Department: Chemistry ![[clear]](close-x.png "Remove this limiter")
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1.
Alemán, Elvin A.
PHOTOCHEMISTRY AND PHOTOPHYSICAL CHARACTERIZATION OF PORPHYRIN and N-CONFUSED PORPHYRIN DYADS: PORPHYRIN PHOTOPHYSICAL PROPERTIES AND ELECTRON AND ENERGY TRANSFER.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► In order to understand and mimic the processes that occur in photosynthesis,…
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▼ In order to understand and mimic the processes that occur in photosynthesis, the photophysical properties of a series of porphyrinic molecules have been investigated. N-Confused tetraphenylporphyrin (NCTPP) differs from tetraphenylporphyrin (H2TPP) by having one of the pyrrolic nitrogens inverted and facing outside the macrocycle, with a C-H group inside. The inverted pyrrole ring in NCTPP results in a change in the pi-system of the macrocycle, leading to photophysical properties that are different than those of H2TPP. The first project was intended to investigate the photophysical properties of the two NCTPP tautomers, as well as several substituted (di- and tetra-) NCTPP derivatives using several spectroscopic techniques, including steadystate absorption and emission spectroscopy, time correlated single photon counting, femtosecond transient absorption and nanosecond transient absorption spectroscopy. The second project consisted of the studies the photophysical characterization of pentameric N-confused porphyrin-zinc tetraphenylporphyrin artificial light-harvesting array (NCP-ZnP4), the photophysical properties of an N-confused-pyromellitimide array (NCP-Pym4), and the photophysical characterization of an N-confused porphyrin-pyrene donor acceptor dyad (NCP-Pyr). The supramolecular systems NCP-ZnP4, NCP-Pym4 and NCP-Pyr represent the first structures where an N-confused porphyrin has been covalently incorporated into an array designed to involve highly efficient photoinduced energy and electron transfer processes. Free base corroles differ from free base porphyrin by having one of meso methine carbons replaced by a direct pyrrolepyrrole linkage. The fourth project in this dissertation involved the photophysical characterization of four free base triphenylcorroles using steady state absorption and emission spectroscopy, and time correlated single photon counting experiments. The photophysical results indicate that similar to NCTPP, there is noticeable solvent dependence on the corrole photophysical properties. It is postulated that these differences result from the presence of two (or more) different tautomers. Although regular tetraphenylporphyrins such as H2TPP and Zntetraphenylporphyrin (ZnTPP) have been extensively used in different artificial photosynthetic systems, their incorporation into arrays presents characterization challenges, and energy and electron transfer mechanisms differ from array to array. The fifth project presented here involved an investigation into the effects of donor-acceptor orientation on the electron transfer (ET) and charge recombination (CR) rate constants. In a series of porphyrin-benzoquinone (PBQ)dyads, methyl groups on the meso phenyl groups were used to control the orientation between the donor and acceptor groups. The rate constants for ET and CR in these compounds are discussed, as well as the ramifications of these results on porphyrin photophysics. The final project in this dissertation involved the study of the photophysical properties of a series of triads, where two ZnTPP electron donor groups were linked, using a flexible dendritic spacer, to a naphthalenediimide acceptor group. The flexibility in these triads permitted the formation of several conformers, which were investigated using steady state and time-resolved spectroscopic techniques as well as semi empirical molecular orbital calculations.
Advisors/Committee Members: Modarelli, David A.
Subjects: Chemistry, Physical
Keywords: Porphyrin Photophysical Properties; N-Confused Porphyrin; Electron Transfer; Energy Transfer
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2.
Baiagern, Silapong.
Multidimensional NMR Studies of the Polymers.
Degree: Doctor of Philosophy, Chemistry, 2008, University of Akron
► The purpose of this work was to apply multinuclear and multidimensional nuclear…
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▼ The purpose of this work was to apply multinuclear and multidimensional nuclear magnetic resonance (NMR) spectroscopy techniques to determine the characteristics of the structure and intermolecular interactions of dendrimers supramolecular assemblies, polyalkylsilane oligomer and Nafion® fluoropolymer. In the one of the studies, a mixture of alkylpolysilane oligomers was characterized by one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy. The oligomeric products were observed to have chains of up to 5-6 silicons. Complete unambiguous resonance assignments were obtained with the help of 1D 1H, 13C, 29Si and 2D 1H{29Si}gHSQC/gHSQC-TOCSY/gHMBC experiments. Finally, the discovery of the quarternary Si atoms by using HMBC technique provides evidence for branching in the structures. In a separate study, multidimensional NMR spectroscopy was used to analyze the supramolecular chemistry of poly(propylene imine) dendrimers that have urea-adamantane as end groups with numerous acidic guest molecules. Data about the close proximity of the host and guest molecules was determined by two-dimensional (2D) nuclear Overhauser enhancement spectroscopy (NOESY). These interactions support a specific binding model for the formation of a stable host-guest complex. Diffusion studies concerning a ratio of host and guest molecule helped to support the data collected. Finally, the Nafion® fluoropolymer, used for proton exchange membranes, was investigated using regional or band selective excitation to perform selective nD NMR experiments. The microstructure of the Nafion® prepolymer with the sulfonyl fluoride functional group was characterized by homonuclear band-selective 19F-19F COSY. When compared with signals in a standard COSY spectrum, the cross-peaks in the selective homonuclear 19F-19F COSY give more intense and cleaner signals. To further simplify the complex cross-peak patterns, a q3 and Gaussian 180° inversion pulse was introduced to remove fluorine homonuclear coupling during the t1 evolution time.
Advisors/Committee Members: Rinaldi, Peter L.
Subjects: Chemistry
Keywords: Multidimensional NMR Studies of the Polymers
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3.
Banerjee, Debasish.
MULTIDIMENSIONAL NMR STUDIES OF THE HYPERBRANCHED POLYMERS AND PHOSPHAZENE SYSTEMS.
Degree: Doctor of Philosophy, Chemistry, 2005, University of Akron
► The purpose of this work was to apply multinuclear and multidimensional nuclear…
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▼ The purpose of this work was to apply multinuclear and multidimensional nuclear magnetic resonance (NMR) spectroscopy techniques for the characterizations of the structure and intermolecular interactions of dendrimers, supramolecular assemblies and inorganic ring systems (cyclophopsphazenes and polyphosphazenes). In one of the studies, Newkome type dendrimers having either a free base or zinc metallated porphyrin core and methyl/ethyl ester termini were characterized by one- and two-dimensional NMR spectroscopy. The results indicate that although back-folding of the arms is absent in case of the 1st generation dendrimers, the Zn-centered 2nd generation dendrimers exhibit considerable back-folding toward the core in deuterated chloroform solutions. In a separate study, the supramolecular chemistry of poly(propylene imine) dendrimers having urea-adamantane as end groups with various acidic guest molecules were analyzed by multidimensional NMR spectroscopy. Two-dimensional (2D) nuclear Overhauser enhancement spectroscopy (NOESY) data provided information about the close proximity of the host and guest molecules. These interactions support a specific binding model for the formation of a stable host-guest complex. These data were well supported by a three-dimensional (3D) heteronuclear single quantum coherence-NOESY experiment and diffusion studies in case of a 13C labeled guest molecule. Finally, the structure and acid-base chemistry of hexachlorocyclotriphosphazene with Lewis acids such as AlCl3, AlBr3 and GaCl3 were investigated using multinuclear NMR spectroscopy. The structure and molecular weight distribution of the phosphazene polymer (formed by the ring opening polymerization of hexachlorocyclotriphosphazene at elevated temperature) were also characterized by 2D 31P-15N heteronuclear multiple quantum coherence (HMQC) and diffusion ordered spectroscopy experiments. The results show the presence of low molecular weight oligomers (in minor proportions) and cyclic tetra-, penta- and hexamer along with a major polymer component.
Advisors/Committee Members: Rinaldi, Peter L.
Keywords: Chemistry, Dendrimer, NMR, Polymer, Phosphazene
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4.
Barone, Natalie V.
The Synthesis and Characterization of Oxygen Containing Porphyrin Analogs and Rhenium Coordination Chemistry for Diagnostic Imaging.
Degree: Master of Science, Chemistry, 2008, University of Akron
► The metal binding chemistry of porphyrin analogs is a rapidly growing area…
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▼ The metal binding chemistry of porphyrin analogs is a rapidly growing area of research. One specific family of analog where one or more of the internal nitrogen positions has been replaced by carbon, known as the carbaporphyrins, is of interest to researchers due to novel organometallic interactions with various metals in the interior of the ring. Within this thesis, a continued investigation of the carbahemiporphyrazines, anti-aromatic phthalocyanine analogs where one or more isoindolene rings has been replaced with benzene rings is presented. The theory, synthesis and characterization of oxygen containing hemiporphyrazines analogues are investigated. These types of oxygen containing rings incorporate either phenol or resorcinol into a carbahemiporphyrazine ring. Due to the redox activity of the phenol or resorcinol, these macrocycles can potentially become aromatic upon oxidation in a fashion similar to that seen in the oxybenziporphyrins. As in the carbahemiporphyrazines, these rings can bind metal ions, forming novel organometallic interactions at the core of the ring. Also presented within this thesis is the single crystal X-ray diffraction characterization of new rhenium(I) tri-carbonyl complexes for possible application as radiopharmaceutical diagnostics. The Re(I) compounds designed to be analogs for next generation d6 technetium imaging agents. These compounds are synthesized in aqueous conditions and are stable upon exposure to air. The single crystal X-ray diffraction elucidation of the Re(I) compounds are grouped into three distinct categories: monodentate complexes, bidentate complexes and tridentate complexes. All of the complexes are octahedral, and the carbonyl ligands arranged in a facial configuration. The complexes are synthesized from the Re(CO)3(H2O)+ synthon.
Advisors/Committee Members: Ziegler, Christopher.
Subjects: Chemistry
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5.
Bauer, Joseph Alan.
Biochemistry of Nitric Oxide Donors: Therapy Vs. Toxicity.
Degree: Doctor of Philosophy, Chemistry, 1999, University of Akron
► A full thickness wound model was used to evaluate the effects of…
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▼ A full thickness wound model was used to evaluate the effects of a topically applied polyethyleneimine-based nitric oxide (NO) donor on wound repair involving aged rats. The NO released, for the linear-PEI-NO group, was significant compared to controls (p less than or equal to 0.001) (with a maximal nitrate level of 40 umol on day 1, and an average sustained delivery of 34 umol/day for the remainder of the study. A PBS-wounded control was performed which demonstrated cleaner and faster healing wounds, similar to normal healing, than either of the polymer application groups. For the first time, we report the toxic effects of a polyethyleneimine based compound, as well as, the toxic effects of sustained delivery of excess levels of NO on the wound repair process. Our findings suggest that there exists vague parameters between therapy and toxicity of NO delivery to wounds. Additionally, the effects of transforming growth factor-beta1 (TGF-beta1) on nitric oxide (NO) production and wound repair were evaluated using a mouse perforated-mesentery, connective tissue repair model. A significant decrease in post-wounding urinary nitrate levels (p less than or equal to 0.10) was observed comparing treatment and control groups after the injection of TGF-beta1. Furthermore, TGF-beta1 treated animals showed significant connective tissue repair as compared to controls without an increase in urinary nitrate levels post-wounding. Our findings support an integrated and synergistic relationship between TGF-beta1 and NO in regulating the diverse mechanisms of wound repair. Lastly, nitrosylcobalamin, a vitamin B12-based, non-toxic carrier of nitric oxide (NO), has been synthesized, isolated and characterized in vitro. A UV/VIS analysis was performed confirming the reduction of the cobalt atom of hydroxocobalamin with the binding of NO, causing a shift in the absorption spectra of Co+3 (lambda max 530) to Co+2 (lambda max 500) with the formation of nitrosylcobalamin. The extinction coefficient (emax) of nitrosylcobalamin, as calculated, was 4.8 (mM-1, cm-1). An IR analysis determined the v(NO) vibrational frequency at 1652 cm-1, supporting the binding of NO and suggesting a bent bonding geometry. The cumulative NO release followed first order kinetics and was pH dependent. Nitrosylcobalamin may offer a "drug targeting" approach as a potential, biologically compatible, and selective pharmacological donor compound.
Advisors/Committee Members: Smith, Daniel J.
Keywords: nitric oxide; nitrosylcobalamin, vitamin B12, wound repair; apoptosis; TGF beta
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6.
Belair, Jeffery P.
The Photophysical Characterization of N-Confused Tetraphenylporphyrin and the Characterization of Zinc N-Confused Tetraphenylporphyrin.
Degree: Master of Science, Chemistry, 2005, University of Akron
► The photophysical properties of both the interior and exterior protonated tautomers of…
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▼ The photophysical properties of both the interior and exterior protonated tautomers of N-confused tetraphenylporphyrin (NCTPP) in coordinating and non-coordinating solvents were investigated using UV-visible absorption spectroscopy and fluorescence spectroscopy. In addition, a series of zinc N-confused tetraphenylporphyrins (Zn(NCTPP)) with a ligand coordinated at the axial site were synthesized from the methods of Girolami, Rauchfuss, and Angelici, and crystallized via slow solvent diffusion. The series includes Zn4 (NCTPP)2 (O2CCH3)3(OH), Zn(NCTPP)(DMSO), and Zn(NCTPP)(Pyridine). The objectives of this research were to probe the reasons normal tetrapyrroles are the macrocycle of choice in biological systems, metallate NCTPP with biologically relevant transition metals, coordinate derivatives of biological ligands to the metal center, and characterize the resultant compounds. We found that Zn4(NCTPP)2(O2CCH3)3(OH) is a model compound for the zinc-dependent aminopeptidase in Aeromonas proteolytica.
Advisors/Committee Members: Ziegler, Christopher J.
Subjects: Chemistry, Inorganic
Keywords: zinc N-confused tetraphenylporphyrin; Zn(NCTPP); zinc; porphyrin; tetrapyrrole; macrocycle; N-confused porphyrin; NCTPP; ligand; coordinated ligand; axial site; Aeromonas proteolytica; model compound; zinc-dependent aminopeptidase; aminopeptidase; acetate
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7.
Bhide, Mahesh.
Nitric oxide delivery from polymeric wound dressings.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► Nitric oxide (NO) has been found to play many diverse physiological roles,…
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▼ Nitric oxide (NO) has been found to play many diverse physiological roles, ranging from a neurotransmitter to an active participant in wound healing. The beneficial effects can be attributed to the role NO plays in angiogenesis, inflammation and tissue remodeling. In the present work, we have developed several polymeric devices using the electrospinning technique for the sustained, site specific delivery of nitric oxide. In one such device, NO is generated using the simple chemistry between ascorbic acid and nitrite (NO2-) ions. The work has been concentrated mainly on the formation of a multilayer transdermal patch, as well as a cream, to obtain a site specific delivery of NO. Mainly two types of multilayered patches were fabricated: the 1st generation patch (which showed NO release for 6-8 h.) and the 2nd generation patch (which showed NO release for 24 h. or more) were using a polyurethane polymer, which encapsulates the active reagents, along with a superabsorbent polymer. The active reagents include nitrite (NO-2) ions bound to an ion exchange resin and microcrystalline cellulose (MCC) stabilized ascorbic acid. These active reagents are encapsulated within the polymer matrix and do not react with each other unless hydrated. Upon hydration ascorbic acid migrates to the resin bound nitrite ions, at which point they undergo a rapid reaction to generate nitric oxide. Samples of the1st and the 2nd generation patches were sent to an outside source for gamma radiation. The samples were returned back in order to study the effect of gamma radiation on the NO release as well as the stability. Similarly, a transdermal multilayered patch was designed using ion exchange resin bound H+, NO-2 and ASC- ions encapsulated in a polyurethane matrix, which also delivered NO. In another experiment, a transdermal patch was developed using polyethyleneimine (PEI) and polyethyleneimine-Cellulose (PEI-Cellulose). PEI and PEI-Cellulose were modified with NO under pressure and electrospun with the polyurethane polymer. For all of the above combinations, release profiles for NO were studied and stability studies were carried out. In addition to a multilayered patch, a topical cream was developed using Pluronic®, ion exchange bound nitrite ions, MCC stabilized ascorbic acid, and salicylic acid. The cream can be applied topically for the site specific delivery of NO. The results show stable, sustained and site specific delivery of NO.
Advisors/Committee Members: Smith, Daniel.
Subjects: Chemistry, Polymer
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8.
Bodle, Eric S.
Multivariate Pattern Recognition of Petroleum-Based Accelerants and Fuels.
Degree: Doctor of Philosophy, Chemistry, 2007, University of Akron
► Arson investigators use a wide variety of methods to detect accelerants in…
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▼ Arson investigators use a wide variety of methods to detect accelerants in fire debris. The complex nature of petroleum-based accelerants leads to misinterpretation of the sample. A novel method has been developed for the extraction and analysis of petroleum-based accelerants using solid phase microextraction (SPME) with separation and detection by GC-FID. Multivariate data analysis is also employed to simplify these data allowing for more accurate classification. SPME in conjunction with multivariate data analysis is a new approach in accelerant sampling and classification. Principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) have been shown to correctly classify a group of household accelerants. These groupings have been compared to the ASTM International classification systems. PCA is shown to be effective in the initial classification of accelerants and is used to establish the class confidence envelopes for the SIMCA models. The SIMCA models are effective in the prediction of class assignment with 98.5% and 97.2% of the test data correctly classified. Sample evaporation was examined to determine any influence on proper classification. Evaporation occurring for over 120 minutes showed significant changes to the classification of gasoline samples. Sample quantity was also examined for gasoline samples. Gasoline’s limit of detection was 50 µl under the conditions studied. The type of compounds extracted varied depending on the amount of accelerant examined. Larger amounts of gasoline resulted in higher concentrations of more volatile compounds extracted. Gasoline has also been evaluated for patterns related to its chemical make-up. Data analysis of the complex gasoline chromatograms occurred with PCA, partial least squares (PLS) and orthogonal partial least squares (OPLS). Patterns correlating to the anti-knock index were observed for the gasoline samples studied. Near-infrared spectroscopy was used to determine the AKI, anti-knock index, values for method validation. PLS was effective in the prediction of AKI number with a ± 0.737 AKI root mean square error of prediction (RMSEP). The OPLS method was also effective giving a ± 0.831 AKI RMSEP.
Advisors/Committee Members: Hardy, James K.
Subjects: Chemistry, Analytical
Keywords: Mulitvariate analysis; solid-phase microextraction; GC-FID; Arson; Accelerants
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9.
Boduroglu, Serhan.
New Supramolecular Approach for Sugar Analysis.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► The main objective of the work presented in this thesis was to…
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▼ The main objective of the work presented in this thesis was to develop new methods for sugar sensing as well as sugar analysis. Boronic acids were chosen as sugar binding motif because of their affinity to sugars. For this purpose a novel type of boronic acid, 3-Pyridinylboronic acid (3pa), was developed. This boronic acid was identified as a key sensing element for reversible sugar complexation in an aqueous solution at physiological pH. In terms of sugar sensing, 3pba was successfully applied to develop a surface-enhanced Raman glucose sensor. In this study, indirect detection of glucose was demonstrated for the first time by using surface-enhanced Raman spectroscopy. Then, taking advantage of the high binding constant of 3pba with sugars, colorimetric detections of monosaccharides were done using absorption spectroscopy in the visible region. The mechanism of the high diol/triol binding of 3pba in a neutral pH was discussed based on the 1H, 13C, and 11B NMR spectroscopic studies. Monosaccharides as well as disaccharides were explored and K constants were verified by the NMR spectroscopy technique. In terms of sugar analysis, 3pba was used to develop an effective ionization agent for ESI-MS analysis of sugars. It was demonstrated that the dynamic covalent supramolecular binding, between the arylboronic acid and sugars allowed convenient in situ derivatization of the sugar analytes. The zwitterionic nature of 3pba allowed intense ion signals of both the corresponding cations and anions to be observed by a simple switching of the ESI-MS polarity. Isomeric monosaccharides, such as fructose, glucose, and galactose, and isomeric disaccharides, such as lactose and sucrose, were ionized and distinguished by a simple ESI-MS2 experiment. Moreover, zwitterionic aryl boronic acid allowed the facile formations of structurally well-defined gas phase ions with inert charge sites on trisaccharides. As a consequence, successful demonstration of sequencing of a trisaccharide was achieved.
Advisors/Committee Members: Hu, Jun.
Subjects: Chemistry, Organic
Keywords: sugars; boronic acid; glucose sensing; SERS
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10.
Campos Ramos, Ricardo E.
STRUCTURE AND EXCITED-STATE DYNAMICS OF AROMATIC NITRILES IN SUPERSONIC FREE JET.
Degree: Doctor of Philosophy, Chemistry, 2005, University of Akron
► Excitation-energy dependence of fluorescence intensity and lifetime has been measured for 4-dimethylaminobenzonitrile…
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▼ Excitation-energy dependence of fluorescence intensity and lifetime has been measured for 4-dimethylaminobenzonitrile (DMABN), 4-aminobenzonitrile (ABN), 4-diisopropylaminobenzonitrile (DIABN) and 1-cyanonaphthalene (1CNN) in a supersonic free jet. In all cases, the fluorescence yield decreases rather dramatically, whereas the fluorescence lifetime decreases only moderately for ( ) excess vibrational energy exceeding about 1000cm-1. This is confirmed by the normalized fluorescence excitation spectrum with the absorption spectrum of the compound in the vapor phase. The result indicates that the strong decrease in the relative fluorescence yield at higher energies is due mostly to a decrease in the radiative decay rate of the emitting state. Comparison of the experimental results with the Time Dependent Density Functional Theory (DDFT) potential energy curves for excited states strongly suggests that the decrease in the radiative decay rate of the amino-benzonitriles at higher energies is due to the crossing of the singlet state by the lower-lying singlet state of very small radiative decay rate. The threshold energy for the fluorescence “break-off” is in good agreement with the computed energy barrier for the crossing. For 1CNN, on the other hand, the observed fluorescence break-off can be best attributed to the crossing of the singlet state by the triplet state. A concerted experimental (mass-selective spectroscopy) and theoretical (correlated quantum chemistry calculation) study of hydrogen-bonded clusters of 1-cyanonaphthalene (1CNN) with water has been carried out to probe geometries of the conformational isomers. The structures of the two low-energy conformers of 1CNN(H2O) and 1CNN(H2O)2 predicted by MP2/cc-pVDZ calculation, are consistent with ionization-loss (ion-dip) infrared spectra of C-H and O-H stretches of the two conformers, identified by ionization-detected hole-burning spectroscopy. The facile loss of a neutral water molecule from the cluster ion of 1CNN(H2O)2, relative to that of 1CNN(H2O), is in accord with the proposed structures of the complexes. Mass selected resonant two-photon ionization (R2PI) and ion-dip infrared spectroscopies are combined with correlated (MP2) quantum chemistry to probe electronic spectra and ground-state of jet cooled dimer and higher clusters of 1-cyanonaphthalene. The results indicate that the dimer has stacked geometries, consistent with the highly efficient excimer formation that follows photoexcitation of the ground-state clusters.
Advisors/Committee Members: Lim, Edward C.
Subjects: Chemistry, Physical
Keywords: STRUCTURE AND DYNAMICS OF AROMATIC NITRILES; SUPERSONIC JET EXPANSION; LASER SPECTROSCOPY LIF MASS HIGH RESOLUTION SPECTROSCOPY
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11.
Carnahan, Melinda K.
Novel Nitric Oxide Donors for Use in Medicinal Applications.
Degree: Doctor of Philosophy, Chemistry, 2009, University of Akron
► The medicinal benefits of the nitric oxide (NO) donor compounds termed diazeniumdiolates…
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▼ The medicinal benefits of the nitric oxide (NO) donor compounds termed diazeniumdiolates are well established and include antithrombic, cytostatic, and vasorelaxant activities. Additionally, fendiline, a coronary vasodilator, increases intracellular NO concentrations via interaction with the calcium cascade. Modification of fendiline with NO generates a new, lipophilic member of the diazeniumdiolate family, fendiline diazeniumdiolate (FDL-NONa), which has increased potential as a pharmaceutical NO donor and multiple applications in the coronary health market. This bifunctional vasodilator, when dissolved in methanol and buffer solution, releases NO to generate a half-life of 1.6 hours at 37°C and pH 7.4. Extension of this half-life can be achieved by varying the water insoluble particulate size of the donor in PBS. Furthermore, excellent binding of FDL-NONa to both glass and metal surfaces provides a direct correlation between coating thickness and NO release profile while decomposition of the compound in vivo generates species which pose no health concern. In additional to numerous functions within the cardiovascular system, NO has also been established as an indispensable participant in the wound healing cascade. Based on these findings, multiple NO-based wound dressings have been developed for employment in impaired wound healing scenarios. One example is the ascorbic acid/nitrite patch, which has displayed very promising results in both diabetic and lechmaniasis wounds, however has several drawbacks including donor half-life, patch stability and product manufacturing costs. To correct these problems, a new two-layer, PAN-NO (polyacrylonitrile modified with nitric oxide) pouch has been developed. Modification of previously electrospun PAN nanofibers results in the formation of a new polymeric PAN-NO patch that provides a 30 min increase in patch half-life, with extension of the total release time by 4 to 5 h and a nearly 17x increase in NO release from the four-layer, ascorbic acid/nitrite patch when modified in sodium trimethylsilanolate/1,4-dioxane or a 4 h increase in patch half-life, with an extension of the total release time by 27 to 28 h and a comparable NO/mg release when modified in sodium methoxide. Insertion of either form of PAN-NO into a heat-sealed, ascorbic acid pouch forms a second generation, NO-donating wound dressing, with reduced manufacturing costs and improved NO release kinetics.
Advisors/Committee Members: Smith, Daniel.
Subjects: Chemistry
Keywords: nitric oxide; PAN; fendiline; diazeniumdiolates
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12.
Cetin, Anil.
TRANSITION METAL COMPLEXES OF PORPHYRIN ANALOGS AND BORATE-BASED COORDINATION COMPLEXES.
Degree: Doctor of Philosophy, Chemistry, 2007, University of Akron
► The synthesis of low-coordinate metal ions has been a focus of bioinorganic…
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▼ The synthesis of low-coordinate metal ions has been a focus of bioinorganic chemists due to their important roles in active sites in enzymes and protein. Although the isolation of these types of complexes is challenging, porphyrin analogs with one or two carbon atoms in the interior position can be good candidates for generating protected low coordinate metal sites. The metal coordination of one or two carbon substituted hemiporphyrazines, namely monocarbahemiporphyrazine and dicarbahemiporphyrazine, was investigated. These porphyrin analogs, in which one or two of the central metal binding nitrogen atoms were replaced with C-H groups, were synthesized in the early 1950s by Linstead and co-workers, but their metal binding chemistry remained unexplored. Several low coordinate metal complexes of dicarbahemiporphyrazine, namely silver, copper, manganese, iron and cobalt were synthesized. Three different cobalt complexes of monocarbahemiporphyrazine in +2 and +3 oxidation states were also synthesized. Porpholactone is another example of a ring modified porphyrin isomer. In this macrocycle one of the four pyrrollic units is oxidized to an oxazolone ring. Metal complexes of porpholactone may be novel catalysts for epoxidation of alkenes. The synthesis and X-ray crystal structure of first manganese complex of the porpholactone 5,10,15,20-tetraphenylporpholactone are reported. The catalytic activity of the complex by using a variety of substrates was explored and it was compared with that of manganese tetraphenylporphyrin. Metal complexes of a sulfur containing borate-based chelating ligand, tris(imazolyl)borate, HB(mt)3- were examined. Three different modes of interaction were observed with divalent closed d shell metal metal cations: Ca(II), Ba(II) and Hg(II). This study exhibits the diversity of binding not typically observed in the scorpionate family. With group II and group XII metals, the HB(mt)3- ligand can act as a non-coordinating anion, can engage in B-H agostic bonding, and can form metal cluster compounds. Molecular organization of guest molecules within nanometer-sized structures is a big challenge in terms of controlling the physical properties and chemical reactivities. In our group, we are investigating borate-based coordination polymer, lead tetrakis(imidazolyl)borate, to organize and sequester anionic guests. A variety of anionic guests were organized within the layers lead(II) borate scaffolds. The possibility of topochemical polymerization of these pre-organized anionic monomers in the crystalline state was explored.
Advisors/Committee Members: Ziegler, Christopher John.
Subjects: Chemistry, Inorganic
Keywords: Porphyrin analogs, hemiporphyrazines, phthalocyanines, borate, borate-based materials
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13.
Chaicharoen, Kittisak.
Mass and Tandem Mass Spectrometric Studies on Synthetic Polymers.
Degree: Doctor of Philosophy, Chemistry, 2008, University of Akron
► Matrix Assisted Laser Desorption Ionization (MALDI) time of flight (ToF) mass spectrometry…
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▼ Matrix Assisted Laser Desorption Ionization (MALDI) time of flight (ToF) mass spectrometry is a technique that has been used widely to characterize synthetic polymers. Mass spectrometric characterization is an essential tool in the determination of the comonomer composition and functionality distribution of synthetic polymers. Tandem mass spectrometry (MS/MS) is a two-dimensional technique that characterizes synthetic polymers in more detail. In this dissertation, poly (methyl methacrylate) (PMMA) and poly (methyl acrylate) (PMA) were examined by mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Particular emphasis was devoted to the elucidation of MS/MS fragmentation mechanisms. Such knowledge is a prerequisite for interpreting MS/MS spectra correctly, so that structural information can be deduced from them with confidence. Within the MS/MS studies, a nomenclature was developed to classify MS/MS fragments in a meaningful manner. Briefly, terminal fragments are labeled by one of the letter codes given in the chart, while internal fragments are labeled by J, K, L, etc. A radical site is indicated by ⦥uro;? and the number of repeat units by the subscript. Both, PMMA and PMA chain ionized by alkali metal addition dissociate in the mass spectrometer by homolytic cleavages along the backbone which produce the incipient radical ions an⦥uro;?, bn⦥uro;?, yn⦥uro;? and zn⦥uro;?. These radical ions undergo consecutive, radical-induced reactions which lead to the ultimately observed MS/MS fragments. Radical ions from PMMA as well as PMA dissociate by β-scissions; those from PMA also dissociate by backbiting reactions which produce abundant internal fragments. Hyperbranched acrylate polymers were analyzed by MALDI mass spectrometry and MS/MS. The MALDI-MS data reveal the composition of the polymer, while the MALDI-MS/MS data provide information about the branching architecture. Upon MS/MS, linear as well as hyperbranched polymers dissociate through 1,5-hydrogen rearrangement over the ester group, as also found for polyesters. This reaction leads to unique products from branched isomers, thereby permitting their differentiation from linear isomers. A centrally functionalized polyethylene glycol (f-PEG) star has been investigated by MALDI-MS and MS/MS methods. The mass spectra confirm the repeating unit of 44, Da corresponding to [C2H4O1], and reveal identity of the functionality distributions generated in the synthesis. The fragmentation patterns observed in the MALDI-MS/MS experiments provide information about the lengths of the PEG chains attached to the central substituent. Polyesters are used in many applications, for example, in adhesives, coatings and for packaging. A polyester produced from an aliphatic diacid and an aliphatic diol was analyzed by MALDI mass and tandem mass spectrometry. The MS/MS data show that such polyesters mainly decompose by 1,5-H rearrangement along the ester bond. This behavior is very similar with that found for polyacrylates, where ester moieties are located in the side chains (pendants) instead of the polymer chain. The discovery of this unique dissociation feature, which has been overlooked thus far, opens the possibility to analyze copolymer sequences and branching geometries in ester-containing polymers based on the fragments generated from competitive and consecutive 1,5-H rearrangements. Tung oils were also examined by MALDI-MS and MALDI-MS/MS methods. The mass spectra indicate a triglyceride structure with three fatty acid ester groups, mainly C-18 eleostearates. From the MALDI-MS/MS results, it is possible to determine how the fatty acid chains have been derivatized by the Diel-Alder reaction.
Advisors/Committee Members: Wesdemiotis, Chrys.
Subjects: Chemistry
Keywords: Mass and Tandem Mass Spectrometry of Polymers
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14.
Chen, Yi.
SYNTHESIS OF THE PENTAVALENT IODINE COMPOUND, DIPHENYLIODOSYL TOSYLATE, AND ITS USE FOR THE OXIDATION OF SULFIDES.
Degree: Master of Science, Chemistry, 2007, University of Akron
► The novel acyclic iodine (V) compound, diphenyliodosyl tosylate (DIT), was synthesized by…
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▼ The novel acyclic iodine (V) compound, diphenyliodosyl tosylate (DIT), was synthesized by the hydroxide-promoted condensation of iodylbenzene to diphenyliodosyl hydroxide, and in situ protonation of the latter with p-toluenesulfonic acid. The solubility and thermal stability of diphenyliodosyl tosylate in common organic solvents were investigated. Diphenyliodosyl tosylate proved to be a useful reagent for the selective oxidation of sulfides to sulfoxides under mild conditions. The oxidation of allyl phenyl sulfide with diphenyliodosyl tosylate was accompanied by epoxide formation and suggests a further investigation of the reactions of DIT with alkenes.
Advisors/Committee Members: Koser, Gerald F.
Subjects: Chemistry, Organic
Keywords: acyclic iodine (V) compound,; diphenyliodosyl tosylate,; selective oxidation,; sulfides to sulfoxides.
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15.
Chun, Joong-Hyun.
NMR STUDIES OF THE HYDRATION EQUILIBRIA OF MESYLATE AND DIALKYL PHOSPHATE DERIVATIVES OF ACETONE; AND INVESTIGATIONS OF NOVEL HYPERVALENT IODINE COMPOUNDS.
Degree: Doctor of Philosophy, Chemistry, 2005, University of Akron
► The aryl-3-iodane, [hydroxy((bis(2,2,2-trifluoroethoxy)phosphoryl)oxy)iodo]benzene (1), was prepared from [hydroxy(tosyloxy)iodo]benzene and sodium bis(trifluoroethyl) phosphate…
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▼ The aryl-3-iodane, [hydroxy((bis(2,2,2-trifluoroethoxy)phosphoryl)oxy)iodo]benzene (1), was prepared from [hydroxy(tosyloxy)iodo]benzene and sodium bis(trifluoroethyl) phosphate in methanol. This novel iodine (III)-phosphate reagent was employed for the conversion of acetone to its a-bis(trifluoroethyl) phosphate derivative, and for ligand-transfer oxidations of various alkyl iodides to the corresponding alkyl bis(trifluoroethyl) phosphates. The use of 1 for oxidative rearrangements of arylalkenes to geminal-bisphosphate esters was also explored. Samples of 1 and the known diphenyl analogue, [hydroxy((bis(phenyloxy)phosphoryl)oxy)iodo]benzene were submitted for single crystal X-ray analysis. Equilibrium constants (KD) for the hydration of a-(mesyloxy)acetone, a-((bis(methoxy)phosphoryl)oxy)acetone, and a-((bis(ethoxy)phosphoryl)oxy)acetone in D2O at 25, 35, 45, and 55 oC were determined by 1H NMR analysis. Plots of log KD versus T-1 enabled calculations of the enthalpy (H) and entropy (S) of hydration for all three substrates. Hydration constants of the ketol phosphates in D2O (KD) and H2O (KH) at 25 oC were also determined by 31P NMR analysis. The hydration constants were employed with reported linear free energy relationships for estimates of Taft polar substituent constants of the (mesyloxy)methyl and bis((alkoxy)phosphoryl)oxy)-methyl groups, and equilibrium constants for hydroxide addition to the ketol phosphates. Hydration of the a-bis(trifluoroethyl) phosphate derivative of acetone in D2O was accompanied by spontaneous hydrolysis of the ketol phosphate to two sets of products. The mechanistic origin of the phosphate products was examined by conducting the hydrolysis in D2O mixed with 18O-labeled H2O. 4,4-Dimethyl-2-nitromethyl-2-(diacetoxyiodo)biphenyl was synthesized from 4,4-dimethyl-2-iodobiphenyl and submitted for single crystal X-ray analysis. A key step in the synthetic procedure was ring-opening of a cyclic iodonium salt with nitromethane anion. A preliminary 1H NMR study of the dynamic behavior of the biaryl-3-iodane was conducted and its cyclization with p-toluenesulfonic acid to a dibenziodonium salt was demonstrated. Efforts to convert the diacetoxyiodane and the corresponding iodo compound to an iodine (III) heterocycle containing the 9-iodaphenanthrene ring system were unsuccessful.
Advisors/Committee Members: Koser, Gerald F.
Subjects: Chemistry, Organic
Keywords: HYDRATION EQUILIBRIA; HYPERVALENT IODINE COMPOUNDS
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16.
Clasp, Trocia N.
THE THEORETICAL STUDY OF TORSION –VIBRATIONAL DYNAMICS IN METHANOL AND THE IMPROVEMENT OF CW-CRDS EXPERIMENTAL APPARATUS.
Degree: Doctor of Philosophy, Chemistry, 2007, University of Akron
► Research using both theory and experimental avenues is integral to understanding intramolecular…
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▼ Research using both theory and experimental avenues is integral to understanding intramolecular vibrational redistribution energy (IVR). Earlier experimental results1 indicated that the large amplitude internal rotation coordinate in methanol accelerates IVR especially when coupled to other small-amplitude vibrations. Theoretical methods such as ab initio calculcations, adiabatic approximation and full-dimensional models are used to to understand how the coupling of the torsional motion to small-amplitude vibrations influences IVR. Experimentally observed spectra of the 3ν1-6ν1 OH stretch overtone region2-4 show that the stretch of the anti CH bond and the torsional motion around the CO bond are coupled to the OH stretch. In this work, we performed ab initio calculations on the (CH3OH→CH2O+2H) reactive channel that takes both static and dynamic correlation effects into account. Our calculations show that a partial double bond between the C-O is formed early in the reaction coordinate. This partial double bond leads to an increase of the torsional barrier height that explains the experimental observations. A four-dimensional model developed by Wang and Perry5 was used to compare the approximate adiabatic separation of the torsion and the CH stretches in methanol6 to an exact solution of the same Hamiltonian. The adiabatic approximation accounts for the correct energy level splittings at low torsional energies including the inverted torsional tunneling splittings, but does not account for the correct 2-fold and 4-fold systematic near degeneracies at high torsional excitation. However, the adiabatic approximation was able to show the origin of the strong IVR coupling and the scaling of the IVR coupling matrix elements. Finally, a high-resolution experimental apparatus was developed to record the spectrum spanning the range of the polyad vCH=2 region. This experimental spectrum will be used to test and challenge the findings of both Perry’s7 and Halonen-Hännien8 ‘s theoretical models.
Advisors/Committee Members: Perry, David S.
Subjects: Chemistry, Physical
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17.
Custer, Paul D.
Transition Metal Coordination for the Construction of Supramolecular Molecules.
Degree: Doctor of Philosophy, Chemistry, 2008, University of Akron
► Many naturally occurring systems are quite large and specific in shape, and…
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▼ Many naturally occurring systems are quite large and specific in shape, and also are relevant for specific biological processes. In the example of proteins, it is commonly known that the shape of the protein is vital to its ability to function. Many of these systems rely on a network of noncovalently bound interactions to form the shape for the species.In an effort to mimic the processes that nature has eloquently perfected, much effort has been put forth in creating model systems to understand these processes. The creation of these supramolecular molecules has become an area of great interest because of their design to specifically recognize and reorganize particular molecules, charged systems, or metal cations.Chapter 1 of this dissertation reviews several methods for the self-assembly of supramolecular systems, including charged systems with host-guest interactions, neutral molecules with metal-alkyne linkages, and the creation of π-tweezers complexes. The synthesis of fac-rhodium-alkyne complexes to be used as building blocks in later supramolecular systems is discussed in Chapter 2. Chapter 3 discusses the synthesis and dynamics of several novel π-tweezer complexes of a fac-rhodium-alkyne compound and silver(I) or copper(I) cations. In Chapter 4, the condensation of the square planar complex cis-(DCPE)Pt(NO3)2, IV-1, with the facial octahedral complex (Me3tacn)Rh(CCPy)3, II-12, results in a self-assembled trigonal bipyramidal cage with Rh(III) and Pt(II) atoms occupying the vertices.
Advisors/Committee Members: Youngs, Wiley J.
Subjects: Chemistry
Keywords: coordination; supramolecular; silver; platinum; rhodium; acetylide; tacn
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19.
Ding, Tang.
THE STRUCTURE, PHOTOPHYSICS AND MODIFICATION OF FREE BASE PORPHYRINOIDS.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► Two high resolution single X-ray crystal structures of meso-substituted free-base corroles are…
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▼ Two high resolution single X-ray crystal structures of meso-substituted free-base corroles are presented: 5,10,15-triphenylcorrole and 5,10,15-tris(pentafluorophenyl)corrole. The internal NH protons are clearly assignable to different nitrogens, which represents the two tautomer limits of corrole. Four free-base corroles with electron-donating or electron withdrawing groups on the para or 2 through 6-positions of the meso phenyl rings were prepared via either Paolesse or Gross conditions and investigated for their absorption and emission properties. Absorption, steady-state, and time resolved fluorescence measurements were performed on all compounds in both nonpolar (dichloromethane) and polar (dimethylacetamide) solvents. The experimental evidence points to hydrogen bonding with an internal N-H group as the most likely factor in the solvent dependent photophysical behavior of these corroles, that is also highly dependent upon substitution. An improved methodology for the N-alkylation of the porphyrin isomer N-confused porphyrin is presented. The combination of polar solvent conditions and the use of the base Cs2CO3 afford externally modified products in high yield without separation difficulties and without the use of large excesses of alkylating reagent. The further transformation and metalation of these products provides opportunities for the construction of metalloenzyme model complexes, peptide adducts, and chromophore assemblies. Using the same strategy, a pyrene can be covalently attached via the external nitrogen of N-confused porphyrin. Absorption, calculation and steady-state measurement were performed on the compound. Calculation indicate a open fashion comformation favored, and the fluorescence of pyrene was turned off, probably due to an energy transfer to N-confused moiety. However, further experiments need to be done to fully understand the interaction between the two moieties. By growing crystals in the presence of an excess of a carboxylate modified monomer, single crystals of Pb[B(Im)4](X) can be obtained, where X is anionic monomer guest. Four molecules were intercalated into the Pb[B(Im)4]-based network solids for topochemical polymerization studies. Interesting transitions were observed for 3-carboxythiophene-leadtetrakis(imidazoly)borate.
Advisors/Committee Members: Ziegler, Christopher J.
Subjects: Chemistry, Inorganic
Keywords: Absorption, porphyrin, corrole, crystal structure, N-confused porphyrin, leadtetrakis(imidazoly)borate
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20.
Dolog, Ivan.
A Study of Charge Transport Phenomena and Nanoscale Investigation of the Modified CdS Surface.
Degree: Doctor of Philosophy, Chemistry, 2009, University of Akron
► The adsorption of 7-ethynyl-2,4,9-trithia-tricyclo[3.3.1.13,7]decane (7ETTD), polyaniline (PANI), triethoxysilane (TES), and poly(methyl methacrylate)…
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▼ The adsorption of 7-ethynyl-2,4,9-trithia-tricyclo[3.3.1.13,7]decane (7ETTD), polyaniline (PANI), triethoxysilane (TES), and poly(methyl methacrylate) (PMMA) on ultrathin sputtered amorphous CdS films has been investigated using inelastic electron tunneling spectroscopy (IETS), in conjunction with multiple reflection adsorption IR spectroscopy. Conductance��“voltage data are recorded for tunnel junctions of the type Al/CdS/7ETTD/Pb over a temperature range of 4K to room temperature and they indicate that the presence of the adsorbed 7ETTD layer on the CdS dramatically modifies the conductance ��“ voltage behavior of the junctions. These measurements show that different conduction mechanisms, including tunneling and possibly hopping, are responsible for charge transfer through the junctions depending on current, temperature, and voltage. WKB fits to the data are used to determine tunnel barrier parameters (height and width) for Al/CdS/Pb junctions with and without adsorbed 7ETTD layers on the CdS. Analysis of the fits shows that tunneling occurs at low bias (less than ~0.2 V) but, at higher bias voltages, modification of the barrier parameters alone is insufficient to account for the observed conductance changes. A frontier orbital model is invoked which does offer a plausible explanation for these conductance changes. The model assumes bias-dependent coupling between HOMO and LUMO states of the adsorbed 7ETTD and surface states on the CdS. The present work suggests that, because of the marked effect on the conductance iv of CdS ultra-thin films, 7ETTD and other similar compounds may be candidates for use in molecular electronic device fabrication. It was found that PANI and TES do not adsorb strongly on amorphous CdS but can be used to modify conductance-voltage behavior. On the other hand, PMMA adsorbs strongly and shows promise as a material for use as a host matrix, in photovoltaic applications. Preliminary work is presented in which CdS nanoparticles size is estimated using surface enhanced Raman spectroscopy and Atomic Force Microscopy, and it has been determined that IETS and conductance-voltage measurement could be extended for the investigation of he CdS nanoparticles electronic properties.Further investigations into the surface properties of CdS are presented. Specifically, a robust technique, based on vertical, “z-lift”, manipulation of a negatively biased oscillating atomic force microscope tip, is extended to CdS and used to create raised columnar nanostructures with high aspect ratios (up to 40 nm high/150 nm wide) on amorphous CdS thin films. The nanostructures��™ height 8��“40 nm can be controlled and correlates with CdS film thickness. An in-house modified electric force microscope is used to record the associated surface charge distribution in the proximity of the nanostructures which is found to be opposite to that of the tip.
Advisors/Committee Members: Mallik, Robert.
Keywords: IETS; CdS; thin tunnel barriers
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21.
Durmus, Semih.
Silver(I) and Gold(I) N-Heterocyclic Carbene Complexes.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► The introduction of N-heterocyclic carbenes (NHCs) to organometallic and inorganic chemistry was…
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▼ The introduction of N-heterocyclic carbenes (NHCs) to organometallic and inorganic chemistry was achieved by the synthesis and isolation of chromium and mercury NHC complexes by Öfele and Wanzlick in 1968. The synthesis and characterization of numerous carbene metal complexes by Lappert et al were a significant contribution to this area of chemistry. NHCs have become an important area of research after the isolation of the first stable carbene by Arduengo in 1991. In chapter 1, the synthesis and biological activities of NHCs and their silver(I) and gold(I) derivatives are discussed. In chapter 2, the synthesis and characterization of an imidazolium-linked cyclophane is discussed as well as its potential use as a medicinal agent. In chapter 3, the synthesis and characterization of a silver(I) NHC complex is reported. The antimicrobial activity of the silver(I) NHC complex is also reported against clinically important bacteria. In chapter 4, the synthesis of a variety of silver(I) NHC complexes and their carbene transfer reactions to gold(I) reagents are reported. The gold(I) NHC complexes are also investigated for their anticancer properties. In chapter 5, the use of urocanic acid as NHC precursor is reported. The synthesis and characterization of the first silver(I) NHC complex derived from biological molecule urocanic acid is discussed as well as its antimicrobial activity.
Advisors/Committee Members: Youngs, Wiley J.
Subjects: Chemistry, Inorganic
Keywords: NHCs; CARBENES; SILVER(I) NHC; GOLD(I) NHC; ANTIMICROBIALS; ANTICANCER; HISTAMINE; HISTIDINE; UROCANIC ACID
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22.
Elam, Chanda LaVortriette.
Synthesis and Functionality of Polymeric Diazeniumdiolates in the Use and Control of Nitric Oxide Release for Severe Medicinal Atherosclerotic Plaque Applications and Human Papillomavirus Treatment.
Degree: Doctor of Philosophy, Chemistry, 2008, University of Akron
► Current research utilizing nitric oxide for its wound healing properties has propelled…
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▼ Current research utilizing nitric oxide for its wound healing properties has propelled researchers to expand current applications. One application is the use of polymeric diazeniumdiolates to increase nitric oxide’s vasodilation properties, namely in the area of atherosclerotic plaque. Earlier commercial use of coated stents in the pharmaceutical arena for arterial blockage showed great promise with the exception of remission of plaque buildup within the stent. The same procedure has been applied to relieve thrombogenic plaque, which has lead to restenosis (re-narrowing) of the coronary artery due to trauma at the site of the stent or coiling. The body’s natural instinct is to cause clotting (thrombosis), thus restenosis, at that site. Instead of using polymeric diazeniumdiolates for stent coating and long-term usage, the polymeric diazeniumdiolate could be used to alleviate the body’s response to restenosis as well as increase the release time of nitric oxide from several days to weeks or longer. The body will naturally process the diamine to its biodegradable by-products and thereby remove them as waste from the body. Studies have shown that nitric oxide-producing PEG derivatives in conjunction with hydrogels have been able to release nitric oxide over a period of a couple of days with a short release time. However, flexibility in the release profile will prove useful in the treatment of atherosclerotic thrombosis and restenosis. At the same time these diazeniumdiolates were tested for applicable use for the treatment of the high-risk human papillomavirus (HPV) types 16 and types 18. Previous research shows that nitric oxide has been effective in the treatment of low-risk HPV, namely plantar warts and the like. It is hypothesized that if the virus is responsive to nitric oxide in its cutaneous, benign growth stage then it is possible that the mucosal, malignant growth is susceptible to nitric oxide treatment. A study using HeLa (wild type, HPV type 18), C33A (mutant, HPV negative) and CaSki (wild type, HPV type 16) cervical cancer cells has been used to determine the effectiveness of nitric oxide on high-risk HPV and determine the genetic process effected in the treatment. Bioavailability testing was performed to determine future drug therapy for nitric oxide producing compounds in the treatment of HPV-induced cervical cancer.
Advisors/Committee Members: Smith, Daniel J.
Subjects: Chemistry
Keywords: nitric oxide; diazeniumdiolate; biomaterials; human papillomavirus
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23.
Elisseva, Tatiana V.
Synthesis and Characterization of Imidazole Complexes of Silanes.
Degree: Doctor of Philosophy, Chemistry, 2008, University of Akron
► The aim of the research was to examine a model system for…
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▼ The aim of the research was to examine a model system for the chemistry that is involved in the biomineralization of SiO2 in certain demosponges. In particular, the interaction of a silica protein, a silicatein, with silicon reagents was modeled. The active site of silicatein contains histidine and serine amino acid side4 chains. Several imidazole-based silane complexes of the general form SiPh3OL were synthesized as a preliminary model. In order to model the histidine-serine sites of the silicatein, the ligands were used that are bound to the silicon via Si-O linkages and also have a potentially chelating imidazole ring. The three OL ligands were derided from the alcohols ROH: 1-hydroxydecyl-imidazole (HOL1), 4-hydroxymethyl-5-methyl-imidazole (HOL2), and 6-imidazole-1-ylmethyl-pyridine-2-ylmethanol (HOL3). Synthesis of the SiPh3OL complexes from chlorosilanes was achieved in two ways. The first one is the reaction of chlorosilanes or alkoxysilanes with the same number of equivalents of ligand and triethylamine or pyridine as a base. The second method is the reaction of chlorosilanes with two equivalents of the imidazole containing ligand, where one equivalent acts as a base for the HCl generated during the reaction. Removal of the HCl by-product from the reaction of SiPh3Cl and HOL was a problematic part of the syntheses of the three SiPh3OL compounds. The use of such bases as pyridine and Et3N yielded products that were less pure than when HOL was used as the base. Compounds with a high reactivity toward hydrolysis were obtained and characterized by a variety of techniques. The syntheses of other complexes of the OL ligands were attempted. The oil Si(OL1)4 was prepared in low yield. Attempt to prepare the compounds SiPh2(OL1)2 and SiPh2(OL2)2 from chlorosilanes and from alkoxysilanes at best gave impure compounds or very complex mixtures. Another project included the syntheses of proposed intermediates which could form during biomineralization. These intermediates are predicted to be high coordinate species extremely sensitive to hydrolysis reactions. To investigate the possible products, the reactions of chlorosilanes: SiPhCl3 and SiCl4 with 1,1‵-methyline imidazole and methyl imidazole and HOL1, respectively were performed. The products of this reaction were solids with specific chemical shifts of 5- and 6-coordinated silicon complexes were characterized by solid state NMR due low solubility.
Advisors/Committee Members: Tessier, Claire A.
Subjects: Chemistry, Inorganic
Keywords: mineralization; silicon deposition; silicon,high-coordinated silicon complexes; N-containing ogranic bases; imidazoles
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24.
El Khoury, Jouliana M.
Development of Nanostructured Core-Shell Materials for Sensing of Sugars in Vivo.
Degree: Doctor of Philosophy, Chemistry, 2005, University of Akron
► The development of new nanostructured optical sensing polymer/nanoparticle composite materials is described.…
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▼ The development of new nanostructured optical sensing polymer/nanoparticle composite materials is described. The materials are potentially useful for in vivo sensing of sugars based on the color changes of the plasmon band and Surface Enhanced Raman Scattering of the gold nanoparticles. In the first section, controlled radical polymerization methods including “grafting to” and “grafting from” techniques were studied to synthesize the polymer shell materials on gold nanoparticle surfaces. The controlled radical polymerization techniques were proven to be essential for producing discrete polymer core-shell nanoparticles. In the second section, the preparation of gold nanoparticles with the molecular recognition sites, boronic acids, at the Au nanoparticle/polymer shell interfaces was investigated. A new thiol linker, 1,4-dimercapto-2,3-dimethyl-butane-2,3-diol, designed and synthesized for molecular self-assembling of the boronic acid sensing elements on gold surfaces, was used. The supramolecular assembling of the dioldithiol linker on gold surfaces was studied in detailed with 1D and 2D NMR spectroscopy in solution. This study provided unique opportunities for the investigation of the mechanisms, energetics and dynamics of the thiol/gold surface interactions. In the third section, 3-pyridinylboronic acid, a model sugar sensor that is being incorporated into the polymer shell/Au nanoparticle interfaces, was shown to be useful for quantifying <1 mM adenosine triphosphate (ATP) and differentiating between ATP and AMP in neutral phosphate buffers by a colorimetric assay. The binding constant and the structure of the sensor/analyte complex were determined by NMR spectroscopic methods.
Advisors/Committee Members: Hu, Jun.
Keywords: biosensors, boronic acid, molecular recognition, SAM on gold, ATP, sugar sensing, dynamic of thiol exchange on gold surface
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25.
Farkas, Natalia.
SCANNING PROBE MICROSCOPE OXIDATION AND HIGH-VOLTAGE PARALLEL WRITING ON METAL AND METAL NITRIDE THIN FILMS.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► Systematic investigation of the scanning probe microscope (SPM) oxidation of transition metal…
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▼ Systematic investigation of the scanning probe microscope (SPM) oxidation of transition metal and metal nitride thin films is presented. An extensive range of process and material specific parameters such as exposure time, voltage, humidity and nitrogen content of the sputtering plasma are investigated. During the intrinsic part of the SPM oxidation of ZrN, the density of the oxide increases until the total oxide thickness is approximately twice the feature height. Further oxide growth is sustainable, and in fact faster yet controlled, as the system crosses over from the space charge limited to a nitrogen-enhanced growth regime. Selective etching of the oxides and nitrides lead us to propose that as the oxidation reaches the ZrN/silicon interface delamination occurs resulting in hollow oxide feature formation through stress-induced plastic flow. Interpretations of the underlying processes and film properties responsible for the unique behavior of ZrN in all regimes are provided along with an explanation for the observed non-linear voltage dependence. To our knowledge, manifestation of three distinct transition points in SPM oxidation kinetics has never been reported. In addition, we exploit the nitrogen-enhanced growth of ZrN to fabricate high-voltage parallel oxide patterns 70 nm in height covering areas in the square centimeter range. The nitrogen-to-oxygen conversion is verified by Auger microprobe analysis. To show the versatility of the inherently simple high-voltage parallel writing technique, we demonstrate pattern transfer onto 15-100 nm thick FeN films. As opposed to ZrN, the iron oxide dissolves during the process fully exposing the substrate beneath and therefore eliminating the need for any post-exposure etching. This comparison is of fundamental interest in that Zr oxidation is driven by oxygen migration, whereas Fe oxidizes by metal ion transport. Implication of the use of patterned ZrN and FeN thin films for biomedical and magnetic applications are also discussed. In particular, with precisely controlled height and methodically designed lateral size, the synthetic FeN arrays are potential candidates for MRI sensitivity and resolution measurements.
Advisors/Committee Members: Ramsier, Rex D.
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26.
Fatkins, David G.
N(EPSILON)-THIOACETYL-LYSINE AS A MULTIFACETED TOOL FOR ENZYMATIC PROTEIN LYSINE N(EPSILON)-DEACETYLATION.
Degree: Master of Science, Chemistry, 2007, University of Akron
► The histone deacetylase (HDAC) family of enzymes catalyze the specific lysine N(epsilon)-deacetylation…
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▼ The histone deacetylase (HDAC) family of enzymes catalyze the specific lysine N(epsilon)-deacetylation of proteins such as the core histone proteins, various transcription factors, alpha-tubulin, and acetyl-coenzyme A synthetase that are respectively involved in transcriptional, cytoskeletal, and metabolic control. HDAC-catalyzed reactions represent an integral component for an emerging intracellular signaling mechanism defined by the protein posttranslational reversible lysine N(epsilon)-acetylation and deacetylation, and the enzymes involved have been targeted for developing novel therapies for metabolic and age-related diseases and cancer. In this study, we disclose the synthesis and characterization of N(epsilon)-thioacetyl-lysine as a multi-faceted tool for enzymatic protein lysine N(epsilon)-deacetylation. In specific, by evaluating multiple peptides containing N(epsilon)-thioacetyl-lysine, i) we developed the first spectrophotometric assay selective for HDAC8 that holds potential for rapid inhibitor screening and selective determination of HDAC8 activity; ii) we identified potent and selective peptide-based inhibitors for SIRT1, SIRT2, and SIRT3 that are the only bona fide human class III protein deacetylase enzymes with known physiological substrates. All these results have far-reaching impact on promoting our fundamental understanding and pharmacological exploitation of HDAC-catalyzed reactions.
Advisors/Committee Members: Zheng, Weiping.
Subjects: Chemistry, Biochemistry
Keywords: Thioacetyl-lysine, HDAC8 assays
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27.
Flores-Santana, Wilmarie.
Polyamines: Stabilization of Biocompatible Polymers for Nitric Oxide Delivery.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► The primary limitation in using water-soluble diazeniumdiolates in topical applications is the…
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▼ The primary limitation in using water-soluble diazeniumdiolates in topical applications is the instability of these compounds in aqueous solutions as a result of their pH dependent NO release. At higher pH values however, the NONOates are stable in the media. This pH restriction renders them useless in water-based creams or ointments. DETAN, EPN, MePN, and PuN have been stabilized with a cationic exchange resin (DOWEX 1 x 4), thus making the bound NONOate stable in water. About 30% of the NONOates were successfully bound to the resin beads. This approach only required an ionic exchange process to activate the release of NO, which follows normal release kinetics, with half-lives ranging from 1-5 h. Topical formulations using a water-based cream with 20 mg of the NONOate-DOWEX complex release up to 0.6 µmoles of NO. Redness was observed in the area where the formulation was applied, but disappeared when the cream was removed. This new approach presents a novel viable way of stabilizing these types of NO releasing drugs, making them suitable for several biomedical applications. Linear polyethylenimine was widely studied as a NO carrier for cardiovascular treatments and other topical applications (e.g. for wart treatments). Electrospinning technology was used to optimize the NO delivery by producing nanofibers, which could encapsulate the NO donors. Optimization of particle size (1 µm) was necessary to enhance the efficiency of the electrospinning system, as well as the distribution of the NO donor in the fiber mat. SEM analysis confirmed the encapsulation of LPEIN particles, LPEIN in methanol solution, LPEIN-Na, LPEIN-Ca, PEIXN-Na, and LPEIN-DOWEX within polyurethane fibers (e.g. Tecophilic® and Tecoflex®). The NO release from LPEIN fibers was analyzed using a Nitric Oxide Analyzer (NOA).
Advisors/Committee Members: Smith, Daniel J.
Subjects: Chemistry, Biochemistry
Keywords: NO, PEI, LPEI, NONOate, Putreanine, Putreanines, Polyurethanes, TP, TF, Drug Delivery systems, Encapsulation, Nanofibers, Electrospinning, LPEINO, Diazeniumdiolate
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28.
Frazier, Laura M.
Superabsorbent Nanofiber Matrices.
Degree: Doctor of Philosophy, Chemistry, 2006, University of Akron
► Although electrospun nanofibers have been around for over a century, only recently…
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▼ Although electrospun nanofibers have been around for over a century, only recently have researchers begun to take advantage of their unique properties. Small fiber diameters, typically from a few hundred nanometers to 1 micron, afford nanofibers a very high surface area to volume ratio as well as small pore size. Combining these characteristics with those of additives makes them useful for a plethora of applications. Nanofibers were electrospun using Tecophilic® (TP), a polyurethane polymer, as well as cross-linked poly(vinylamine) (PVAm). Two types of structured hydrogels were produced by adding different superabsorbents, Waterlock® (WL) and sodium polyacrylate (SPA), to the spinning solution. The superabsorbent particles were encapsulated in the nanofiber matrix, allowing the particles to absorb copious amounts of water while remaining in a structured environment. The nanofibers containing WL were tested for maximum absorbency of water and synthetic urine, absorbency rate and tensile strength. The nanofibers containing SPA particles were tested for maximum water absorbency and absorbency rate. To improve the surface absorption, a surfactant was added both as a thin top layer and as part of the entire nanofiber construct. Water droplet tests were performed to determine the surface absorptivity. TP was also spun with the NO donor molecules, LPEINO-Ca and LPEINO-Na. Both LPEINO samples were in particle form; the particles were added to the TP solution along with an absorbent material, either WL superabsorbent or microcrystalline cellulose. Quadrol® was added to stabilize the NO donor. Nitric oxide release profiles were performed on the nanofibers in order to determine how much NO was being released from the fibers. Sterilization and stability studies were performed on the fibers to ascertain what effect sterilization has on NO release and at what point the NO donor destabilizes and ceases to be effective. Poly(vinylamine) was crosslinked on the spin creating a water insoluble nanofiber matrix. FITC-labeled albumin was added to the solution prior to spinning. After washing the nanofibers with water, the presence of the FITC-labeled albumin was confirmed using fluorescence. Images of the FITC-labeled albumin were produced using fluorescent microscopy. Results from this experiment indicated that nanofibers could be useful in protein stabilization.
Advisors/Committee Members: Smith, Daniel J.
Subjects: Chemistry, Biochemistry
Keywords: electrospinning; nanofibers; superabsorbents; nitric oxide donors
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29.
Furlong, Danelle Lynn.
ENZYME CATALYZED SYNTHESIS IN IONIC LIQUIDS.
Degree: Master of Science, Chemistry, 2007, University of Akron
► The synthesis of industrially important polymers can suffer from low conversion because…
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▼ The synthesis of industrially important polymers can suffer from low conversion because of the need to use fairly harsh synthetic conditions including high temperature, high pressure and low pH. The use of enzymes as cataylsts can help to reduce the demand for these harsh synthetic conditions, allow the synthesis to be performed under more mild conditions, and are renewable catalysts. For this reason, enzymes can reduce chemical waste and offer a greener approach to polymer synthesis. One significant limitation in these reactions is the incompatibility of solvents needed for reactants, products, and catalyst. Enzymes are most active in an aqueous based solvent, while the polymer being produced typically has higher solubility in an organic based solvent. One method to bridge these contradicting conditions has been to use a new class of solvents known as ionic liquids. These solvents are comprised of various cations and anions to influence physical characteristics such as melting an boiling points, viscosity, and hydrophobicity. While polymer synthesis has been accomplished with several different ionic liquids and using enzymes as the catalyst, no in-depth characterization of enzymatic activity in ionic liquids has not been published.
Advisors/Committee Members: Espe, Matthew.
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30.
Fu, Ruiling.
USING HIGH-FIELD NMR TO IDENTIFY THE BIOACTIVE COMPOUNDS IN EXTRACTS OF BLACK RASPBERRY.
Degree: Master of Science, Chemistry, 2007, University of Akron
► Recently, food based approaches for treatment of cancer have been explored. Experimental…
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▼ Recently, food based approaches for treatment of cancer have been explored. Experimental animal research provided compelling evidence that black raspberries could inhibit the proliferation of oral, esophageal, and colon cancer cells. Studies indicated that black raspberry’s phenolic antioxidants especially the anthocyanins, which are responsible for the fruit color, may play an important chemopreventive role. Nineteen different black raspberries from different farms and cultivars were studied using a high-field nuclear magnetic resonance (NMR) spectrometer that was equipped with a cryogenic probehead. The one-dimensional 1H-NMR spectra were entirely integrated in 0.004 ppm intervals, which created 2101 data bins that were subjected to principal component analysis (PCA). PCA is a statistical technique for pattern recognition that reduces the information in the large data sets. Principal components (PCs) were calculated using both correlation and covariance matrices. In the correlation matrices, which were more sensitive to the minor constituents, the data was normalized by dividing the standard deviation. In the covariance method, the eigenvalues retained the original data, therefore, it gave more weight to larger values. By comparing the cumulative weighting of PCs, the first seven PCs accounted for 84% of the variability in the correlation matrices and 86% of the variability in the covariance matrices. The NMR data from 19 black raspberry samples were used as data for correlation matrices. Regression analysis against the variable of total monomeric anthocyanin content showed that PC1, PC2 and PC5 were important in distinguishing between samples. In the covariance method, PC 1, PC 7, and PC 5 were identified as the most important. According to the absolute eigenvector values, it was found that the 1st and 2nd ranked bins correspond to the methyl peak of cyanidin 3-rutinoside and the 3rd and 4th ranked bins correspond to the methyl peak of cyanidin 3-xylosylrutinoside. Multidimensional and selective excitation NMR experiments were also used to identify the structures of bioactive components. Correlation spectroscopy (COSY), heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC) and selective 1D total correlation spectroscopy (TOCSY) were used to verify the peak assignments of known metabolites and to identify peaks that did not correspond to these known metabolites. Once identified, the additive or synergistic anticancer effects of active compounds can be confirmed by future cancer bioassays. This unique approach will serve as a model to others examining the chemopreventive activity of antioxidant-rich food sources.
Advisors/Committee Members: Rinaldi, Peter.
Subjects: Chemistry, Analytical
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