Theses

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  • Synthesis and Application of Chiral Palladium-Phosphane Precatalyst in Enantioselective C-N Cross-Coupling
    Synthesis and Application of Chiral Palladium-Phosphane Precatalyst in Enantioselective C-N Cross-Coupling
    The various strategies and reaction conditions towards the synthesis of benzene-, naphthalene-, and phenanthrene-based dicyclohexylbiaryl phosphanes are presented. A chiral third generation Buchwald-type precatalyst has been synthesized, employing the non-commercially available ligand, (R)-dicyclohexyl(2'-methoxy-[1,1'-binaphth-2-yl])phosphane, (R)-Cy2MOP, and a dimeric methanesulfonate-bridged palladacycle based on a 2-aminobiphenyl scaffold. Application of the palladacyclic precatalyst in an enantioselective variant of the BuchwaldHartwig reaction is demonstrated in the desymmetrization of prochiral α-(2-bromobenzyl)malonamides via intramolecular N-arylation. The scope of the catalysis in the presence of the precatalyst has been investigated with efforts towards optimizing yields, catalyst loading, and enantioselectivities. Attempts towards the isolation of a potential reaction intermediate in the form of a stable amido-bound palladium complex are discussed. Finally, strategies towards gaining mechanistic insight on the origin of the enantiomeric excess are discussed.
    Synthesis and Investigation of Perfluorinated Polystannanes
    Synthesis and Investigation of Perfluorinated Polystannanes
    Two fluorinated tetraaryl stannanes, 1 and 2 were synthesized in good yields. X-ray crystallography revealed deviation from ideal tetrahedral geometry with C-Sn-C bond angles between 107.89°-112.7° for 1 and 104.69°-120.76° for 2. Dichlorides 4 and 5 were synthesized using a redistribution reaction between SnC1₄ and 1-2. These dichlorides also deviated from tetrahedral geometry with bond angles between 101.79°-128.44° for 4 and 99.23°-125.9° for 5. Polymerizaton of 4 and 5 by Wurtz coupling produced polymers 10 and 11. Absolute molecular weights in the range of 1.16 x 10⁵-2.92 x 10⁷ Da was estimated for 10 and 1.47 x 10⁵ Da for 11. UV/VIS spectroscopy gave values of 332 nm and 328 nm that are blue shifted to other polystannanes. The unexpected cleavage of a tin-aryl bond produced tin trihydrides 8 and 9. Polymerization of 8-9 produced the network polymers 12 and 13 with [wavelength]max values of 354 nm and 350 nm.
    Synthesis and characterization of ferrocenyl stannanes and polyferrocenyl stannanes
    Synthesis and characterization of ferrocenyl stannanes and polyferrocenyl stannanes
    A novel polymer polybis(dimethyl stannyl)ferrocene was synthesized through both metal catalyzed intermolecular dehydrogenative condensation and ring-opening polymerization. This polymer was the first evidence of a dibridged polyferrocenyl stannane, and was found to be of low to moderate molecular weight by gel permation chromatography and 1H NMR spectroscopy. This polymer displayed extensive electronic communication observed previously synthesized monobridged ferrocenyl stannane polymers. The first tristanna-bridged 3.3]ferrocenophane was discovered through an amine coupling of a tin amine, and 1,1’bis(dimethyl stannyl) ferrocene. The [3.3]ferrocenophane displayed a strong interaction between connected ferrocenes despite the large distance, (8.49 Å) between Fe centers. Finally, a new and improved synthesis of 1,1,2,2-tetramethyldistanna-[2]ferrocenophane was found. This metal catalyzed intramolecular dehydrogenative coupling employs Pd2(dba)3 as a catalyst and yields 90% product. All products were characterized where possible 1H, 13C, and 119Sn NMR and UV-Visible spectrocopy, as well as through cyclic voltammetry and DFT modeling.
    Synthesis and characterization of theranostic agents for photoacoustic imaging and therapy.
    Synthesis and characterization of theranostic agents for photoacoustic imaging and therapy.
    In this work, phase-change contrast agents were developed for photoacoustic (PA) imaging and therapy. They consist of superheated liquid perfluorocarbon and gold nanoparticles capped by a Poly-(Lactide-co-Glycolic Acid) (PLGA) polymer shell. The phase transition from liquid to gas bubble can be remotely triggered by a laser source. In their liquid state, upon laser irradiation, these agents generated strong PA signals which were proportional to the laser fluence and particle sizes. The vaporization threshold decreased with increasing particle size, and was 850, 670 and 420 mJ/cm2 for 2, 5, 10 μm-sized PLGA particles loaded with 35 nm GNPs, respectively. Cell culture studies, including passive uptake by the cancer cells and mechanical damage to the cancer cells caused by the vaporization inside the cells are also investigated. These agents show potential as photoacoustic imaging contrast and cancer therapy agents for clinical applications.
    Synthesis and structure-property studies of organic dyes possessing unique fused thiophene π-spacers
    Synthesis and structure-property studies of organic dyes possessing unique fused thiophene π-spacers
    This thesis examines the synthesis of metal-free organic dyes for light-harvesting applications within the DSSC manifold. All DSSC organic dyes possess a similar donor-π-spacer-acceptor (D-π-A) motif. Here, triphenylamine (TPA) is employed as a donor owing to its redox stability and cyanoacetic acid has been utilized as an acceptor due to its electron-withdrawing ability. Thiophenes are ubiquitous in organic materials chemistry owing to their exceptional charge transport behavior, and in this body of work, π-spacers incorporating benzodithiophene and thiophene-quinones have been incorporated into a DSSC dye and their utility explored. Fused thiophene cores are non-innocent π-spacers. Non-innocent, in this context, is defined as π-spacers that incorporate a secondary chromophore or redox active species (benzodithiophene or quinone).
    Synthesis of Classical and Non-Classical CMOS Transistor Fault Models Mapped to Gate-Level for Reconfigurable Hardware-Based Fault Injection
    Synthesis of Classical and Non-Classical CMOS Transistor Fault Models Mapped to Gate-Level for Reconfigurable Hardware-Based Fault Injection
    One of the main goals of fault injection techniques is to evaluate the fault tolerance of a design. To have greater confidence in the fault tolerance of a system, an accurate fault model is essential. While more accurate than gate level, transistor level fault models cannot be synthesized into FPGA chips. Thus, transistor level faults must be mapped to the gate level to obtain both accuracy and synthesizability. Re-synthesizing a large system for fault injection is not cost effective when the number of faults and system complexity are high. Therefore, the system must be divided into partitions to reduce the re-synthesis time as faults are injected only into a portion of the system. However, the module-based partial reconfiguration complexity rises with an increase in the total number of partitions in the system. An unbalanced partitioning methodology is introduced to reduce the total number of partitions in a system while the size of the partitions where faults are to be injected remains small enough to achieve an acceptable re-synthesis time.
    Synthesis of Metal-Coordinating Arenediynes And Study Of Their Reactivity in Bergman Cyclization
    Synthesis of Metal-Coordinating Arenediynes And Study Of Their Reactivity in Bergman Cyclization
    The Bergman cycloaromatization (BC) in which a cis-alkene-1,2-diyne (enediyne) cyclizes to form a p-benzyne diradical, typically is a very endothermic reaction, requiring a substantial amount of energy (i.e. high temperature) for it to proceed. This reaction received very little attention until a decade after its discovery, when the natural enediynes were isolated and shown to be the most active antitumor agents every discovered. Having BC at the heart of their mode of action, these natural enediynes have been very challenging to mimic from synthetic standpoints. Of particular interest is to be able to design and synthesize an enediyne that is stable at room temperature, while also being capable of being triggered to undergo BC under ambient conditions. Although a relatively new concept, metal-induced BC reactions have generally been known to decrease the demanding energy barrier. The work presented here describes several synthetic strategies towards arenediyne crown eithers and the synthesis of several arenediyne hydrazone/Schiff base ligands with extended n-systems. These synthesized enediynes are useful ligands, capable of metal-cordination and hence potentially decreasing the BC energy barrier. BC reactions of enediyne intermediates are also reported.
    Synthesis of Nanotips Through Femtosecond Laser Ablation of Glass with Assisted Gas
    Synthesis of Nanotips Through Femtosecond Laser Ablation of Glass with Assisted Gas
    Nanotips are the key nanostructures for many applications. Until now, the nanotips of only the crystalline materials have been produced via various deposition methods which require sophisticated equipment, high vacuum, and clean room operations. This thesis proposes a single step, rapid synthesis method using femtosecond laser irradiation at megahertz frequency with background flow of nitrogen gas at ambient conditions. Amorphous nanotips are obtained without the use of catalyst. The nanotips grow from highly energetic plasma generated when target is irradiated with laser pulses. The vapor condensates, nanoparticles and droplets from the plasma get deposited back on to the hot target surface where they experience force imbalance due to which the stems for the nanotips growth are initiated. Once the stems are generated, the continuous deposition of vapor condensates [sic] provides building materials to the stems to complete the growth of nanotips. Further study found that the growth of the nanotips is influenced by laser parameters and gas conditions.
    Synthesis of silver nanoparticles on a solid surface using a classical photographic method
    Synthesis of silver nanoparticles on a solid surface using a classical photographic method
    A classical photographic method, the Becquerel method, produces a positive image comprised of silver nanoparticles on a silver surface. The particles are grown by exposing an iodised silver plate to light in the blue or ultraviolet, which initiates the formation of particles, followed by development (growth) with light in the red portion of the spectrum. Because the Becquerel method is essentially a means of producing a surface of patterned nanoparticles, it also has potential technological applications. This thesis is a systematic investigation of the Becquerel method. . It was determined that the initiation of nanoparticles is effective for wavelengths in the range 447 to 254 nm. The sudden rise in nanoparticle production around 447 nm implicates direct excitation of the AgI layer in the initiation step; however, the behaviour of the action spectrum at shorter wavelengths implies an electron-mediated mechanism. It is possible that both direct excitation and electron-mediated processes occur in the ultraviolet. Scanning electron micrographs indicate that nanoparticle morphology may be dependent on the initiation wavelength, with longer wavelengths producing a variety of shapes, while shorter wavelengths produce primarily dots. Nanoparticle growth (development) was achieved with all wavelengths studied; however, shorter wavelengths photons were more effective than longer wavelengths. The results from a study of the aging of the AgI film suggested that there is period of one or two days during which the film ‘matures,’ becoming more effective for nanoparticle production.
    Synthetic Aperture Imaging : Applications In High-Frequency Ultrasound
    Synthetic Aperture Imaging : Applications In High-Frequency Ultrasound
    Synthetic Aperture (SA) is an imaging method that uses the motion of a single-element transducer to synthesize the effect of a larger array transducer. In synthetic aperature ultrasound imaging (SAUI), a single-element transducer which works as both the transmitter and receiver is used to record pulse echoes in a region of interest at multiple, sequential locations. The SA imaging inverse problem is the processing of these signals to form a high-resolution image of the ROI. The aim of this project is to implement SAUI in the frequency domain and incorporate the effects of the beam pattern into image reconstruction algorithm.The images reconstructed applying the new SA algorithms to the simulated and experimental data demonstrate the effectiveness of some of the proposed methods in improving the lateral resolution beyond the focal point.The principles, simulated and experimental results, and implementation issues of the new algorithms are describe in this thesis.
    Synthetic aperture imaging in acoustic microscopy
    Synthetic aperture imaging in acoustic microscopy
    Acoustic microscopy (AM) provides micro-meter resolution using a highly focused single-element transducer. A drawback in AM is a relatively small depth of field, resulting in poor resolution outside the focus. Synthetic aperature focusing technique (SAFT) can be used to improve the image resolution throughout the field of view. SAFT mathematically synthesizes the effect of an array transducer and produces dynamic focusing and depth-independent resolution. SAFT in time domain with and without apodization, TD-SAFT and ATD-SAFT, respectively, and in frequency domain (FD-SAFT) were implemented and tested using simulated and experimental radio-frequency data from an acoustic microscope at 400 MHz. Lateral resolution of all the SAFT reconstructed images were better than those of the conventional B-mode images. While TD-SAFT and FD-SAFT permformed better than ATD-SAFT in improving the lateral resolution, ATD-SAFT provided lower side lobes. In conclusion, SAFT improves resolution in AM outside the focal region.
    Synthetic futurism:  exploring the possibilities of limitless architectural change and growth
    Synthetic futurism: exploring the possibilities of limitless architectural change and growth
    Buildings do not have to burst out of the ground with a predetermined identity. They have an inherent need to grow, change and reinvent themselves to reflect the changes among the people and context. In the ever-changing condition of the context, the design of a building must be conscious of and attuned to the growing needs of society. It cannot assume it is destined for a singular purpose, as instead it is defined by a continuity of growth and reinvention. With the onset of contextual changes, the fleeting moment of a design’s conception becomes less significant. In turn, what rises in import is the integration of contingency to allow a design to metabolize the effects of the contextual change and synthesize new solutions within a flexible, absorptive system. Each added component through its relationship with subcomponents and previously existing elements can serve to create diversity, continuity and flexible internal hierarchies between continuous servant and served space. The summation of the Group Form that results from the melding of many parts can allow the buildings identity to shift as the individual parts reform and change to form new cohesive identities. By manufacturing the base and set of core components, a radically diverse system can grow beyond the limits of the originating elements, adding malleability to the many comprising identities.