planning software package for use with automated chemistry workstations has been developed. The main objective of this research is reaction optimization, a very general problem in many areas of chemistry, but the approach is quite general. The algorithms developed for parallel, adaptive experimentation include the successive focused grid search (SFGS), multidirectional search (MDS), parallel multidirectional search (PMDS'), parallel simplex search (PSS), parallel screening each member of a set of catalysts across a range of concentration (Parascreen), and several two-tiered methods that enable broad screening followed by in-depth searches. Project 2 focuses on the growth and improvement of the PhotochemCAD software. Laboratory researchers often face the problem of organizing and managing large quantities of experimental data, as well as comparing their data with literature data. In the photochemical sciences, the core data include the spectral properties of diverse substances. One wants to know the absorption and emission properties of a compound, have pointers to the literature, and be able to perform calculations using such spectral data. A versatile software package (PhotochemCAD) has been developed that includes a database of spectral data with literature references for over 150 compounds of natural and synthetic origin. Features are available for performing diverse calculations of interest across the photochemical sciences, including Förster energy transfer, oscillator strength, multicomponent analysis, blackbody radiator, etc. This development effort has much in common with research aimed at creating versatile software programs that address the needs of experimentalists in laboratory settings.
Prediction of Peptide Maps in CZE and MEKC Systems
(2005-04-24) Shen, Yang; Edmond F. Bowden, Committee Member; Charles B. Boss, Committee Member; Morteza G. Khaledi, Committee Chair
A new Quantitative Structure-Migration Relationships(QSMR) model was developed to predict the electrophoretic mobilities of peptides in capillary zone electrophoresis(CZE). A three-step strategy was used: first, select the best charge-size term from the existing models; second, develop a muilti-linear regression(MLR) model to study the linear characteristics of peptide mobility using the best charge-size term and other descriptors; third, generate an artificial neural network(ANN) to investigate the nonlinear behavior of peptide mobility and use this ANN model to predict peptide migration behavior in CZE. To test the robustness of the QSMR model, it was applied to the data published by another research group. Very accurate predictions were achieved. To study the influence of peptide sequence on the migration of a peptide in CZE, a series of 'sequence-related' descriptors were developed. These descriptors were used to develop MLR models for peptide mobility prediction. With the 'sequence-related' descriptor, more accurate mobility could be predicted for peptides with same amino acid composition but different sequences. Group contribution approach(GCA) was used to determine the individual contribution of each amino acid residue and both N-, C- terminal to the peptide mobility in Tween20 system. Data of a relatively small number of peptides were used for this purpose. The sum of individual contributions was calculated for each peptide and used as a new descriptor in developing MLR models for the prediction of peptide mobilities in Tween20 system. Good preliminary results were achieved.
Spectroscopic Studies of Activation of Dehaloperoxidase by Hydrogen Peroxide
(2010-07-28) Wang, Zao; Tatyana I. Smirnova, Committee Chair; Stefan Franzen, Committee Co-Chair; Edmond F. Bowden, Committee Member
ABSTRACT ZAO ,WANG. Spectroscopic Studies of Activation of Dehaloperoxidase by Hydrogen Peroxide. ( Under the direction of Tatyana I. Smirnova and Stefan Franzen.) The focus of this research is to use stopped-flow UV-visible and rapid freeze-quench electron paramagnetic resonance (EPR) spectroscopic methods to study the peroxidase activity of the enzyme dehaloperoxidase (DHP) from Amphitrite ornata. DHP is the first characterized hemoglobin which has a naturally occurring peroxidase function. It has been discovered that ferric DHP can catalyze the dehalogenation of halophenol to quinones in the presence of H2O2, which is a peroxidase function. However, ferrous DHP is also capable of binding oxygen reversibly, which is a hemoglobin function. It is still not understood how this bi-functional protein can act as both a hemoglobin and a peroxidase, because hemoglobin function require ferrous form as starting oxidation state but peroxidase require ferric form as starting oxidation state. This work has addressed three separate questions. First, I studied the autoreduction reaction of DHP under CO atmosphere. The study demonstrates that the Cys 73 residue is not required for autoreduction of DHP under CO atmosphere. Mutation of Cys 73 to serine also does not affect the mechanism of the DHP reaction with hydrogen peroxide. Second, the study demonstrates that in the absence of a substrate, DHP reacts with hydrogen peroxide forming Compound II, that, under conditions used, decays after 2 seconds to form Compound RH. In the presence of the substrate, TCP (2,4,6-trichloropenol) Compound II reacts with TCP forming Ferric DHP and DCQ (2,4-dichloroquinone).
Structure-Property Relationships for Electron Transfer Kinetics in Metal Tris(bipyridine) Core Dendrimers
(2005-07-28) Hong, Young-Rae; Edmond F. Bowden, Committee Member; Christopher B. Gorman, Committee Chair; David A. Shultz, Committee Member; Kenneth W. Hanck, Committee Member
Structure property relationship in the redox-active core dendrimers were systematically studied by probing the rate and driving force for electron transfer. An isostructural series of redox-active, metal tris(bipyridine) core dendrimers were synthesized for this purpose. Various synthetic routes were attempted to introduce the bulky dendritic moieties to the bipyridine units with high yields. Heterogeneous electron transfer kinetics was studied by electrochemical methods. In the second generation of these dendrimers, a large attenuation of electron transfer rate was observed qualitatively. A newly designed thin layer electrode was constructed and utilized to study heterogeneous electron transfer kinetics in the second generation dendrimers. In the finite condition, the slow heterogeneous electron transfer kinetics in second generation dendrimers could be studied by computer simulation. Homogeneous electron self-exchange kinetics was studied by nuclear magnetic resonance spectroscopy. The rate attenuation of electron transfer with dendrimer generation was not the same as the behavior found in heterogeneous, electrochemical electron transfer rate determinations. While a large attenuation was observed between the zeroth and first generation, the attenuation of electron transfer between the first and second generation was insignificant. This was rationalized by the concept of core mobility. The redox core in slow exchange limit can move in a non-rate limiting fashion toward a neighboring redox core with the result that the structural effect of the dendrimer is reduced and electron transfer is facilitated in larger dendrimers. For further studies, thermodynamic activation parameters were also obtained by variable temperature nuclear magnetic resonance studies.
Synthesis and Characterization of Amphiphilic Iron-Sulfur Core Dendrimers
(2005-07-31) Dembowa, Aneta; Daniel L. Feldheim, Committee Member; Edmond F. Bowden, Committee Member; Christopher B. Gorman, Committee Chair
Synthesis of water soluble carboxylate-terminated Fe4S4-core was carried out. Convergent method was chosen to build three generations of dendrons. Several synthetic schemes were explored. The syntheses were conducted with 4,4-bis(hydroxyphenyl)penthanol as a repeat unit and N,N-dimethyl thiocarbamate and methyl ester or methoxy-methyl as protecting groups. The conditions for deprotection and ligand exchange have been proposed. 1H, 13C and MALDI-MS were used to characterize synthesized molecules.
Synthesis and Reactivity of Ruthenium Amine and Amido Complexes.
(2005-03-01) Conner, David M; David Shultz, Committee Member; Edmond F. Bowden, Committee Member; T. Brent Gunnoe, Committee Chair; James Martin, Committee Member
Late transition metal complexes with non-dative and π-donating ligands are important substrates in a variety of synthetic transformations including C-N or C-O bond forming processes and C-H bond activation reactions. Examples of such complexes are few relative to early and middle transition elements in high oxidation states, and the understanding of the chemistry of such systems with amido, oxide, imido, or oxo ligands has lagged compared to related M-C or M-H linkages. A series of Ru(II) amido complexes of the type TpRu(L)(L')NHR (L = L' = PMe3 or P(OMe)3 or L = CO and L' = PPh3; R = H, Ph, or tBu) were prepared and characterized. These complexes exhibit basic reactivity and will deprotonate C-H bonds as evidenced by the reactivity with weak acids such as 1,4-cyclohexadiene or phenylacetylene. The nucleophilicity of the complexes was also examined by reaction with ethylbromide. In addition, oxidation of the phenyl amido complexes with AgOTf, Cp2FePF6, or I2 resulted in 4,4' carbon-carbon coupling of the aryl group of the anilido ligands to produce the bimetallic complexes [TpRu(L)(L')NHC6H4-]2[X]2 (X = OTf -, PF6-, or I-). The five-coordinate amido complexes (PCP)Ru(CO)NHR (PCP = C6H3(CH2PtBu2)2; R = H or Ph) were synthesized and characterized. The parent amido complex was prepared by deprotonation of (PCP)Ru(CO)(NH3)Cl and the phenyl amido
Synthesis of Gold/Polymer Composites, Micelle/Polymer Composites, and Polymer Nanocapsules. Diffusion Studies and Encapsulation of Guest Molecules.
(2002-08-13) Marinakos, Efstathia (Stella) Maria; Daniel L. Feldheim, Committee Chair; Edmond F. Bowden, Committee Member; David A. Shultz, Committee Member; T. Brent Gunnoe, Committee Member
The template synthesis of core / shell particles is described. One template employed as the core is a gold particle. Polymers employed as the shell are polypyrrole, poly(N-methylpyrrole), and poly(3-methylthiophene). The gold core of the composite particle is removed to yield a hollow polymer capsule, the core dimensions of which are determined by the dimensions of the template. Shell thickness is also controlled easily. Permeability of the shell is varied according to shell composition, oxidation state of the polymer, and incorporated counterion. Attaching rhodamine B, anthraquinone, or horseradish peroxidase to the gold particle template prior to shell formation and removal of the core results in encapsulation of the molecule. A second template employed as the core is a micelle. Micelle core / polymer shell particles may possibly be further utlilized as an encapsulation method by solubilizing a molecule in the core of the micelle prior to polymer shell formation.
Synthesis of Phthalocyanines for Use in Electronic Materials.
(2005-07-11) Youngblood, William Justin; Edmond F. Bowden, Committee Member; Daniel L. Comins, Committee Member; Daniel L. Feldheim, Committee Member; Jonathan S. Lindsey, Committee Chair
This dissertation describes the synthesis of phthalocyanines having specialized structures that provide for electrochemical studies of their fundamental properties and/or for direct preparation of phthalocyanine-based electronic materials. Much of the synthetic effort herein is directed toward the development of a particular class of phthalocyanine, herein referred to as benzimidazoporphyrazines. Benzimidazoporphyrazines are desirable substitutes for typical phthalocyanines in applications requiring phthalocyanine-based materials. The value of benzimidazoporphyrazines is derived from their geometry, which provides four substitution positions at peripheral carbon atoms that lie along the N-N axes of the macrocycles. The modular construction of pigment arrays that include phthalocyanines may be greatly facilitated with the use of benzimidazoporphyrazines. The history of research in benzimidazoporphyrazines is brief, and has not heretofore provided access to benzimidazoporphyrazines bearing substituents that may serve as synthetic handles for modification of the pigments after their formation. This report details the development of synthetic methodology to prepare benzimidazoporphyrazines that bear useful synthetic handles. The synthesis of a set of such pigments is also described. Additionally, the new pigments (and one pigment array) are studied with regard to structural confirmation, as well as by photochemical and electrochemical means.
The Use of Biodegradable Poly(b-amino ester) and Poly(b-amino amide) Microspheres as an Experimental Therapeutic Delivery Vector for Selective Cancer Cell Targeting
(2005-02-25) Shipton, Matthew Kent; Dr. Daniel Feldheim, Committee Chair; David A. Shultz, Committee Member; Edmond F. Bowden, Committee Member
The design, synthesis, and use of new biodegradable polymers for drug delivery applications is an area of ever increasing interest. Polymeric drug delivery systems have several advantages compared to conventional drug delivery methods such as liposomes and antibodies. Since liposomes are spherical vessels made of phosphorolipids, they are tiny particles which can be taken up by the macrophages. Antibodies, meanwhile, have the disadvantage that most receptor sites on tumor cells are also present on healthy cells. Several of these advantages include localized delivery, improved drug efficiency, and drug protection of certain medications which may degrade rapidly when inside the body. Poly(b-amino esters) and Poly(b-amino amides) are ideal polymers for the encapsulation, delivery, and release of various therapeutic agents to cancer cells, which have an acidic extra cellular pH level, near 6.8. Poly(b-amino esters) and Poly(b-amino amides) are specifically designed to degrade by hydrolysis of the ester and amide bonds respectively, in the polymer backbone. Microspheres of Poly(b-amino ester) and Poly(b-amino amide) are formed via a double emulsion process using Rhodamine B-Isothiocyanate (RBITC) labeled Bovine Serum Albumin (BSA) as the encapsulate. The fluorescence intensity of the RBITC-BSA released from the polymer sphere was measured as a way of testing polymer backbone hydrolysis. The polymer microspheres were placed into different solutions of varying pH ranges. The pH range extended from pH 5.5 to pH 7.4. The hydrolyzed polymer byproducts were removed and the resulting supernatant tested for fluorescence intensity. The results showed polymer hydrolysis and release of labeled BSA at pH 6.8 and lower.