672 research outputs found
Insoluble Methylene Bridged Glycoluril Dimers as Sequestrants for Dyes
No full textContamination of water bodies by micropollutants including industrial dyes is a worldwide health and environmental concern. We report the design, synthesis, and characterization of a series of methylene bridged glycoluril dimers (G2W1 – G2W4) that are insoluble in water and that differ in the nature of their aromatic sidewalls (G2W4: benzene, G2W3: naphthalene, G2W1 and G2W2: triphenylene). We tested G2W1 – G2W4 along with comparator H2 as solid state sequestrants for a panel of five dyes (methylene blue, methylene violet, acridine orange, rhodamine 6G, methyl violet 6B). We find that catechol-walled H2 (OH substituents) is a superior sequestrant compared to G2W1 – G2W4 (OMe substituents). X-ray crystal structures for G2W1 and G2W3 suggest that the OMe groups fill their own cavity and thereby decrease their abilities as sequestrants. H2 achieved a removal efficiency of 94% for methylene blue whereas G2W1 demonstrated a 64% removal efficiency for methylene violet; both sequestration processes were largely complete within 10 minutes.We thank the National Science Foundation (CHE-1807486) for past financial support. We thank the National Institute of General Medical Sciences of the National Institutes of Health (R35GM153362) for current financial support of this project. S.P. thanks the University of Maryland for the G. Forrest Woods Fellowship and the Charlotte Kraebel PhD ’59 Endowed Award in Organic Chemistry
Electronic Supporting Data: Tetrachloroanthracene Walled Glycoluril Dimer Undergoes Self-Association and 1:1, 2:2, and 1:3 Host•Guest Binding
No full textWe report the design, synthesis and characterization of a tetrachloroanthracene walled methylene bridged glycoluril dimer (H1). According to 1H NMR spectroscopy and symmetry considerations we formulate H1 as a C2v-symmetric monomer in DMSO but it exists as a C2h-symmetric dimer (H1•H1) in water. The H1•H1 dimer persists below 25 uM in water and displays high thermodynamic stability (Ks ≥ 1.8 x 106 M-1). H1•H1 is also stable up to 70 ˚C in water. We investigated the binding of H1 with a panel of five dyes by isothermal titration calorimetry and 1H NMR spectroscopy and found that H1 engages with dyes with several different stoichiometries of binding. For example, NMeAc and Berb are capable of causing the dissociation of H1•H1 resulting in the formation of the 1:1 intracavity dye complexes H1•NMeAc and H1•Berb. In contrast, Rh6G and ThT do not dissociate the H1•H1 dimer and instead stack on the exterior of the dimer to form Rh6G•H1•H1•Rh6G and ThT•H1•H1•ThT, respectively. Finally, 3 equivalents of NDI+ causes dissociation of H1•H1 and binds both intracavity and on the exterior to form the H1•(NDI+)3 complex.We thank the National Science Foundation (CHE-1807486) for past financial support. We thank the National Institute of General Medical Sciences of the National Institutes of Health (R35GM153362) for current financial support of this project
Electronic Supporting Data: Aromatic Wall Extension of Glycoluril-Derived Molecular Clips Enhances Binding of Planar Aromatic Dyes
No full textSee the Supporting Information document.We report the synthesis and characterization of a new methylene bridged glycoluril dimer featuring anthracene walls (H2). H2 displays good solubility in water (≥7 mM) but undergoes self-association at concentrations above 2 mM. 1H NMR experiments establish that H2 binds cationic dyes inside its cavity with a -stacked geometry that places the cationic residues at the ureidyl carbonyl portals of H2. The binding constants of both naphthalene-walled clip H1 and anthracene-walled clip H2 toward a panel of dyes were measured by direct or competitive UV/Vis or fluorescence titrations in phosphate buffered saline (PBS). Binding constants cover the range from 103 – 108 M-1. Dyes that feature cationic NMe2 groups bind more strongly than analogous dyes with cationic NH2 groups. We find that pi-extension of the aromatic walls from H1 to H2 generally results in an ≈ 10-fold increase in binding affinity. Host•guest complexes of H1 and H2 with planar cationic dyes benefit from substantial cation-pi interactions.We thank the National Science Foundation (CHE-1807486) for past financial support. We thank the National Institute of General Medical Sciences of the National Institutes of Health (R35GM153362) for current financial support of this project.https://doi.org/10.1002/chem.20250217
Black Lives Matter Reading Group: Hosted by Dr. Camille Isaacs
No full textSlides that accompanied a lecture by Dr. Camille Isaacs on the work of author and activist Desmond Col
Insoluble Acyclic Cucurbit[n]uril-Type Receptors Capture Iodine from the Vapor Phase
No full textSee the written Supporting Information file.Nuclear energy makes large contributions toward meeting global energy needs, but societal concerns remain high given the impacts of the intended release of radioactive materials including 129I and 131I. In this paper we explore the use of a homologous series of acyclic CB[n] type hosts (H1–H4) as adsorbents of iodine from the vapor phase. We find that H2–H4, but not H1 – perform well in this application with uptake capacities of 2.2 g g−1, 1.5 g g−1, and 1.9 g g−1, respectively. The chemisorptive uptake process involves partial oxidation of catechol walled H2 to quinone walled host and capture of I3− and I5−. Solid H2 can be regenerated by treatment with Na2S2O4 and reused at least five times. The x-ray crystal structure of H2 is also reported.We thank the National Science Foundation (CHE-1807486) for past financial support. We thank the National Institute of General Medical Sciences of the National Institutes of Health (R35GM153362) for current financial support of this project. S.P. thanks the University of Maryland for the G. Forrest Woods Fellowship and the Charlotte Kraebel PhD'59 endowed award in organic chemistry.https://doi.org/10.1002/chem.20240317
Problem Sets for Organic Spectroscopy
No full textThis folder contains organic structural spectroscopy problems used by Dr. Isaacs in his Chemistry 460 course at the University of Maryland. Each problem contains 1H, 13C, DEPT, COSY, HSQC, and HMBC NMR spectra that were simulated using the commercially available software from Advanced Chemistry Development. These problems can be used in two different ways: 1) the students are provided the structure and asked to assign all the resonances, and 2) the students are given the spectra and asked to deduce the structures. The answer key is password protected. Instructors can email Dr. Isaacs at [email protected] to request the password.These materials were prepared as part of the broader impacts work of Dr. Isaacs NSF grant CHE-1807486
Citizenships and Identities. Inclusion, Exclusion, Participation
No full textA distinguished transnational, transgenerational and transdisciplinary group of researchers, working together in six research teams, shows how citizenship has developed, emphasizing continuities and breaking points, particularly but not only in European countries. It also addresses the question of 'identities' and the ways that this very ambiguous concept is used in different historical and historiographical contexts. This is the final volume produced by the CLIOHRES FP6 Network of Excellence designed and coordinated by Isaacs (2005-2010; 51 volumes all available on www.cliohres.net, 180 researchers; 31 countries; 4.500.000€ grant). It presents the final results of the Network's research. Central coordinator of the Network, Isaacs is editor of the volume, author of the Introduction and contributor to one of the collaborative chapters. The volume shows that 'citizenship' is understood in very different ways in different parts of Europe today. It examines how this situation has arisen, and how citizenship has been defined and analysed in different historical and historiographical contexts
Discrete and Polymeric Complexes Comprising Bis-nor-seco-CB[10] and Oligoammonium Ions
No full textABSTRACT
Title of Document: DISCRETE AND POLYMERIC COMPLEXES COMPRISING BIS-NOR-SECO-CB[10] AND OLIGOAMMONIUM IONS
Regan C. Nally, Ph.D., 2009
Directed By: Professor Lyle D. Isaacs
Department of Chemistry and Biochemistry
Supramolecular architectures composed of multiple components are challenging to produce, as the enthalpic gain must be greater than the entropic penalty of strict geometrical arrangements. Therefore, it is the goal of supramolecular chemists to strategically design and synthesize molecules that will exhibit selectivity toward formation of a particular complex. This dissertation describes the formation of supramolecular architectures of increasing size and is organized in the following way.
Chapter 1 introduces the reader to the field of supramolecular polymer chemistry.
Chapter 2 describes the synthesis of a series of monovalent ditopic guests (II-1 - II-6) and their complexation properties toward double cavity cucurbituril host bis-ns-CB[10]. We observed the preferential formation of 1:1, 2:2, and oligomeric complexes rather than the desired n:n supramolecular polymers. Guest II-7 which contains a longer biphenyl spacer successfully precludes the formation of the 1:1 complex but results in the formation of the 2:2 complex (bis-ns-CB[10]2*II-72) rather than supramolecular polymer. Guest II-8 is heterovalent and ditopic and is shown to reversibly form 2:2 and 1:2 complexes (bis-ns-CB[10]2*II-82 and bis-ns-CB[10]*II-82) in response to changes in host:guest stoichiometry. Lastly, this equilibrium can be manipulated by the addition of exogenous CB[6] which selectively targets the hexanediammonium ion binding region of II-8 and delivers the penta-molecular complex bis-ns-CB[10]*II-82*CB[6]2.
Chapter 3 describes the formation of a main chain supramolecular polymer from a mixture of poly(diallyldimethylammonium chloride) (III-1) and bis-ns-CB[10]. The bis-ns-CB[10] molecular container behaves as a molecular handcuff, bringing together two ends of individual polymers to form III-1n* bis-ns-CB[10]m, resulting in an extension of the length of polymer. The effect of bis-ns-CB[10] on the physical properties of the polymer was investigated using viscometry in aqueous solution. A decrease in the ηrel was observed upon increasing concentrations of bis-ns-CB[10] to a solution of III-1. Atomic force microscopy (AFM), and diffusion-ordered spectroscopy (DOSY) were performed to probe the mode of interaction between polymer III-1 and bis-ns-CB[10]. Collectively, the data supports the two roles for bis-ns-CB[10]: 1) as a deaggregation agent, and 2) as a molecular handcuff that non-covalently links individual polymer strands resulting in overall extension of the polymer
The Life and Work of George Isaacs
No full textThis is the first comprehensive examination of the life, work and significance of the colonial writer George Isaacs, the “thorough Bohemian” who was the author of the first novel published in South Australia, The Queen of the South. Under the apt pseudonym of “A. Pendragon”, Isaacs captured the dynamic atmosphere of the colonial era in his writing, which ranged from plays to poetry and from journalism to prose. But he did not fit comfortably into colonial society. Set apart by an unconventional private life, his Jewish heritage, his fierce intelligence and his willingness to speak and write his mind, he led a surprisingly varied life across two hemispheres and two Australian colonies. Isaacs was largely forgotten after his death. This chronological biography redresses this neglect by establishing the details of his life and writing. An Appendix provides a bibliography of his published and unpublished works. Opening chapters examine Isaacs’ youth in England, with an emphasis on his first precocious publication, his enthusiasm for antiques, his influential connections, his travels and his immigration to South Australia. Following chapters discuss Isaacs’ productive years in Australia, where, despite poverty, imprisonment and chronic ill-health, he visited the Victorian goldfields, wrote plays that were performed around the world, and had great influence in Gawler. There, he was a founder of the Humbug Society, influential in the Gawler Institute and responsible for an Australian anthem. One of Isaacs’ plays, based on Frankenstein, was possibly the first published science fiction in Australia. This opinionated man left a significant imprint on his society and its literature. He did not become famous or wealthy, but his activities and his writing provide a useful counterpoint to the conventional interpretation of a successful life. As an inaugural study, The Life and Work of George Isaacs contributes another strand to our knowledge of Australian colonial literature and provides a foundation for further research. On a more intimate level, it is a paradigm of a colonial scribe—a case study of one immigrant’s struggles to live as a writer in the evolving society of colonial Australia.Thesis (Ph.D.) -- University of Adelaide, School of Humanities, 201
Author Correction: Discovery and refinement of genetic loci associated with cardiometabolic risk using dense imputation maps
No full textCorrection to: Nature Genetics https://doi.org/10.1038/ng.3668, published online 26 September 2016.
In the version of the article published, the surname of author Aaron Isaacs is misspelled as Issacs
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