- Immobilization of catalysts in poly(p-xylylene) nanotubes
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This paper describes the immobilization of a TEMPO-derivative and a copper catalyst in ethinyl-functionalized poly(p-xylylene) nanotubes which are readily prepared by the Tubes by Fiber Templates (TUFT) process. Catalyst conjugation to the nanotubes is achieved via the Cu-catalyzed azide alkyne cycloaddition (CuAAC). The TEMPO-functionalized nanotubes are successfully used as recyclable catalysts for oxidation of benzyl alcohol. Recycling studies show that the TEMPO-modified nanotubes can be reused 20 times without loss of catalytic activity. Conjugation of the nanotubes with a bipyridine moiety provides a material that allows for immobilization of metal catalysts. Treatment with a Cu(i)-salt leads to a hybrid material, which shows high activity as a recyclable catalyst in the CuAAC. Recycling experiments reveal that these Cu-nanotubes can be reused for 18 runs.
- Hepperle, Johannes A.M.,Mitschang, Fabian,Bier, Anna K.,Dettlaff, Barbara K.,Greiner, Andreas,Studer, Armido
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- Design, Synthesis, EPR-Studies and Conformational Bias of Novel Spin-Labeled DCC-Analogues for the Highly Regioselective Labeling of Aliphatic and Aromatic Carboxylic Acids
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Novel types of spin-labeled N,N′-dicyclohexylcarbodiimides (DCC) are reported that bear a 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) residue on one side and different aromatic and aliphatic cyclohexyl analogues on the other side of the diimide core. These readily available novel reagents add efficiently to aliphatic and aromatic carboxylic acids, forming two possible spin-labeled amide derivatives with different radical distances of the resulting amide. The addition of aromatic DCC analogues proceeds with excellent selectivity, giving amides where the carboxylic acid is exclusively connected to the aromatic residue, while little or no selectivity was observed for the aliphatic congeners. The usefulness of these adducts in structural studies was demonstrated by EPR (electron paramagnetic resonance) measurements of biradical adducts of biphenyl-4,4′-dicarboxylic acids. These analyses also reveal high degrees of conformational bias for aromatic DCC derivatives, which further underlines the powerfulness of these novel reagents. This observation was further corroborated by quantum chemical calculations, giving a detailed understanding of the structural dynamics, while detailed information on the solid state structure of all novel reagents was obtained by X-ray structure analyses.
- G?lz, Jan Philipp,NejatyJahromy, Yaser,Bauer, Mirko,Muhammad, Ashraf,Schnakenburg, Gregor,Grimme, Stefan,Schiemann, Olav,Menche, Dirk
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- Urushiol detection using a profluorescent nitroxide
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A method to visually detect minute amounts of urushiol, the toxic catechol from poison oak, poison ivy, and poison sumac, has been developed utilizing the reaction of a profluorescent nitroxide with the B-n-butylcatecholboronate ester formed in situ from urushiol and B-n-butylboronic acid. The resulting N-alkoxyamine is strongly fluorescent upon illumination with a fluorescent lamp, allowing the location of the toxic urushiol contamination to be visualized. This methodology constitutes the groundwork for the future development of a spray to detect urushiol to avoid contact dermatitis, as well as to detect catecholamines for biomedical applications.
- Braslau, Rebecca,Rivera, Frank,Lilie, Erin,Cottman, Mariellen
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- Spin-labelled diketopiperazines and peptide-peptoid chimera by Ugi-multi-component-reactions
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For the first time, spin-labelled coumpounds have been obtained by isonitrile-based multi component reactions (IMCRs). The typical IMCR Ugi-protocols offer a simple experimental setup allowing structural variety by which labelled diketopiperazines (DKPs) and peptide-peptoid chimera have been synthesized. The reaction keeps the paramagnetic spin label intact and offers a simple and versatile route to a large variety of new and chemically diverse spin labels.
- Sultani, Haider N.,Haeri, Haleh H.,Hinderberger, Dariush,Westermann, Bernhard
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- EPR Studies of V-ATPase with Spin-Labeled Inhibitors DCC and Archazolid: Interaction Dynamics with Proton Translocating Subunit c
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Vacuolar-type H+-ATPases (V-ATPases) have gained recent attention as highly promising anticancer drug targets, and therefore detailed structural analyses and studies of inhibitor interactions are very important research objectives. Spin labeling of the V-ATPase holoenzyme from the tobacco hornworm Manduca sexta and V-ATPase in isolated yeast (Saccharomyces cerevisiae) vacuoles was accomplished by two novel methods involving the covalent binding of a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) derivative of N,N′-dicyclohexylcarbodiimide (DCC) to the essential glutamate residue in the active site and the noncovalent interaction of a radical analogue of the highly potent inhibitor archazolid, a natural product from myxobacteria. Both complexes were evaluated in detail by electron paramagnetic resonance (EPR) spectroscopic studies and double electron-electron resonance (DEER) measurements, revealing insight into the inhibitor binding mode, dynamics, and stoichiometry as well as into the structure of the central functional subunit c of these medicinally important hetero-multimeric proton-translocating proteins. This study also demonstrates the usefulness of natural product derived spin labels as tools in medicinal chemistry. Near and DEER: Electron paramagnetic resonance (EPR) and double electron-electron resonance (DEER) studies of V-ATPase in complex with spin-labeled inhibitors DCC and archazolid have enabled insight into the noncovalent binding dynamics and analysis of the enzyme′s key functional subunit c. These studies also demonstrate the general utility of natural product derived spin labels as innovative tools for chemical biology.
- G?lz, Jan Philipp,Bockelmann, Svenja,Mayer, Kerstin,Steinhoff, Heinz-Jürgen,Wieczorek, Helmut,Huss, Markus,Klare, Johann P.,Menche, Dirk
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- Multi-responsive copolymers: Using thermo, light- and redox stimuli as three independent inputs towards polymeric information processing
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We report on triple responsive polymers, exhibiting a distinct and reversible lower critical solution temperature in water that can be altered by light and redox stimuli, and we suggest their evaluation for molecular information processing.
- Schattling, Philipp,Jochum, Florian D.,Theato, Patrick
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- THE OXIDATION OF SECONDARY AMINES BY ALKANESULFONIC PERACIDS
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Alkanesulfonic peracids are efficient oxidation agents for the conversion of secondary amines to the corresponding nitroxyl radicals.
- Safiullin, R. L.,Enikeeva, L. R.,Bukin, I. I.,Mukhametova, G. A.,Shishlov, N. M.,et al.
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- Preparation and properties of biphenyl and cholesterol derivatives with nitroxide radicals
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Series of biphenyl as well as cholesterol derivatives with nitroxide radicals have been prepared to investigate their magnetic/liquid crystalline characters. Weak antiferromagnetic interactions in the low temperature region with no liquid crystalline character have been observed in all cholesterol and several biphenyl derivatives prepared while a cyanobiphenyl derivative with TEMPO substituent have been found to show ferromagnetic interactions in the low temperature region on the one hand and smectic liquid crystalline behavior at elevated temperatures on the other hand.
- Nakatsuji,Mizumoto,Kitamura,Akutsu,Yamada
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- Hierarchically structured, blue-emitting polymer hybrids through surface-initiated nitroxide-mediated polymerization and water templated assembly
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A facile and robust approach for fabricating structured, blue-emitting polymer hybrids is explored by grafting poly(styrene) incorporating π-conjugated oligo(fluorene) side-chains, to fluoromica silicate layers through surface-initiated nitroxide-mediated polymerization (SI-NMP). It is expected that the polymer intercalation can effectively reduce π-stacking, chain-chain interactions, twists and bends, and interfacial effects, leading to significant difference in the electronic/optoelectronic properties, and improved optical, thermal and chemical stability of the materials. The experimental results indicate that the bottom-up strategy is rational and efficacious. The hybrids exhibit a blue photoluminescence quantum yield (PL-QY) as high as 0.90, even in the solid, which makes the materials appealing for polymer light-emitting devices (PLEDs). The materials also show significantly enhanced thermal, and chemical stabilities with respect to the organic precursors. If processed under specific controlled conditions, the hybrids spontaneously assemble into highly ordered microporous films, where an organization of matter at different length scales is obtained. Since the introduction of surface patterning in the active layer could enhance the extraction of light generated in the device, this hierarchical organization is a promising tool for the further development of optimized hybrid PLEDs.
- Leone, Giuseppe,Giovanella, Umberto,Bertini, Fabio,Hoseinkhani, Sajjad,Porzio, William,Ricci, Giovanni,Botta, Chiara,Galeotti, Francesco
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- A Simple Synthesis of 4-Amino-2,2,6,6-tetramethyl-1-piperidinyloxy Radical
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A simple synthesis of the title compound starting from 4-hydroxy-2,2,6,6-tetramethyl-1-piperidyloxy radical (2) based on sulfonate-azide exchange method is described.
- Bushmakina, N. G.,Misharin, A. Yu.
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- Nitrogen-oxygen stable free radical with aggregation-induced emission function, and preparation method thereof
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The invention discloses a nitrogen-oxygen stable free radical with an aggregation-induced emission function, and a preparation method thereof. The nitrogen-oxygen stable free radical has a structure represented by a formula shown in the description; and in the formula, R1, R2, R3 and R4 are respectively and independently selected from C1-6 alkyl groups or heterochain groups optionally substitutedwith other elements, and R5 is hydrogen, NH2, a carbonyl group, a hydroxyl group, an oxygen-linked alkyl group, or a heterochain group optionally substituted with other elements. The preparation method comprises the following steps: synthesizing teramethylpiperidinyl-1-oxy with a hydroxyl group from tetramethyl piperidinol, synthesizing a tetraphenylethylene intermediate from 2-bromo-1,1,2-triphenylethylene and 4-methylphenylboronic acid, and brominating the tetraphenylethylene intermediate to obtain tetraphenylethylene with a benzyloxybromo group; carrying out a nucleophilic substitution reaction on a nitrogen-oxygen stable free radical and the tetraphenylethylene with the benzyloxybromo group at room temperature for 2-12 h; and performing purification by adopting a column chromatographyseparation process to obtain a nitrogen-oxygen stable free radical product with the aggregation-induced emission performance.
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Paragraph 0022-0023
(2020/03/03)
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- Synthesis and fluorescence properties of six fluorescein-nitroxide radical hybrid-compounds
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Six fluorescein-nitroxide radical hybrid-compounds (2ab, 3ab, 4, and 5) were synthesized by the condensation of 5- or 6-carboxy-fluorescein and 4-amino-TEMPO (2ab), 5- or 6-aminofluorescein and 4-carboxy-TEMPO (3ab), and fluorescein and 4-carboxy-TEMPO (4), or by reaction of the 3-hydroxyl group of fluorescein with DPROXYL-3-ylmethyl methanesulfonate (5). Fluorescence intensities (around 520 nm) after reduction of the radical increased to 1.43-, 1.38-, and 1.61-folds for 2a, 2b and 3b respectively; 3a alone exhibited a decrease in intensity on reduction. Since 4 was readily solvolyzed in PBS or even methanol to afford fluorescein and 4-carboxy-TEMPO, its fluorescence change could not be measured. Hybrid compound 5 containing an ether-linkage between the fluorescein phenol and 3-hydroxymethyl-DPROXYL hydroxyl centers, was stable and on reduction, showed a maximum increase (3.21-fold) in relative fluorescence intensity in PBS (pH 5.0), despite its remarkably low absolute fluorescence intensity.
- Sato, Shingo,Endo, Susumu,Kurokawa, Yusuke,Yamaguchi, Masaki,Nagai, Akio,Ito, Tomohiro,Ogata, Tateaki
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- Pd immobilized in mesoporous silica particles as recyclable catalysts for suzuki-miyaura coupling: Cooperative effects exerted by co-immobilized amine functionalities
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A bifunctional heterogeneous palladium catalyst bearing additional basic sites was successfully prepared by sequential Cu-catalyzed 1,3-dipolar alkyne-azide cycloaddition and thermal nitroxide-exchange reaction of surface-bound alkoxyamines. This catalyst shows high activity in the Suzuki-Miyaura cross-coupling. The additional basic functionality acts cooperatively since an analogous heterogeneous Pd catalyst lacking the amine functionality is less active. Such catalysts can be recycled up to ten times without loss of activity. Georg Thieme Verlag Stuttgart. New York.
- Dickschat, Arne T.,Surmiak, Sabrina,Studer, Armido
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supporting information
p. 1523 - 1528
(2013/08/23)
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- MODIFIED ZNO NANOPARTICLES
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Process for the preparation of modified zinc oxide nanoparticles, which comprises reacting zinc oxide nanoparticles, which are dissolved in a solvent, in the presence of ammonia or amines with a tetraalkyl orthosilicate and optionally with an organosilane, with the proviso that the reaction takes place at a content of less than 5% by weight of water, based on the total amount of solvent and water. Modified zinc oxide nanoparticles which have Si—O-alkyl groups and are soluble in organic solvents, obtainable by this process for the preparation. Liquid or solid formulations which comprise modified ZnO nanoparticles. Inanimate organic materials, for example plastics or coatings, which comprise modified ZnO nanoparticles. Method of stabilizing inanimate organic materials against the effect of light, free radicals or heat, where modified ZnO nanoparticles, which optionally comprise UV absorbers and/or stabilizers as further additives, are added to the materials.
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- Preparation of bifunctional mesoporous silica nanoparticles by orthogonal click reactions and their application in cooperative catalysis
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The synthesis of bifunctional mesoporous silica nanoparticles is described. Two chemically orthogonal functionalities are incorporated into mesoporous silica by co-condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes. Post-functionalization is achieved by orthogonal surface chemistry. A thiol-ene reaction, Cu-catalyzed 1,3-dipolar alkyne/azide cycloaddition, and a radical nitroxide exchange reaction are used as orthogonal processes to install two functionalities at the surface that differ in reactivity. Preparation of mesoporous silica nanoparticles bearing acidic and basic sites by this approach is discussed. Particles are analyzed by solid state NMR spectroscopy, elemental analysis, infrared-spectroscopy, and scanning electron microscopy. As a first application, these particles are successfully used as cooperative catalysts in the Henry reaction. Cooperative clicking: Bifunctional mesoporous silica particles were synthesized by orthogonal surface chemistry. A thiol-ene reaction, a copper-catalyzed 1,3-dipolar cycloaddition and a radical nitroxide exchange reaction were used as orthogonal processes for the introduction of the acid and base functionalities (see scheme). Catalytic activities of these bifunctionalized inorganic/organic hybrid materials were studied on the Henry reaction. Copyright
- Dickschat, Arne T.,Behrends, Frederik,Bühner, Martin,Ren, Jinjun,Wei?, Mark,Eckert, Hellmut,Studer, Armido
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supporting information
p. 16689 - 16697
(2013/03/14)
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- Electron paramagnetic resonance (EPR) study of spin-labeled camptothecin derivatives: A different look of the ternary complex
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Camptothecin (CPT) derivatives are clinically effective poisons of DNA topoisomerase I (Top1) able to form a ternary complex with the Top1-DNA complex. The aim of this investigation was to examine the dynamic aspects of the ternary complex formation by means of site-directed spin labeling electron paramagnetic resonance (SDSL-EPR). Two semisynthetic CPT derivatives bearing the paramagnetic moiety were synthesized, and their biological activity was tested. A 22-mer DNA oligonucleotide sequence with high affinity cleavage site for Top1 was also synthesized. EPR experiments were carried out on modified CPT in the presence of DNA, of Top1, or of both. In the last case, a slow motion component in the EPR signal appeared, indicating the formation of the ternary complex. Deconvolution of the EPR spectrum allowed to obtain the relative drug amounts in the complex. It was also possible to demonstrate that the residence time of CPT "trapped" in the ternary complex is longer than hundreds of microseconds.
- Ricci, Antonio,Marinello, Jessica,Bortolus, Marco,Sánchez, Albert,Grandas, Anna,Pedroso, Enrique,Pommier, Yves,Capranico, Giovanni,Maniero, Anna Lisa,Zagotto, Giuseppe
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p. 1003 - 1009
(2011/04/25)
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- Oxidation of alkylcatecholboranes with functionalized nitroxides for chemical modification of cyclohexene, perallylated polyglycerol and of poly(butadiene)
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The present communication reports on the synthesis of alkoxyamines by hydroboration of olefins with catecholborane and subsequent oxidation by using nitroxides. Oxidation occurs via a radical process and the intermediately formed C-radicals are trapped by the nitroxides to form the corresponding alkoxyamines. If functionalized nitroxides are used, the method allows incorporation of interesting functional moieties via this approach. The novel method is applied for chemical modification of cyclohexene as a test substrate. More importantly, it is also shown that the reaction sequence can be used for chemical modification of macromolecules containing multiple double bonds. This is documented by successful functionalization of poly(butadiene) and of perallylated polyglycerol. Functionalized poly(butadiene)s can be prepared by a reaction sequence comprising olefin hydroboration and nitroxide induced oxidation to give poly(alkoxyamines). If the nitroxide is charged with aninteresting functional moiety such as a sugar derivative or a polyethylene glycol tail, the trapping process delivers the corresponding functionalized chemically modified poly(olefins) in a one-pot process.
- Wagner, Christine B.,Studer, Armido
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supporting information; experimental part
p. 5782 - 5786
(2011/01/12)
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- Reaction of Nitroxides with Sulfur Containing Compounds II [1]. Preparation of Nitroxides Bearing an Isothiocyanate Substituent in View of the Nitroxyl Group Reduction with Thiophosgene
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The reaction of thiophosgene with 2,2,6,6-tetramethylpiperidine-1-oxyl (used as a model nitroxyl radical) was examined. 2,2,6,6-Tetramethylpiperidine and 2,2,6,6-tetramethyl-1-hydroxypiperidine were identified as products. The reaction is not competitive with the reaction of thiophosgene with an amino group. Thus, three nitroxides with an isothiocyanate group were synthesized from thiophosgene and the nitroxides containing the amino substituent.
- Zakrzewski, Jerzy,Hupko, Jarosllaw,Kryczka, Krzysztof
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p. 843 - 850
(2007/10/03)
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- Synthesis, electrosynthesis and electrochemical properties of substituted 2,2,6,6-tetramethylpiperidine and the respective stable nitroxyl radicals. XIV
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The various derivatives of 2,2,6,6-tetramethylpiperidine and their stable nitroxyl radicals were investigated by means of chemical, electrochemical and empirical calculation methods. The titration results were calculated by means of TURBO BASIC with PKAS and MINIGLASS algorithm, and the prototropic experimental data were obtained. The reaction ways were calculated on the basis of the formation enthalpie values which were calculated by means of AM 1 (MOPACK) method. On the basis of a voltammetry and an electrolysis under controlled potential the reaction products were analyzed and the yields of the investigated processes were received. The various quasireversible redox reactions of the type stable nitroxyl radical oxoannonium cation were investigated by means of a cyclic voltammetry and electrochemical impedance spectroscopy. The mechanisms of the investigated reactions have been discussed and the reaction schemes are presented. - Key words: derivatives of 2,2,6,6-tetramethylpiperidine; electrolysis; electrochemical impedance spectroscopy; formation enthalpy values; prototropic constants
- Avrutskaya, Inna A.,Novikov, Vasilii T.,Dziegiec, Jozef,Grzejdziak, Andrzej,Krzyczmonik, Pawel,Scholl, Henryk
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- INFLUENCE OF CHEMICAL STRUCTURE OF NITROXYL SPIN LABELS ON THEIR REDUCTION BY ASCORBIC ACID
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The influence of structure on the reduction of nitroxyl spin labels by ascorbic acid was examined using both piperidine and pyrrolidine nitroxyls.A five-fold molar excess of ascorbic acid and pH of 7.4 were used.The nitroxyl concentration was measured by electron spin resonance spectrometry.The five-membered (pyrrolidine) nitroxyls were more stable than the six-membered derivatives.Ring substituents also influenced the reaction.The anionic derivatives were more stable than the unionized compounds which, in turn, were more stable than the amines (cations at pH 7.4).
- Couet, W. R.,Brasch, R. C.,Sosnovsky, G.,Lukszo, J.,Prakash, I.,et. al.
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p. 1165 - 1172
(2007/10/02)
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- Synthesis of alpha- and beta-glycosides containing spin labels, as probes for studies of carbohydrate-protein interaction.
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Nitroxide spin-labeled alpha-D-glycopyranosides were synthesized in good yield and in a highly stereoselective manner by reaction of per-O-benzyl-alpha-D-glycopyranosyl bromides with 2,2,6,6-tetramethyl-4-piperidinol under the bromide ion-catalyzed conditions devised by Lemieux et al. After hydrogenolysis, the deblocked intermediates were oxidized to give the desired, spin-labeled alpha-D-glycopyranosides. Nitroxide spin-labeled beta-D-glycopyranosides, as well as a beta-maltoside, were synthesized by standard methods. The synthesis is also described of 2-amino-2-deoxy-D-glucose and -D-galactose derivatives having a spin label at C-2, and of the spin-labeled compound 1-[4-(beta-D-galactopyranosyloxy)phenyl]-3-(2,2,6,6-tetramethylpiperidin-1-oxyl -4-yl)-2-thiourea.
- Plessas,Goldstein
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p. 211 - 220
(2007/10/02)
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- Nitroimidazoles and compositions thereof
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Nitroimidazoles of the formula STR1 wherein R1 and R2 are as hereinafter set forth, are described. The nitroimidazoles are useful as hypoxic-cell radiosensitizers, as well as being useful as antiprotozoal agents.
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- 148. Formation of N-Hydroxy-amines of Spin Labeled Nucleosides for 1H-NMR. Analysis
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Amine-oxide radical 1a was efficiently converted to the corresponding N-hydroxy-amine 2a with sodium dithionite in acetone/water.This reaction was used to develop a procedure for monitoring the NMR. spectra of sodium dithionite reduced amine-oxide radicals and of novel reduced amine-oxide-labeled nucleosides.
- Ozinskas, Alvydas J.,Bobst, Albert M.
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p. 1407 - 1411
(2007/10/02)
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