Chemistry Commons^™

Unraveling Sources Of Cyanate In The Marine Environment: Insights From Cyanate Distributions And Production During The Photochemical Degradation Of Dissolved Organic Matter, Rui Wang, Jihua Liu, Yongle Xu, Li Liu, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

Cyanate is a nitrogen and energy source for diverse marine microorganisms, playing important roles in the nitrogen cycle. Despite the extensive research on cyanate utilization, the sources of this nitrogen compound remain largely enigmatic. To unravel the sources of cyanate, distributions and production of cyanate during photochemical degradation of natural dissolved organic matter (DOM) were investigated across various environments, including freshwater, estuarine, coastal areas in Florida, and the continental and slope regions of the North American mid-Atlantic Ocean (NATL). Cyanate production was also examined during the photochemical degradation of exudates from a typical strain of Synechococcus, an important phytoplankton …

Potentially Massive And Global Non-Pyrogenic Production Of Condensed "Black" Carbon Through Biomass Oxidation, Aleksandar I. Goranov, Hongmei Chen, Jianshu Duan, Satish C. B. Myneni, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

With the increased occurrences of wildfires worldwide, there has been an increase in scientific interest surrounding the chemistry of fire-derived "black" carbon (BC). Traditionally, wildfire research has assumed that condensed aromatic carbon (ConAC) is exclusively produced via combustion, and thus, ConAC is equated to BC. However, the lack of correlations between ConAC in soils or rivers and wildfire history suggests that ConAC may be produced non-pyrogenically. Here, we show quantitative evidence that this occurs during the oxidation of biomass with environmentally ubiquitous hydroxyl radicals. Pine wood boards exposed to iron nails and natural weather conditions for 12 years yielded a …

Photoacid-Catalyzed C–C And C–O Bond Formation And The Synthesis Of Triazole - Containing Bis(Indolyl)Methanes, Jason Saway

Seton Hall University Dissertations and Theses (ETDs)

From photosynthesis to transition metal-type photocatalysts, the conversion of light energy into chemical energy is a fundamental process in chemistry. While photochemistry is not new to the world of science, there has been a renewed interest in the field, specifically with the use of photocatalysts. There is a wide variety of compounds that function as photocatalysts, ranging from transitions metal complexes, organic dyes, and photoacids. Photoacids, which have typically been used for polymer synthesis and the pH modulation of biological systems and have recently gained popularity due to their catalytic potential. These compounds offer an efficient, cost-effective way to conduct …

Synthesis And Characterization Of Terbium(Iii) Complexes: Can We Manipulate The Emission Signature?, Ryan Gagnon

Belmont University Research Symposium (BURS)

Successful Lewis acid/base reactions of terbium(III) nitrate with 2,2’-bipyrdine (22’bpy), 1,10-phenanthroline (phen), and 2,6-pyridine dimethanol (pydm) have yielded the products: Tb(22’bpy)₂(NO₃)₃, Tb(phen)₂(NO₃)_3, and [Tb(pydm)₃](NO₃)₃, respectively. In accord with the well-known antenna-effect, the absorption spectrum of each complex is similar to the spectrum of the free ligand, while the emission spectrum of the complex is identical for the free terbium(III) ion. In contrast, the substitution of a ligand containing a third-row nonmetal strategically placed near the terbium may force interaction between the 3p nonmetal …

Predicting The Reactivities And Reaction Mechanisms Of Photochemically Produced Reactive Intermediates, Benjamin Barrios Cerda

Dissertations, Master's Theses and Master's Reports

Photochemically produced reactive intermediates (PPRIs) such as the hydroxyl radical, carbonate radical (CO₃^•-) singlet oxygen (¹O₂) and triplet state of chromophoric dissolved organic matter (³CDOM^*) are formed in sunlit natural waters upon photoexcitation of chromophoric dissolved organic matter (CDOM). PPRIs react with the organic compounds involved in key environmental processes, resulting in transformation products of smaller molecular weight than their parent compounds. Photochemical transformation of these key water constituents due to their reactions with PPRIs may pose potential effects on human and aquatic ecosystems. Consequently, there is a need …

Approaches In Molecular Engineering To Optimize The Desired Properties Of Photoactive Molecules, Douglas Joseph Breen

Chemistry and Chemical Biology ETDs

Within this dissertation, photochemical systems that bear significance to next-generation photonic materials and devices are explored. Notable advances in the design, synthesis, and characterization of three distinct groups of photoactive molecules are achieved through molecular design and spectroscopic analysis. First, novel ruthenium sulfoxide complexes bearing substituted phosphine ligands are found to provide extraordinary control over photoisomerization quantum yields. A comparison of these complexes reveals ground-state characteristics that are instrumental in this reactivity, while a novel spectroscopic technique provides rare structural evidence for an O-bonded metastable isomer. Ruthenium complexes bearing chelating carbene-sulfoxide ligands rapidly thermally revert from the O-bonded metastable isomer …

Esipt-Enabled Alkyne Migration Provides Rapid Access To Benzoxazinones, Andrés G. Muñoz

Electronic Theses and Dissertations

Benozoxazinones have long been of interest to agrochemical scientists and medicinal chemists because of their widespread biological activity. These scaffolds are also of interest to synthetic chemists, who recognize the utility of benzoxazinones for accessing functionalized heterocycles. The use of efavirenz, a benzoxazinone-based reverse transcriptase inhibitor used in the treatment of HIV-1, has brought increased attention to this privileged pharmacophore. While there exist numerous strategies for synthesizing benzoxazinones, methods that do not require the use of acutely toxic and environmentally hazardous reagents are lacking. Consequently, there is a need to develop new methods for constructing this valuable scaffold. Herein, we …

Schiff Base Containing Pyridine Groups Functionalized Water-Soluble Phthalocyanine: Synthesis, Photo-Physicochemical Properties, And Bovine Serum Albumin Binding Behavior, Öznur Dülger, Ali̇ Erdoğmuş

Turkish Journal of Chemistry

The novel pyridine bearing schiff base substituted metal-free (9), zinc(II) phthalocyanine (10), and its quaternized derivative (11) were designed and synthesized. These phthalocyanines were fully characterized by spectroscopic methods (FT-IR, UV-Vis, MALDI-TOF, and ¹H NMR). The photo-physicochemical properties of these phthalocyanines were investigated in both DMSO and DMF for 10 and in both DMSO and aqueous solution for 11. The addition of pyridine bearing Schiff base groups as peripheral ligands showed an improvement in the photophysical and photochemical properties. In addition, a spectroscopic investigation of the binding behavior of the water-soluble zinc (II) phthalocyanine …

Computational Investigations Of The Photochemical Properties Of B12-Dependent Systems: From Solution To Enzymes., Megan Toda Mackintosh

Electronic Theses and Dissertations

The photochemical properties of the B₁₂ family of molecules (cobalamins = Cbls) have been known for many years yet only until the 21^st century have applications for the light-sensitivity of Cbls come to the surface. Photolabile Cbls can be used for the delivery of therapeutics with spatial and temporal control, in the generation of hydroxyl radicals, and in nature, as demonstrated in the catalytic cycle of coenzyme B₁₂-dependent photoreceptors. This dissertation describes the use of computational methods to explore the photochemical properties of Cbl systems including antivitamins B₁₂, a thiolato-cobalamin, and the coenzyme B …

Design, Synthesis And Characterization Of Carbohydrate Based Macrocycles, Photo Responsive Derivatives, And Glycoconjugates Based Low Molecular Weight Gelators, Surya Bahadur Adhikari

Chemistry & Biochemistry Theses & Dissertations

Functional glycoconjugates are important classes of compounds with many applications in different research fields. Our lab has been studying the synthesis and applications of different classes of glycoconjugates ranging from macrocycles to sugar heterocycle derivatives. Due to the importance of these compounds, our research is based on development of synthetic methods for various carbohydrate derivatives. This dissertation includes introduction and overview of projects, followed by the synthesis and studies of several different series of glycomacrolactones. The second project focuses on two classes of photoresponsive molecules, the coumarins and diarylethenes. The third project involves the synthesis and self-assembling properties of isoxazole-based …

Aqueous Photochemistry Of 2-Oxocarboxylic Acids: Evidence, Mechanisms, And Atmospheric Impact, Marcelo I. Guzman, Alexis J. Eugene

Chemistry Faculty Publications

Atmospheric organic aerosols play a major role in climate, demanding a better understanding of their formation mechanisms by contributing multiphase chemical reactions with the participation of water. The sunlight driven aqueous photochemistry of small 2-oxocarboxylic acids is a potential major source of organic aerosol, which prompted the investigations into the mechanisms of glyoxylic acid and pyruvic acid photochemistry reviewed here. While 2-oxocarboxylic acids can be contained or directly created in the particles, the majorities of these abundant and available molecules are in the gas phase and must first undergo the surface uptake process to react in, and on the surface, …

Tellurorhodamine Photocatalysts In Aerobic Oxidation Reactions: Development Of Synthetic Methods And Reaction Mechanisms, Irving D. Rettig

Dissertations and Theses

Aerobic oxidation photocatalysis involves the use of oxygen as an oxidant species, coupled to a light driven catalyst to achieve useful chemical transformations. Catalytic aerobic oxidation reactions can be defined as either oxidase-like, in which O₂ acts as an electron donor/acceptor but is not incorporated into the reaction products, or oxygenase-like where O₂ acts as an electron donor/acceptor and is incorporated into the reaction products. A multitude of inorganic catalysts have been developed that can achieve a wide scope of oxidase-like or oxygenase-like reactivity, however, it is rare for a catalyst to be capable of both. We report …

The Emerging Applications Of Sulfur (Vi) Fluorides In Catalysis, Nicholas Ball, Cayo Lee, Jonathan E. Elisabeth, Nathan C. Friede, Glenn M. Sammis

Pomona Faculty Publications and Research

The past decade has witnessed remarkable growth of catalytic transformations in organic sulfur(VI) fluoride chemistry. This Perspective concentrates exclusively on foundational examples that utilize catalytic strategies to synthesize and react S(VI) fluorides. Key mechanistic studies that aim to provide insight toward future catalytic systems are emphasized.

Novel N-Derivatized-7-Nitroindolines For The Synthesis Of Photocleavable Crosslinkers, And For Solid Phase Peptide Synthesis, Hector Patricio Del Castillo

Open Access Theses & Dissertations

7-Nitroindoline-based photochemistry has focused mostly on N-acyl-7-nitroindolines, which have been used as photocleavable protecting groups for carboxylic acids that can be efficiently removed by illumination with UV-light. They offer an alternative to the more commonly used o-nitrobenzyl-based photocleavable protecting groups. N-acyl-7-nitroindolines can also be used as photochemical acylating agents in inert solvents. For example, they have found application in peptide fragment condensation, the convergent synThesis of N-glycopeptides, and the synThesis of peptide thioesters, forming amide and thioester bonds with amine and thiol nucleophiles, respectively, under neutral conditions. The photochemical activation of N-acyl-7-nitroindolines can occur with UV light (λ = 350 …

Photoassisted Synthesis Of Complex Polyheterocycles Via Rational Design Of Tailored Photoprecursors, Tina Alanna Holt

Electronic Theses and Dissertations

Natural products remain the most common source for drug leads, although diversity-oriented synthesis of unnatural complex molecules is gaining momentum. Our lab has been developing experimentally simple and straightforward approaches to complex molecular architectures via photochemical reactions involving a minimal number of experimental steps. In order to achieve this, photoprecursors were assembled via high yielding reactions. Next, we deployed photoinduced cycloadditions to create complex 3-dimentional structures. Lastly, with this obtained primary photoproduct, post-photochemical transformations were used to further grow its scaffold complexity.

One method to increase scaffold complexity is the [4+2] intramolecular cycloadditions of azaxylylenes, which are developed through standard …

Investigation Of Emissions And Chemistry Of Formic Acid And Acetic Acid In Wildfire Smoke, Catherine Elizabeth Wielgasz

Graduate Student Theses, Dissertations, & Professional Papers

Formic acid (HCOOH) and acetic acid (CH₃COOH) are two of the most ubiquitous organic acids in the atmosphere. Chemical transport models consistently underestimate HCOOH and CH₃COOH concentrations in environments including fire smoke, implying our incomplete understanding of their global budget. Emissions and secondary production of HCOOH and CH₃COOH within complex mixtures in fire smoke is uncertain.

I used measurements from the NSF/NCAR C-130 aircraft during the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) campaign to investigate emissions and photochemical production of HCOOH and CH₃COOH from smoke plumes. First, …

Hemithioindigo-Based Photoswitchable Self- Complementary Hydrogen Bond Arrays, Suendues Noori

Electronic Thesis and Dissertation Repository

Hydrogen bonded materials are slowly conquering grounds in the literature because of their dynamic features which stem from their reversible interactions. Incorporating the ability for light to chemically modify these interactions provides a unique template for innovative, efficient and self-healing materials. This thesis explores the design, synthesis, and characterization of nine derivatives of a well-known organic compound – hemithioindigo – with dual function; as a photoswitch and a novel self-complementary hydrogen bond array. The supramolecular complexes formed moderate to strong associations (63 M^-1 to 1100 M^-1) with spontaneous Gibbs free energy values (-10.3 kJ/mol to -17.3 kJ/mol) …

Iron Speciation In Pm2.5 From Urban, Agriculture, And Mixed Environments In Colorado, Usa, Joseph R. Salazar, David J. Pfotenhauer, Frank Leresche, Fernando L. Rosario-Ortiz, Michael P. Hannigan, Sirine C. Fakra, Brian Majestic

Chemistry and Biochemistry: Faculty Scholarship

Atmospheric iron solubility varies depending on whether the particles are collected in rural or urban areas, with urban areas showing increased iron solubility. In this study, we investigate if the iron species present in different environments affects its ultimate solubility. Field data are presented from the Platte River Air Pollution and Photochemistry Experiment (PRAPPE), aimed at understanding the interactions between organic carbon and trace elements in atmospheric particulate matter (PM). 24-hr PM2.5 samples were collected during the summer and winter (2016–2017), at three different sites on the Eastern Colorado plains: an urban, agricultural, and a mixed site. Downtown Denver had …

Seasonal Differences In The Optical Properties Of Chromophoric Dissolved Organic Matter At Hoag’S Pond, Wa, Kimberly Wallace

WWU Honors College Senior Projects

Dissolved organic matter (DOM) plays an important role in carbon cycling in lakes and ponds. DOM sources may vary with elevation due to vegetation differences. To examine this, optical properties of chromophoric dissolved organic matter (CDOM) were investigated between a season with heavy rainfall (wet season) and a season without much rainfall (dry season) in Hoag’s Pond, Washington, USA. This is the first study of CDOM optical properties on Hoag’s pond. Data shows that there is an increase of CDOM in Hoag’s Pond during wet season as compared to dry. Three-dimensional fluorescence excitation-emission matrices (EEM’s) showed that Hoag’s Pond contains …

Analytic Gradients For State-Averaged Multiconfiguration Pair-Density Functional Theory, Thais R. Scott, Matthew R. Hermes, Andrew M. Sand, Meagan S. Oakley, Donald G. Truhlar, Laura Gagliardi

Scholarship and Professional Work - LAS

Analytic gradients are important for efficient calculations of stationary points on potential energy surfaces, for interpreting spectroscopic observations, and for efficient direct dynamics simulations. For excited electronic states, as are involved in UV–Vis spectroscopy and photochemistry, analytic gradients are readily available and often affordable for calculations using a state-averaged complete active space self-consistent-field (SA-CASSCF) wave function. However, in most cases, a post-SA-CASSCF step is necessary for quantitative accuracy, and such calculations are often too expensive if carried out by perturbation theory or configuration interaction. In this work, we present the analytic gradients for multiconfiguration pair-density functional theory based on SA-CASSCF …

Elucidation Of Radical Cation Trapping Chemistry: Using Electrochemical And Photochemical Techniques To Qualitatively Assess The Kinetics Behind Anodic Oxidative Cyclizations, Luisalberto Gonzalez

Arts & Sciences Electronic Theses and Dissertations

While the field of organic chemistry has grown throughout the decades, its primary concern has always been on the generation, conversion, and study of molecular structures. Within that philosophy, the development of new reactions affords chemists the ability to overcome previous synthetic barriers or develop more elegant and simple synthetic routes to difficult-to-construct molecules. Within that realm, electrochemistry is seeing increased attention due its ability to generate highly reactive intermediates, recycle chemical reagents, and reverse the polarity of known functional groups. One example of such an application is the use of electrochemistry to form radical cations. While radical cations have …

Charge Transfer And Plasmon-Pumped Molecular Excitation Mechanisms In Surface Enhanced Photochemistry, Tefera Entele Tesema

Chemistry and Chemical Biology ETDs

Photochemistry that can be driven at low incident photon flux on optically excited plasmonic nanoparticles is attracting increasing research interest because plasmon-driven reactions offer new pathways for efficient conversion of the abundant solar energy into fuel. The confinement of the electromagnetic field by plasmonic metal nanoparticle and consequent field enhancement gives a dual advantage of ultrasensitive in situ and operando spectroscopic methods to monitor enhanced field-driven photochemical transformation. Charge carrier driven either via direct or indirect excitation mechanism are well-established pathways in plasmon-driven reactions to date. However, the excitation mechanism via plasmon-pumped electron transition from an occupied molecular orbital (HOMO) …

Systematic Development Of Photocatalysts, Mary Victoria Bobo

Theses and Dissertations

Photocatalysis is a rapidly growing field and a powerful synthetic tool that has recently seen many advancements, showing immense promise to replace classic catalysis with a mild and elegant alternative methodology. Visible light driven catalysis relies on redox stable transition metal and organic based photoactive catalysts (photocatalysts) that absorb visible light efficiently and facilitate electron/energy transfer. The desire for greener and more renewable catalytic methods has caused research to shifted away from traditional transition metals (due to scarcity and environmental toxicity) and toward organic based photocatalysts. Due to similar photophysical and electrochemical characteristics of each of these classes of photocatalysts …

Applications Of Triplet-Photosensitizers And Development Of Photochemical Methods, Luke V. Lutkus

Dissertations and Theses

Photochemistry focuses on various aspects of the interaction of light with molecules. This work entails new methodology for fundamental measurements of photochemistry along with novel applications of triplet-photosensitizers. Herein described are two separate methodologies developed for the determination of the quantum yield. A method for the singlet oxygen quantum yield was developed that utilizes the reaction between singlet oxygen and dimethyl sulfoxide (DMSO) to produce dimethyl sulfone. The rate of the reaction is measured by the pressure decrease that results from the consumption of oxygen from the headspace of a sealed system. It was found that the rate of pressure …

Structural Annotation Of Electro- And Photochemically Generated Transformation Products Of Moxidectin Using High-Resolution Mass Spectrometry, Lisa Kotthoff, Sarah-Louise O'Callaghan, Jan Lisec, Tanja Schwerdtle, Matthias Koch

Articles

Moxidectin (MOX) is a widely used anthelmintic drug for the treatment of internal and external parasites in food-producing and companion animals. Transformation products (TPs) of MOX, formed through metabolic degradation or acid hydrolysis, may pose a potential environmental risk, but only few were identified so far. In this study, we therefore systematically characterized electro- and photochemically generated MOX TPs using high-resolution mass spectrometry (HRMS). Oxidative electrochemical (EC) TPs were generated in an electrochemical reactor and photochemical (PC) TPs by irradiation with UV-C light. Subsequent HRMS measurements were performed to identify accurate masses and deduce occurring modification reactions of derived TPs …

Newly Synthesized Peripherally Octa-Substituted Zinc Phthalocyanines Carrying Halogenterminated Phenoxy-Phenoxy Moiety: Comparative Photochemical And Photophysicalfeatures, Erkan Kirbaç, Ali̇ Erdoğmuş

Turkish Journal of Chemistry

This study reports the 3 new phthalonitrile derivatives, namely 4, 5 Bis-[4-(4-bromophenoxy) phenoxy] phthalonitrile (1), 4,5 Bis-[4-(4-chlorophenoxy) phenoxy]phthalonitrile (2), and 4, 5 Bis[4-(4-fluorophenoxy) phenoxy] phthalonitrile (3). Their octasubstituted zinc phthalocyanines (4, 5, 6) are reported for the first time in this study. The resulting compounds were characterized by utilizing some spectroscopic methods, such as UV-Vis, 1HNMR, FT-IR spectroscopy, as well as mass spectraand elemental analysis. To show photosynthesizer's potential, emission (FF), singlet oxygen (1O2), and photodegradation quantum yields (ΦΔ, Φd) of octaperipherally phthalocyanines (Pcs) were performed in the solutions, such as biocompatible solvent DMSO (dimethyl sulfoxide) as well as DMF …

C(Sp2)-C(Sp3) Cross-Coupling Of Aryl Halides And Active C(Sp3)-H Bonds Via Dual Catalysis: Organic Photocatalysis/Nickel Redox Catalysis, Nicholas Armada

Department of Chemistry: Dissertations, Theses, and Student Research

Convenient catalytic methodologies that can facilitate the formation of C-C bonds are undoubtedly of great interest in synthetic organic chemistry. Recent reports in literature have showcased hybrid catalytic methods that couple Ni-redox catalysis and photocatalysis to enable C-H activation of tetrahydrofuran (THF) and subsequent cross-coupling with aryl halides in appreciable yields and under relatively mild reaction conditions.^1-2 However, these studies used expensive, heavy metal-containing photocatalysts and both report difficulty obtaining low-specificity across their scopes of aryl-halides. The following report will shed light on a class of photo-excitable small organic molecules that – in conjunction with a catalytic Ni-redox cycle …

Production Of Singlet Oxygen (1O2) During The Photochemistry Of Aqueous Pyruvic Acid: The Effects Of Ph And Photon Flux Under Steady-State O2(Aq) Concentration, Alexis J. Eugene, Marcelo I. Guzman

Chemistry Faculty Publications

The photochemistry of pyruvic acid (PA) in aqueous atmospheric particles contributes to the production of secondary organic aerosols. This work investigates the fate of ketyl and acetyl radicals produced during the photolysis (λ ≥ 305 nm) of 5-100 mM PA under steady state [O₂(aq)] = 260 μM (1.0 ≤ pH ≤ 4.5) for photon fluxes between 1 and 10 suns. The radicals diffuse quickly into the water/air interface of microbubbles and react with dissolved O₂ to produce singlet oxygen (¹O₂^*). Furfuryl alcohol is used to trap and bracket the steady-state production of …

Organic-Inorganic Hybrid Composites: Superhydrophobic Polymer Coatings With Photoreactive Perfluorinated Phthalocyanines, Abdul Azeez

Seton Hall University Dissertations and Theses (ETDs)

ABSTRACT

We report partly fluorinated and silicon-based polymers that incorporate inorganic/organic materials capable of generating reactive oxygen species (ROS) using only visible light and air. Polyvinylidene fluoride (PVDF), which incorporated a known perfluorinated phthalocyanine photosensitizer, F₆₄PcZn, supported on silicon and titanium oxides was further modified via chemical surface roughening to exhibit enhanced hydrophobicity when used as a coating. Water contact angles as high as ~159° have been observed, vs. ~ 92° for the unmodified polymer. The polymer matrix, however, does not resist the ROS it produces as evidenced by spectroscopic and SEM data. A polysiloxane matrix was similarly …

Self-Assembly, Integration, Characterizations And Applications Of Plasmonic And Excitonic Nanomaterials, Bijesh Kafle

Chemistry and Chemical Biology ETDs

Plasmon on metal nanoparticles can efficiently confine, amplify light at the nanoscale. This property is beneficial for different applications such as harvesting energy of the broad solar spectrum, highly sensitive spectroscopy, photocatalysis, and many other optoelectronic applications. For plasmonic applications, it is necessary to understand the fundamental physical properties of the individual, coupled plasmonic nanomaterials, and their interaction with the surrounding environment, which is not fully understood yet. In this dissertation, the chemical and optical interaction in plasmonic interfaces has been investigated. Plasmon-enhanced photochemistry of p-aminothiophenol as a model molecule is investigated using highly sensitive surface-enhanced Raman spectroscopy (SERS). The …