SYNTHESIS, CHARACTERIZATION AND REACTIVITY OF ORGANIC BISMUTH COMPOUNDS by Xiaodi Kou, Ph.D., 2007 Department of Chemistry Texas Christian University Advisor: Dr. Tracy A. Hanna, Associate Professor of Chemistry As an environmentally benign element, bismuth has found more and more applications in advanced materials. Our research is aimed at two aspects of bismuth oxide materials. Our goal is to provide precursors for bismuth oxide. Bismuth trioxide is an important component of many ferroelectric materials, but the development of bismuth precursors is still very limited. Another goal of our research is to synthesize homogenous model systems for the catalyst of the SOHIO process. In the SOHIO process, propene is selectively oxidized to acrolein or selectively ammoxidized to acrylonitrile. The detailed mechanism of the process remains controversial. Several molybdenum and Mo/Bi bimetallic systems have been studied, but no bismuth model has been reported before. In the second chapter, I reported the isolation and full characterization of twelve bismuth aryloxide complexes, Bi(OAr)3. The substituents steric effect and electronic effects on the synthesis were studied. Phenyl substituents were utilized to study the bismuth-arene interactions. I also synthesized complexes with allyl or benzyl substituents very close to the bismuth center. These complexes can be good model systems to study the SOHIO process. The bismuth aryloxides we synthesized can also be used as sol-gel precursors for bismuth oxide materials. In the third chapter, I reported the synthesis of bismuth aryloxide amides Bi(OAr)n(NR)3-n, using a ligand exchange method (Bi(OAr)3 + Li(NR)---Bi(OAr)n(NR)3-n). The ligand exchange method is versatile for several kinds of bismuth aryloxide as well as an antimony aryloxide. The bismuth aryloxide amides were spectroscopically characterized, and four of them were characterized by X-ray diffraction. The bismuth aryloxide amides are also good precursors for Bi2O3 materials. They are volatile, light stable and low melting, with excellent solubility and tunable thermal stability. In the fourth chapter, I reported the isolation of ten monosubstituted alkali metal calix[8]arene complexes. Preliminary results were also obtained for reactions of the mono substituted alkali metallocalix[8]arenes with several kinds of bismuth compounds.

Performance of nanoscale ZnO-based systems depends on the nanomorphology and surface conditions, in particular surface defect states. We investigated the impact of the surface/interface phenomena on the defect-related properties for ZnO-containing nanocrystalline systems. To probe these surface-related effects we employed photoluminescence (PL) spectroscopy. Among others, we studied ZnO-containing nanocrystalline specimens grown by wet precipitation with size and morphology controlled by the synthesis parameters. We observed a strong correlation between defect-related luminescence and morphological sample variations. For example, there was a consistent relationship between the surface/volume ratio and the relative intensity of the PL defect emission, indicating strong influence of the optically-active surface states. Commercially available ZnO nanopowders from several vendors were investigated by PL. Observation of the size effects was somewhat overshadowed by the sample-to-sample differences in quality, and thus defects' content and abundance. Temperature-dependent PL measurements in the bound-exciton (BEx) range were performed to elucidate surface-related corrections to the excitons thermodynamics. Specially, calculations for the excitonic activation energies indicated strong dependences of the nanocrystal size on the predominant BEx dissociation channels. Also, we observed nonlinear dependences of BEx peak broadening on temperature suggesting surface phonon contributions. We used remote plasma treatments to tailor surface defect properties of ZnO nanopowders. We report on the plasma-driven modifications of defect optical signatures such as BEx and visible luminescence. Besides, plasma treatments revealed size-dependent effects in the studied specimens. PL was used to study ZnO nanoparticles embedded into a polymethyl methacrylate (PMMA) matrix by bulk polymerization. We found that the polymer encapsulation enhances room-temperature excitonic luminescence by several orders of magnitude, similar to the effects of low temperatures on the as-received nanoparticles. At the same time, relative intensities of the visible defect luminescence did not change noticeably after the PMMA embedding. Intensity-dependent PL experiments showed no indication of a random lasing threshold, thus we attributed the observed phenomena to the influence of the PMMA/ZnO interfaces.

A micro-indentation tool is used to estimate the strength of the Woodford Shale from whole core samples through the geometrical attributes (diameter and depth) of a `dimple' produced by the tool on the rock's surface. The measured dimples are correlated graphically with the unconfined compressive strength and internal friction angle of the Woodford and integrated with contemporary stress data from earthquake focal mechanisms and mapped active faults. Right-lateral strike-slip motion on a deep, unnamed potential splay of the Wilzetta fault (Cherokee Platform, Lincoln County, Oklahoma) is representative of the contemporary stress state of the region. Vertical or near-vertical factures striking ~ 030&deg from SHaz (~ 077&deg) are the mechanical discontinuities most likely to be reactivated and allow fluids to flow along their surfaces. This reactivation will occur if the magnitude of pressure sources such as pore pressure or fluid pressure exceeds the reactivation pressure for that fracture surface.

Research suggests that motivation for drug abuse treatment increases as psychological and social problems increase, but decreases as criminal thinking increases. Despite these two constructs having opposing influences on motivation, they are positively correlated such that high amounts of one are associated with high amounts of the other. The current study demonstrated these confounding relationships in a large data set including 7,623 men and women from 8 correctional-based treatment centers from two states. Although the hypothesis that criminal thinking would moderate the psychosocial dysfunction--treatment motivation relationship was not strongly supported, two revealing findings presented themselves. First, criminal thinking and psychosocial dysfunction differentially predict different stages of treatment motivation. Secondly, suppression effects reveal that most of the relationship between psychosocial dysfunction and criminal thinking is unrelated to treatment motivation, and thus their high correlation with each other and inverse relationships to motivation are less challenging. Implications for treatment are discussed.

This project examines ancient volcanic boulders derived from the Laurentian shelf and contained in Ordovician off-shelf sediment gravity-flow deposits in the Marathon fold-thrust belt, West Texas. Thirty-six volcanic clasts up to 70 cm across were analyzed from the Lower Ordovician Marathon Formation, Middle Ordovician Fort Peña Formation, and Upper Ordovician Woods Hollow Shale. The clasts are unmetamorphosed but show variable low-temperature alteration. Major and trace element geochemical analyses show a compositional range from alkali basalt through trachyandesite to trachyte. Trace element contents for both the mafic and felsic clasts indicate within-plate settings with an OIB-type source for the volcanism. Felsic clasts in the Fort Peña Formation yielded U-Pb zircon ages of ~706 Ma. These data indicate that the volcanic clasts were derived from one or more Neoproterozoic intrapate volcanic terranes, possibly rift-related, that developed near or along the southern Laurentian margin.

Differential dissolution and erosion are significant controls during evolution of most karsted environments. If rock matrix, grain size, and cementation are homogenous and consistent, the rock dissolves in a quantifiable manner, producing a predictable karst environment. However, because carbonate rock is neither homogenous nor consistent, differential dissolution and erosion result in karst topography, which appears non-quantifiable and unpredictable. Previous studies have shown that heterogeneity, solubility, competency and joint frequency of the host rock control differential dissolution and erosion in karsted terrains. This study suggests that the additional parameters of slope, bed thickness, joint orientation, and bed dip are also important controls on karst development.

Controlled delivery of antibacterial agents remains a topic of widespread significance, given the need for sustained release of therapeutically relevant concentrations. Porous Si (PSi), and the mesoporous form in particular, possesses useful properties relevant to its use in medical therapies such as drug delivery and tissue engineering. For drug delivery, both the biodegradability of mesoporous Si and its ability to nanostructure a given encapsulated substance present marked advantages. In this work we have systematically investigated the influence of the properties of mesoporous silicon on both controlled release and antibacterial assay for the case of the loaded antibacterial drug triclosan and its activity versus Staphylococcus aureus. Specifically, the role of Si porosity, loading method, surface chemistry and particle morphology on the above outcomes are explored. For long term stabilization of the drug-loaded PSi, preliminary experiments regarding organosilicon and organotitanium surface coatings have also been carried out. The role of PSi porosity on drug delivery has been highlighted by a comparison between the properties of triclosan loaded into porous silicon with high (81%), medium (65-75%), and low porosity (13%). The significant differences in triclosan release behavior are demonstrated in their corresponding antibacterial disk diffusion assays. A remarkable sustained triclosan release beyond 100 days from mesoporous silicon matrices was revealed, combined with an enhanced concentration of released triclosan. Due to the high surface area of these mesoporous materials, surface chemistry is expected to have a significant impact on drug delivery. Since freshly-etched PSi with its hydride-terminated surface possesses a relatively rapid degradation rate in aqueous media, derivatization of PSi by oxidation or chemical modification is needed. In this study, a relatively long octyl chain is covalently attached to the mesoporous silicon surface, which possesses hydrophobicity and inhibits aqueous dissolution. A combination of thermogravimetric analysis, X-ray diffraction, electron microscopy, and FT IR spectroscopy, in addition to triclosan release and antibacterial assays, are employed for this purpose. A preliminary study involving organosilica and organotitania surface coatings on PSi was also conducted. FT IR spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analyses, and subsequent antibacterial assays confirm that the coating is present.

The human immunodeficiency virus type 1 (HIV-1) causes the acquired immune deficiency syndrome (AIDS). Three essential enzymes are necessary for HIV-1 replication: reverse transcriptase (RT), integrase (IN), and protease (PR). Current drugs target RT and PR, but there is substantial interest in inhibitors targeted at IN, which catalyzes the integration of the proviral DNA into the host cell's DNA. The only two reported classes of compounds considered lead molecules for clinically useful HIV IN inhibitors are the dicaffeoyltartaric acids, of which L-chicoric acid (L-CA) is the lead compound, and the second are the aryl diketo acids (DKAs). These compounds prevent proviral DNA integration and inhibit HIV-1 replication at non-toxic concentrations in cell culture. Our research focused on: 1) scaffold modification of L-CA; 2) catechol modification of L-CA; and 3) synthesis of hybrid DKA/catechol molecules. In the first part, three conformationally restricted cyclopentane analogues of L-CA were synthesized and tested against HIV IN, and HIV replication. Several showed good anti-HIV IN activity, with the isomer having caffeoyl groups on the opposite side of the ring from the carboxyl group being the most active, thus suggesting this preferred conformation in the IN active site. Neither the rigid analogues nor a synthesized open-chain analogue had significant anti-HIV replication activity. In the second part, six 2-pyridone analogues of L-CA were synthesized, but only one had moderate anti-HIV IN and anti-HIV activity supporting the conclusion that catechols are required for anti-HIV and anti-HIV IN activity and that simple 2-pyridones are not bioisosteres of catechols. In the third part, six synthesized DKA/catechol hybrids were potent IN inhibitors with the compound with the diketo acid and catechol moiety in a meta-orientation being the most active, even more so than L-CA and some DKA drug candidates. Against HIV replication, only two compounds showed moderate activity, but less so than either L-CA or simple DKAs. The results suggest that caffeoyl are preferred to simple catechol groups and one caffeoyl group is sufficient for inhibition of either HIV IN or HIV replication. Methyl esters in all the above series were less active than their corresponding acids in both assays.

A GIS study of landslides in the lower Los Amigos sub-basin in Peru, where human influence on drainage is nearly non-existent, was performed to determine environmental variables controlling landslides. GIS layers consisted of slope, landslides (381 digitized), Soils, and elevation. I applied Ripleys K-function to estimate spatial extent of correlation between the landslides. The MIKE-SHE hydrologic model was used to determine the unsaturated soil-water pressure in the soil profile. Spatial regressions were performed between landslide counts in a 1X1 km grid and environmental variables: slope, aspect, distance of landslide from nearest river, and soil-water pressure. My conclusions are that landslides were spatially correlated at about 2km lengths, and variations of pore-water pressure in the soils significantly controlled landslide occurrence. Landslides along river meander paths may be an important factor that controls the evolution of foreland basins

The diversity, richness and abundance of the Myristicaceae family of plants were assessed in a tropical moist forest in Madre de Dios, Peru. There were 15 species among three genera, Iryanthera, Otoba and Virola at the Los Amigos Conservation Concession. Using a novel mapping technique, geographic coordinates were assigned to 9026 individual trees (¡Ý 0.5 m in height) in approximately 30 hectares of forest. All mapped trees were identified to species, and measured for biometric parameters such as DBH (diameter at breast height) and height, and a voucher specimen was collected with duplicates deposited at various herbaria. These georeferenced data were used to analyze preferred association with one of the two major habitats, seasonally flooded forests (SFF) and terra firme forests (TFF), and used to analyze spatial patterns of distribution adhering to either a random, uniform or clumped distributions.