Published ETD Collection
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Item 1,3-Dipolar and 1,3,6-Tripolar Reactivity of 3-hydroxy- and 3-amino-1-N-arylazopropenes for Heterocycle Formation(2019-12) Bolinger, Andrew Arch 1989-; May, Jeremy A.; Coltart, Don M.; Teets, Thomas S.; Do, Loi H.; Gilbertson, Scott R.; Cirino, Patrick C.3-Alkoxy-1-N-aryl azopropene structural motifs in the Eschenmoser-Tanabe Fragmentation pathway have been known for almost 50 years, yet one unexploited feature of these intermediates is their putative 1,3-dipole. Described here is a transformation leveraging this reactivity to synthesize an important class of oxygen heterocycles, β,γ-fused bicyclic γ-lactones, by the simple combination of an ester or acyl pyrrole, an α-epoxy-2-nitrophenyl hydrazone, and a base. The products of this reaction, including those containing quaternary centers, are generated with high (up to >25:1) diastereoselectivity. Conveniently, both syn- and anti-fused bicyclic systems can be generated stereoselectively by simply changing the counter-ion of the base, LiHMDS and KHMDS, respectively. This dissertation also describes the development of a new functional group, 3-amino-1-azopropene, and its use in novel annulation strategies leading to N-heterocycles, which are important structures found in drugs and biologically active natural products. The 3-amino-1-azopropene functional group possesses multiple nucleophilic sites and, as such, is expected to inspire the development of a wide range of new synthetic methods and/or find applications in the development of new drugs and materials. Lastly, as part of the continuing effects to develop new reactions for the formation of saturated heterocycles, the conjugated π systems of azoalkenes in 3-hydroxy-azopropenes and 3-amino-1-azopropene were utilized in a [4+2] cyclization reaction in order to achieve ring closure. Compounds were prepared in high (up to >25:1) diastereoselectivity from a cascading Tsuji-Trost [4+2] cycloaddition, producing a wide array of fused tetrahydrofuran- and pyrrolidine- tetrahydropyridazine derivatives.Item 1,4–Conjugate Addition with Pyrrole and Indole Enones & Propargylic Substitution using Boronic Acids as Nucleophiles with Gallium and Silver Catalysts(2021-08) Boylan, Amy; May, Jeremy A.; Gilbertson, Scott R.; Cuny, Gregory D.; Miljanić, Ognjen Š.; Guloy, Arnold M.This dissertation covers two projects: 1,4–conjugate addition on pyrrole and indole enones, and propargylic substitution using boronic acid as nucleophiles and silver/gallium catalysts. b-(2-indole)-enones and b-(2-pyrrole)-enones, both historically problematic substrate types with 1,4–conjugate addition reactions, were extensively examined. Analysis of isomer- related reaction rate trends showed that proximity of a heteroatom to the enone b-carbon was favorable to reaction rate and increased resonance electron donation also increased reaction rate. These enantioselective conjugate addition reaction were ultimately enhanced by using a less electron deficient catalyst and a base additive, ammonium carbonate. After many reactions and substrates were studied, this base was shown to have an advantage effect on enhancing the conjugate addition reaction but had an adverse effect on the starting material, which lead to other side reactions with this conflicted system. For the second project, three methods have been developed for nucleophilic propargylic substitutions that have been useful in forming tertiary carbons: (IPr)GaCl3/AgSbF6 with boronic acid at 23°C, AgSbF6 with boronic acid at 40°C, and GaCl3 with boronic acid at -78°C. A combination of AgSbF6 and IPrGaCl3 along with boronic acids at lower temperatures have been shown to decrease reaction times for the formation of nucleophilic substitution through the displacement of propargylic alcohols. GaCl3 with boronic acid at -78°C proved to be the best conditions for the formation of the quaternary carbon centers. An expanded substrate scope and nucleophile scope have been developed for the formation of the tertiary carbon centers and quaternary carbon centers using these three methodItem 1. Attempts to Prepare Porous Materials Based on Thiols and Fluorinated Precursors 2. Self-Sorting of Complex Libraries during Kinetically Controlled Acylations(2015-08) Liang, Xiao 1990-; Miljanić, Ognjen Š.; Cai, Chengzhi; Coltart, Don M.; Xu, Shoujun; Conrad, Jacinta C.This thesis presents three studies in supramolecular chemistry. First is the synthesis and characterization of dynamic covalent disulfide bond based metal-organic framework (MOF), second is development of the fluorinated and imine-based non-covalent organic framework (nCOF), and the third is of molecular recognition between nucleophiles and acyl chlorides. Chapter One follows the ligand design and post-synthetic tailoring as the two most important strategies in synthesizing new metal-organic frameworks (MOFs). Organic dynamic covalent ligand 4,4’-dithiobisbenzoic acid (DTBA) was designed to synthesize a new MOF with metal Cu. These new Cu-DTBA MOF crystals were then tested by reduction on reversible disulfide moieties in the organic ligand but the resulting product could not be further recrystallized. Cu-DTBA templated inter-molecular self-sorting between two disulfide ligands could be achieved successfully, but intra-molecular self-sorting from the single cross-linked disulfide ligand produced a different type of material which did not show the exchangability of disulfide bonds. Chapter Two shows the development of the nCOFs’ structures based on the previous trispyrazole nCOF studies. The necessity of the terminal pyrazole and its trigonal ligand topology were confirmed by synthesizing and characterizing the following two nCOFs. Partially fluorinated trisphenyl nCOF replaced the terminal pyrazole by phenyl ring, which eliminated the hydrogen bonding, as well as linear imine-based nCOF which formed a different topology. The single crystal X-ray result of the two showed a three-dimensional infinite network structure, but with very little voids that cannot be useful as porous solids. Chapter Three introduces the simultaneous ordering and categorizing processes, i.e., self-sorting, which can occur under both thermodynamic and kinetic control. Thermodynamically controlled self-sorting phenomena widely exist in nature, while kinetically controlled self-sorting usually requires stimuli to help simplify the complex. Therefore, acylations between nucleophiles and acyl chlorides as fully kinetically controlled self-sorting systems were conducted. A series of [2×2] systems was conducted in order to find reactivity differences among nucleophiles as well as acyl chlorides. Furthermore, nine successful [3×3] systems achieved successful self-sorting with high selectivity.Item 1. C-C Bond Formation via Soft Enolization and Umpolung-like Chemistry 2. Electrophilic Fluorination of Organozinc Reagents(2020-12) Aderibigbe, Sabrina Olunike Wande; Daugulis, Olafs; May, Jeremy A.; Gilbertson, Scott R.; Chen, Tai-Yen; Ozerov, Oleg V.Synthetic methodology development towards convenient C-C bond and C-F bond formation is a desirable synthetic tool for industry and academia. Using commercially available substrates towards chemical transformations is often a strategy used to simplify the process of synthesizing compounds. This dissertation focuses on the synthetic methodology development of C-C and C-F bond formation for broad applicational utility. This dissertation will discuss two synthetic strategies towards C-C bond formation, soft enolization and Umpolung-like chemistry. The direct synthesis of 1,3-diketones and β-keto thioesters using in good yields and with wide substrate tolerance was possible using our soft enolization strategy using crude acyl chlorides. Another C-C bond strategy explored was an Umpolung-like approach towards α-functionalization of ketones. Ketones are synthetically important functional group and have wide applicational uses within chemistry and biology. The α-functionalization of ketones and their derivatives via addition of their corresponding (aza) enolates to alkyl halides is a fundamental synthetic transformation but has been historically less explored despite its potential widespread utility. Our approach towards uses a novel β-silylated azoalkenes intermediate towards anti-diastereoselective α-alkylation of ketones. In addition, we explored a streamlined approach towards monofluorohydrocarbon formation via electrophilic fluorination of organozinc compounds. We hope this will have wide applicational utility as C-F bonds are important within agrochemistry and pharmaceutical chemistry.Item 1. SELF-SORTING OF DYNAMIC IMINE LIBRARIES UNDER CHEMICAL AND PHYSICAL STIMULI; 2. CHARACTERIZATION OF POROUS MATERIALS BASED ON A FLUORINATED TETRAZOLE(2016-05) Hsu, Chia-Wei 1984-; Miljanić, Ognjen Š.; Daugulis, Olafs; Baldelli, Steven; Cuny, Gregory D.; Thummel, Randolph P.Chapter 1 introduces the self-sorting processes of dynamic combinaotrial libraries (DCLs) under thermodynamic and kinetic control. Based on the concept of dynamic combinatorial chemistry (DCC), disulfide exchange, imino bond formation, transesterification, and metal-ligand interaction are widely utilized to perform the re-equilibration of molecules. Simplification of multicomponent systems and the manipulation toward the direction of equilibrium are reviewed. Chapter 2 of this dissertation describes an application of a new external stimulus—adsorption on the silica gel surface—to dynamic imine libraries constructed of as many as four aldehydes and four anilines. During the elution process, imines keep trading their components, resulting in the amplification of the least polar imine which travels down the silica gel-based column the fastest. This process is then iteratively repeated to isolate the next least-polar component in the remaining imine library, eventually simplifying the library from n2 into n members. In Chapter 3, we demonstrated iterative simplification of a dynamic imine library constructed from 10 aldehydes and 10 anilines using three orthogonal external stimuli. First, mild oxidation (using molecular iodine as an oxidant) was applied to oxidize the most electron rich imine with the rapid imine exchange. In the second self-sorting step, we obtained a halogenated [2×2] sub-system with bromo- and chloro-substituted imines from the imine library. Third and final step was a slow distillation of the residual imines from the column, leading to the amplification of the least volatile imine in 61% yield. Ultimately, this [10×10] imine library is simplified into two major products and one sub-system after iterative self-sorting. Chapter 4 will describe the synthesis and characterization of a porous material based on an extensively fluorinated aromatic tristetrazole. This molecule crystallizes in a porous structure which is held together through [N−H…H] hydrogen bonds and electrostatic interactions between C–F units in these molecules. This porous material is compositionally stable up to 270 °C and shows selective adsorption of CO2 over N2 (15:1 in mmol g−1) at 195 K and 760 mmHg.Item 1. Synthesis of New Polyfluoroaryl Materials. 2. New Transition Metal Catalysts for Enantioselective C – H Bond Functionalization.(2021-12) Lieu, Thien Ngoc; Daugulis, Olafs; Miljanić, Ognjen Š.; Wu, Judy I-Chia; Teets, Thomas S.; Rimer, Jeffrey D.1. Synthesis of new polyfluoroaryl materials. Polyfluorinated porous materials are essential in sequestration of fluorine pollutants due to their high water resistance and fluorophilic ability. In 2014, our and Dr. Miljanic group introduced a triangular porous material prepared from perfluoro organic compounds, showing remarkably selective adsorption toward halogenated hydrocarbons. Based on the precedent published in 2014, we attempted to increase the pore size of this material by inserting 2,2’-bipyridine groups on each linkage arm. Furthermore, modification of central arene groups was accomplished by using 1,3,5-triazine or 1,3,5-trifluorobenzene. In addition, ferrocene based fluorine material and two tetragonal fluorine compounds containing pyrene and tetraphenylethylene core were successfully synthesized by using copper catalysis as a main step. Among these compounds, tetraphenylethylene-based structure showed different emissive behaviors under ‘wet’ and ‘dry’ conditions. Other fluorinated tetraphenylethylene compounds such as (Z)/(E)-bis(pentafluorophenyl)stilbene, and tris(pentafluorophenyl)ethylene were synthesized using copper catalysis. In addition, their reactivity and selectivity in photocyclization reactions was also explored. 2. New transition metal catalysts for enantioselective C – H bond functionalization. Enantioselective carbon-hydrogen bond functionalization using transition metal catalysis is one of the most powerful tools in organic synthesis. This method offers a straightforward route to obtain enantiopure isomer compounds. Thus, in the second part of this dissertation, two new types of potential chiral catalysts were developed and their reactivity was explored. A series of new C3-symmetric tridentate sulfur-containing ligands were synthesized. Various transition metals such as rhodium, iridium, ruthenium, and copper were coordinated to these ligands. In addition, catalytic activity of copper(I) and ruthenium (II) complexes was proved in carbene and nitrene C-H insertion reactions. Finally, aminoquinoline-directed enantioselective coupling of sp2 C-H bonds with alkenes using new cobalt catalyst was explored. The catalyst tolerates a broad substrates scope such as styrenes and aliphatic alkenes, giving low to medium level of enantioselectivity. This result may open an opportunity in asymmetric functionalization using bidentate directing groups, which sp far has proven very difficult.Item A MM/QM Approach to Simulating Electron/Hole Separation Kinetics of Organic Polymers Bulk-Heterojunctions(2016-12) Kelley, Allen 1982-; Bittner, Eric R.; Lubchenko, Vassiliy; Cheung, Margaret S.; Xu, Shoujun; Gilbertson, Scott R.We investigate the electronic dynamics of model organic photovoltaic (OPV) system consisting of polyphenylene vinylene (PPV) oligomers and [6,6]-phenyl C61-butyric acid methylester (PCBM) blend using a mixed molecular mechanics/quantum mechanics (MM/QM) approach. The π-MDX code is introduced and a methodology that allows the quantum treatment of the π systems of large clusters of molecules near the interface is developed. Using a heuristic model that connects energy gap fluctuations to the average electronic couplings and decoherence times, we provide an estimate of the state-to-state internal conversion rates within the manifold of the lowest few electronic excitations. We find that the lowest few excited states of a model interface are rapidly mixed by C=C bond fluctuations and low frequency torsional modes such that the system can sample both intermolecular charge-transfer and charge-separated electronic configurations on a time scale of 20fs. We show that the electronic dynamics of the OPV are dramatically altered by varying the positions of the molecules simulated at the interface. Our simulations support an emerging picture of carrier generation in OPV systems in which interfacial electronic states can rapidly decay into charge-separated and current producing states via coupling to vibronic degrees of freedom.Item A Ratiometric Probe for Rapid Evaluation of Transfer Hydrogenation Efficiency(2023-12) Young, Yen An; Do, Loi H.; Carrow, Bradley P.; Comito, Robert J.; Şen, Mehmet; Teets, Thomas S.The aim of this thesis is to design and synthesize a luminescent cyclometalated Ir(III) complex with ratiometric response to transfer hydrogenation reaction, intended for better understanding and quantifying the Small-Molecule Intracellular Metal Catalysts (SIMCats) efficiency. Chapter 1 gives an introduction to luminescent probes, cyclometalated Ir complexes, transfer hydrogenation reaction, and SIMCats. It provides background knowledge and shows how we designed the ratiometric Ir complex (RIC). Chapter two shows the experimental procedure and results from synthesis, characterization, photophysical properties studies, and the transfer hydrogenation studies using a plate reader. The RIC575 probe coverts to RIC525 upon reduction, exhibiting a 50 nm hypsochromic shift in its emission maximum. This hypsochromic shift was later proved to be significant enough for ratiometric quantification. 10 different Cp*Ir catalysts were study with RIC575 using well plate and plate reader.Item A Renaissance of the (Anti)Aromaticity Concept in Modern Applications of Organic Chemistry(2021-08) Wen, Zhili; Wu, Judy I-Chia; May, Jeremy A.; Cai, Chengzhi; Teets, Thomas S.; Grabow, Lars C.This dissertation focuses on applying computational quantum chemical tools to explore modern applications of aromaticity and antiaromaticity in organic chemistry. Even though all sophomore organic chemistry students learn about the concepts of aromaticity and antiaromaticity, these ideas continue to find exciting applications in active areas of research. The topics covered in this dissertation include understanding the effects of supramolecular self-assembly on the electronic properties of organic pigments and understanding the origin of acidity differences in popular photoacids. We found that organic pigments with bifunctional hydrogen bonding sites, such as indigo, isoindigo, diketopyrrolopyrrole, and naphthodipyrrolidone, can self-assemble through hydrogen bonding interactions, showing increased [4n] π-electron antiaromaticity and lower LUMO energy levels. The reciprocal relationship between hydrogen bonding and antiaromaticity gain makes them good candidates for components of n-type organic field-effect transistor (OFET) materials. We found that π-polarization of acridone compounds can perturb the numbers and positions of Clar sextet rings. Decreasing numbers of Clar sextets are connected to experimental observations of a narrowing HOMO-LUMO gap and increased charge mobility in hydrogen-bonded assemblies of quinacridone and epindolidione. We also found that many organic acids that are Hückel aromatic in the ground state can convert to Baird antiaromatic in the excited state, triggering facile proton transfer. Stronger photoacids show enhanced “antiaromaticity relief” upon releasing a proton. Together this series of works highlight examples of the underlying effects of (anti)aromaticity in organic chemistry and increase chemical understanding.Item A Rhodium-Catalyzed [(4+2)+2] Cycloaddition of Allenediene for the Synthesis of Medium-Sized Rings(2018-08) Wang, Dihuang 1991-; Gilbertson, Scott R.; May, Jeremy A.; Do, Loi H.; Das, Joydip; Halasyamani, P. ShivThe synthesis of the compounds with medium-sized rings, especially those with a 5,8-fused ring system embedded into the structure, had long been pursued due to their ubiquitousness in numerous natural products and pharmaceutical molecules. These rings could be efficiently synthesized using metal-catalyzed higher order cycloaddition. In our studies, a previously-reported Rh-catalyzed [4+2+2] cycloaddition was developed and optimized to generate fused systems with a cyclooctadiene core from allenedienes and external alkynes. Upon screening of various metal complexes, ligands and solvents, a rhodium-BozPHOS complex was found to have the best reactivity. This cycloaddition between allenedienes and alkynes showed moderate yield and good substrate tolerance, showing good synthetic potential.Item A Structure-Activity Relationship Study with Isoquinolinone Compounds and Stromal Antigen 2 Mutant Ewing’s Sarcoma Cells and Synthesis of Small Molecules for Anticancer Activity Through TEAD Palmitoylation Inhibition(2023-04-26) Yang, Christian; Gilbertson, Scott R.; Lee, T. Randall; Comito, Robert J.; Chen, Tai-Yen; Pati, DebanandaThere are two distinct projects that will be discussed in this dissertation. The first section will be focused on the structure-activity relationship study with isoquinolinone compounds, and the second on the synthetic approach to small molecules that inhibit the growth of cancer cells through the Hippo signaling pathway. Ewing’s sarcoma is the second most commonly diagnosed pediatric bone cancer. While there are common forms of general treatment available, there are little to no treatments for recurrent cases, as well as malignant tumors. Our collaborators at the Baylor College of Medicine found in a high throughput screening an isoquinolinone compound, StagX1, which is selectively active in inhibiting and decreasing the cell viability of STAG 2 mutant cancer cells in an environment of wild type cancer cells. SAR studies have been performed to find new derivatives with increased the efficacy, general solubility, and plasma stability. Different delivery systems, such as liposomes, have been implemented to help identify the true active compound towards the cancer cell lines. The Hippo signaling pathway is a cell signaling pathway that was recently linked to cancer development and immunotherapy. Mutation or malfunction in the signaling pathway leads to irregular cell growth, especially in the case of tumor cells. To support cell regulation and prevent cancer cell proliferation, the TEAD protein is prohibited from undergoing palmitoylation, in which cell proliferation and anti-apoptosis is prevented. Two small hydrophobic structures were discovered through virtual ligand screening by our collaborators. Two initial synthetic routes were completed to initiate efficient production of products and further advancement in biological and SAR studies.Item A Study of Molecular Orientation at Neat Liquid-Mica Interface by Sum Frequency Generation (SFG) Spectroscopy(2022-05-08) Zhang, Yuwei; Baldelli, Steven; Guloy, Arnold M.; Zastrow, Melissa L.; Xu, Shoujun; Bao, JimingThe solid-liquid interface is usually different to bulk liquids since the symmetry break at the interface and provide a nonuniform environment. The rearrangement at solid-liquid interface is central in nanoscale science and technology, due to its influence in the process, such as lubrication, corrosion, heterogeneous reaction, electrochemistry and wetting. The advent of experimental techniques provides a detail information of the solid-liquid interface. Among these different new techniques of studying the interfacial structures, sum frequency generation vibrational spectroscopy shows advantageous to study the solid-liquid interface due to its unique ability in yielding vibrational spectra at such interfaces. Muscovite mica is an important substrate to investigate the ionic liquids structure at the interface. This is largely because it is atomically smooth and flat. A series of studies of ionic liquids at mica interface through surface force apparatus (SFA) and the atomic force microscopy (AFM). In order to compare the orientation of mica-ionic liquids interface, a series of ionic liquids were studied by using sum frequency generation vibrational spectroscopy. Through SFG simulation orientation analysis, it showed that the imidazole ring of ionic liquids, [BMIM][BF4], [BMIM][Tf2N], [BMIM][DCA], and [BMIM][SCN] were almost orientated nearly parallel to the mica surface with their butyl chain toward liquids. The butyl chain is orientated more closed to the normal rather than parallel to the mica surface. To compare the effect of different functional groups of molecules on the muscovite mica, a series of alcohols, nitriles, and alkane were also studied at the muscovite mica interface by using sum frequency generation vibrational spectroscopy. However, the orientation on mica surface still needs to study more in detail since the complexity of orientation of neat liquid on mica surface is introduced by the multiple interactions on mica surface, such as electrostatics, hydrogen bonding, van der Waals and dipole interaction between mica and liquid and liquid itself. A small change of structure and mica surface can make orientation of liquid on mica surface dramatically different.Item AAg2(M'xM1-x)[VO4]2: Synthesis and Structure-Property Relationships(2015-08) Bratsch, Michaela 1988-; Guloy, Arnold M.; Moeller, Angela; Jacobson, Allan J.; Brgoch, Jakoah; Yang, Ding-ShyueThis dissertation focuses on the synthesis and characterization of the AAg2(M’1 xMx)[VO4]2 series of compounds. These compounds are modifications of the parent type of compound, AAg2M[VO4]2. We have investigated the following parameters: i) the charge and size of the spacer ion (A), ii) the charge, size, and spin of the magnetic cation (M), and iii) the ratio (M’:M) of the solid solution series. In this research we specifically targeted the honeycomb (1:2) and kagome (1:3) lattices for the solid solution series, AAg2(M’1-xMx)[VO4]2. This provides an opportunity to tune the magnetic lattices by varying the M-site cations. The M-site cations utilized in this research are non-magnetic cations, Mg2+, Zn2+, In3+, and the magnetic cations, Ni2+ (S = 1), Co2+ (S = 3/2), Mn2+ (S = 5/2), Fe3+ (S = 5/2), and Cr3+ (S = 3/2). These cations provided an opportunity to probe different magnetic interactions in the compounds. The A-site cations that have been studied in this research were: Rb+, K+, Ba2+, Sr2+, and Ag+. With decreasing ionic radius, from Rb+ to Ba2+ the crystal structure is P3, and for Sr2+ and Ag+ the crystal structure is C 2/c. The structure and phase purity of the compounds were confirmed by XRD measurements. SEM-EDX was used to investigate the chemical compositions, and confirm the ratio of the M’ and M cations (stoichiometry). Raman spectroscopy in combination with DFT calculations has been conducted as a local probe to monitor the environment of the [VO4]3- unit and confirms that the surrounding of the [VO4]3- is in either a 1:2 (honeycomb) or 1:3 (kagome) ratio of M’:M. The thermodynamic properties of this series were investigated. These confirmed that the cations Ni2+ and Co2+ are ferromagnetic and follow a mean field theory behavior and that Mn2+, Fe3+, and Cr3+ are antiferromagnetic. The physical properties measurements indicate the bulk magnetic properties of the compounds are in agreement with the chemical composition. Neutron diffraction measurements performed on RbAg2(In1/3Cr2/3)[VO4]2 and AgAg2Cr[VO4]2 provided further information about the magnetic behaviors of these compounds.Item Ab Initio Calculations of Intramolecular Exciton Transfer with Reduced Modes in Donor-Bridge-Acceptor Species(2016-05) Yang, Xunmo 1988-; Bittner, Eric R.; Lubchenko, Vassiliy; Xu, Shoujun; Coltart, Don M.; Stein, Gila E.We present a new, fully ab initio approach for computing intramolecular charge and energy transfer rates. Using a time-convolutionless master-equation approach, parameterized with couplings obtained from an accurate quantum-chemical approach, we benchmark the approach against experimental results and predictions from Marcus theory for triplet energy transfer for a series of donor-bridge-acceptor systems. An important component of our analysis is the use of a projection operator scheme that parses out specific internal nuclear motions that accompany the electronic transition. Using an iterative Lanczos method, we concentrate the coupling between the electronic and nuclear degrees of freedom into a small number of reduced harmonic modes. We find that using only a single reduced mode--termed the "primary mode" or "Lanczos modes", one obtains an accurate evaluation of the golden-rule rate constant and insight into the nuclear motions responsible for coupling the initial and final electronic states. In particular, the irreducible representation of the primary mode reveals hidden details of the dynamics. For the cases considered here, the primary modes belong to totally symmetric irreducible representations of the donor and acceptor moieties. Upon investigating the molecular geometry changes following the transition, we propose that the electronic transition process can be broken into two steps, in the agreement of Born-Oppenheimer approximation: a fast excitation transfer occurs, facilitated by the "primary Lanczos mode" (PLM), followed by slow nuclear relaxation on the final electronic diabatic surface. We apply the method to a larger, "star" molecule, that has been experimentally shown that its exciton transfer pathway can be radically modified by mode-specific infrared excitation of its vibrational mode. The primary mode and rate constants we obtain generally agree with the experiments.Item Adsorption of Surfactants and Mixed Surfactants at the Hydrophilic Silica/Water Interface Studied Using Total Internal Reflection Raman Spectroscopy and Target Factor Analysis(2016-12) Ngo, Dien 1984-; Baldelli, Steven; May, Jeremy A.; Yang, Ding-Shyue; Xu, Shoujun; Wong, Stephen T.Adsorption of dimethyldodecylamine oxide (DDAO), Triton X-100 (TX-100), and their mixtures at the hydrophilic silica/water interface has been studied using total internal reflection (TIR) Raman spectroscopy and target factor analysis (TFA). The use of a vibrational spectroscopic technique gives rise to information about the adsorbed layer at the molecular level. The combination of a linear technique like TIR Raman and TFA helps determine the contribution of each surfactant in the mixed adsorbed layer on the silica surface. The first part of the study is on the adsorption of pure surfactants, DDAO and TX-100, on the silica surface with and without 0.20 M NaCl in the bulk solutions. The alkyl chains of DDAO were found to be in a liquid-like medium and were not significantly affected by the presence of sodium chloride. The conformation and orientation of the alkyl chains of DDAO were generally independent of surfactant concentrations. The DDAO adsorption isotherms, however, were clearly affected by the addition of NaCl to the surfactant solution. Before the intersection point between the isotherm curves obtained with and without 0.20 M NaCl, the adsorbed amount of DDAO on the silica surface is higher without the presence of NaCl. However, after the intersection point, the adsorption isotherm of DDAO with NaCl is higher than that without NaCl. The adsorption isotherms of TX-100 show an S-shape and a dramatic increase of the adsorbed amount due to the co-existence of both monomers and aggregates at the interface. Mixtures of DDAO and TX-100 were investigated in the second part of the study. The adsorption of TX-100 from solutions without 0.20 M NaCl on the silica surface was greatly enhanced in the mixtures when it was at very low concentrations. The adsorption of DDAO in this case, however, was only clearly enhanced at its low bulk concentration. The adsorption measurements of mixed surfactants with 0.20 M NaCl in the bulk solution demonstrated the role of pre-adsorbed DDAO in enhancing the adsorption of TX-100 at the interface. TFA is very helpful in determining the contribution of each surfactant to the mixed spectra and in understanding the adsorption mechanism of mixed surfactants.Item Advancing the capabilities of plasmonic and semiconductor nanostructures for light-powered applications(2022-04) Ngo, Nhat Minh; Lee, T. Randall; Guloy, Arnold M.; Harth, Eva M.; Brgoch, Jakoah; Varghese, Oomman K.Light-powered applications are attracting increasing attention in the rapidly developing field of nanomaterials, especially in photocatalysis and biomedical technologies. Such progress requires effective designs and fabrication methods for high-performance nanoparticles. The fabrication of nano-sized particles significantly increases the surface-to-volume ratio, which leads to cost reductions. Wet chemistry synthesis of nanoparticles offers precise control over the size and morphology of nanoparticles, as well as good scalability for bulk applications. Many light-active nanostructures suffer from shortcomings that arise from limited properties inherent to the nature of their structures as well as the inability to utilize the high-intensity region of the solar spectrum. Rational designs of new plasmonic nanostructures can lead to remarkably unique optical properties that offer emergent applications. Doping metal oxide semiconductors can tune the bandgap and recombination rate of the semiconducting nanoparticles, making them more effective photocatalysts. On the other hand, noble metal-semiconductor hybridizations can offer unique synergies that are beneficial for the intended applications. Chapter 1 of this dissertation provides a detailed review of an important class of plasmonic nanoparticles know as "metal nanostars". Chater 2 describes the synthesis and characterization of an entirely new metal nanostar; namely, semi-hollow gold-silver nanostars (hAuAgNSts). This unique bimetallic plasmonic nanostructures offers a new operational window in the ultraviolet and visible regions of the electromagnetic spectrum for metal nanostars that is complementary to the existing optical windows of conventional silver nanostars (AgNSts) and gold nanostars (AuNSts). The capability to tune the localized surface plasmon resonance (LSPR) peak of hAuAgNSts in the visible region enables their usage in many solar-powered applications, such as photocatalysis or photovoltaics, and makes better use of the high-energy flux of this region of the solar spectrum. Importantly, the fabricated bimetallic nanostars exhibit greater stability than traditional AuNSts. Chapter 3 of this dissertation reports a quick and easy method to fabricate cuprous oxide-coated silver core-shell nanoparticles Ag@Cu2O. The method offers tunable shell thicknesses, leading to highly tunable extinction behavior of the core-shell nanoparticles in the center of the solar spectrum. This semiconductor-plasmonic combination significantly reduces the recombination rate of photogenerated electron-hole pairs in the composite core-shell nanostructures; moreover, the Ag@Cu2O hybrid particles showed significantly enhanced hydrogen generation rates in photocatalytic tests. Chapter 4 of this dissertation describes facile procedures for the syntheses of uniform, monodisperse titanium dioxide (TiO2) and doped titanium dioxide nanoparticles. The bandgap and electron-hole recombination rates of the doped particles were successfully reduced by doping separately with niobium and tantalum. Dually-doped NTTO nanoparticles exhibited an even larger bandgap reduction compared to both singly doped NTO or TTO nanoparticle analogs. The photocatalytic hydrogen evolution rates of the doped TiO2 nanoparticles were also enhanced when compared to pristine TiO2 nanoparticles and reached the highest rate in the dually doped NTTO nanoparticles.Item An Ionic Twist on the Synthesis, Electrochemical and Spectroscopic Properties of Corroles, Porphyrins and Diruthenium Complexes(2022-04-12) Osterloh, Ryan; Guloy, Arnold M.; Kadish, Karl M.; Fabre, Taiya S.; May, Jeremy A.; Teets, Thomas S.This dissertation focuses on the utilizing electroanalytical methods to assess the properties of newly synthesized or electrosynthesized multi-redox active molecules such as metal-metal bonded diruthenium paddlewheel complexes, metallocorroles and porphyrins in non-aqueous and/or aqueous media. Several series of investigated compounds are examined by cyclic voltammetry, spectroelectrochemistry, NMR and UV-vis spectroscopy, and, in some cases, single crystal X-ray analysis. Properties of the neutral, reduced or oxidized forms of the examined species are utilized to determine the specific site of electron transfer (i.e. metal-, macrocycle- or substituent-centered) and an emphasis is placed on establishing electrochemical and/or other related linear free energy relationships between the various quantitative properties and empirical solvent or inductive parameters with the aim of offering powerful prediction tools intended to guide the direction of future work. In addition, the versatility of anions such as cyanide or fluoride to act as either complexing ligands or reductants via an anion induced electron transfer (AIET) is explored and a new diagnostic criterion is offered for determining ligand noninnocence in metallocorroles based on the AIET phenomenon.Item Applications of atomic magnetometry in magnetic resonance imaging and magnetic molecular sensing(2012-08) Yu, Dindi 1984-; Xu, Shoujun; Baldelli, Steven; Kouri, Donald J.Atomic magnetometry was presented as a technique suitable in magnetic resonance imaging (MRI) and magnetic molecular sensing. The magnetometer was based on nonlinear magneto-optical rotation promoted by Cs atoms in a vapor cell with antirelaxation coating. A sensitivity of 150 fT/Hz^{1/2} for dc magnetic elds was achieved. Applications of atomic magnetometry in MRI were demonstrated using the remote detection scheme. Using a gadolinium chelate as the pH contrast agent, we demonstrated the response as 0.6 s-1mM-1 per pH unit at the ambient magnetic eld for the pH range 6-8.5. A stopped ow scheme was used to directly measure spin-lattice relaxation time T1 to determine the relaxivity values. The unknown pH value of a solution was measured using only 50 micro M of this contrast agent. For magnetic molecular sensing, three key parameters were considered, namely sensitivity, spatial resolution and molecular speci city. To enhance the sensitivity of the magnetometer, the sample region was separated from the detection region. This arrangement lessened noise due to air turbulence and altered the design of the magnetic shields that would allow a gradiometer con guration. With an improved sensitivity of 80 fT/Hz^{1/2}, we demonstrated that 7000 streptavidin-coated magnetic microparticles could produce 650 pT predicting single particle detection during one second measuring time. Spatial information was obtained using a scanning magnetic imaging scheme. The spatial resolution was 20 m with a detection distance of more than 1 cm. Using force-induced remnant magnetization spectroscopy, the molecular speci city was achieved. Magnetically labeled human CD4+ T cells were used as an example. Quantitative correlation was shown, which could be used in human immunode ciency virus diagnosis. Future works were discussed.Item Apratoxin D – A Formal Total Synthesis; Asymmetric Synthesis of all Four Stereoisomers of Mefloquine Hydrochloride; α-Alkylation and α-Arylation of N-alkoxyenamines and α-Epoxy-N-sulfonyl Hydrazones(2019-12) Elmore, Kyle Lee 1987-; Coltart, Don M.; May, Jeremy A.; Teets, Thomas S.; Do, Loi H.; Cuny, Gregory D.Apratoxin D, a potent inhibitor of cancer cell growth, particularly against H-460 human lung cancer cells, was synthesized for the first time by our lab in 2012. We endeavored to improve upon that synthetic route proposing an alternative strategy for a more flexible pathway to the polyketide fragment. Specifically, this allowed a modular process that could result in variable substituents at the C-37 carbon, which has been shown to be critical in the inhibitory activity of the apratoxins. In the first chapter, we present an effective strategy based off of an organocopper asymmetric allylation of α,ß-unsaturated-N-acyloxazolidinones, demonstrating good diastereoselectivity (9:1) and yield. Second, we present an asymmetric (er > 99:1) total synthesis of all four stereoisomers of mefloquine hydrochloride which are subsequently used for biological assays to evaluate its use as a TP53 readthrough enhancer. Mefloquine has shown effectiveness at enhancing TP53 readthrough alongside aminoglycoside G418, marking its potential in cancer treatment in cases of TP53 nonsense mutations. Finally, we present a new strategy for umpolung based functionalization of ketones and aldehydes through a copper catalyzed nucleophilic addition of Grignard reagents to N-alkoxyenamines. Classic enolate based α-functionalization of carbonyls is inherently limited due to the SN2 pathway of the transition state. Umpolung strategies allow access to a greater range of α-functionalized products. This was accomplished with as little as 30 mol % loading of CuBr•DMS with 77% yield, and in-situ removal of the 3,5-isoxazolidinone to reveal the ketone directly. Additionally, we expand upon our previously published umpolung strategy for α-arylation and α-alkylation of α-epoxy-N¬-sulfonyl hydrazones to aliphatic systems, demonstrating its effectiveness across a range of sp, sp2, sp3 hybridized Grignard nucleophiles with excellent diasteroselectivity (>25:1 syn:anti) and yield (64-89%). Classic enolate chemistry cannot produce the difficult to form α-substituted ß-hydroxy carbonyl compounds with α-quarternary centers. Our strategy can access these products with good diastereoselectivity (up to 9:1 syn:anti) and yield (36-80%). Additionally, we propose a mechanism for this reaction and support this with computational data accounting for the observed selectivity in both the unsubstituted and α-methyl substituted substrates.Item Aromaticity-Modulated Noncovalent Interactions in Small Organic Molecules(2020-08) Sharma Paudel, Hari Ram; Wu, Judy I-Chia; Bittner, Eric R.; Lubchenko, Vassiliy; Cai, Chengzhi; Briggs, James M.This dissertation focuses on computational explorations of the relationships between aromaticity and noncovalent interactions (e.g., hydrogen bonding, π-stacking, and σ-hole bonding) in self-assembling organic systems. Even though the concepts of (anti)aromaticity and noncovalent interactions are typically considered in organic chemistry textbooks to be largely separate, theoretical investigations based on hydrogen bonded purine and pteridine quartets, σ-hole bonded ketocyclopolyenes, as well as hydrogen bonded and π-stacked assemblies of deltamide, squaramide, and croconamide derivatives show that these effects are mutually influential. Noncovalent interactions that polarize the ring π-electrons of monomers and increase aromatic character are strengthened, while those that decrease aromatic character in monomers are weakened. Geometric, magnetic, and energetic criteria of aromaticity were employed to quantify the effects of different types of noncovalent interactions on the aromatic and antiaromatic character of self-assembling monomers. We found that purine and pteridine quartets that associate through four pairs of hydrogen bonding interactions can display markedly different association strengths, even with the same secondary electrostatic interactions present, and show instead that these variations are the result of aromaticity gain in monomers. We found that tetrel, pnictogen, chalcogen, and halogen bonding interactions are stronger if they increase the aromatic character of interacting substrates but are weaker if they increase the antiaromatic character of interacting substrates. Hydrogen bonded and π-stacked monomers of deltamide, squaramide, and croconamide derivatives show increased aromatic character. Together these findings suggest the importance of considering “aromaticity gain” as an important structural feature in the rational design of self-assembling monomers and their chemical properties.