You limited your search to:

  Partner: UNT Libraries
 Department: Department of Chemistry
Computational Studies on Group 14 Elements (C, Si and Ge) in Organometallic and Biological Compounds.

Computational Studies on Group 14 Elements (C, Si and Ge) in Organometallic and Biological Compounds.

Date: May 2007
Creator: Yu, Liwen
Description: A series of computational studies were carried out on Group 14 (C, Si and Ge) elements in organometallic and biological compounds. Theoretical studies on classical and H-bridged A3H3+ (A=C, Si and Ge) as p ligands with different organometallic fragments at B3LYP and B3P86 level reveal a reverse charge transfer from ligand to metal in Si and Ge complexes whereas in C complexes there is a small charge transfer from metal to ligand. The H-bridged complexes are more stable than the complexes based on Si3H3+ and Ge3H3+ ligands with terminal hydrogens. The stability of the bridged systems increases from Si to Ge. Corrective scale factors for computed harmonic CºO vibrational frequencies for 31 organometallic complexes have been determined at the HF and B3LYP levels. The scaled B3LYP frequencies exhibit a greater reliability than do HF frequencies. Experimental data have shown that Si/Ge-substituted decapeptides are advantageous over their C analog in vitro and in vivo studies in modern hormone therapy. A computational investigation was carried out on the synthesized decapeptides focusing on position 5 containing Si and Ge. The results have shown that there are some differences in C, Si and Ge-containing analogs. However, further investigations are needed to elucidate the observed ...
Contributing Partner: UNT Libraries
Photophysical properties of pyrene, 2,7 diazapyrene and 1,3-bis(β-naphthyl)propane.

Photophysical properties of pyrene, 2,7 diazapyrene and 1,3-bis(β-naphthyl)propane.

Date: August 2007
Creator: Boateng, Stephen
Description: The luminescence properties of Van Der Waals' dimers and clusters of pyrene and diazapyrene have been investigated. Excimers, dimeric species which are associative in an excited electronic state and dissociative in their ground state, have long been established and play an important role in many areas of photochemistry. My work here focuses on the luminescence and absorption properties of ground state dimers/aggregates, which are less understood, and allows further characterization of the ground state and excited state association of these aromatic molecules.
Contributing Partner: UNT Libraries
Synthesis and characterization of diphosphine ligand substituted osmium and ruthenium clusters.

Synthesis and characterization of diphosphine ligand substituted osmium and ruthenium clusters.

Date: August 2007
Creator: Kandala, Srikanth
Description: The kinetics for the bridge-to-chelate isomerization of the dppe ligand in H4Ru4(CO)10(dppe) have been investigated by UV-vis and NMR spectroscopies over the temperature range of 308-328 K. The isomerization of the ligand-bridged cluster 1,2-H4Ru4(CO)10(dppe) was found to be reversible by 31P NMR spectroscopy, affording a Keq = 15.7 at 323 K in favor of the chelating dppe isomer. The forward (k1) and reverse (k-1) first-order rate constants for the reaction have been measured in different solvents and in the presence of ligand trapping agents (CO and PPh3). On the basis of the activation parameters and reaction rates that are unaffected by added CO and PPh3, a sequence involving the nondissociative migration of a phosphine moiety and two CO groups between basal ruthenium centers is proposed and discussed. The substitution of the MeCN ligands in the activated cluster 1,2-Os3(CO)10(MeCN)2 by the diphosphine ligands dppbz proceeds rapidly at room temperature to furnish a mixture of bridging and chelating Os3(CO)10(dppbz) isomers and the ortho-metalated product HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C4H4]. Thermolysis of the bridging isomer 1,2-Os3(CO)10(dppbz) under mild conditions gives the chelating isomer 1,1-Os3(CO)10(dppbz), molecular structure of both the isomers have been determined by X-ray crystallography. The kinetics for the ligand isomerization has been investigated by UV-vis ...
Contributing Partner: UNT Libraries
Study of Copper Electrodeposition on Ruthenium Oxide Surfaces and Bimetallic Corrosion of Copper/Ruthenium in Gallic Acid Solution

Study of Copper Electrodeposition on Ruthenium Oxide Surfaces and Bimetallic Corrosion of Copper/Ruthenium in Gallic Acid Solution

Date: August 2007
Creator: Yu, Kyle K.
Description: Ruthenium, proposed as a new candidate of diffusion barrier, has three different kinds of oxides, which are native oxide, electrochemical reversible oxide and electrochemical irreversible oxide. Native oxide was formed by naturally exposed to air. Electrochemical reversible oxide was formed at lower anodic potential region, and irreversible oxides were formed at higher anodic potential region. In this study, we were focusing on the effect of copper electrodeposition on each type of oxides. From decreased charge of anodic stripping peaks and underpotential deposition (UPD) waves in cyclic voltammetry (CV), efficiency of Cu deposition dropped off indicating that interfacial binding strength between Cu and Ru oxides was weakened when the Ru surface was covered with irreversible oxide and native oxide. Also, Cu UPD was hindered by both O2 and H2 plasma modified Ru surfaces because the binding strength between Cu and Ru was weakened by O2 and H2 plasma treatment. Cu/Ru and Cu/Ta bimetallic corrosion was studied for understanding the corrosion behavior between diffusion barrier (Ta and Ru) and Cu interconnects under the post chemical mechanical planarization (CMP) process in semiconductor fabrication. Gallic acid is used in post CMP slurry solution and is known well as antioxidant which is supposed to oxidize ...
Contributing Partner: UNT Libraries
Electrodeposition of Copper on Ruthenium Oxides and Bimetallic Corrosion of Copper/Ruthenium in Polyphenolic Antioxidants

Electrodeposition of Copper on Ruthenium Oxides and Bimetallic Corrosion of Copper/Ruthenium in Polyphenolic Antioxidants

Date: August 2007
Creator: Venkataraman, Shyam S.
Description: Copper (Cu) electrodeposition on ruthenium (Ru) oxides was studied due to important implications in semiconductor industry. Ruthenium, proposed as the copper diffusion barrier/liner material, has higher oxygen affinity to form different oxides. Three different oxides (the native oxide, reversible oxide, and irreversible oxide) were studied. Native oxide can be formed on exposing Ru in atmosphere. The reversible and irreversible oxides can be formed by applying electrochemical potential. Investigation of Cu under potential deposition on these oxides indicates the similarity between native and reversible oxides by its nature of inhibiting Cu deposition. Irreversible oxide formed on Ru surface is rather conductive and interfacial binding between Cu and Ru is greatly enhanced. After deposition, bimetallic corrosion of Cu/Ru in different polyphenols was studied. Polyphenols are widely used as antioxidants in post chemical mechanical planarization (CMP). For this purpose, different trihydroxyl substituted benzenes were used as antioxidants. Ru, with its noble nature enhances bimetallic corrosion of Cu. Gallic acid (3,4,5 - trihydroxybenzoic acid) was chosen as model compound. A mechanism has been proposed and validity of the mechanism was checked with other antioxidants. Results show that understanding the chemical structure of antioxidants is necessary during its course of reaction with Cu.
Contributing Partner: UNT Libraries
Synthesis and host-guest interaction of cage-annulated podands, crown ethers, cryptands, cavitands and non-cage-annulated cryptands.

Synthesis and host-guest interaction of cage-annulated podands, crown ethers, cryptands, cavitands and non-cage-annulated cryptands.

Date: May 2003
Creator: Chen, Zhibing
Description: Symmetrical cage-annulated podands were synthesized via highly efficient synthetic strategies. Mechanisms to account for the key reaction steps in the syntheses are proposed; the proposed mechanisms receive support from the intermediates that have been isolated and characterized. An unusual complexation-promoted elimination reaction was studied, and a mechanism is proposed to account for the course of this reaction. This unusual elimination may generalized to other rigid systems and thus may extend our understanding of the role played by the host molecules in "cation-capture, anion-activation" via complexation with guest molecules. Thus, host-guest interaction serves not only to activate the anion but also may activate the leaving groups that participate in the complexation. Complexation-promoted elimination provides a convenient method to desymmetrize the cage while avoiding protection/deprotection steps. In addition, it offers a convenient method to prepare a chiral cage spacer by introducing 10 chiral centers into the host system in a single synthetic step. Cage-annulated monocyclic hosts that contain a cage-butylenoxy spacer were synthesized. Comparison of their metal ion complexation behavior as revealed by the results of electrospray ionization mass spectrometry (ESI-MS), alkali metal picrate extraction, and pseudohydroxide extraction with those displayed by the corresponding hosts that contain cage-ethylenoxy or cage-propylenoxy spacers reveals ...
Contributing Partner: UNT Libraries
Explorations with optically active, cage-annulated crown ethers.

Explorations with optically active, cage-annulated crown ethers.

Date: May 2003
Creator: Ji, Mingzhe
Description: A variety of optically active macrocyclic crown ethers that serve as "host" systems that are capable of differentiating between enantiomeric "guest" molecules during host-guest complexation have been prepared via incorporation of chiral elements into the crown ring skeleton. The ability of these crown ethers to recognize the enantiomers of guest salts, i.e., (+) a-methyl benzylamine and to transport them enantioselectively in W-tube transport experiments were studied. The ability of these crown ethers to perform as chiral catalysts in an enantioselective Michael addition was studied. The extent of asymmetric induction, expressed in terms of the enantiomeric excess (%ee), was monitored by measuring the optical rotation of the product and comparing to the literature value.
Contributing Partner: UNT Libraries
Design and Synthesis of Novel Cage-Functionalized Crown Ethers: A New Class of Ag Complexants.

Design and Synthesis of Novel Cage-Functionalized Crown Ethers: A New Class of Ag Complexants.

Date: August 2003
Creator: Lai, Huiguo
Description: Three different types of cage crown ethers have been prepared and their complexation properties with Ag(I) have been studied. Atomic absorption, fluorescence quenching, and UV absorption have been used to study the interaction between the hosts (cage crown ethers) and guests (Ag+). For the cage-annulated crown ethers that contain aromatic rings, cation-π and π-π interactions may contribute significantly to the overall complexation ability of the host system. Piperazine groups may cooperate, and the piperazine nitrogen atoms provide unshared electrons, which may form a complex with Ag+. In addition, relatively soft donor atoms (e.g., Br) are well-suited for complexation with Ag+, which is a softer Lewis acid than alkali metal cations.
Contributing Partner: UNT Libraries
Synthesis and X-ray Diffraction Structure of 8,9-Dichloropyrrolo[1,2-a]perimidin-10-one

Synthesis and X-ray Diffraction Structure of 8,9-Dichloropyrrolo[1,2-a]perimidin-10-one

Access: Use of this item is restricted to the UNT Community.
Date: August 2003
Creator: Chen, Tao
Description: Treatment of dichloromaleic anhydride and 1,8-diaminonaphthalene in either benzene or toluene under refluxing conditions gives low yields of the new heterocyclic compound 8,9-dichloropyrrolo[1,2-a]perimidin-10-one. This product has been isolated and characterized in solution by NMR, IR, and UV/vis spectroscopies, and the solid-state structure of 8,9-dichloropyrrolo[1,2-a]perimidin-10-one has been established by X-ray crystallography. The nature of the HOMO and LUMO levels of 8,9-dichloropyrrolo[1,2-a]perimidin-10-one has been studied by extended Hückel molecular orbital calculations.
Contributing Partner: UNT Libraries
Interfacial Electrochemistry and Surface Characterization: Hydrogen Terminated Silicon, Electrolessly Deposited Palladium & Platinum on Pyrolyzed Photoresist Films and Electrodeposited Copper on Iridium

Interfacial Electrochemistry and Surface Characterization: Hydrogen Terminated Silicon, Electrolessly Deposited Palladium & Platinum on Pyrolyzed Photoresist Films and Electrodeposited Copper on Iridium

Date: December 2003
Creator: Chan, Raymond
Description: Hydrogen terminated silicon surfaces play an important role in the integrated circuit (IC) industry. Ultra-pure water is extensively used for the cleaning and surface preparation of silicon surfaces. This work studies the effects of ultra-pure water on hydrogen passivated silicon surfaces in a short time frame of 120 minutes using fourier transform infrared spectroscopy – attenuated total reflection techniques. Varying conditions of ultra-pure water are used. This includes dissolved oxygen poor media after nitrogen bubbling and equilibration under nitrogen atmosphere, as well as metal contaminated solutions. Both microscopically rough and ideal monohydride terminated surfaces are examined. Hydrogen terminated silicon is also used as the sensing electrode for a potentiometric sensor for ultra-trace amounts of metal contaminants. Previous studies show the use of this potentiometric electrode sensor in hydrofluoric acid solution. This work is able to shows sensor function in ultra-pure water media without the need for further addition of hydrofluoric acid. This is considered a boon for the sensor due to the hazardous nature of hydrofluoric acid. Thin carbon films can be formed by spin coating photoresist onto silicon substrates and pyrolyzing at 1000 degrees C under reducing conditions. This work also shows that the electroless deposition of palladium and ...
Contributing Partner: UNT Libraries
Copper Electrodeposition on Iridium, Ruthenium and Its Conductive Oxide Substrate

Copper Electrodeposition on Iridium, Ruthenium and Its Conductive Oxide Substrate

Date: December 2003
Creator: Huang, Long
Description: The aim of this thesis was to investigate the physical and electrochemical properties of sub monolayer and monolayer of copper deposition on the polycrystalline iridium, ruthenium and its conductive oxide. The electrochemical methods cyclic voltammetry (CV) and chronocoulometry were used to study the under potential deposition. The electrochemical methods to oxidize the ruthenium metal are presented, and the electrochemical properties of the oxide ruthenium are studied. The full range of CV is presented in this thesis, and the distances between the stripping bulk peak and stripping UPD peak in various concentration of CuSO4 on iridium, ruthenium and its conductive oxide are shown, which yields thermodynamic data on relative difference of bonding strength between Cu-Ru/Ir atoms and Cu-Cu atoms. The monolayer of UPD on ruthenium is about 0.5mL, and on oxidized ruthenium is around 0.9mL to 1.0mL. The conductive oxide ruthenium presents the similar properties of ruthenium metal. The pH effect of stripping bulk peak and stripping UPD peak of copper deposition on ruthenium and oxide ruthenium was investigated. The stripping UPD peak and stripping bulk peak disappeared after the pH ≥ 3 on oxidized ruthenium electrode, and a new peak appeared, which means the condition of pH is very important. ...
Contributing Partner: UNT Libraries
Synthesis and characterization of 2-chloro-3-benzylthiopyrrolo[1,2-a]- benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one.

Synthesis and characterization of 2-chloro-3-benzylthiopyrrolo[1,2-a]- benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one.

Date: December 2003
Creator: Huang, Shih-Huang
Description: The reaction between o-phenylenediamine and 2,3-dichloromaleic anhydride has been probed and found to give 2,3-dichloropyrrolo[1,2-a]- benzimidazol-1-one as the major product. Chlorine substitution in 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one by added benzylthiol occurs in the presence of pyridine to provide the corresponding monosulfide and disulfide derivatives. The first benzylthiol ligand undergoes reaction at the C-3 position of the five-membered pyrrolo-1-one ring, with the addition of the second benzylthiol ligand occurring at the remaining chlorine-substituted carbon. The mono- and disulfide derivatives have been isolated and characterized in solution by NMR, IR, and UV-vis spectroscopies, and the solid-state structure of 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one has been established by X-ray crystallography.
Contributing Partner: UNT Libraries
Investigation of the Pressure Dependence of SO3    Formation

Investigation of the Pressure Dependence of SO3 Formation

Date: December 2003
Creator: Naidoo, Jacinth
Description: The kinetics of the pressure dependent O + SO2 + Ar reaction have been investigated using laser photolysis resonance fluorescence at temperatures of 289 K, 399 K, 581 K, 699 K, 842 K and 1040 K and at pressures from 30-665 torr. Falloff was observed for the first time in the pressure dependence. Application of Lindemann theory yielded an Arrhenius expression of k(T) = 3.3 x 10-32exp(-992/T) cm6 molecule-1 s-1 for the low pressure limit and k(T) = 8.47 x 10-14exp(-468/T) cm3 molecule-1 s-1 for the high pressure limit at temperatures between 289 and 842 K. The reaction is unusual as it possesses a positive activation energy at low temperature, yet at higher temperatures the activation energy is negative, illustrating a reaction barrier.
Contributing Partner: UNT Libraries
Study of Interactions Between Diffusion Barrier Layers and Low-k Dielectric Materials for Copper/Low-k Integration

Study of Interactions Between Diffusion Barrier Layers and Low-k Dielectric Materials for Copper/Low-k Integration

Date: December 2003
Creator: Tong, Jinhong
Description: The shift to the Cu/low-k interconnect scheme requires the development of diffusion barrier/adhesion promoter materials that provide excellent performance in preventing the diffusion and intermixing of Cu into the adjacent dielectrics. The integration of Cu with low-k materials may decrease RC delays in signal propagation but pose additional problems because such materials are often porous and contain significant amounts of carbon. Therefore barrier metal diffusion into the dielectric and the formation of interfacial carbides and oxides are of significant concern. The objective of the present research is to investigate the fundamental surface interactions between diffusion barriers and various low-k dielectric materials. Two major diffusion barriers¾ tatalum (Ta) and titanium nitride (TiN) are prepared by DC magnetron sputtering and metal-organic chemical vapor deposition (MOCVD), respectively. Surface analytical techniques, such as X-ray photoelectronic spectroscopy (XPS), transmission electron microscopy (TEM), and atomic force microscopy (AFM) are employed. Ta sputter-deposited onto a Si-O-C low dielectric constant substrate forms a reaction layer composed of Ta oxide and TaC. The composition of the reaction layer varies with deposition rate (1 Å-min-1 vs. 2 Å-sec-1), but in both cases, the thickness of the TaC layer is found to be at least 30 Å on the basis of ...
Contributing Partner: UNT Libraries
Fabrication and light scattering study of multi-responsive nanostructured hydrogels and water-soluble polymers.

Fabrication and light scattering study of multi-responsive nanostructured hydrogels and water-soluble polymers.

Date: December 2003
Creator: Xia, Xiaohu
Description: Monodispersed microgels composed of poly-acrylic acid (PAAc) and poly(N-isopropylacrylamide) (PNIPAM) interpenetrating networks were synthesized by 2-step method with first preparing PNIPAM microgel and then polymerizing acrylic acid that interpenetrates into the PNIPAM network. The semi-dilute aqueous solutions of the PNIPAM-PAAc IPN microgels exhibit an inverse thermo-reversible gelation. Furthermore, IPN microgels undergo the reversible volume phase transitions in response to both pH and temperature changes associated to PAAc and PNIPAM, respectively. Three applications based on this novel hydrogel system are presented: a rich phase diagram that opens a door for fundamental study of phase behavior of colloidal systems, a thermally induced viscosity change, and in situ hydrogel formation for controlled drug release. Clay-polymer hydrogel composites have been synthesized based on PNIPAM gels containing 0.25 to 4 wt% of the expandable smectic clay Na-montmorillonite layered silicates (Na-MLS). For Na-MLS concentrations ranging from 2.0 to 3.2 wt%, the composite gels have larger swelling ratio and stronger mechanical strength than those for a pure PNIPAM. The presence of Na-MLS does not affect the value of the lower critical solution temperature (LCST) of the PNIPAM. Surfactant-free hydroxypropyl cellulose (HPC) microgels have been synthesized in salt solution. In a narrow sodium chloride concentration range from 1.3 ...
Contributing Partner: UNT Libraries
Reactivity of Oxide Surfaces and Metal-Oxide Interfaces: Effects of Water Vapor Pressure on Ultrathin Aluminum Oxide Films, and Studies of Platinum Growth Modes on Ultrathin Oxide Films and Their Effects on Adhesion

Reactivity of Oxide Surfaces and Metal-Oxide Interfaces: Effects of Water Vapor Pressure on Ultrathin Aluminum Oxide Films, and Studies of Platinum Growth Modes on Ultrathin Oxide Films and Their Effects on Adhesion

Date: May 2004
Creator: Garza, Michelle
Description: The reactivity of oxide surfaces and metal-oxide interfaces play an important role in many technological applications such as corrosion, heterogeneous catalysis, and microelectronics. The focus of this research was (1) understanding the effects of water vapor exposure of ultrathin aluminum oxide films under non-ultrahigh vacuum conditions (>10-9 Torr) and (2) characterization of Pt growth modes on ultrathin Ta silicate and silicon dioxide films and the effects of growth modes on adhesion of a Cu overlayer. These studies were conducted with X-ray photoelectron spectroscopy (XPS). Ni3Al(110) was oxidized (10-6 Torr O2, 800K) followed by annealing (1100K). The data indicate that the annealed oxide film is composed of NiO, Al2O3 and an intermediate phase denoted here as "AlOx". Upon exposure of the oxide film at ambient temperature to increasing water vapor pressure (10-6 - 5 Torr), a shift in both the O(1s) and Al(2p)oxide peak maxima to lower binding energies is observed. In contrast, exposure of Al2O3/Al(polycrystalline) to water vapor under the same conditions results in a high binding energy shoulder in the O(1s) spectra which indicates hydroxylation. Spectral decomposition provides further insight into the difference in reactivity between the two oxide films. The corresponding trends of the O(1s)/Ni0(2p3/2) and Al(2p)/Ni0(2p3/2) spectral ...
Contributing Partner: UNT Libraries
Adherence/Diffusion Barrier Layers for Copper Metallization: Amorphous Carbon:Silicon Polymerized Films

Adherence/Diffusion Barrier Layers for Copper Metallization: Amorphous Carbon:Silicon Polymerized Films

Date: May 2004
Creator: Pritchett, Merry
Description: Semiconductor circuitry feature miniaturization continues in response to Moore 's Law pushing the limits of aluminum and forcing the transition to Cu due to its lower resistivity and electromigration. Copper diffuses into silicon dioxide under thermal and electrical stresses, requiring the use of barriers to inhibit diffusion, adding to the insulator thickness and delay time, or replacement of SiO2 with new insulator materials that can inhibit diffusion while enabling Cu wetting. This study proposes modified amorphous silicon carbon hydrogen (a-Si:C:H) films as possible diffusion barriers and replacements for SiO2 between metal levels, interlevel dielectric (ILD), or between metal lines (IMD), based upon the diffusion inhibition of previous a-Si:C:H species expected lower dielectric constants, acceptable thermal conductivity. Vinyltrimethylsilane (VTMS) precursor was condensed on a titanium substrate at 90 K and bombarded with electron beams to induce crosslinking and form polymerized a-Si:C:H films. Modifications of the films with hydroxyl and nitrogen was accomplished by dosing the condensed VTMS with water or ammonia before electron bombardment producing a-Si:C:H/OH and a-Si:C:H/N and a-Si:C:H/OH/N polymerized films in expectation of developing films that would inhibit copper diffusion and promote Cu adherence, wetting, on the film surface. X-ray Photoelectron Spectroscopy was used to characterize Cu metallization of ...
Contributing Partner: UNT Libraries
Studies in regiospecific oxidation reactions of 1-methyl-pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione.

Studies in regiospecific oxidation reactions of 1-methyl-pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione.

Date: May 2004
Creator: Vappala, Indu
Description: Baeyer-Villiger oxidation of 1-methylpentacyclo[5.4.0.02,6.03,10.05,9] undecane-8,11-dione, performed by using m-chloroperbenzoic acid in 1:1 molar ratio, resulted in the formation of monolactone. The corresponding dilactone, was synthesized by reacting 1-methyl-PCU-8,11-dione with m-chloroperbenzoic acid in 1:2 molar ratio. 6-Methyl-1,4,4a,8a-tetrahydro-1,4-methanonaphthalene-5,8-dione was converted into the corresponding exo-6,7-monoepoxide via treatment with 30% aqueous hydrogen peroxide. Epoxidation of this monoepoxide by using m-chloroperbenzoic acid afforded the corresponding bis-epoxide. Ceric ammonium nitrate (CAN) promoted oxidation of 1-methyl-PCU-8,11-dione afforded "methylated lactones" and a "methylated alkene."
Contributing Partner: UNT Libraries
Baeyer-Villiger Oxidation of 1,7- & 1,9-dibromopentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione

Baeyer-Villiger Oxidation of 1,7- & 1,9-dibromopentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione

Access: Use of this item is restricted to the UNT Community.
Date: May 2004
Creator: Akinola, Adeniyi O.
Description: Baeyer-Villiger oxidation of 1,9-dibromopentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (1,9-dibromo-PCU-8,11-dione) was performed by using an excess amount of m-chloroperbenzoic acid (3 equivalents) and resulted in the formation of the corresponding monolactone. The reaction would not proceed to the dilactone stage. The structure of the reaction product was established unequivocally via single crystal X-ray diffraction. Baeyer-Villiger oxidation of 1,9-dibromo-PCU-8,11-dione using ceric ammonium nitrate (CAN) was also performed and afforded a mixture of lactones. Only one of these lactones, which also contained an alkene functionality, could be isolated and characterized. 1,7-dibromo-PCU-8,11-dione was also reacted with CAN, yielding the mono-lactone, which has also been characterized.
Contributing Partner: UNT Libraries
Preparation and characterization of praseodymium oxide films and powders.

Preparation and characterization of praseodymium oxide films and powders.

Access: Use of this item is restricted to the UNT Community.
Date: May 2004
Creator: Shang, Yajuan
Description: Nanocrystalline praseodymium oxide films have been successfully generated on stainless steel substrates. The electrochemical deposition was performed in the cathode compartment of a divided electrochemical cell with a regular three-electrode configuration. The green films obtained by electrodeposition were then annealed at high temperatures for 1-3 hours. X-ray diffraction revealed the fluorite structure of Pr6O11 and the crystallite size was calculated. X-ray photoelectron spectroscopy was employed to study the composition of the oxide films and also the oxidation state of Pr. Scanning electron microscopy was utilized to study the surface texture and microstructure of deposits. Fourier transform infrared spectrometery was used to investigate the composition of the films. The effects of different conditions on the green films were also studied such as different pH values of the electrolyte solution, different deposition modes, different supporting electrolytes and different applied current densities. Sintering experiments were conducted to investigate the properties of the green films. Praseodymium oxide powders were also successfully prepared by combining electrochemical methods with sintering processes. The praseodymium oxide powders were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The crystallite sizes of the powders were evaluated.
Contributing Partner: UNT Libraries
Modeling the chemical and photophysical properties of gold complexes.

Modeling the chemical and photophysical properties of gold complexes.

Date: August 2004
Creator: Barakat, Khaldoon A.
Description: Various gold complexes were computationally investigated, to probe their photophysical, geometric, and bonding properties. The geometry of AuI complexes (ground state singlet) is very sensitive to the electronic nature of the ligands: σ-donors gave a two-coordinate, linear shape; however, σ-acceptors yielded a three-coordinate, trigonal planar geometry. Doublet AuIIL3 complexes distort to T-shape, and are thus ground state models of the corresponding triplet AuIL3. The disproportionation of AuIIL3 to AuIL3 and AuIIIL3 is endothermic for all ligands investigated, however, σ-donors are better experimental targets for AuII complexes. For dimeric AuI complexes, only one gold center in the optimized triplet exciton displays a Jahn-Teller distortion, and the Au---Au distance is reduced versus the ground state distance (i.e., two reasons for large Stokes' shifts).
Contributing Partner: UNT Libraries
Layered Double Hydroxides: Synthesis, Characterization, and Interaction of Mg-Al Systems with Intercalated Tetracyanonickelate(II)

Layered Double Hydroxides: Synthesis, Characterization, and Interaction of Mg-Al Systems with Intercalated Tetracyanonickelate(II)

Date: August 2004
Creator: Brister, Fang Wei
Description: The square-planar tetracyanonickelate(II) anion was intercalated into 2:1 and 3:1 Mg-Al layered double hydroxide systems (LDHs). In the 2:1 material, the anion holds itself at an angle of about 30° to the layers, whereas in the 3:1 material it lies more or less parallel to the layers. This is confirmed by orientation effects in the infrared spectra of the intercalated materials and by X-ray diffraction (XRD) data. The measured basal spacings for the intercalated LDH hosts are approximately 11 Å for the 2:1 and approximately 8 Å for the 3:1. The IR of the 2:1 material shows a slight splitting in the ν(CN) peak, which is suppressed in that compound's oriented IR spectrum, indicating that at least some of the intercalated anion's polarization is along the z-axis. This effect is not seen in the 3:1 material. A comparison between chloride LDHs and nitrate LDHs was made with respect to intercalation of tetracyanonickelate(II) anions. Both XRD data and atomic absorption spectroscopy (AAS) data of the LDH tetracyanonickelates confirms that there are no significant differences between the products from the two types of starting materials. The presence of a weak ν(NO) peak in the IR spectra of those samples made from nitrate ...
Contributing Partner: UNT Libraries
Thermodynamics of Mobile Order Theory: Solubility and Partition Aspects

Thermodynamics of Mobile Order Theory: Solubility and Partition Aspects

Date: August 2004
Creator: De Fina, Karina M.
Description: The purpose of this thesis is to analyze the thermochemical properties of solutes in nonelectrolyte pure solvents and to develop mathematical expressions with the ability to describe and predict solution behavior using mobile order theory. Solubilities of pesticides (monuron, diuron, and hexachlorobenzene), polycyclic aromatic hydrocarbons (biphenyl, acenaphthene, and phenanthrene), and the organometallic ferrocene were studied in a wide array of solvents. Mobile order theory predictive equations were derived and percent average absolute deviations between experimental and calculated mole fraction solubilities for each solute were as follows: monuron in 21 non-alcoholic solvents (48.4%), diuron in 28 non-alcoholic solvents (60.1%), hexachlorobenzene (210%), biphenyl (13.0%), acenaphthene (37.8%), phenanthrene (41.3%), and ferrocene (107.8%). Solute descriptors using the Abraham solvation model were also calculated for monuron and diuron. Coefficients in the general solvation equation were known for all the solvents and solute descriptors calculated using multilinear regression techniques.
Contributing Partner: UNT Libraries
Investigation of Structure and Properties of Low Temperature Deposited Diamond-Like Carbon Films

Investigation of Structure and Properties of Low Temperature Deposited Diamond-Like Carbon Films

Date: August 2004
Creator: Pingsuthiwong, Charoendee
Description: Electrodeposition is a novel method for fabrication of diamond-like carbon (DLC) films on metal substrates. In this work, DLC was electrochemically deposited on different substrates based on an anodic oxidation cyclization of acetylene in liquid ammonia. Successfully anodic deposition was carried out for DLC onto nickel substrate at temperatures below -40°C. Comparative studies were performed on a series of different carbon sources (acetylene, sodium acetylide, and a mixture of acetylene and sodium acetylide). The films were characterized using a variety of methods including Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), XPS valence band spectra, and/or scanning electron microscopy (SEM). Raman spectroscopy is used as a bench mark technique to verify the presence of deposited DLC films, to access the films homogeneities, and to provide the ratio of the different carbon phases, mainly disordered graphite (D) and graphite (G) phases in the films. A combination of the Raman with FTIR and valence band spectra analysis allowed the distinction between hydrogenated DLC and unhydrogenated DLC films. Three different kinds of DLC [(1) hydrogenated DLC (a-C:H); (2) tetrahedral hydrogenated DLC (ta-C:H); and (3) graphitic-like DLC] were deposited depending upon the deposition conditions and substrates. Temperature and current density are ...
Contributing Partner: UNT Libraries