Physical Sciences and Mathematics Commons^™

Tethered Axial Coordination As A Control Modality In Rhodium(Ii)-Catalyzed Carbene Transfer Reactions, Anthony Dean Abshire

Doctoral Dissertations

Rhodium(II) paddlewheels are versatile carbene transfer catalyst that are broadly applied in insertion reactions, cycloadditions, and ylide transformations. The effects of axial coordination in rhodium(II)-catalyzed carbene transfer reactions are still little understood due to compounding factors that are difficult to isolate. Traditionally, researchers study axial coordination by addition of Lewis base additives. To ensure interaction between the Lewis base and catalyst, high molar equivalents are used. This can also have the undesired effect of hampering the activity of the catalyst and suppressing the yield of the reaction. We have developed ligands with a tethered Lewis base to overcome these issues. …

Influence Of Tethered, Axially Coordinated Ligands On Rh(Ii,Ii)-Catalyzed Carbene Transfer Reactions, Cristian E. Zavala

Doctoral Dissertations

Dirhodium (II,II) paddlewheel complexes have become ubiquitous in diazo-mediated carbene transfer reactions. The Rh(II,II)-carbene intermediate is capable of a large variety of transformations such as cyclopropanation, C-H and X-H (O, N, S, Si, B) insertion reactions, cyclopropenations, and ylide transformations. Cyclopropanation reactions resulting in the formation of functionalized cyclopropane structures has always been a major focus in Rh(II,II)-carbene chemistry. Improvements on catalytic performance in cyclopropanations has largely focused on the modification of the bridging ligands and has resulted in Rh(II,II) catalysts that exhibit high reactivity and selectivity in cyclopropanation reactions. However, high enantio- and diastereoselectivity is not easily achieved with …

Small Molecule Activation By Transition Metal Complexes: Studies With Quantum Mechanical And Machine Learning Methodologies, Justin Kyle Kirkland

Doctoral Dissertations

One of the largest areas of study in the fields of chemistry and engineering is that of activation of small molecules such as nitrogen, oxygen and methane. Herein we study the activation of such molecules by transition metal compounds using quantum mechanical methods in order to understand the complex chemistry behind these processes. By understanding these processes, we can design and propose novel catalytic species, and through the use of data-driven machine learning methods, we are able to accelerate materials discovery.

Catalytic Aziridination With A Borate-Containing N-Heterocyclic Tetracarbene Iron Complex, Preeti Pradip Chandrachud

Doctoral Dissertations

Aziridines, the nitrogen analog of epoxides, are an important class of compounds. They are present in many biologically active compounds having antibacterial and antitumor properties. Along with biological significance, it can also be considered as a synthetic tool for various functional group transformations. Being an important functional group we focused on the development of synthetic methodology using alkenes as substrates and organic azides as the nitrene source [C₂ (carbon2)+ N₁ (nitrogen1) addition reaction].

For the potential use as an aziridination catalyst a macrocyclic N-heterocyclic tetracarbene (NHC) ligand system was developed. First, the neutral NHC ligand was used …

Synthesis And Characterization Of Support-Modified Nanoparticle-Based Catalysts And Mixed Oxide Catalysts For Low Temperature Co Oxidation, Andrew Justin Binder

Doctoral Dissertations

Heterogeneous catalysts are responsible for billions of dollars of industrial output and have a profound, if often understated, effect on our everyday lives. New catalyst technologies and methods to enhance existing catalysts are essential to meeting consumer demands and overcoming environmental concerns. This dissertation focuses on the development of catalysts for low temperature carbon monoxide oxidation. CO [carbon monoxide] oxidation is often used as a probe reaction to test overall oxidation activity of a given catalyst and is an important reaction in the elimination of toxic pollutants from automotive exhaust streams. The work included here presents three new heterogeneous catalysts …

Synthesis Of A Bifunctional Heterogeneous Catalyst For The Conversion Of Lignocellulosic Biomass Into Precursors For Alternative Fuels And Fine Chemicals, Matthew David Dembo

Masters Theses

The overall goal of the research described here is to develop synthetic routes to bifunctional reagents that can be tethered into silicate matrices derived from the tin functionalized cube, Si₈O₂₀(SnMe₃)₈. The critical functional group required for reaction with cubic silicate building block is a chlorosilane, and we additionally wish to incorporate both acid and ionic liquid groups. Once in hand, a crosslinking metathesis reaction will incorporate these reagents into porous silicate matrices derived from the Si₈O₂₀ cube, creating platforms with both acid and ionic liquid groups tethered to their …

Utility Of 1,2,4-Triazoles As Catalysts For Orr In Fuel Cells, Chinmay Nagesh Dabke

Masters Theses

The Oxygen Reduction Reaction (ORR) taking place at the cathode of a fuel cell is catalyzed by Platinum due to its high activity and good stability in the acidic polymer electrolyte membrane fuel cell (PEMFC) environment. Due to its prohibitive cost and limited reserves, it is not practical to use Pt as the catalyst for mass commercialization. By taking inspiration from nature, we have devised a series of catalysts which will help in replacing Platinum at the cathode in commercial fuel cells. To gauge the activity of various ligands, metal salts and carbon surfaces, adsorbed experiments were carried out and …

Homogeneous And Heterogeneous Approaches To 1,2,4-Triazine-Accelerated Copper-Catalyzed Azide-Alkyne Cycloadditions, Ashleigh Lauren Prince

Doctoral Dissertations

Over the last decade, the domain of click chemistry has grown exponentially and has significantly impacted the fields of organic synthesis, medicinal chemistry, molecular biology, and materials science. The ideal model of a click reaction has become the copper-catalyzed azide-alkyne cycloaddition (CuAAC). Inherent limitations of CuAAC, including high temperatures, long reaction times, and difficult purifications, have been minimized by the development of nitrogen-based ligands. Herein, we present a novel application of 1,2,4-triazines by investigating their use as accelerants for CuAAC.

A diverse library of 1,2,4-triazines were synthesized in order to examine the molecular determinants of their catalytic activity. These ligands …

Hairy Particles: Polymer Brush-Supported Organocatalysts And Asymmetric Mixed Homopolymer Brushes, Xiaoming Jiang

Doctoral Dissertations

This dissertation presents the synthesis and studies of polymer brush-supported organocatalysts and asymmetric mixed homopolymer brushes grafted on particles. The brushes were synthesized from initiator-functionalized particles by surface-initiated “living” radical polymerizations.

Polymer brush-supported organocatalysts were designed to combine the advantages of both soluble polymer- (high activity) and crosslinked insoluble polymer-supported catalysts (recyclability). Chapter 1 describes the synthesis of a polymer brush-supported 4-N,N-dialkylaminopyridine (DAAP) catalyst from initiator-functionalized latex particles by surface-initiated nitroxide-mediated radical polymerization (NMRP). The hairy particles efficiently catalyzed the acylation of secondary alcohols and Baylis-Hillman reaction and were recycled  six times with no or negligible decrease in the …