jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: M. S. A. Abdel-Mottaleb
Source: Journal of Chemistry (article, 2019-01-02)
Field: Materials Science — Materials Chemistry

On the Nature of Interplay among Major Flexibility Channels in Molecular Rotors As a part of our interest in the excited-state dynamics of flexible materials, we have undertaken a theoretical investigation to the photo-induced reactions of 2-[4-(dimethylamino)benzylidene]malononitrile (BMN) by a combination of the density functional theory, its extended time-dependent (TD-DFT) single reference, and ab initio molecular dynamic (MD) simulations. The results showed that double-bond twisting and the neighbor single-bond twisting togetherness in the excited singlet state is the most important nonradiative deactivation channel to the ground state. Double- and single-bond twisting insert clear intersections among the potential energy surfaces of the singlet states (especially S 1 /S 0 ) leading to fluorescence quenching. Furthermore, effects of molecular dynamic simulations on molecular properties in the femtosecond to picosecond time domain are studied to validate the results. In agreement with the experimental results, the findings conclude the existence of a flexible geometry-dependent single emission band. Such a study may give information on how the molecule could be externally modified/fixed to yield a desired effect, i.e., more fluorescence or more nonradiative decay. Chemistry ; Excited state ; Picosecond ; Density functional theory ; Quenching (fluorescence) ; Femtosecond ; Molecular physics ; Singlet state ; Molecular geometry ; Single bond ; Yield (engineering) ; Molecule ; Ab initio ; Molecular dynamics ; Ground state ; Chemical physics ; Fluorescence ; Atomic physics ; Computational chemistry ; Quantum mechanics ; Thermodynamics ; Physics ; Laser Luminescence and Fluorescent Materials ; Photochemistry and Electron Transfer Studies ; Molecular Junctions and Nanostructures
Authors: Brent L. Russell
Source: W&M Publish (College of William & Mary) (article, 2019-01-01)
Field: Chemistry — Physical and Theoretical Chemistry

Utilization of Unnatural Amino Acids in the Development of Novel Functions and Probing Applications The utilization of unnatural amino acids opens the door for thousands of ways to expand the chemical diversity of proteins, providing functional groups for chemical manipulation that would otherwise be impossible. The ability to site-specifically incorporate unnatural amino acids confers a degree of control and specificity over these reactions that allows for precision probing and engineering of pathways and functions. A number of these chemical possibilities will be explored in this thesis. The utilization of fluorotyrosines in green fluorescent protein marks the first step towards developing a novel, physiologically relevant fluorescent biosensor. The use of unnatural amino acids in Utag, a medically relevant enzyme, allows for the exploration of the utility of fluorescent bioconjugations in developing a noninvasive screen for prostate cancer. Finally, the unique radical pathway of a multifunctional globin, dehaloperoxidase, will be explored via the utilization of 3-fluorotyrosine. In short, unnatural amino acids allow for the exploration and development of novel reactions and applications of proteins that have before been out of reach. Computer science ; Amino acid ; Chemistry ; Biochemistry Various Chemistry Research Topics
Authors: 昌徳 蝦名
Source: Hokkaido University Collection of Scholarly and Academic Papers (Hokkaido University) (article, 2019-03-25)
Field: Chemistry — Physical and Theoretical Chemistry

Theoretical Study on the Excited States and Emission Mechanisms of Metal Complexes with Multiple-Emissions Excited state ; Chemistry ; Physics ; Atomic physics Photochemistry and Electron Transfer Studies ; Lanthanide and Transition Metal Complexes ; Organic Light-Emitting Diodes Research
Authors: Matthew Robert Cottle
Source: Carolina Digital Repository (University of North Carolina at Chapel Hill) (article, 2019-08-15)
Field: Materials Science — Polymers and Plastics

Synthesis of novel conjugated polymers and copolymers Conjugated polymers have found many uses as high-strength materials in the automotive and aerospace industries as well as the active components in thin film transistors, light emitting diodes and solar cell devices. There are few pathways to the synthesis of soluble conjugated polymers and side reactions or stringent polymerization conditions are prevalent in many of them. This work describes the synthesis of several conjugated polymers via Ni(0)-catalyzed coupling or Stille coupling. First, poly(2,5-benzophenone) macroinitiators are synthesized via Ni(0)-catalyzed coupling and incorporated, as the middle block, into coil-rod-coil triblock copolymers with poly(lactide). The study of the effects of ligand type, solvent type, reaction temperature, and reaction time in the Ni(0)-catalyzed coupling of 2-benzenesulfonyl-1,4-dichlorobenzene are then presented. Next, the synthesis of poly(paraphenylene) containing a thermally removable solubilizing group is shown. The optical bandgap was shown to decrease as the solubilizing group undergoes two thermolysis steps to afford native poly(paraphenylene). Furthering this work, alternating donor-acceptor polymers are synthesized via Stille coupling that also contain thermally removable solubilizing groups. These materials are characterized by NMR, GPC, DSC, TGA, and UVvis. Conjugated system ; Copolymer ; Polymer ; Polymer science ; Chemistry ; Polymer chemistry ; Organic chemistry Synthesis and properties of polymers
Authors: Jiancheng Zhu
Source: NCSU Libraries Repository (North Carolina State University Libraries) (article, 2019-11-26)
Field: Chemistry — Organic Chemistry

Benzimidazolyl Palladium Complexes as Highly Active Bifunctional Catalysts for Sustainable Cross-Coupling, C–H Functionalization and Hyperpolarization, and Approach to Light-mediated Fluoroethylation of Heteroarenes. ZHU JIANCHENG.Benzimidazolyl Palladium Complexes as Highly Active Bifunctional Catalysts for Sustainable Cross-Coupling, C-H Functionalization and Hyperpolarization, and Approach to Light-mediated Fluoroethylation of Heteroarenes.(Under the direction of Bifunctional ; Surface modification ; Palladium ; Catalysis ; Hyperpolarization (physics) ; Chemistry ; Coupling (piping) ; Photochemistry ; Combinatorial chemistry ; Materials science ; Stereochemistry ; Organic chemistry ; Nuclear magnetic resonance spectroscopy ; Physical chemistry Catalytic C–H Functionalization Methods ; Fluorine in Organic Chemistry ; Radical Photochemical Reactions
Authors: Chen Qiang | Thoms Stefan | Stöttinger Sven | Schollmeyer Dieter | Müllen Klaus | Narita Akimitsu | Basché Thomas
Source: Institutional Repositories DataBase (IRDB) (article, 2019-10-07)
Field: Chemistry — Organic Chemistry

Dibenzo[hi,st]ovalene as Highly Luminescent Nanographene: Efficient Synthesis via Photochemical Cyclodehydroiodination, Optoelectronic Properties, and Single-Molecule Spectroscopy Dibenzo[hi,st]ovalene (DBOV), as a new nanographene, has demonstrated promising optical properties, such as red emission with a high fluorescence quantum yield of 79% and stimulated emission, as well as high thermal stability and photostability, which indicated its promise as a light-emitting and optical gain material. However, the previous synthetic routes required at least 12 steps. This obstructed access to different derivatives, e.g., to obtain crystals suitable for X-ray diffraction analysis and to tune the optoelectronic properties. Here, we report an efficient synthetic pathway to DBOV based on a sequential iodination-benzannulation of bi(naphthylphenyl)diyne, followed by photochemical cyclodehydroiodination (PCDHI). This protocol included a fused bischrysene as a key intermediate and furnished scalable amounts of meso-substituted DBOV derivatives with different substituents. DBOV with 2,6-dimethylphenyl groups could be used for single-crystal X-ray analysis, revealing the precise structure of the DBOV core. The optoelectronic properties of the DBOV derivatives were investigated by UV-vis absorption and fluorescence spectroscopy, cyclic voltammetry, and density functional theory calculations. Single-molecule spectroscopy at room and low temperatures provided novel insights into the photophysics of DBOV embedded in a polymer film. As a result of weak coupling of the optical transitions to the matrix, single-molecule emission spectra at 4.5 K showed narrow vibronic lines. The fluorescence autocorrelation function covering 9 orders of magnitude in time displayed high contrast photon antibunching and bunching, from which the fluorescence decay rate and the triplet population and depopulation rates could be retrieved. Remarkably, the intersystem crossing rate into the triplet state decreased by more than an order of magnitude at low temperature, demonstrating that temperature can be a crucial parameter to boost single photon emission of an aromatic hydrocarbon. Intersystem crossing ; Fluorescence ; Spectroscopy ; Quantum yield ; Population ; Emission spectrum ; Luminescence ; Absorption spectroscopy ; Fluorescence spectroscopy Synthesis and Properties of Aromatic Compounds ; Luminescence and Fluorescent Materials ; Organic Electronics and Photovoltaics
Authors: Salem Wehbé, Layale
Source: theses.fr (ABES) (article, 2019-12-18)
Field: Materials Science — Materials Chemistry

Identification et caractérisation des phosphoprotéines phosphatases, PP4 et PP2A, comme nouveaux régulateurs négatifs de la voie IMD chez la Drosophile Les facteurs de transcription NF-κB sont des régulateurs essentiels de la réponse immunitaire innée hautement conservée au cours de l’évolution. Leur activation excessive est hautement délétère et est associée au développement de maladies inflammatoires chroniques. Il est donc particulièrement intéressant de caractériser les mécanismes moléculaires régulant leur activation. Au cours de ce travail, nous avons exploré le rôle de phosphoprotéines phosphatases dans la régulation de la voie IMD-NF-κB chez la drosophile. Homologue de la voie de signalisation activée en aval du récepteur TNFα et des récepteurs Toll-like chez les mammifères, cette voie contrôle les infections bactériennes chez la drosophile à travers l’activation du facteur de transcription de type NF-κB, Relish. Nous avons identifié les phosphatases PP2A et PP4 comme de nouveaux régulateurs négatifs de la voie IMD. En combinant des approches génétiques et moléculaires nous avons montré que ces phosphatases agissent au niveau du complexe IKK et du facteur de transcription Relish respectivement, pour la régulation fine de la voie IMD. Ainsi ce travail fournit la première preuve de la régulation négative de la voie IMD par des phosphoprotéines phosphatases et met l’accent sur la haute conservation des fonctions de PP2A et de PP4 dans la régulation des voies NF-κB. Nos résultats offrent ainsi de nouvelles perspectives pour la caractérisation des mécanismes moléculaires régulant la voie IMD. Transcription (linguistics) ; Phosphatase ; Transcription factor ; Protein phosphatase 2 High voltage insulation and dielectric phenomena ; Electrostatic Discharge in Electronics ; Pulsed Power Technology Applications
Authors: Matteo Panza
Source: IRL - University of Missouri, St. Louis (University of Missouri–St. Louis) (article, 2019-01-01)
Field: Chemistry — Organic Chemistry

Towards Completely Automated Glycan Synthesis Carbohydrates are ubiquitous both in nature as biologically active compounds and in medicine as pharmaceuticals. Although there has been continued interest in the synthesis of carbohydrates, chemical methods require specialized knowledge and hence remain cumbersome. The need for development of rapid, efficient and operationally simple procedures has come to the fore. This dissertation focuses on the development of a fully automated platform that will enable both experts and non-specialists to perform the synthesis of glycans. Existing automated methods for the synthesis of oligosaccharides are highly sophisticated, operationally complex, and require significant user know-how. By contrast, high performance liquid chromatography (HPLC) equipment-based automation introduced by our lab represents a highly accessible method of synthesis. This approach offers operational simplicity by delivering all reagents using standard liquid handling components and convenient real-time reaction monitoring of every step using detectors and standard computer software and interface. Many operations still require the operator intervention, and the entire technology remains semi-manual. Building upon promising preliminary results, this dissertation aimed to generate a universal platform for the fully automated synthesis of glycans. To achieve the complete automation of the solid phase synthesis that has the potential to revolutionize glycan synthesis, this dissertation focuses on the following aspects: 1) the development of new concepts for chemical glycosylation applicable to stereoselective formation of challenging 1,2-cis glycosidic bonds; 2) implementation of autosamplers and switch valves as new components to achieve operator-less automation; and 3) the development of new chemically stable resins for solid phase synthesis. With these key developments, we have acquired a reliable and simple platform for fully-automated oligosaccharide synthesis. The proof of concept was assessed by the synthesis of a number of target glycans. Synthesis of carbohydrates and other classes of biomolecules using this user-friendly and fully-automated platform will accelerate discovery in many scientific disciplines, most prominently chemistry, automation, and therapeutic-agents development. Glycan ; Computer science ; Chemistry ; Biochemistry Carbohydrate Chemistry and Synthesis ; Glycosylation and Glycoproteins Research ; Chemical Synthesis and Analysis
Authors: Camilli, L | Sun, J | Grillo, A | Caridad, J | Passacantando, M | Di Bartolomeo, A
Source: Research Explorer (The University of Manchester) (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

Ge-based layered materials with high anisotropy Silicon Nanostructures and Photoluminescence ; Material Science and Thermodynamics ; 2D Materials and Applications
Authors: Katharina S. Wetzel
Source: Repository KITopen (Karlsruhe Institute of Technology) (article, 2019-01-01)
Field: Chemistry — Physical and Theoretical Chemistry

Novel Approaches Towards Sequence-Definition in Polymer Chemistry Using Multicomponent Reactions Das sich rasch weiterentwickelnde Gebiet der sequenz-definierten Polymere ist durch hochdefinierte, in der Natur vorkommende Biomakromoleküle wie DNA oder Peptide inspiriert, deren definierte Primärstruktur komplizierte biochemische Prozesse ermöglichen. Sowohl die einzigartigen katalytischen Eigenschaften von Enzymen, als auch die Fähigkeit von DNA, die fundamentalen Informationen eines Organismus zu speichern und replizieren, erklären die Faszination, die Sequenzdefinition in der Polymerchemie birgt. Während Polymerchemiker weltweit nach mehr Kontrolle in der Polymerstruktur streben, ist die Präzision der Natur weiterhin unerreichbar. In dieser Arbeit wurden neue Ansätze untersucht, die die etablierte Passerini Dreikomponentenreaktion nutzen und mit anderen leistungsfähigen Reaktionen, wie der 1,2,4-Triazolin-3,5-dion (TAD) Diels-Alder Klick Reaktion oder der Ringschlussmetathese kombiniert, um die Vielseitigkeit bereits bekannter Ansätze noch zu übertreffen. Große, definierte Makrozyklen wurden über einen templat-freien Ansatz durch Zyklisierung linearer Vorstufen gebildet. Die Vorstufen wurden in einem zweistufigen iterativen Reaktionszyklus basierend auf bidirektionalem Wachstum mit einem dafür geeigneten AB-Monomer erhalten und für Untersuchungen von Struktur-Aktivitäts-Zusammenhängen in der Ringschlussmetathese verwendet. Ein zweiter Ansatz greift auf den gleichen zweistufigen iterativen Ansatz zurück und verwendet dabei erstmals neun verschiedene Monomere. Durch das unabhängige Variieren von Seitenkette und Rückgrat wurden zweifach sequenzdefinierte Makromoleküle erhalten. Diese wurden mittels Tandem Massenspektrometrie ausgelesen, wobei sich zeigte, dass es sich um interessante Verbindungen für die Datenspeicherung handelt, die durch die Erhöhung der frei wählbaren Einheiten pro Wiederholeinheit eine erhöhte Datenspeicherkapazität ermöglichen. In einem dritten Ansatz wurde die Passerini Reaktion mit der dazu orthogonalen TAD Diels-Alder Klick Reaktion in einem schutzgruppen-freien Ansatz kombiniert. Die wirksame und effiziente Kombination der beiden Reaktionen führte zu einem idealen iterativen Wachstum und erlaubte die schnelle Synthese von langen Sequenzen. Durch Übertragung des Ansatzes auf die Festphasensynthese konnte eine umfassende Vergleichsstudie von Festphasensynthese und der Synthese in Lösung durchgeführt werden, die die Vor- und Nachteile beider Strategien hervorhebt. Die vorliegende Arbeit strebt danach, literaturbekannte Ansätze zur Sequenzdefinition, die auf der Passerini Reaktion basieren, in Vielseitigkeit und Anwendbarkeit der erhaltenen Makromoleküle zu übertreffen. Chemistry ; Stereochemistry ; Molecular biology ; Biology Various Chemistry Research Topics
Authors: Matteo Campanelli | Tiziana Del Giacco | Filippo De Angelis | Edoardo Mosconi | Marco Taddei | Fabio Marmottini | Ferdinando Costantino
Source: ChemRxiv (preprint, 2019-10-07)
Field: Chemistry — Inorganic Chemistry

A Solvent Free Synthetic Route for Cerium(IV) Metal-Organic Frame-works with UiO-66 Architecture and Their Photocatalytic Application A novel solvent-free synthesis for Ce-UiO-66 metal-organic frameworks (MOFs) is presented. The MOFs are obtained by simply grinding the reagents, cerium ammonium nitrate (CAN) and the carboxylic linkers, in a mortar for few minutes with the addition of a small amount of acetic acid (AcOH) as modulator (1.75 eq, o.1 ml). The slurry is then transferred into a 1 ml vial and heated at 120°C for 1 day. The MOFs have been characterized for their composition, crystallinity and porosity and employed as heterogenous catalysts for the photo-oxidation reaction of substituted benzylic alcohols to benzaldaldehydes under near ultraviolet light irradiation. The catalytic performances, such as yield, conversion and kinetics, exceed those of similar systems studied by chemical oxidation and using Ce-MOF as catalyst. Moreover, the MOFs were found to be reusable up to three cycles without loss of activity. Density functional theory (DFT) calculations gave an estimation of the band-gap shift due to the different nature of the linkers used and provide useful information on the catalytic activity experimentally observed. Catalysis ; Cerium ; Reagent ; Photocatalysis ; Crystallinity ; Metal-organic framework ; Porosity ; Chemistry ; Solvent ; Yield (engineering) ; Materials science ; Chemical engineering ; Inorganic chemistry ; Organic chemistry Metal-Organic Frameworks: Synthesis and Applications ; Chemical Synthesis and Reactions ; Polyoxometalates: Synthesis and Applications
Authors: Jia Liu | Xu‐Liang Nie | Zhongping Yin | Da‐Yong Peng | Xugen Shi
Source: Zeitschrift für Kristallographie - New Crystal Structures (article, 2019-12-07)
Field: Chemistry — Inorganic Chemistry

Crystal structure of 5-((bis(pyridin-2-ylmethyl)amino)methyl)quinolin-8-ol, C<sub>22</sub>H<sub>20</sub>N<sub>4</sub>O Abstract C 22 H 20 N 4 O, monoclinic, P 2 1 / n (no. 14), a = 11.1861(14) Å, b = 8.1418(10) Å, c = 20.461(3) Å, β = 97.433(1)°, V = 1847.8(4) Å 3 , Z = 4, R gt ( F ) = 0.0357, wR ref ( F 2 ) = 0.1002, T = 296(2) K. Monoclinic crystal system ; Crystal structure ; Chemistry ; X-ray crystallography ; Crystallography ; Stereochemistry ; Physics ; Diffraction Crystal structures of chemical compounds ; Molecular Sensors and Ion Detection ; Synthesis and biological activity
Authors: Rany Rotem
Source: BOA (University of Milano-Bicocca) (article, 2019-02-19)
Field: Materials Science — Biomaterials

Development of Reliable Experimental Models for the Study of the Biological Behavior of Drug Nanocarriers The curative effectiveness of current and new drugs is often limited by poor pharmacokinetics in-vivo. The use of nanoparticles as drug carriers seems promising in solving this problem. In this work we aimed to further explore and improve common drug delivery components and techniques. Starting with the synthesis of nanoparticles with a controlled number of molecular recognition ligands, we used bulky ligands and gel separation to obtain nanoparticles with a discrete number of chemical functional groups, used later to conjugate the same number of molecular recognition ligands. These nanoparticles later showed substantial difference in the in-vivo behavior. A second project focused on the in-depth characterization of the relationship between hydrophobic inorganic nanoparticles and the polymer surfactants used to enable their water dispersibility, as well enabling their functionalization. This investigation was done through separate quantification of polymer and inorganic nanoparticles and assessment of stability. Our results showed that the removal of excess polymer from such systems can result in loss of colloidal stability. A third project was aimed to describe the mechanism of polymeric nanoparticle’s endosomal escape and provide a platform for qualitative investigation and enhancement of this process. This goal was accomplished through two complementary in-vitro experiments testing two proposed mechanisms of endosomal escape. These results raised a key consideration when matching a particle capable of endosomal escape to a specific cell type as well as methods reduce interaction with serum proteins. A fourth project focused on developing an assay to quantify cytosolic delivery of nanoparticles and theoretically assessed the possibility of using fluorescence resonance energy transfer (FRET) - which was found to be not practical in this case - as well as implementing a pro-fluorophore to generate a measurable signal. Our preliminary results indicate this method might indeed be useful for this purpose in the future. Nanocarriers ; Drug ; Biochemical engineering ; Computer science ; Pharmacology ; Medicine ; Engineering Nanoparticle-Based Drug Delivery
Authors: Alexander Spore
Source: D-Scholarship@Pitt (University of Pittsburgh) (article, 2019-06-21)
Field: Materials Science — Materials Chemistry

TUNING APPLICATION AND ADJUSTING PROPERTIES OF METAL-ORGANIC FRAMEWORKS VIA SMALL MODIFICATIONS This dissertation describes how metal-organic framework (MOF) stability, properties, and performance can change with minor variation. Three topics of this dissertation include (i) examination of water vapor and liquid stability in ionic MOFs (ii) shell modification of MOFs for incorporation into mixed-matrix membranes (MMMs) and (iii) selection of MOFs for polyphosphazene polymer MMMs. Metal-organic framework ; Ionic liquid ; Materials science ; Polymer ; Membrane ; Thermal stability ; Nanotechnology ; Chemical engineering ; Ionic bonding ; Polyphosphazene ; Chemical stability ; Polymer chemistry ; Chemistry ; Organic chemistry ; Engineering ; Ion ; Composite material ; Adsorption ; Catalysis Magnesium Oxide Properties and Applications
Authors: Samantha L. Flores‐López | Luis Adrián Ramírez Montoya | J.Á. Menéndez | Miguel A. Montes‐Morán | Ana Arenillas
Source: DIGITAL.CSIC (Spanish National Research Council (CSIC)) (article, 2019-10-20)
Field: Chemistry — Spectroscopy

Influence of polymerization conditions on carbon xerogels porous structure Authors thank the financial support received from the Ministerio de Economia, Industria y Competitividad from Spain (CTQ2017-87820-R) and PCTI-Asturias-FEDER (Project IDI/2018/000118). Polymerization ; Porosity ; Chemical engineering ; Materials science ; Carbon fibers ; Polymer chemistry ; Chemistry ; Polymer ; Composite material ; Composite number Aerogels and thermal insulation