Master of Science, Miami University, 2014, Chemistry and Biochemistry

Multicomponent reactions (MCRs) are the most atom economic, highly selective, and convergent type of reaction. This allows for a reaction to have a wide scope and allows for maximization of the complexity of a product. Catalyzing these MCRs with asymmetric catalysis is a novel way to introduce stereocontrol into highly complex molecules with various functional groups. Asymmetric catalysis is considered the most efficient method for constructing highly functionalized optically active stereopure compounds. There are three pillars of asymmetric catalysis: biocatalysis, transition metal catalysis, and organocatalysis. This research focuses on two of these pillars, transition metal catalysis and organocatalysis, working cooperatively to catalyze this MCR. The focus is to educate or refresh the audience on the basic topics that make up the complexity of the MCRs being catalyzed by cooperative asymmetric catalysis. Ultimately to explore the cooperative catalysts used to synthesize both the racemic and asymmetric three fused ring products (9-((4-methoxyphenyl)amino)-2,3,4,4a,9,9a-hexahydro-1H-xanthen-4a-ol).

Committee: Hong Wang (Advisor); Scott Hartley (Committee Member); Richard Taylor (Committee Member); David Tierney (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

Net reductive cross-coupling reactions have gained increasing interest over the last two decades due to their ability to directly couple two electrophiles, avoiding the need to synthesize nucleophilic intermediates in turn streamlining carbon-carbon (C-C) bond formation. These cross-electrophile couplings (XEC) reactions have proven to be instrumental in the development of late-stage drug modification pathways due to their ability to easily generate Csp2-Csp3 bonds. While many of these transformations rely on the use of powdered metal reductants as a source of electrons, the heterogenous mixtures can be problematic for industrial processes due to difficulties with agitation and safety concerns over copious amounts of pyrophoric metal powders. An alternative approach that circumvents the use of metal powders is electrochemical XEC (eXEC) cross-coupling. By leveraging electrical current as a source of electrons, eXEC offers a high precision over the delivery of electrons to a system and is inherently easy to scale-up. While electroreductive cross-electrophile coupling (eXEC) represents an attractive strategy for the direct C–C coupling of two electrophiles, these reactions generally suffer from limited scope compared to reactions with chemical and metal reductants. Chapter 2 demonstrates that mediator-assisted electrocatalysis is a general strategy for the enhancement of eXEC reactions. While eXEC reactions catalyzed by a variety of widely available ligand−nickel complexes are low yielding when applied to reductive couplings of challenging substrates, reactions with the same complexes generate products in near-quantitative yield when a redox-matched mediator is included. We identify a library of catalyst−mediator systems that provide complementary reactivity and enable coupling of a range of substrate classes in high yields. These catalyst systems are applicable to both chemical and electrochemical reduction, but some require electroreduction due to the low potential (open full item for complete abstract)

Committee: Christo Sevov Dr. (Advisor); David Nagib Dr. (Committee Member); Christopher Hadad Dr. (Committee Member) Subjects: Chemistry; Experiments; Organic Chemistry

Master of Science, Miami University, 2022, Chemical, Paper and Biomedical Engineering

Hexagonal boron nitride (hBN) is a material recently discovered to exhibit surprising catalytic activity for the oxidative dehydrogenation of hydrocarbons. Previous studies indicate that redox sites can be produced on hBN, which suggests that hBN may also have potential in other oxidation reactions. In this work, hBN is instead tested as a catalyst and catalytic support for the oxidation of methanol over a temperature range of 210-360 °C. Methanol oxidation additionally reveals changes in surface active sites due to the formation of characteristic products for acid, basic, and redox active sites. Thermal treatment and sonication of hBN are demonstrated to have significant effects on conversion and product selectivity during methanol oxidation reactions. Dispersion of vanadium oxide on hBN yields increased redox activity and methanol conversion due to formation of VOx groups on the surface of hBN. The supported vanadium catalyst is shown to have superior performance when hBN is also exposed to thermal treatment and sonication. Raman, XRD, and FTIR studies are performed to characterize changes in the catalyst due to treatment or vanadium dispersion. Experiments are also performed to measure changes in active sites due to in situ functionalization of hBN during propane oxidation.

Committee: Keith Hohn (Advisor); Catherine Almquist (Committee Member); Jason Boock (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2021, Chemistry

The purpose of this dissertation is to develop new synthetic routes built upon addressing green chemistry concepts such as energy efficient designs, use of renewable energy, use of renewable material, recyclable/reusability catalysts and develop biodegradable products. In this dissertation chapter 2, we describe the first report on complete aerobic oxidative dehydrogenation of any derivative of tetrahydroisoquinoline. This photocatalytic platform is achieved using off-the-shelf Ru(bpy)3Cl2 photosensitizer, sunlight, atmospheric oxygen/air and ambient temperature. The discovery of this new photocatalytic pathway was made possible through the combination theoretical calculations and droplet-based photoreaction screening platform that employs mass spectrometry for quantitative and qualitative monitoring of reaction intermediates and products in real-time. The optimized conditions were transferred to solution-phase isoquinoline synthesis, where 71.7% total yield could be produced in less than 4 h of reaction time using sun energy. Chapter 3 in this dissertation focusses on development of a new photocatalytic screening system based on catalytic oxygenation of small molecules using recyclable/reusable fullerene-C60. Here we developed a catalytic system for small molecules using interfacial reactivity of heterogeneous fullerene-C60 ¬catalyst – single component system. Fullerene-C60 is significant in photochemistry and is widely studied. In the work, we used characteristics of fullerene to develop a heterogeneous catalyst by binding the fullerene to a surface (e.g., thread or paper), which can be reused and/or recycled. Combination of this capability along with electrospray-based reaction screening enabled the discovery of easy, fast, green, and sustainable chemistry reaction processes such as photo-oxygenation and photo dehydro-dimerization. Chapter 4 features biodegradable Polylactide polymer catalytic synthesis from renewable material and the use of mass spectromet (open full item for complete abstract)

Committee: Abraham Badu-Tawiah (Advisor); Martin Haesemeyer (Committee Member); Anne Co (Committee Member); Vicki Wysocki (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2020, Chemistry

The products of chemical synthesis touch every aspect of life in a modern industrial world, from the materials in our devices and tools, to the fuels that power them, and the medicines that keep us healthy. Steady improvements in these chemistries yield commensurate gains in quality of life, and realizing those improvements is a fundamental drive for the discovery of new, efficient methods. Efficient synthesis enables the transfer of time and resources spent on preparing molecules instead to their study and application. Classical synthetic strategies involve iterative transformation of pre-installed functionality, which can be both laborious to perform and limiting to starting functional groups. This stepwise approach can be effectively side-stepped by transformation of ubiquitous and inert C-H bonds to desired motifs in a strategy known as C-H functionalization. While many different methods to effect C-H functionalization exist, perhaps the most direct is achieved via hydrogen atom abstraction to access reactive carbon-centered radicals. These radicals can be engaged with a variety of radical traps, generating a wide range of different bonds, and enabling more streamlined synthesis. In line with the spirit of more deliberately designed, and therefore efficient, synthesis, computational methods have become increasingly more popular and provide prospective insights into experimental design and reaction discovery. Retrospective study and analysis of known reactivity via computation modeling also provides a framework that synthetic chemists can leverage for the design of new chemistry. These insights are rendered with a level of detail that is either difficult to attain with traditional experiments (e.g. molecular structure, bond strengths, electronegativities, etc.) or impossible (e.g. transition state structures). The physical chemical parameters of radicals, in particular, can be well-modeled with the theoretical chemical approaches of density functional theory. (open full item for complete abstract)

Committee: David Nagib Ph.D. (Advisor); Dehua Pei Ph.D. (Committee Member); Craig Forsyth Ph.D. (Committee Member); Steffen Lindert Ph.D. (Committee Member) Subjects: Chemistry; Organic Chemistry

Doctor of Philosophy, The Ohio State University, 2016, Chemistry

Hydrogen-bond donor (HBD) catalysis has emerged as a remarkable platform for the activation of reactants through non-covalent interactions. This class of organocatalysts provides a sustainable alternative to transition metal catalysis and avoids the difficulties associated with trace metal removal. Classically, HBD catalyst interactions proceed in two major pathways: direct activation or anion recognition. Enhanced HBD catalysts that display improved performance under both modes of action allow for the discovery of new reactivity patterns that have previously been unattainable. Two new classes of elegantly designed non-covalent catalysts have been explored in the synthesis and functionalization of heterocycles. Boronate ureas, an internal Lewis acid assisted urea, are particularly well suited for the direct activation of molecules containing nitro-functionality. Donor-acceptor cyclopropanes are useful building blocks in synthetic chemistry due to the electronic nature of the strained ring and the intrinsic functionality. Boronate ureas were applied toward development of the first cycloaddition of nitrones with nitrocyclopropane carboxylates in the presence of an enhanced non-covalent catalyst. The highly functionalized 1,2-oxazinane core synthesized in this single step is a prominent scaffold in many bioactive targets. With this strategy, a small library of oxazinane products has been synthesized in up to 99% yield and 4:1 dr. A second class of enhanced catalysts, silanediols, have a propensity to recognize the ether functionality. This molecular recognition was exploited in the context of direct epoxide activation for carbon dioxide fixation. Typically, with organocatalytic cyclic carbonate formation, very few types of functional groups are able to affect this transformation under mild conditions; often, high temperatures, long reaction times, and high pressures of carbon dioxide are necessary for desired product formation. With only 10 mol % of a silanediol (open full item for complete abstract)

Committee: Anita Mattson (Advisor); Thaliyil Rajanbabu (Committee Member); David Nagib (Committee Member) Subjects: Organic Chemistry

Doctor of Philosophy, The Ohio State University, 2015, Chemistry

Small molecules that participate in molecular recognition via hydrogen bonding interactions provide a powerful platform for a host of applications. It has been established that these types of molecules can function as therapeutic agents, anion sensors, and organocatalysts. Advancements upon the state of the art in these areas can be realized by developing functional groups that have yet to be explored in the context of hydrogen bond donor molecular recognition such as silanediols. Although silanediols have been investigated in the context of self-assembly and have a long history of serving as monomers in materials chemistry, examples of silanediol based therapeutic agents and anion sensors have only recently been described in the literature. At the outset of our research program, there had been no reports of silanediols participating in hydrogen bond donor catalysis. The silanediol functionality offers a unique scaffold for the construction of a novel class of hydrogen bond donor catalysts. Guanidine, urea, and thiourea moieties make up a majority of the early dual hydrogen bond donor catalysis literature. It was then discovered that squaramides functioned well as hydrogen bond donor catalysts, and in some cases, provided improvement over more traditional (thio)urea catalysis. While numerous research programs existed aimed at improving the activity of (thio)urea hydrogen bond donor catalysts via manipulation of the substituents neighboring to the (thio)urea core, the introduction of squaramides demonstrated that gains could be made by changing the functional group at the heart of the catalyst design. We proposed silanediols would be a new class of enhanced hydrogen bond donor catalyst based on inherent shape, solubility, acidity, and other molecular recognition properties unique to the silanediol. Inspiration for this approach was provided by a 2006 report from the Kondo lab in which they reported a dinaphthylsilanediol that was capable of binding to acetate, chlor (open full item for complete abstract)

Committee: Anita Mattson Ph.D. (Advisor); Forsyth Craig Ph.D. (Committee Member); Nagib David Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2014, Chemistry

Strategic enhancement of urea organocatalysts using internally coordinated Lewis acids has allowed for the discovery of new and useful reactions. Specifically, the incorporation of transition metals onto urea scaffolds has been shown to improve catalytic activity when compared to traditional urea and thiourea catalysts. An example of this enhancement has been demonstrated in the development of hybrid urea palladacycles that have been shown to be highly active, hydrogen bond donor catalysts in the activation of substrates not amenable to traditional urea catalysis, such as alkylidene malonates. Other internal Lewis acids such as platinum, silicon and boron have also been incorporated onto urea scaffolds, and the new catalysts have been compared in their abilities to activate new substrates such as nitrocyclopropane carboxylates and nitrodiazoesters. Correlations between catalyst structure and activity show that increased acidity due to internally coordinated Lewis acids is one of the important factors in urea catalyst design. To compare the internal Lewis acids' effects on acidity and on catalyst activity, the pKas of differently internally-coordinated catalysts have been determined and found to range from a highly acidic 6.8 for a coordinated palladium to a weakly acidic 16.0 for a silicate urea. Boronate ureas surveyed had intermediate pKas of 7.5 and 9.5. The different catalysts' abilities to activate both nitrocyclopropanes and nitrodiazoesters by coordination to the nitro group have also been investigated by studying the rates of these reactions. An internally coordinated difluoroboronate urea has been determined to be the best catalyst for both reaction systems. Using urea catalysts, a new organocatalytic coupling strategy has also been discovered. Specifically, nitroamines and nitrimines have been identified as urea-activated handles allowing for useful carbon–heteroatom and carbon–carbon coupling reactions. This reaction mode has been shown to (open full item for complete abstract)

Committee: Anita Mattson (Advisor) Subjects: Chemistry; Organic Chemistry

Master of Science, The Ohio State University, 1920, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1919, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

Ultrafast carrier and spin dynamics of photoexcited yttrium iron garnet (Y3Fe5O12, YIG) are studied to demonstrate that it is an efficient photocatalyst for oxygen (O2) evolution half-reaction in the electrolysis of water. Producing hydrogen as an alternative fuel to traditional carbon-based fuels requires efficient catalysis of both H2 and O2 production from water. O2 production is the limiting factor in water splitting as it is a 4e- transfer process. An efficient O2 evolution photocatalyst requires a material with proper band alignment and low carrier recombination. Recent advances have shown that a spin polarized catalyst can enhance water splitting to produce paramagnetic O2 from diamagnetic water. A photocatalyst utilizes the carriers excited by light, preferably sunlight, to perform catalysis. Photoexcitation is an ultrafast process occurring on an attosecond time scale whereas the electron transfer in catalysis between the semiconductor and water is a slow process occurring in millisecond time scale. Therefore, understanding carrier and spin dynamics between photoexcitation and catalysis is necessary to identify a potential efficient photocatalyst such as YIG. For this purpose, we used time resolved extreme ultraviolet (XUV) reflection absorption and magnetic circular dichroism (MCD) spectroscopies to study the photoexcited dynamic of YIG. These techniques allow us to probe the surface sensitive, element specific and spin resolved carrier dynamics that occur in YIG after photoexcitation. The details of the instrumentation for these techniques are discussed in detail in Chapter 2. YIG is a ferrimagnetic n-type semiconductor with a valence band containing majority of O 2p and a conduction band with Fe 3d contributions. The Fe atoms occupy tetrahedral (Td) and octahedral (Oh) lattice sites in a 3:2 ratio formed by O atoms. An above bandgap excitation causes electrons to transfer from O 2p to Fe 3d orbitals. These electrons can be probed with linear trans (open full item for complete abstract)

Committee: Robert Baker (Advisor); Fengyuan Yang (Committee Member); John Herbert (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

There is a constant need for the development of streamlined and efficient methods to rapidly introduce molecular complexity. Methods that rely on traditional functional group interconversion often become lengthy and suffer detrimental side reactivity when other reactive moieties are present. To address this challenge, C-H functionalization has emerged as a powerful tool to rapidly synthesize and diversify molecules. C-H bonds are ubiquitous within organic molecules. C-H functionalization allows the direct conversion of C-H bonds to a more valuable functional group. However, because of the small distinctions between C-H bonds, selective C-H functionalization presents unique challenges to overcome. Using bespoke radical chaperones paired with Metal Hydrogen-Atom Transfer, three selective transformations of simple alcohols and amines to more medicinally relevant motifs have been developed. (1) By pairing MHAT with photocatalysis we have developed a dual Co/Ir-catalyzed aza-Heck cyclization to synthesize vinyl oxazolines and oxazoles from allylic alcohol-derived oxime imidates, overcoming previous Pd-based limitations. (2) Towards the construction of various heterocycles, we have developed a strategy to convert amines to a variety of sultams utilizing metal hydrogen atom transfer (MHAT). (3) Utilizing chiral copper catalysis, enantioselective -amination of amines to synthesize chiral diamines has also been achieved via regioselective 1,5-hydrogen atom transfer.

Committee: David Nagib (Advisor); Jon Parquette (Committee Member); Christo Sevov (Committee Member) Subjects: Chemistry

PhD, University of Cincinnati, 2024, Arts and Sciences: Chemistry

This dissertation represents an in-depth investigation into the rapidly evolving field of electrocatalytic conversion, which holds significant promise for advancing renewable energy applications. The primary objective of this research is to harness electrocatalysis for the efficient transformation of small molecules into valuable feedstocks. A key focus is on the synthesis and application of electrocatalysts, particularly metalated porphyrins, to expedite reaction kinetics and improve product selectivity. In this dissertation, we present several novel molecular catalysts tailored for distinct electrochemical transformations. Central to this dissertation is the development of novel electrocatalysts, exemplified by the synthesis of an innovative iron porphyrin complex (FePEGP) featuring a strategically placed poly(ethylene glycol) unit. Controlled-potential electrolysis using FePEGP exhibited an impressive Faradaic efficiency of 98% and a current density of –7.8 mA/cm2 at –2.2 V vs. Fc/Fc+ in acetonitrile with water as the proton source. Our mechanistic investigations revealed that the PEG unit's presence enhances catalytic kinetics, leading to improved CO2 reduction efficiency. This catalyst demonstrates exceptional selectivity and activity in the electrochemical reduction of carbon dioxide to carbon monoxide, offering a promising avenue for sustainable energy generation. Collaborative research endeavors with the University of Tennessee have further expanded the scope of this work, particularly in exploring tin porphyrin complexes (SnPEGP) for hydrogen evolution. SnPEGP displayed high activity (–4.6 mA/cm2 at –1.7 V vs. Fc/Fc+) and selectivity (H2 Faradaic efficiency of 94%) in acetonitrile with trifluoroacetic acid (TFA) as the proton source. Spectroelectrochemical analysis and quantum chemical calculations suggested an Electron-Chemical-Electron-Chemical (ECEC) pathway for proton reduction mediated by the tin porphyrin catalyst. Through synergistic e (open full item for complete abstract)

Committee: Jianbing Jiang Ph.D. (Committee Chair); Peng Zhang Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

To keep pace with newly emerging and evolving diseases, the field of drug discovery requires the development of modern synthetic strategies. Limiting the number of chemical steps and generation of waste in the construction of complex molecular scaffolds is essential to improving this process. The ubiquity of the C-H bond in both natural products and pharmaceuticals makes it an ideal target for late-stage synthetic modifications. However, selective C-H activation, specifically in complex molecular settings, remains a major challenge. Taking inspiration from Nature's enzymatic C-H oxidizing catalyst, cytochrome P450, uniquely reactive organic intermediates were discovered and designed to selectively modify inert C-H bonds. The radical and iodane selective functionalizations of C-H bonds described herein aim to expedite the drug discovery process by innovations in organic synthesis.

Committee: David Nagib (Advisor); Christopher Hadad (Committee Member); Jon Parquette (Committee Member) Subjects: Chemistry; Organic Chemistry

Master of Science in Chemistry, Youngstown State University, 2023, Department of Biological Sciences and Chemistry

Global climate change is a major crisis with no solution in sight due to the continual production of greenhouse gases (GHGs). Carbon dioxide (CO2) is a major GHG whose atmospheric concentration has been rising constantly from increased human activities that lead to its formation. Developing new applications for CO2 is a viable means for reducing its atmospheric concentration and consequently controlling global climate change. N-heterocyclic carbenes (NHCs) are known to form molecular adducts when exposed to CO2, in this work, the adduct 1,3-bis(2,4,6-trimethylphenyl) imidazolium carboxylate (IMes-CO2), where Mes = 2,4,6-trimethylphenyl or mesityl, was prepared by reacting CO2 with the corresponding carbene (IMes), which was prepared by deprotonation of the imidazolium chloride (IMes-Cl) salt at the C2 position with potassium hexamethyldisilazide (KHMDS). Synthesis of IMes-CO2 was confirmed via nuclear magnetic resonance and infrared spectroscopy, thermogravimetric analysis and mass spectrometry. The chemical nature of IMes-CO2 was studied via attempted catalytic hydrogenation reactions at varying reaction conditions. The analytical results obtained showed that IMes-CO2 was generally unreactive at room temperature and 30 atm of H2 pressure for up to 3 days. Moreover, the solvated adduct would slowly dissociate unless a background pressure of CO2 was supplied. In Pd/C-catalyzed hydrogenation reactions, the C2-CO2 bond of IMes-CO2 is broken and the C2 is rehydrogenated, regenerating the imidazolium, as observed in the reappearance of the H2 peak position above 10 ppm in the 1H-NMR spectrum. However, no further reduction occurred, as the H1 peak corresponding to the C=C double bond of the imidazole ring remained at 7.74 ppm, along with the aromatic H4 peak at 7.09 ppm and the IMes methyl peaks at 2.37 ppm and 2.18 ppm. Likewise, spectroscopic signatures for CO2 reduction products (formate, oxalate, methanol, etc.) were not observed. Nevertheless, the mesityl imidazolyl (open full item for complete abstract)

Committee: Clovis Linkous PhD (Advisor); Josef Simeonsson PhD (Committee Member); John Jackson PhD (Committee Member) Subjects: Analytical Chemistry; Chemistry; Organic Chemistry

Doctor of Philosophy, The Ohio State University, 2023, Biochemistry Program, Ohio State

Cyclobutane pyrimidine dimers (CPD) are carcinogenic DNA photolesions formed between two adjacent thymine bases in genomic DNA by UV irradiation. DNA photolyases are ancient photoenzymes that evolved to specifically recognize, bind to and repair these lesions using blue light in ultrafast timescale. Comprehensive molecular level understanding of enzymatic CPD cycloreversion is lacking. We highlight various molecular factors from both enzyme active site and substrate itself, that modulate various electron transfer (ET) and bond rearrangement steps involved in the repair photocycle and determine the overall quantum repair yield. We tracked the real time repair dynamics of carefully planned enzyme and substrate variants using femtosecond spectroscopy. We found that active site amino acids modulate solvation around the cofactor-lesion pair and influence associated ET parameters. Steric and electrostatic properties of the substrate and the enzyme active site dictate the dimer splitting yield by tuning bond cleavage and futile ET steps. Finally, we found that the photolyases have evolved to fit the lesion in a specific binding configuration to maximize electronic coupling with electron donating cofactor and selectively destabilize various intermediates to achieve modest to high repair yields.

Committee: Dongping Zhong (Advisor) Subjects: Biochemistry; Biophysics; Chemistry

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Chemical Engineering

The issue of global warming brought on by the buildup of greenhouse gases, particularly CO2, has presented a serious threat to human survival over the past few years. As a result, the recovery and utilization of CO2 have emerged as critical areas of focus in environmental science and catalysis. The electrocatalytic conversion of CO2 into multi-carbon (C2+) products with higher commercial value has drawn the most interest among these initiatives. This dissertation will focus on a fundamental understanding of how to improve the electrochemical CO2-to-C2+ products conversion by modulating the coverage and binding strength of essential intermediates (e.g., *CO, *CH2CHO, and *O), as well as controlling the activation energy for crucial elementary steps (i.e., C–C coupling for C2+ products and *CH2CHO hydrogenolysis for ethylene). The approaches to achieve these goals can be summarized as: CO electroreduction kinetics investigation, tandem catalyst design, high-density planar defect exposure, and oxygen-bound intermediate regulation. Specifically, Chapter 2 would elucidate how CO-dependent kinetics of higher-order products distinguish different mechanistic sequences, kinetically relevant intermediates and *CO adsorption strength. With the aid of a flow electrolyzer integrated with gas diffusion electrode, the *CO dimerization is identified as the rate-determining step for ethylene and ethanol production. Kinetic studies also reveal that product-specific active sites are responsible for activity and selectivity toward specific C2+ products. In Chapter 3, a model tandem catalyst is prepared to verify the local CO concentration and the CO spillover effect in CO2 electroreduction toward C2+ products. More importantly, it is demonstrated as how to combine the modulation of both tandem catalyst compositions and spatial arrangement of two active sites for maximizing *CO utilization efficiency. Besides the *CO coverage, the *CO adsorption strength is anothe (open full item for complete abstract)

Committee: Jingjie Wu Ph.D. (Committee Chair); Vesselin Shanov Ph.D. (Committee Member); Wei Liu Ph.D. (Committee Member); Junhang Dong Ph.D. (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2023, Chemical Engineering

Investigating the impact of the structure of heterogeneous catalysts on performance is crucial for designing catalysts with enhanced activity. A significant challenge is creating uniform catalytic materials since current synthetic methods tend to produce materials with a wide distribution of catalytic sites. Indeed, materials that are seemingly simple have been revealed to be staggeringly complex, including materials such as zeolites, alumina, silica, and aminosilane modified materials called amino-silicas. Amino-silica heterogeneous catalysts are widely used in many applications, including pharmaceuticals, carbon dioxide adsorption, and biomass upgrading. Amino-silica materials can be designed with cooperative interactions to enhance catalytic performance in different reactions, such as the aldol reaction and condensation. One common mesoporous support is Santa Barbara Amorphous 15 (SBA-15). SBA-15 has exceptional properties, including thermal stability and high surface area. The porosity of SBA-15 can be tuned through synthesis conditions. In this dissertation, we demonstrate that limiting the micropore volume in SBA-15 can further increase the overall catalytic performance. This result indicates that catalytic sites located within micropores are inactive during catalytic reactions, disproving the previous assumption that all sites have equal contributions. We conduct a poisoning test to quantify the catalytic sites on both regular (REG) and negligible-micropore (NMP) SBA-15. The results of site quantification demonstrate that amine-functionalized SBA-15 has multiple types of catalytic sites with different activities, including high activity, medium activity, low activity, and inactive sites. With our new understanding of different types of sites in aminosilica materials, it was intriguing to re-evaluate previous observations (e.g., surface density) through the lens of whether the difference was associated with the activity of the sites or the fraction of catal (open full item for complete abstract)

Committee: Nicholas Brunelli (Advisor); Yiying Wu (Committee Member); Lisa Hall (Committee Member); Aravind Asthagiri (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Toledo, 2023, Chemistry

Transition metal chemistry has revolutionized the modern world. However, some of the most important catalytic transformations rely on scarce and expensive precious metals with high toxicity. Iron is an attractive alternative to most precious metals as it is the most abundant transition metal on Earth, and also in biological systems, making it both inexpensive and minimally toxic. Though its development lags severely behind those of metals in Groups 9 and 10, homogeneous iron catalysis provides ample opportunity to develop new methods for achieving the same chemical scaffolds. Specifically, we are interested in iron-mediated methods for coupling of N-heteroarenes with aryl- and heteroarylboronic acids and esters for generating pharmaceutical building blocks and ligand precursors. The current state-of-the-art synthetic routes for bi(hetero)aryl compounds rely on the palladium-catalyzed Suzuki-Miyaura reaction. The direct Suzuki-Miyaura-type C2-arylation of pyrrole with heteroarylboronic acids and esters catalyzed by an iron-tetraazamacrocycle is reported in chapter 2. An abbreviated optimization of reaction conditions is reported alongside the development of an improved work-up, relative to previous reports. The reaction of pyrrole with 22 heteroarylboronic acids and 14 heteroarylboronic esters is presented, including the synthesis of 17 novel 2-heteroarylpyrrole compounds. Products were characterized by NMR spectroscopy and high-resolution mass spectrometry. Testing the use of tert-butylhydroperoxide as an oxidant instead of molecular oxygen lead to oxidation of boronic acids. Additionally included in this chapter is discussion of major by-products of the cross-coupling reactions and various control experiments. In chapter 3, we expanded our studies to the regioselectivity of arylation of mono- and disubstituted pyridines with phenylboronic acid. Most methods for the direct arylation of pyridine suffer from poor regioselectivity. In contrast to the original r (open full item for complete abstract)

Committee: Mark Mason (Committee Chair) Subjects: Chemistry; Organic Chemistry

Doctor of Philosophy, The Ohio State University, 2022, Chemistry

Two projects are presented here. The first project is a cationic cobalt(I)- catalyzed intramolecular Diels-Alder reaction. The cationic cobalt catalyst generated in-situ from a cobalt (II) precatalyst, which is reduced by activated Zn and is activated by NaBArF was shown to catalyze the reaction of several diene-enes and diene-ynes to afford the Diels-Alder products in moderate to good yields and in some cases high enantioselectivities. In the second project we studied the mechanism of the reaction of Cp2TiCl with trisubstituted epoxides. We found that the proposed intermediate in these reactions Cp2Ti(H)Cl is thermally unstable and spontaneously decomposes to Cp2TiCl and H2 gas.

Committee: T.V. RajanBabu (Advisor); Psaras McGrier (Committee Member); Jovica Badjic (Committee Member) Subjects: Chemistry