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Pd-Based Photocatalysts For Heck C-C Cross-Coupling Reactions, Suha Ali Alshehri

Masters Theses

Heck C-C cross-coupling reaction has been widely employed in synthetic organic chemistry because of its high efficiency and simplicity, however the conventional Heck C-C cross-coupling reaction conditions involve the use of an expensive toxicant phosphine-ligated palladium complexes, and high temperature. To address these drawbacks, a highly efficient, homogeneous photocatalyst based on BODIPY for the Heck C-C cross-coupling reactions of aryl iodide and methyl acrylate in DMF solvent under inert conditions has been developed. The 4-Py-BDP-Pd, 3-Py-BDP-Pd and, 2-Py-BOD-Pd catalysts were synthesized and purified using column chromatography. The optical properties of products and intermediates were studied by UV/vis absorption and fluorescence …

Synthesis And Characterization Of A Two Station Starburst Pseudorotaxane, Janaka Prasad Kaviraj Kavikarage

Masters Theses

Mechanically interlocked molecules (MIMs) are arranged with mechanical bonds. These molecules cannot be separated without breaking the required covalent bonds. There are different kinds of MIMs, such as rotaxanes, catenanes, suitanes, borromean rings, and molecular knots. These MIMs are stabilized by non-covalent interactions such as hydrogen bonds, π-π stacking, and ion-dipole interactions. Dialkylammonium ions, bis(pyridinium)ethane dications, viologen species, and naphthalene diimide π-deficient groups are typical examples of recognition motifs for crown ethers.

In the research described here, we synthesized a new axle, based on a combination of benzobis(imidazolium) (BBI) and viologen species. The axle contains two recognition sites: one is …

Metal Complexes Of Bis(Pyrazolyl)Methane-Based Ditopic Ligands, Pubudu Nuwan Perera Hapuarachchige

Masters Theses

No abstract provided.

A Novel Palladium Bodipy Photocatalyst For Sonogashira Carbon-Carbon Cross-Coupling, Prahadeesh Nagaretnam

Masters Theses

No abstract provided.

Synthesis And Characterization Of Starburst Pseudorotaxanes And Their Metallic Derivatives, Shalini D. Kadinappulige

Masters Theses

Mechanically Interlocked Molecules (MIMs) are interlocked molecular architectures, characterized by the fact that they are linked through a mechanical bond. Catenanes, rotaxanes, molecular knots, and Borromean rings are typical examples for these molecules. Since MIMs are not connected by covalent bonds, hydrogen bonding, π- π stacking, and/or electrostatic interactions help bring the components together. Dialkyl-ammonium centers, bis(pyridinium)ethane dications, viologen species, and naphthalenediimide π-deficient groups are well known as recognition motifs for crown ethers. In the research described here, we have synthesized several pseudorotaxanes and their tricyclohexyltin metallic derivatives, based on benzobis(imidazolium) (BBI) salts as axles, in combination with the 15DN38C10 …

Design, Synthesis, And Characterization Of Chemical Tools To Study Peroxisomal Import, Jhalak N. Timilsena

Masters Theses

Peroxisomes are dynamic and interconnected single lipid membrane bound organelles found in the eukaryotic cells which are involved in various biochemical processes including the b-oxidation of very long chain and branched chain fatty acids, metabolism of reactive oxygen and nitrogen species, and reduction of hydrogen peroxide among others. These organelles are known to host numerous proteins and enzymes depending on the cellular environment. All of the proteins needed in the peroxisomes are encoded in the nucleus and synthesized in the cytosol which are then transported to the peroxisomes with the help of a sophisticated protein-transport machinery. Pex5 is one of …

Synthesis, Characterization And Mechanistic Studies Of Biomimetic Dinuclear Copper(Ii) Complexes, Millaniyage Nuwanthaka Prasad Jayaweera

Masters Theses

Dinuclear copper complexes are significant synthetic targets due to their use as model compounds for the active sites of type 3 copper proteins like catechol oxidase. A distinct class of ligands used in these studies are built on a phenol core to witch various donor side-arms were appended at the 2 and 6 positions of the arene ring. In our quest to quantify the influence of electron donating or withdrawing groups attached to the central arene ring, we have designed a set of ligands that, upon coordination to copper(II) centers, would produce complexes of the general structure. During this research …

Developing A Basket-Shaped Host Molecule Based On P-Tert-Butylcalix[4]Arene Featuring Urea Groups For Encapsulating Volatile Guest Molecules, Lokugama Widanelage Vidula Priyadarshana

Masters Theses

Molecular baskets are a group of synthetic host molecules which are designed to govern the inclusion of small guest molecules. The basic structural features of basket-shaped host molecules are a cavity for holding a much smaller guest molecule and tunable gates for keeping the guest molecule inside. These types of gates can be tuned by changing temperature, concentration, pH, etc. In this research group's previous study, a molecular basket of cal ix[ 4]arene with carboxylic acid groups was synthesized by functionalizing calix[4]arene's phenol hydroxyl groups with benzyl bromide building blocks. In the study detailed here, 1 , l '-((5-(bromomethyl)-1,3-phenylene)bis(methylene))bis(3-isopropylurea) was …

Solvation Properites Of Supercritical Carbon Dioxide Using Chirped-Pulse Fourier-Transform Microwave Spectra Of Carbon Dioxide / 1, 1-Difluoroethene (Dfe) Mixtures, Tulana Ariyaratne Subasinghe Arachchige

Masters Theses

Supercritical carbon dioxide (sc-C0₂) is a highly utilized industrial substance identified as an excellent solvent and a surfactant, which is cheaper and less hazardous than other typical solvents. The higher solubility of fluorinated hydrocarbons than their hydrocarbon (HC) analogs is not well understood and the theory behind the microsolvation of sc-C0₂ cannot be fully explained with the existing chemical information. Microwave spectroscopy is a good method of identifying the structural arrangement of clusters made from fluorinated HCs and C0₂. I n this project, microwave scans of the four different mixtures of 1 , 1-difluoroethene (DFE) …

Studying Carbon Dioxide Solvent Properties By Microwave Spectroscopic Investigations Of Vinyl Fluoride/Carbon Dioxide Clusters And Developing New Approaches To Decode Rotational Spectra, Prashansa Kannangara

Masters Theses

Supercritical carbon dioxide (sc-C0₂) is an excellent green solvent, but its properties are not thoroughly understood. For example, fluorinated compounds have higher than expected solubility in sc-C0₂. Microwave spectroscopy is one way to learn more about sc-C0₂ because it can be used to determine detailed structures of small clusters of molecules. The purpose of this investigation was to study weak hydrogen bonding interactions in complexes of fluorinated ethylene (solute) with carbon dioxide (C0₂, solvent). Investigations on dimers with one C0₂ molecule and fluorinated ethylene were carried out previously and found two different …

Synthesis Toward A Molecular Container Based On P-Tert-Butylcalix[4]Arene With Gate Features, Balasooriya Appuhamilage Dinesh Madushan Balasooriya

Masters Theses

Nowadays molecular and supramolecular chemistry have endless examples for the development of smart devices. Among those applications, nano-baskets of calixarenes play vital roles in host-guest chemistry. One of the main appealing concepts of this field is the development of host molecules with gate features. These hosts are designed and constructed for the delivery of chemical or biochemical species that are volatile, or reactive, or sensitive to normal solution environment and they are mainly functioned by predefined groups that are responsive toward stimuli such as concentration, temperature, pH and so on. In our previous study, we found that benzyl bromides can …

Synthesis And Characterization Of Biomimetic Dinuclear And Tetranuclear Copper Complexes, Syed Rahmath Ullah Joy

Masters Theses

Seven new copper(II) complexes were prepared from the condensation reaction of 4-tert-butyl-2,6-diformylphenol with two equivalents of bis(pyrazolyl)ethanamine or 3,5-dimethyl-bis(pyrazolyl)ethanamine moieties in the presence of two equivalents of various copper(II) starting materials having different counter ions (i.e. acetate - AcO^-, perchlorate - CIO₄^-, tetrafluoroborate - BF₄^-, nitrate - NO₃^-, and chloride - Cl^-). The resulting copper(II) complexes were characterized in solid state by single crystal X-ray crystallography, and in solution by UV-Vis and ESI/MS spectroscopies.

X-ray crystallographic studies showed that in solid state two types of …

Pd-Based Photocatalysts For Sonogashira C-C Cross-Coupling Reactions, Komadhie Charuka Dissanayake

Masters Theses

Sonogashira C-C cross-coupling reaction has been heavily used for its simplicity, flexibility and value. Although the original Sonogashira C-C cross coupling reaction conditions entail the use of 0.5 mol% of Pd catalyst, 2 mol% of Cul as co-catalyst at room temperature, the experimental conditions used in laboratories to prepare some compounds vary substantially, especially with respect to the reaction time, temperature and loading amount of the catalysts. The most significant drawback of the conventional Sonogashira reaction is the use of Cul as it leads to the formation of homocoupling product when the reaction is exposed to air or oxidizing agents. …

Red Emissive Bodipy Dyes As Sensitizers For Near-Infrared Emission Of Lanthanide Complexes & Structural & Spectroscopic Studies Of Quinoline-Functionalized Bodipy Dyes, Adedayo Ayodeji Kukoyi

Masters Theses

Bioimaging has become a significant tool for the visualization of biological events and the detection of numerous biomarkers. However, detection sensitivity is compromised by background signal from the biofluid which interferes with signals from the probes that usually emit in the visible region Alternative probes such as those that emit in the near-infrared (NIR) region are necessary to overcome these shortcomings. Lanthanide ions have demonstrated efficiency with sharp characteristic emission in the visible and (NIR) region. Emission however is mostly achieved by indirect sensitization process in which energy from the triplet state of a sensitizer is transferred to the excited …

Functionalized Bodipy Dyes For Near-Infrared Emission Of Lanthanide Complexes, Rukshani Wickrama Arachchi

Masters Theses

For many decades, fluorophores have been used to investigate natural systems, but autofluorescence and photobleaching diminish the detection capacity. Recently, BODIPY based lanthanide complexes have been synthesized and their photophysical properties have been investigated. These complexes exhibit higher emission efficiencies at NIR region with longer NIR lifetimes upon exciting at longer wavelength.

In this study, two BODIPY based lanthanide complexes were synthesized and their photophysical properties were evaluated. BODIPY based ligands were synthesized with phenanthroline as the ligand binding group. These ligands exhibit strong absorption at 527 nm and 532 nm, fluorescence at 540 nm and 548 nm with 0.55 …

Molecular Recognition Profiles Of Molecular Cocrystals, Ian C. Tinsley

Masters Theses

The manner in which molecules recognize each other holds critical importance to nearly every area of science. This significance stems from the key underpinning of molecular assembly to our most basic understanding of chemical processes. Whether these interactions relate to small-molecule catalytic transformations or complex physiological processes, the structural features responsible for molecular association play into the well-known adage that form follows function where material property arises from the collective structural features of the molecular components. Because the form of chemical systems is derived from a complex blend of covalent and non-bonded contacts, codifying each contributor has become essential for …

Bodipy-Based Red Sensitizers For Near-Infrared Emission Of Lanthanide Complexes, Priyangika Prasadini Senevirathne

Masters Theses

During the past 20 years there has been a remarkable growth in the use of the fluorescence technique in biological studies. Fluorescence and time-resolved fluorescence spectroscopy are considered primary research tools in the field of biochemistry. Currently, fluorescence spectroscopy is a dominant methodology and used widely in biotechnology and medical diagnosis process. One impediment in using fluorescent probes is the fluorescence of biological substrates and fluorescence of diagnostic probes are significantly overlapped, and it decreases the detection sensitivity. Also, commercially available probes require UV or near-UV light excitation, causing severe degradation of biological substrates. Near-infrared emitting lanthanide complexes can overcome …

Behavior Of Different Sizes Of Strontium Titanate Substrates In Electrochemical Modifications, Shuxin Luo

Masters Theses

In our previous atomic force microscopy (AFM) studies of 5 mm x 5 mm single crystal SrTiO₃ (STO(100)) substrates, rutile TiO₂ crystals were found on the substrates surfaces after electrochemical modification. These crystals were found mainly in the area of contact between the substrate and the gold-coated alligator clip that was not supposed to be immersed into the electrolyte and that served as a connection between the STO working electrode and the potentiostat circuit. The size and density of the crystals were found to depend on electrochemical potential, its polarity, the length of modifying time, and the total …

Synthesis And Characterization Of Cu(Ii)-Cu(I) Mixed Valence Complexes, Hansani T. Lekam Wasam Liyanage

Masters Theses

Our study was focused on synthesis and characterization of new family of metal complexes that mimic the active site of copper containing enzymes. Our approach focused on preparing a series of metalloligands which vary systematically in structure and use them in combination with additional metallic centers to synthesize our desired complexes.

We synthesized a main ligand, which is named as HL^Q 2Pz, which contain a quinoline body, one amide bond and two pyrazolyl rings. We synthesized a copper complex by deprotonating HL^Q 2Pz using KOH. The ligand coordinated to the copper(II) center through its quinoline nitrogen, two of …

Synthesis And Characterization Of Dicopper(Ii) Complexes With Biological Relevance, Ashley E. Hall

Masters Theses

The research discussed in this study focused on the design, synthesis, and characterization of new model complexes that mimic the type-3 enzyme, catechol oxidase, which oxidizes catechols to their corresponding quinones. Our approach focused on the design and synthesis new model complexes that contain a dicopper(II) center that can be fine-tuned in a variety of ways, such as sterics and exogeneous bridging molecules. This method allows a multitude of complexes to be created and compared to determine how the overall structure affects the catecholase activity of the complexes.

Two ligands were synthesized; they contain a phenolate body, two amide groups, …

Structures And Nuclear Quadrupole Coupling Tensors Of 1,2-Dichloroethane, 1-Chloro-2-Fluoroethane And 2,3-Dichloropropene Studied Using Microwave Spectroscopy And Computational Chemistry, Asela Sampath Dikkumbura

Masters Theses

The Fourier-transform microwave (FTMW) spectra of 1,2-dichloroethane (12DCE), 1-chloro-2-fluoroethane (1C2FE) and 2,3-dichloropropene (23DCP) have been studied in the 6 to 18 GHz range to determine experimental rotational constants, nuclear quadrupole coupling constants (NQCC) and quartic centrifugal distortions constants. These three molecules have different spatial arrangements (anti and gauche) resulting from different relative orientations of chlorine and/or fluorine atoms about the C-C single bond. The lowest energy anti conformer of 12DCE is non-polar and it is not detectable by microwave spectroscopy, but rotational spectra of gauche-12DCE with three isotopologues, gauche-1C2FE with three isotopologues, and both anti- …

Theoretical Investigations Of Difluorobenzene Interacting With Ne And Infrared Analysis Of 1,1-Dichloroethylene From Synchrotron Data, Seri P. Kamari

Masters Theses

The intermolecular interactions between two molecules are of great importance in proteins, polypeptides, DNA binding, and drug binding interactions. Dimers of chemical rings such as difluorobenzene with hydrogen containing molecules such as acetylene (HCCH) and atoms such as neon are classic systems for investigating weak interactions; however, the microwave spectrum of 1,2-difluorobenzene...Ne does not behave as expected. Possible explanation of this phenomenon is that there is some large amplitude motion perturbing the spectrum.

A computational study was performed to analyze the potential energy surface (PES) of Ne or Ar with ortho, meta, and para difluorobenzene, and reveal the …

Functionalized Bodipy Dyes For Dye-Sensitized Solar Cells, Mahmoud A. Elkhalifa

Masters Theses

It is predicted that more than 20 terawatts of carbon-free energy will be demanded by 2050 to maintain a sufficient energy supply for the increasing global population, and photovoltaics are predicted to contribute significantly to the global energy needs. Dye-sensitized solar cells (DSCs) are an emerging class of photovoltaics (PV) that has produced promising power conversion efficiencies at low costs. Currently, electron recombination, dye aggregation, weak adsorption, and inefficient absorbance are among of the largest contributors to low DSC efficiencies.

BODIPY dyes are one of the most promising classes of dyes emerging for DSC application. These low molecular weight fluorophores …

Investigation Of Β-Cyclodextrin's Ability In Differentiating Chiral Guest Molecules And Synthesis Of 1,6-Diphenyl-2,4-Hexadiene-1,6-Dione, Guang Yang

Masters Theses

This research work comprised two projects. The first one mainly focused on the synthesis of 12 alanine derivatives and analysis of their interactions with β-cyclodextrin through ¹H NMR titration. And the other project was an investigation of the conjugation effect of alkynones in its addition reactions with tributyltin hydride.

The synthesis of the alanine derivatives involved methyl esterification of alanine and then the substitution of an NH hydrogen with a benzoyl group. A total of 4 different substitution groups, labeled as the "A" groups, were introduced on the para-position of the benzoyl's phenyl group. Since alanine has one chiral …

Novel Bodipy Dyes For Dye-Sensitized Solar Cells, Hafsah Klfout

Masters Theses

Dyes-sensitized solar cells (DSCs) are of importance to efficient conversion of solar energy to electricity. The modern version of a DSC is a titanium dioxide nanoparticles-based electrochemical device, in which solar energy is absorbed by dye molecules and electrons from excited dye molecules are injected into the conduction band of titanium dioxide nanoparticle. The electrons are then transported through a network of interconnected TiO₂ particles to the fluorine- tin -oxide layer to the external circuit. In this process dye molecules are crucial to the device's energy conversion efficiency.

Boron-dipyrromethenes, known as BODIPY dyes, show strong absorption in the visible …

Derivatization And Separation Of Natural Estrogens (Estrone, 17Β-Estradiol, And Estriol) Using Gas Chromatography With Flame Ionization Detection (Gc-Fid), Dena L. Guptill

Masters Theses

A major cause of concern for estrogens found in the environment is that even at very low concentrations (10-100 ng/L) they can have a negative effect on aquatic ecosystems by disrupting endocrine systems. Due to the increasing importance of monitoring the levels of estrogens in the environment, a detection method was developed to identify and quantify three natural estrogens (estrone, 17β-estradiol and estriol) using gas chromatography with flame ionization detection (GC-FID). In addition, the efficacy of two derivatizing agents, N,O-bis(trimethylsilyl) acetamide (BSTA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), was evaluated. The GC detector (FID) was most responsive with E3, followed by E1 and …

A Simpler Route To Building Photochromic Cinnamaldehyde Semicarbazones, Byron R. Ebbert

Masters Theses

Photochromic semicarbazones are an interesting group of compounds that show potential in a broad range of applications, including as a more environmentally friendly replacement for photochromic metal complex compounds. Previous work has shown the feasibility to synthesize photochromic cinnamaldehyde semicarbazones (CSCs) from a benzaldehyde and a protected acetaldehyde Wittig reagent. A new, quicker, and cheaper approach to constructing these CSCs from crotonaldehyde was explored in this research. A three reaction sequence would convert crotonaldehyde to a CSC; first, an allylic bromination of the semicarbazone with N-bromosuccinimide (NBS); second, an Arbuzov reaction to prepare the semicarbazone phosphonate; and finally a condensation …

Morphological And Surface Chemistry Characteristics Of Silica Nanoparticle Based Cryogels From Specific Processing Parameters, Ben Walusiak

Masters Theses

The goal of this research was to determine the effects of processing conditions on the morphology and surface chemistry of silica nanoparticle based cryogels. All processing conditions resulted in a change in morphology or surface chemistry compared to the starting material, CAB-O-SIL HS5 fumed silica. N₂ adsorption isotherms were used to characterize surface area and pore size distributions of fumed silica and silica cryogels. TGA (thermogravimetric analysis) was performed on all samples in order to characterize the adsorbed water and hydroxyl group content of the silica surface. Solid state ²⁹Si NMR was also used to evaluate surface chemistry …

Extracellular Gluco-Oligosaccharide Degradation By Caulobacter Crescentus, Gerald N. Presley, Matthew J. Payea, Logan R. Hurst, Annie E. Egan, Brandon S. Martin, Gopal R. Periyannan

Gopal R. Periyannan

The oligotrophic bacterium Caulobacter crescentus has the ability to metabolize various organic molecules, including plant structural carbohydrates, as a carbon source. The nature of β-glucosidase (BGL)-mediated gluco-oligosaccharide degradation and nutrient transport across the outer membrane in C. crescentus was investigated. All gluco-oligosaccharides tested (up to celloheptose) supported growth in M2 minimal media but not cellulose or CM-cellulose. The periplasmic and outer membrane fractions showed highest BGL activity, but no significant BGL activity was observed in the cytosol or extracellular medium. Cells grown in cellobiose showed expression of specific BGLs and TonB-dependent receptors (TBDRs). Carbonyl cyanide 3-chlorophenylhydrazone lowered the rate of …

Extracellular Gluco-Oligosaccharide Degradation By Caulobacter Crescentus, Gerald Presley, Matthew Payea, Logan Hurst, Annie Egan, Brandon Martin, Gopal Periyannan

Faculty Research and Creative Activity

The oligotrophic bacterium Caulobacter crescentus has the ability to metabolize various organic molecules, including plant structural carbohydrates, as a carbon source. The nature of β-glucosidase (BGL)-mediated gluco-oligosaccharide degradation and nutrient transport across the outer membrane in C. crescentus was investigated. All gluco-oligosaccharides tested (up to celloheptose) supported growth in M2 minimal media but not cellulose or CM-cellulose. The periplasmic and outer membrane fractions showed highest BGL activity, but no significant BGL activity was observed in the cytosol or extracellular medium. Cells grown in cellobiose showed expression of specific BGLs and TonB-dependent receptors (TBDRs). Carbonyl cyanide 3-chlorophenylhydrazone lowered the rate of …