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Diffusion of Na²² in the Molten PbCl₂-NaCl System
The object of this thesis is to establish the diffusion coefficient of Na ion in PbCl2-NaCl mixtures and to compare its relationship to the other species.
Diffusion of Pb210 and Cl36 in the Molten PbCl2-NaCl System
Since 1955 research has been conducted at North Texas State College on diffusion in molten salts. The object of this work was a continuation of the diffusion studies, specifically the diffusion of Pb210 and Cl36 in molten PbCl2-NaCl mixtures.
Diphosphine Ligand Activation Studies with Organotransition-Metal Compounds
Thermolysis of CoRu(CO)7(m -PPh2) (1) in refluxing 1,2-dichloroethane in the presence of the diphosphine ligands 2,3-bis(diphenylphosphino)maleic anhydride (bma) and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) furnishes the new mixed-metal complexes CoRu(CO)4(μ -P-P)(μ -PPh2) [where P-P = bma (3); bpcd (6)], along with trace amounts of the known complex CoRu(CO)6(PPh3)(μ -PPh2) (4). The requisite pentacarbonyl intermediates CoRu(CO)5(μ -P-P)(μ -PPh2) [where P-P = bma (2); bpcd (5)] have been prepared by separate routes and studied for their conversion to CoRu(CO)4(μ -P-P)(μ -PPh2). The complexes 2/3 and 5/6 have been isolated and fully characterized in solution by IR and NMR spectroscopy. The kinetics for the conversion of 2→3 and of 5→6 were measured by IR spectroscopy in chlorobenzene solvent. On the basis of the first-order rate constants, CO inhibition, and the activation parameters, a mechanism involving dissociative CO loss as the rate-limiting step is proposed. The solid-state structure of CoRu(CO)4(μ -bma)(μ -PPh2) (3) reveals that the two PPh2 groups are bound to the ruthenium center while the maleic anhydride π bond is coordinated to the cobalt atom. Thermolysis of the cluster Ru3(CO)12 with the bis(phosphine)hydrazine ligand (MeO)2PN(Me)N(Me)P(OMe)2 (dmpdmh) in toluene at 75°C furnishes the known clusters Ru4(CO)12[μ -N(Me)N(Me)] (9) and Ru3(CO)11[P(OMe)3] (10), in addition to the new cluster Ru3(CO)10(dmpdmh) (8) and the phosphite-tethered cluster Ru3(CO)9[μ -P(OMe)3] (11). The simple substitution product Ru3(CO)10(dmpdmh), a logical intermediate to clusters 9-11, was synthesized by treating Ru3(CO)12 and dmpdmh with Me3NO in CH2Cl2 at room temperature, and independent thermolysis reactions using cluster 8 were shown to yield clusters 9-11. The tetrahedrane cluster FeCo2(CO)9(μ3-S) reacts with the redox-active ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) to give the disubstituted cluster FeCo2(CO)7(bpcd)(μ3-S) as the sole product. This diphosphine-substituted cluster contains a cobalt-bound, chelating bpcd ligand. The solid-state structure has been unequivocally established by X-ray diffraction analysis. Cyclic voltammetric studies on FeCo2(CO)7(bpcd)(μ3-S) reveal the presence of two quasireversible …
Diphosphine Ligand Substitution in H4Ru4(CO)12: X-ray Diffraction Structures and Reactivity Studies of the Diphosphine Substituted Cluster Products
The tetraruthenium cluster H4Ru4(CO)12 has been studied for its reactivity with the unsaturated diphosphine ligands (Z)-Ph2PCH=CHPPh2, 4,5-bis (diphenylphosphino)-4-cyclopenten-1,3-dione, bis(diphenyphosphino)benzene and 1,8- bis(diphenyl phosphino)naphthalene under thermal, near-UV photolysis, and Me3NO-assisted activation. All three cluster activation methods promote loss of CO and furnish the anticipated substitution products that possess a chelating diphosphine ligand. Clusters 1, 2, 3 and 4 have been characterized in solution by IR and NMR spectroscopies, and these data are discussed with respect to the crystallographically determined structures for all new cluster compounds. The 31P NMR spectral data and the solid-state structures confirm the presence of a chelating diphosphine ligand in all four new clusters. Sealed NMR tubes containing clusters 1, 2, 3 and 4 were found to be exceeding stable towards near-UV light and temperatures up to ca. 100°C. The surprisingly robust behavior of the new clusters is contrasted with the related cluster Ru3(CO)10(bpcd) that undergoes fragmentation to the donor-acceptor compound Ru2(CO)6(bpcd) and the phosphido-bridged compound Ru2(CO)6 (µ-PPh2)[µ-C=C(PPh2)C(O)CH2C(O)] under mild conditions. The electrochemical properties have been investigated in the case of clusters 1 and 2 by cyclic voltammetry, and the findings are discussed with respect to the reported electrochemical data on the parent cluster H4Ru4(CO)12.
Directing Transition Metal Catalysis of Second and Third Row Metals through Ligand Design
Ligand design is important due to a ligand's ability to tune properties of the transition metals, such as catalytic activity and selectivity. Gold(I) catalysts can be directly impacted by ligands electronically as well as with steric bulk when undergoing enantioselective and regioselective reactions. In the dissertation, a series of gold(I) acyclic diaminocarbenes were synthesized and used to explore the 1,6 enyne cyclization/hydroarylation. The use of metal templated synthesis of the gold(I) acyclic diaminocarbenes allowed for the gradual increase in steric bulk of the catalysts. In the end, it was shown that electronics play the major role in the regioselectivity for the 1,6 enyne cyclization/hydroarylation but localized steric bulk can control the catalytic reaction if placed strategically. Cross-coupling reactions used to form carbon-carbon or carbon-heteroatom bonds are important in the production of pharmaceutical chemicals on a large scale. Iron, an extremely cheap and earth abundant first row transition metal, has had some success in cross-coupling reactions. Iron does not go through the same catalytic cycle for cross-coupling as most transition metals, the most common of which is palladium. In the dissertation, a ligand was developed to induce Iron to undergo the same cycle as palladium. In addition, the same ligand was placed on palladium(II) and reduced to try to form and isolate a catalytically active palladium(0) complex.
Discontinuous Thermal Expansions and Phase Transformations in Crystals at Higher Temperatures
The purpose of this investigation is to make more detailed studies of transformations. Fourteen compounds have been examined by high temperature X-ray diffraction for this purpose. The investigations have been carried out in such a way as to reveal: 1. the existence of transformations, 2. the influence of polarizability on thermal expansion, 3. the anisotropy of expansion, and 4. the discontinuity of thermal expansion.
Disease Tissue Imaging and Single Cell Analysis with Mass Spectrometry
Cells have been found to have an inherent heterogeneity that has led to an increase in the development of single-cell analysis methods to characterize the extent of heterogeneity that can be found in seemingly identical cells. With an understanding of normal cellular variability, the identification of disease induced cellular changes, known as biomarkers, may become more apparent and readily detectable. Biomarker discovery in single-cells is challenging and needs to focus on molecules that are abundant in cells. Lipids are widely abundant in cells and play active roles in cellular signaling, energy metabolism, and are the main component of cellular membranes. The regulation of lipid metabolism is often disrupted or lost during disease progression, especially in cancer, making them ideal candidates as biomarkers. Challenges exist in the analysis of lipids beyond those of single-cell analysis. Lipid extraction solvents must be compatible with the lipid or lipids of interest. Many lipids are isobaric making mass spectrometry analysis difficult without separations. Single-cell extractions using nanomanipulation coupled to mass spectrometry has shown to be an excellent method for lipid analysis of tissues and cell cultures. Extraction solvents are tunable for specific lipid classes, nanomanipulation prevents damage to neighboring cells, and lipid separations are possible through phase dispersion. The most important aspect of single-cell analysis is that it uncovers the extent of cellular heterogeneity that exists among cellular populations that remains undetected during averaged sampling.
Donor-Acceptor Artificial Photosynthetic Systems: Ultrafast Energy and Electron Transfer
Mother nature has laid out a beautiful blueprint to capture sunlight and convert to usable form of energy. Inspired by nature, donor-acceptor systems are predominantly studied for their light harvesting applications. This dissertation explores new donor-acceptor systems by studying their photochemical properties useful in building artificial photosynthetic systems. The systems studied are divided into phthalocyanine-porphyrin-fullerene-based, perylenediimide-based, and aluminum porphyrin-based donor-acceptor systems. Further effect of solvents in determining the energy or electron transfer was studied in chapter 6. Such complex photosynthetic analogues are designed and characterized using UV-vis, fluorescence spectroscopy, differential pulse voltammetry and cyclic voltammetry. Using ultrafast transient absorption spectroscopy, the excited state properties are explored. The information obtained from the current study is critical in getting one step closer to building affordable and sustainable solar energy harvesting devices which could easily unravel the current energy demands.
Donor-Acceptor Systems: Photochemistry and Energy Harvesting Applications
Donor-acceptor systems have unique properties that make them ideal candidates for solar energy harvesting through mimicry of natural photosynthesis. This dissertation is focused on unraveling those unique properties in various types of donor-acceptor systems. The systems investigated are categorized as closely linked, push-pull, supramolecular, and multi-unit. As part of the study, photosynthetic analogues based on BF2-chelated dipyrromethene (BODIPY), porphyrin, phthalocyanine, truxene, ferrocene, quinone, phenothiazine (PTZ), perylenediimide (PDI), fullerene (C60), dicyanoquinodimethane (DCNQ), tetracyanobutadiene (TCBD), and triphenylamine (TPA) are investigated. The effects of proximity between donor-acceptor entities, their geometrical orientation relative to each other, push-pull character of substituents, and competitive energy and electron transfer are examined. In all systems, primary events of photosynthesis are observed, that is absorption and energy transfer and/or electron transfer is witnessed. Ultrafast transient absorption spectroscopy is utilized to characterize the photo-induced events, while other methods such as steady-state luminescence, cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and computational calculations are used to aid in the characterization of the donor-acceptor systems, in particular their applicability as solar energy harvesters.
The Dropping Gallium Electrode in Fused Salts
This paper is an attempt to appraise the usefulness of the dropping gallium electrode (DGE) in fused LiNO3-KNO3, to compare it with the dropping mercury electrode (DME), and to study the DGE in fused LiCl-KCl.
Earth Abundant Transition Metal Catalysts for Activation and Functionalization of Light Hydrocarbons
Light hydrocarbons activations, functionalization, and reactions have been a subjects of catalysis research for decades but dominated by the rarer and more expensive noble metals. Switching over to using the more earth abundant third row transition metals could be more economical and less toxic but come with their own challenges. Their use as catalysts with light hydrocarbons could be employed better utilize and more efficiently use our hydrocarbon resources that the world still depends on.
Effect of Fluorine and Hydrogen Radical Species on Modified Oxidized Ni(pt)si
NiSi is an attractive material in the production of CMOS devices. The problem with the utilization of NiSi, is that there is no proper method of cleaning the oxide on the surface. Sputtering is the most common method used for the cleaning, but it has its own complications. Dry cleaning methods include the reactions with radicals and these processes are not well understood and are the focus of the project. Dissociated NF3 and NH3 were used as an alternative and XPS is the technique to analyze the reactions of atomic fluorine and nitrogen with the oxide on the surface. A thermal cracker was used to dissociate the NF3 and NH3 into NFx+F and NHx+H. There was a formation of a NiF2 layer on top of the oxide and there was no evidence of nitrogen on the surface indicating that the fluorine and hydrogen are the reacting species. XPS spectra, however, indicate that the substrate SiO2 layer is not removed by the dissociated NF3 and NiF2 growth process. The NiF2 over layer can be reduced to metallic Ni by reacting with dissociated NH3 at room temperature. The atomic hydrogen from dissociated ammonia reduces the NiF2 but it was determined that the atomic hydrogen from the ammonia does not react with SiO2.
The Effect of Ozonation in Reducing Trihalomethane Formation Potential
Trihalomethanes such as chloroform, dichlorobromomethane, dibromochloromethane, and bromoform are formed when natural water is chlorinated in water treatment. This investigation explores the use of ozone to remove organic precursors from natural water, thus decreasing trihalomethane formation potential. The data suggest a mechanism involving formation of secondary precursors after prolonged contact with ozone, suggesting that trihalomethane precursors may be minimized by using low doses of ozone and short contact time.
The Effect of Photo-Sensitized Mercury on Mixtures of Isobutane and Isobutene
A study of the effect of photo-sensitized mercury on mixtures of isobutane and isobutene.
Effects of Web-based Instruction in High School Chemistry.
The intent of this study is to identify correlations that might exist between Web-based instruction and higher assessment scores in secondary education. The study framework was held within the confines of a public high school chemistry classroom. Within this population there were students identified as gifted and talented (GT) as well as those without this designation. These two classifications were examined for statistically higher assessment scores using a two-tailed t-test. Results indicated that females outperformed males on pre- and post- instructional unit tests. All subgroups improved their logical-thinking skills and exhibited positive attitudes towards Web-based instruction. In general, Web-based instruction proved beneficial to improving classroom performance of all GT and non-GT groups as compared to traditional classroom instruction.
Electric Dichroism Spectroscopy in the Vacuum Ultraviolet
When a molecule, which possess a permanent dipole moment is exposed to an intense electric field, its absorption spectrum may be altered. These alterations are manifest as shifts in energy and as changes in band shape and intensity. The electric dichroism of absorption bands can be used to probe the excited state that is formed when a molecule undergoes a transition. The properties that may be investigated include transition polarization, excited state dipole moment and mean polarizability, and field-induced mixing of symmetrically equivalent excited states. The theoretical model and experimental devices that have been developed to determine these properties are presented and discussed. The data, taken in total, and its combination with other existing evidence, adds credence to the assignment of the second excited singlet of aldehydes and ketones to be extravalent, accompanied by relatively large delocalization of electronic charge, and polarized in-planiie and perpendicularly to the C-0 axis.
Electrochemical Deposition of Metal Organic-Modified-Ceramic Nanoparticles to Improve Corrosion and Mechanical Properties
Corrosion is an unstoppable process that occurs spontaneously in many areas of industry, specially, oil and gas industries. Therefore, the need of developing protective coating to lower the cost of corrosion is very consistent. Among different methods, electrodeposition has been a popular method since it offer many advantages such as low cost, ability to control the surface and thickness of the coating, ability to perform at low temperature and pressure, and very convenience. Ceramic nanoparticles have been widely incorporated into metal coating and used as a protective layer to improve both corrosion and hardness properties. Diazonium synthesis was used to modify cerium oxide nanoparticles by grafting with ferrocene for use in nickel nanocomposite coating. Citric acid and citrate salt were used as stabilizing ligands for yttrium oxide and praseodymium oxide nanoparticles in nickel plating solution to prevent the formation of hydroxide, thus, higher amount of nanoparticles was able to incorporate into nanocomposite coatings. These fabricated coatings were evaluate for the corrosion and mechanical properties using many different instruments and electrochemical techniques. As modified cerium oxide, stabilized yttrium oxide or praseodymium oxide added into nickel coatings. The results showed an increase in hardness and corrosion resistance leading to the overall improvement compare to pure nickel coating.
Electrochemical Deposition of Nickel Nanocomposites in Acidic Solution for Increased Corrosion Resistance
The optimal conditions for deposition of nickel coating and Ni-layered double hydroxide metal matrix composite coatings onto stainless steel discs in a modified all-sulfate solutions have been examined. Nickel films provide good general corrosion resistance and mechanical properties as a protective layer on many metallic substrates. In recent years, there has been interest in incorporation nano-dimensional ceramic materials, such as montemorillonite, into the metal matrices to improve upon the corrosion and mechanical properties. Layered double hydroxides have been used as corrosion enhancer in polymer coatings by increasing mechanical strength and lowering the corrosion rate but until now, have not been incorporated in a metal matrix by any means. Layered double hydroxides can be easily synthesized in a variety of elemental compositions and sizes but typically require the use of non-polar solvents to delaminate into nanodimensional colloidal suspensions. The synthesis of a Zn-Al LDH has been studied and characterized. The effects of the non-polar solvents dimethylformamide and n-butanol on the deposition and corrosion resistance of nickel coatings from a borate electrolyte bath have been studied, a nickel-LDH nanocomposite coating has been synthesized by electrochemical deposition and the corrosion resistance has been studied. Results indicate an improvement in corrosion resistance for the coatings with minimal change in the nickel matrix's internal strain and crystallite size.
Electrochemical Deposition of Zinc-Nickel Alloys in Alkaline Solution for Increased Corrosion Resistance.
The optimal conditions for deposition of zinc-nickel alloys onto stainless steel discs in alkaline solutions have been examined. In the past cadmium has been used because it shows good corrosion protection, but other methods are being examined due to the high toxicity and environmental threats posed by its use. Zinc has been found to provide good corrosion resistance, but the corrosion resistance is greatly increased when alloyed with nickel. The concentration of nickel in the deposit has long been a debated issue, but for basic solutions a nickel concentration of 8-15% appears optimal. However, deposition of zinc-nickel alloys from acidic solutions has average nickel concentrations of 12-15%. Alkaline conditions give a more uniform deposition layer, or better metal distribution, thereby a better corrosion resistance. Although TEA (triethanolamine) is most commonly used to complex the metals in solution, in this work I examined TEA along with other complexing agents. Although alkaline solutions have been examined, most research has been done in pH ≥ 12 solutions. However, there has been some work performed in the pH 9.3-9.5 range. This work examines different ligands in a pH 9.3-9.4 range. Direct potential plating and pulse potential plating methods are examined for optimal platings. The deposits were examined and characterized by XRD.
Electrochemical Dissolution of ZnO Single Crystals
The separation of oxidation-reduction reactions into individual half-cells with a resulting "mixed potential" is well known as a dissolution mechanism for metals; however, the mechanism by which non-conducting crystals lose ions to the solution has been studied only slightly.
The Electrochemical Properties of the Mercury/lithium Nitrate-potassium Nitrate Eutectic Interface
The original purpose of this investigation was to attempt to apply the coulostatic method directly to a molten salt system. The inability to duplicate the reported capacity data for this system resulted in an investigation of the probable cause of this discrepancy between the data obtained by these different methods (14, 15).
The Electrochemical Reduction of Methyl Vinyl Ketone in Aqueous Solutions
This work is an in-depth study of a system with an approach designed to determine the electrode processes and the factors or conditions which control them.
Electrochemical Study of Under-Potential Deposition Processes on Transition Metal Surfaces
Copper under-potential deposition (UPD) on iridium was studied due to important implications it presents to the semiconductor industry. Copper UPD allows controlled superfilling on sub-micrometer trenches; iridium has characteristics to prevent copper interconnect penetration into the surrounding dielectric. Copper UPD is not favored on iridium oxides but data shows copper over-potential deposition when lower oxidation state Ir oxide is formed. Effect of anions in solution on silver UPD at platinum (Pt) electrodes was studied with the electrochemical quartz crystal microbalance. Silver UPD forms about one monolayer in the three different electrolytes employed. When phosphoric acid is used, silver oxide growth is identified due to presence of low coverage hydrous oxide species at potentials prior to the monolayer oxide region oxide region.
Electrochemical synthesis of CeO2 and CeO2/montmorillonite nanocomposites.
Nanocrystalline cerium oxide thin films on metal and semiconductor substrates have been fabricated with a novel electrodeposition approach - anodic oxidation. X-ray diffraction analysis indicated that as-produced cerium oxide films are characteristic face-centered cubic fluorite structure with 5 ~ 20 nm crystal sizes. X-ray photoelectron spectroscopy study probes the non-stoichiometry property of as-produced films. Raman spectroscopy and Scanning Electron Microscopy have been applied to analyze the films as well. Deposition mode, current density, reaction temperature and pH have also been investigated and the deposition condition has been optimized for preferred oriented film formation: galvanostatic deposition with current density of -0.06 mA/cm2, T > 50oC and 7 < pH < 10. Generally, potentiostatic deposition results in random structured cerium oxide films. Sintering of potentiostatic deposited cerium oxide films leads to crystal growth and reach nearly full density at 1100oC. It is demonstrated that in-air heating favors the 1:2 stoichiometry of CeO2. Nanocrystalline cerium oxide powders (4 ~ 10 nm) have been produced with anodic electrochemical synthesis. X-ray diffraction and Raman spectroscopy were employed to investigate lattice expansion phenomenon related to the nanoscale cerium oxide particles. The pH of reaction solution plays an important role in electrochemical synthesis of cerium oxide films and powder. Cyclic voltammetry and rotation disk electrode voltammetry have been used to study the reaction mechanisms. The results indicate that the film deposition and powder formation follow different reaction schemes. Ce(III)-L complexation is a reversible process, Ce3+ at medium basic pH region (7~10) is electrochemically oxidized to and then CeO2 film is deposited on the substrate. CE mechanism is suggested to be involved in the formation of films, free Ce3+ species is coordinated with OH- at high basic pH region (>10) to Ce2O3 immediately prior to electrochemically oxidation Ce2O3 to CeO2. CeO2 / montmorillonite nanocomposites were electrochemically produced. X-ray …
Electrodeless Discharge of Isopropyl Alcohol
Gases at satisfactory pressures fluoresce in the presence of radio frequency radiation (6). Such fluorescent gases have been used to probe fields of radio frequency oscillation and their emission spectra have been recorded and studied. Ions with multiple charges also exist in these gases, (6). In 1941 Oliver (12) observed the fluorescence of an isobutane- isobutene gaseous mix flowing to a pump through a glass tube which was wrapped by a spiral antenna of a sevenmegacycle transmitter. A white deposit was noticed at a bend in the tubing on the pump side of the fluorescing section of the gas (12, p. 8). In 1957 Blacknall (3) studied the fluorescence and reaction products of propylene in the antenna region of sevenmega- cycle radiation, The oscillator employed by Blacknall was an ARC-5/T-22 military surplus transmitter of range 7.00 to 9.10 megacycles, which he operated at 7.00 megacycles. Blacknall observed a drop in pressure and the formation of a brown deposit in the region of the coil. Blacknall did not report an analysis of this product. In 1959 Armstrong (1) repeated Blacknall's experiments and modified Blacknall's apparatus into an improved design. He also performed an analysis on Blacknall's product. Blacknall used a vertical open-end mercurial manometer with which to measure pressure in his system and as a result introduced mercury vapor into his system. Armstrong tried to minimize the amount of mercury introduced by covering his manometric mercury with a layer of octyl sebacate, "octoil". Armstrong used a spiral-would antenna wrapped around his reaction vessel and reported the formation of spiral brown rings coincident with the copper wire of the antenna. There was a white product deposited in a spiral interlaced with the spiral of dark brown material. No definite identification was reported by Armstrong other than reporting, his solid material as isotactic …
Electrodeposit of Nickel
The purpose of this study is to investigate the varying conditions in types of solutions, concentrations of solutions, hydrogen-ion concentration, current densities and potentials in the electro deposition of nickel.
Electrodeposition of Cadmium
This thesis presents findings of experiments conducted to determine the most feasible method to electroplate metal.
Electrodeposition of Molybdenum-Based Coatings from Aqueous Alkaline Solutions for Enhanced Corrosion Resistance
Zn-Mo coatings are very promising environment friendly anticorrosive coatings as replacement materials for cadmium and chromium (VI) based conversion layers. Electrodeposition has become a favorable technique in fabricating coatings due to its low cost, ease of use, and overall experimental control of coating quality. Very little research so far has been done for the electrodeposition of Zn-Mo coatings under alkaline conditions. In this work, Zn and Zn-Mo coatings were electrochemically deposited on stainless steel from an aqueous alkaline citrate solution. An organic compound, vanillin, was added to the electrolyte as a leveling agent for improving interlayer adherence and corrosion resistance of Zn-Mo coatings. Ni-Mo alloys have been known to possess high tensile strength and excellent corrosion protection of steels, and MoTe2 layers have a potential for the application in anticorrosive coatings due to their hydrophobic properties. In this study, MoTe2-Ni-Mo coatings were deposited on stainless steel using both sputtering and electrodeposition methods. These coatings with high corrosion resistance and other desirable properties are in demand in the oil and gas industry since they can protect and thus extend the lifetime of the underlying materials when exposed to aggressive environments. The Zn-Mo and MoTe2-Ni-Mo coatings were evaluated for chemical composition and corrosion behavior using different types of instrumental and electrochemical techniques. The addition of vanillin to the electrolyte did not change the crystalline structure or composition of the Zn-Mo coating, however, the corrosion resistance of the coating was significantly improved by the leveling effect of vanillin during the electrodeposition. The corrosion resistance of the Ni-Mo coating was also enhanced by applying the hydrophobic MoTe2 monolayer on the top surface.
Electronic Effects in Dihaloketenes
The objective of this investigation was to determine the electronic effects of the halogen atoms in dihaloketenes such as dichloroketene and dibromoketene.
The Electronic Spectrum of (-)-S-(pS)-2,5,3',6'-Tetrahydro-2.2-Paracyclophane-2-Carboxylic Acid
A new, efficient route was used in the synthesis of [2.2]-paracyclophane-2-carboxylic acid. The acid as then resolved and the Birch reduction performed yielding one enantiomer of tetrahydro-[2.2]-paracyclophane-2-carboxylic acid. The ultraviolet spectrum of tetrahydro-[2.2]-paracyclophane- 2-carboxylic acid in isopenthane shows one absorption at 206 nm (Emax = 5,271). There are three bands observed in the circular dichroism spectrum in isopentane at 236 nm ([] = 1.8 X 104), 201 nm ([0] = -16 X 104) and a positive band indicated below 180 nm but not observed. The bands were assigned and possible reasons for the occurrence of a mr'r* transition at unexpectedly long wavelengths are discussed.
Elemental Analysis of Brainstem in Victims of Sudden Infant Death Syndrome
A brainstem-related abnormality in respiratory control appears to be one of the most compelling mechanisms for sudden infant death syndrome (SIDS). The elements calcium, copper, iron, potassium, magnesium, sodium, phosphorus, sulfur, and zinc were analyzed by inductively coupled plasma atomic emission spectroscopy in the brainstem of 30 infants who died from SIDS and 10 infants who died from other causes (control). No differences were found between SIDS and control for any element except for more calcium in the SIDS group. A multivariate analysis of the data failed to group the majority of SIDS and control subjects in different clusters. Further research is required to determine the biological significance of the higher calcium found in the SIDS group.,
Elucidation of Photoinduced Energy and Electron Transfer Mechanisms in Multimodular Artificial Photosynthetic Systems
Multimodular designs of electron donor-acceptor systems are the ultimate strategy in fabricating antenna-reaction center mimics for artificial photosynthetic applications. The studied photosystems clearly demonstrated efficient energy transfer from the antenna system to the primary electron donor, and charge stabilization of the radical ion pair achieved with the utilization of secondary electron donors that permits either electron migration or hole transfer. Moreover, the molecular arrangement of the photoactive components also influences the route of energy and electron transfer as observed from the aluminum(III) porphyrin-based photosystems. Furthermore, modulation of the photophysical and electronic properties of these photoactive units were illustrated from the thio-aryl substitution of subphthalocyanines yielding red-shifted Q bands of the said chromophore; hence, regulating the rate of charge separation and recombination in the subphthalocyanine-fullerene conjugates. These multicomponent photosystems has the potential to absorb the entire UV-visible-NIR spectrum of the light energy allowing maximum light-harvesting capability. Furthermore, it permits charge stabilization of the radical ion pair enabling the utilization of the transferred electron/s to be used by water oxidizing and proton reducing catalysts in full-scale artificial photosynthetic apparatuses.
ESR Studies of Group IV Substituted Anilines
The purpose of the investigation described herein was to investigate the degree of delocalization of the unpaired electron in ion radicals formed in the oxidation process of compounds with aromatic rings connected by means of various groups and atoms not entering the ring; then, to establish the relationship of coupling constants in radical cations with substituent σ values. The parent cation radical, in which the co-planar ion was derived from N,N-dimethylaniline, was selected in order to maximize the substituent effects on coupling constants and to obtain couplings at several positions (specifically, CH3, N, and ring protons).
Evaluation of Adsorption and Microcoulometric Methods for Determination of Halogenated Organic Compounds in Water
Two adsorption/microcoulometric methods have been investigated for total organic halogen (TOX) in water. TOX, a proposed water-quality parameter, is a rapid, surrogate method to detect halides microcoulometrically and does not require compound identification before water quality can be judged. An XAD resin is used to concentrate organic halides that are eluted by a two-step, two-solvent procedure, followed by analysis using :chromatography or pyrolysis to convert organic halides to halide. In the granular activated carbon (GAC) method, the entire GAC-organic halide sample is pyrolyzed. TOX measurements of model compounds are comparable by both methods, but GAC was found to be superior to XAD for adsorption of chlorinated humics in drinking water and chlorinated lake water.
The Exchange of Bismuth Tetra-Iodide and Bismuth Ions in an Ion-Precipitate System
This paper is a study of the exchange of bismuth tetra-iodide and bismuth ions in an ion-precipitate system.
Experimental and Theoretical Studies of Polycarbocyclic Compounds
Part I. Diels-Alder cycloadditions of 1,2,3,4,9,9-hexachloro-1α,4α,4aα,8aβ-tetrahydro-l,4-methanonaphthalene (32) and 1,2,3,4,9,9-hexachloro-lα,4α,6,7- tetrahydro-l,4-methanonaphthalene (33) to 4-methyl- and 4-phenyl-l,2,4-triazoline-3,5-dione [MTAD and PTAD, respectively] and to N-methylmaleimide (NMM) have been studied. The structures of several of the resulting cycloadducts were determined by X-ray crystallographic methods. The observed stereoselectivity of each of these Diels-Alder reactions was further investigated via application of theoretical methods. Thus, semiempirical (AMI) and ab initio molecular orbital calculations were used to calculate relative energies. Ab initio calculations were employed to perform frontier molecular orbital analyses of diene-dienophile interactions.
Experimental and Theoretical Study of Electronic Transitions in Phosphorus, Phosphoryl, and Thiophosphoryl Trichlorofluorides
This thesis is an investigation of the vacuum uv spectra of the phosphorus, phosphoryl, and thiophosphoryl trichlorofluorides in the region 1250 to 3000A. Assignments for absorption bands are made utilizing results from photoelectron spectra and ab initio calculations, oscillator strengths for absorption bands, and CNDO/2 molecular orbital calculations. Results from CNDO/2 calculations are compared with theoretical calculations, and experimental data are discussed with regard to the bonding in the compounds.
An Experimental Study of the Electrodeposition of Lead
This thesis aimed to study some of the general principles underlying electrodeposition together with experimental facts regarding the effects of changing constituents of the plating solutions, variations in hydrogen-ion concentrations, and variation in current density used in the electrodeposition of lead.
Exploration of Transition Metal-Containing Catalytic Cycles via Computational Methods
Styrene production by a (FlDAB)PdII(TFA)(η2-C2H4) complex was modeled using density functional theory (DFT). Benzene C-H activation by this complex was studied via five mechanisms: oxidative addition/reductive elimination, sigma-bond metathesis, concerted metalation deprotonation (CMD), CMD activation of ethylene, and benzene substitution of ethylene followed by CMD of the ligated benzene. Calculations provided evidence that conversion of benzene and ethylene to styrene was initiated by the fifth pathway, arylation via CMD of coordinated benzene, followed by ethylene insertion into the Ru-Ph bond, and then β-hydrogen elimination. Also, monomer (active species)/dimer equilibrium concentrations were analyzed. The results obtained from present study were compared with that of a recently reported RhI complex to help identify more suitable catalysts for the direct production of styrene from ethylene and benzene. Second, theoretical studies of heterobimetallic {Ag–Fe(CO)5}+ fragments were performed in conjunction with experiments. The computational models suggested that for this first example of a heterodinuclear, metal-only FeAg Lewis pair (MOLP) that Fe(CO)5 acts as a Lewis base and AgI as a Lewis acid. The ῡCO bands of the studied molecules showed a blue shift relative to those measured for free Fe(CO)5, which indicated a reduction in Fe→CO backbonding upon coordination to silver(I). Electrostatic interaction is predicted via DFT as the dominant mode of Fe—Ag bonding augmented by a modest amount of charge transfer between Ag+ and Fe(CO)5. Third, computational analyses of hypothetical transition metal-terminal boride [MB(PNPR)] complexes were reported. DFT, natural orbital analysis (NBO), and multiconfiguration self-consistent field (MCSCF) calculations were employed to investigate the structure and bonding of terminal boride complexes, in particular the extent of metal dπ - boron pπ bonding. Comparison of metal-boride, -borylene and –boryl bond lengths confirms the presence of metal-boron π bonds, albeit the modest shortening (~ 3%) of the metal-boron bond suggests that the π-bonding is weak. Their instabilities, …
Explorations with Polycarbocyclic Cage Compounds
A variety of novel cage-functionalized pyridyl containing crown ethers have been prepared for use in selective alkali metal complexation studies. A highly preorganized, cage-functionalized cryptand also has been designed and has been synthesized for use as a selective Li+ complexant. The alkali metal picrate extraction profiles of these cage-functionalized crown ethers also have been studied. Novel cage-functionalized diazacrown ethers have been prepared for selective alkali metal complexation studies. Alkali metal picrate extraction experiments have been performed by using this new class of synthetic ionophores to investigate the effects of cage-annulation and the influence of N-pivot lariat sidearms upon their resulting complexation properties. Novel pyridyl containing calix[4]arene receptors were prepared. Analysis of their respective 1H NMR and 13C NMR spectra suggests that calix[4]arene moieties in the ligand occupy the cone conformation. The complexation properties of these host molecules were estimated by performing a series of alkali metal picrate extraction experiments. An optically active cage-functionalized crown ether which contains a binaphthyl moiety as the chiral unit was prepared. The ability of the resulting optically active crown ether to distinguish between enantiomers of guest ammonium ions (i.e., phenylethylamonium and phenylglycinate salts) in transport experiments was investigated. Hexacyclo[11.2.1.02,12.05,10.05,15.010,14]hexadeca-6,8-diene-4,11-dione was prepared from hexacyclo[7.4.2.01,9.03,7.04,14.06,15] pentadeca-10,12-diene-2,8-dione. Unanticipated but remarkable acid and base promoted rearrangements of this new cage dione to novel polycyclic systems were observed and subsequently were investigated. The structures of the new systems thereby obtained were determined unequivocally by application of X-ray crystallographic methods. It is noteworthy that the reactions reported herein each provide the corresponding rearranged product in high yield in a single synthetic step. Pi-facial and regioselectivity in the thermal Diels-Alder cycloaddition between hexacyclo[11.2.1.02,12.05,10.05,15.010,14]hexadeca-6,8-diene- 4,11-dione and ethyl propiolate have been explored. This reaction proceeds via stereospecific approach of the dienophile toward the syn face of the diene p -system. However, [4+2]cycloaddition proceeds with …
β, β'-π-Extended Porphyrins: Exploration of Functionalization and Aromatic Character
Seventeen new dithiophenyl- and napthodithiophenyl- fused porphyrins were synthesized; from these an additional 7 porphyrin oligomers were also synthesized. Additionally freebase 2,7-dimethoxytriphenylene fused porphyrin was also synthesized from a freebase precursor. Aromatic indices NICS and AICD were used to evaluate these new molecules.
Fluorination Effect on the Conformational Properties of Alkanes
A Series of fluorophores of the general formular P(CF2)nP and P(CF2)n-1CF3 has been synthesized. Copper catalyzed coupling of 1-bromopyrene and the corresponding mono and di-iodoperfluoroalkanes were used in most cases. For the n=3 dimer, a novel 1,w-perfluoroalkylation of pyrene via bis-decarboxylation of hexafluorogultaric acid was utilized. These compounds, along with suitable hydrocarbon analogs, are being used to study the flexibility of fluorocarbon chains using emission. We have found that the excimer formation for the fluorinated pyrene monomers is highly dependent on concentration and is less efficient than for pyene. Excimer formation for the fluorinated pyrene dimers is much more efficient than for the fluorocarbon monomers and is only slightly concentraion dependent. Steady-state emission spectra indicate hydrocarbon dimers-models form excimers more efficiently than the fluorinated dimers suggesting the fluorinated chains are stiffer than the hydrocarbons. We conducted the temperature-dependent studies and quantified the conformational difference.
A Fractionation Column for the Separation of Products of the Alkylation of Isobutane and Isobutene
This thesis describes a fractionation column method of separating isobutane and isobutene to isolate isooctane.
FT-NMR and Raman Spectroscopic Studies of Molecular Dynamics in Liquids
NMR relaxation and Raman lineshape analysis are well known methods for the study of molecular reorientational dynamics in liquids. The combination of these two methods provides another approach to tackle the characterization of molecular dynamics in liquids. Investigations presented here include (1) NMR relaxation study of polycyclic compounds in solution, (2) the study of nitromethane reorientational dynamics using the NMR and Raman methods, and (3) Raman lineshape analysis of reorientation hexafluorobenzene/benzene mixtures.
GC/MS Analysis of Chlorinated Organic Compounds in Municipal Wastewater After Chlorination
A study has been conducted for the qualitative and Quantitative analysis of chlorinated organic compounds in water. The study included the adaptation of Amberlite XAD macroreticular resin techniques for the concentration of municipal wastewater samples, followed by GC/MS analysis. A new analytical method was developed for the determination of volatile halogenated organics using liquid-liquid extraction and electron capture gas chromatography. And, a computer program was written which searches raw GC/MS computer files for halogen-containing organic compounds.
General Chemistry Topic Coverage (GCTC) comparison between community colleges and universities in the United States.
This study is based on survey responses of 224 general chemistry instructors at United States (U.S.) community colleges and universities representing 46 states. The mean values of General Chemistry Topic Coverage (GCTC) score, developed by this researcher specifically for this dissertation study as a measure of course content, were statistically analyzed. The aim of this study is to answer five research questions: (a) Is there a difference in mean GCTC scores between U.S. community colleges and four-year colleges and universities? (b) If there is a difference in mean GCTC score between the two study groups, what are the observed differences in subtopics covered between community colleges and four-year colleges and universities? (c) Considering both community colleges and universities, is there a difference in mean GCTC score between the different designated U.S. regions? (d) Considering both community college and university professors, is there a difference in GCTC score for professors with a master's degree compared to those with a doctorate?, and (e) Is there a correlation between GCTC score and the percentage of students that major in science? Results indicate that there is a statistically significant difference in course content between community colleges and universities, there is a statistically significant difference between different U.S. regions, there is no statistically significant difference between professors with an earned master's versus those with an earned doctorate degree, and there is no statistically significant correlation between general chemistry course content and the percentage of a professor's students majoring in science. Details of the observed differences between community college and university course content are discussed, and recommendations for future research are presented.
Halogenated 2-Oxetanones
The purpose of this investigation is threefold: (1) to examine in detail the cycloaddition of halogenated ketenes and carbonyl compounds, (2) to study the decarboxylation of the resulting halogenated 2-oxetanones,and (3) to investigate the effect of halogens in the halogenated 2-oxetanones on the nucleophilic addition reaction.
High-Energy, Long-Lived Charge-Separated States via Molecular Engineering of Triplet State Donor-Acceptor Systems
Molecular engineering of donor-acceptor dyads and multimodular systems to control the yield and lifetime of charge separation is one of the key goals of artificial photosynthesis for harvesting sustainably solar energy. The design of the donor-acceptor systems mimic a part of green plants and bacterial photosynthetic processes. The photochemical events in natural photosynthesis involve the capturing and funneling of solar energy by a group of well-organized chromophores referred to as an ‘antenna' system causing an electron transfer into the ‘reaction center,' where an electron transfer processes occur resulting a long-lived charge separated state. Over the last two to three decades, many efforts have been directed by the scientific community designing of multi-modular systems that are capable of capturing most of the useful sunlight and generating charge separated states of prolonged lifetimes with adequate amounts of energy. In this dissertation, we report on the design and synthesis of donor–acceptor conjugates with the goal of modulating the yield and lifetime of their charge separated states and hence, improving the conversion of light energy into chemical potential. In simple donor-acceptor systems, generally, the energy and electron transfer events originate from the singlet excited state of the donor or acceptor and can store the greatest amount of energy but must be fast to out compete intersystem crossing. To address this limitation, we have designed novel donor –acceptor conjugates that use high-energy triplet sensitizers in which electron transfer is initiated from the long lived triplet state of the donor. The triplet photosensitizers used were palladium(II) porphyrin and platinum(II) porphyrin. Heavy metal effect in these porphyrins promoted intersystem crossing and the energies of their excited state was quite high. For the case of palladium (II) porphyrin the energy stored was found to 1.89 eV and that of platinum(II) porphyrin 1.84 eV. In addition to using triplet …
High Temperature Enthalpies of the Lead Halides: Enthalpies and Entropies of Fusion
The objectives of this investigation were: 1. To establish calorimetrically the transition temperature for the orthorhombic to cubic transition exhibited by PbF₂ and to determine the enthalpy of this transition. 2. To determine if the solid-solid phase transitions claimed in the literature for PbCl₂, PbF₂, PbBr₂, and PbI₂ were of thermodynamic importance, and if so, to determine the enthalpies of transition. 3. To determine if the discontinuous thermal expansions reported by Hsu for the lead halides were of thermodynamic importance. 4. To obtain reliable heat content data for the lead halides in both the solid and liquid states.
Homoleptic and Heteroleptic Platinum(II) Complexes for Organic Light Emitting Diodes and Humidity Sensors: Synthesis, Characterization, and Applications
This dissertation focuses on the design, synthesis, characterization of platinum (II) pyridylazolate complexes and develop high performance organic light emitting diodes (OLEDs) and design and execute high-sensitivity humidity sensors based on the luminescent metal-organic complexes of platinum. A majority of existing platinum compounds do not dissolve in organic solvents, making it difficult to analyze the photophysical characteristics of complexes in solution, a key part of understanding chemical photophysical properties. Furthermore, due to the poor quantum yield, it is inefficient for use in devices such as OLEDs. Chapter 2 reports the synthesis and characterization of a novel heteroleptic platinum(II) pyridylazolate complex with high solubility and quantum yield. The photochemistry of the complex is studied, including efficiency, emission profiles, and lifetimes at different temperatures. Chapter 3 reports the power efficiency (lm/W), current efficiency (cd/A), external quantum efficiency (EQE), luminance and operating voltage (V) of OLED devices made with the heteroleptic platinum(II) pyridylazolate complex. The relation between thickness of hole transport layer and electron transport layer on performance of devices has been studied through building a variety of devices. Chapter 4 includes application of a homoleptic platinum(II) pyridylazolate complex in humidity sensor. In many environments, the relationship between moisture content and emissive wavelength has been investigated. This research reveals that regardless of the humidity level, there is a link between increasing the temperature and decreasing the moisture absorption capacity of the complex.
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