TY - JOUR A1 - Michalik-Onichimowska, Aleksandra A1 - Kern, Simon A1 - Riedel, Jens A1 - Panne, Ulrich A1 - King, Rudibert A1 - Maiwald, Michael T1 - "Click" analytics for "click" chemistry - A simple method for calibration-free evaluation of online NMR spectra JF - Journal of magnetic resonance N2 - Driven mostly by the search for chemical syntheses under biocompatible conditions, so called "click" chemistry rapidly became a growing field of research. The resulting simple one-pot reactions are so far only scarcely accompanied by an adequate optimization via comparably straightforward and robust analysis techniques possessing short set-up times. Here, we report on a fast and reliable calibration-free online NMR monitoring approach for technical mixtures. It combines a versatile fluidic system, continuous-flow measurement of H-1 spectra with a time interval of 20 s per spectrum, and a robust, fully automated algorithm to interpret the obtained data. As a proof-of-concept, the thiol-ene coupling between N-boc cysteine methyl ester and ally] alcohol was conducted in a variety of non-deuterated solvents while its time-resolved behaviour was characterized with step tracer experiments. Overlapping signals in online spectra during thiol-ene coupling could be deconvoluted with a spectral model using indirect hard modeling and were subsequently converted to either molar ratios (using a calibration free approach) or absolute concentrations (using 1-point calibration). For various solvents the kinetic constant k for pseudo-first order reaction was estimated to be 3.9 h(-1) at 25 degrees C. The obtained results were compared with direct integration of non-overlapping signals and showed good agreement with the implemented mass balance. (C) 2017 Elsevier Inc. All rights reserved. KW - NMR spectroscopy KW - Reaction monitoring KW - Automated data evaluation KW - Thiol-ene click chemistry Y1 - 2017 U6 - https://doi.org/10.1016/j.jmr.2017.02.018 SN - 1090-7807 SN - 1096-0856 VL - 277 SP - 154 EP - 161 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Harmanli, İpek A1 - Tarakina, Nadezda A1 - Antonietti, Markus A1 - Oschatz, Martin T1 - "Giant" nitrogen uptake in ionic liquids confined in carbon pores JF - Journal of the American Chemical Society N2 - Ionic liquids are well known for their high gas absorption capacity. It is shown that this is not a solvent constant, but can be enhanced by another factor of 10 by pore confinement, here of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EmimOAc) in the pores of carbon materials. A matrix of four different carbon compounds with micro- and mesopores as well as with and without nitrogen doping is utilized to investigate the influence of the carbons structure on the nitrogen uptake in the pore-confined EmimOAc. In general, the absorption is most improved for IL in micropores and in nitrogen-doped carbon. This effect is so large that it is already seen in TGA and DSC experiments. Due to the low vapor pressure of the IL, standard volumetric sorption experiments can be used to quantify details of this effect. It is reasoned that it is the change of the molecular arrangement of the ions in the restricted space of the pores that creates additional free volume to host molecular nitrogen. Y1 - 2021 U6 - https://doi.org/10.1021/jacs.1c00783 SN - 0002-7863 SN - 1520-5126 VL - 143 IS - 25 SP - 9377 EP - 9384 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Reinecke, Antje A1 - Koetz, Joachim T1 - "Green" gold nanotriangles: synthesis, purification by polyelectrolyte/micelle depletion flocculation and performance in surface-enhanced Raman scattering JF - RSC Advances N2 - The aim of this study was to develop a one-step synthesis of gold nanotriangles (NTs) in the presence of mixed phospholipid vesicles followed by a separation process to isolate purified NTs. Negatively charged vesicles containing AOT and phospholipids, in the absence and presence of additional reducing agents (polyampholytes, polyanions or low molecular weight compounds), were used as a template phase to form anisotropic gold nanoparticles. Upon addition of the gold chloride solution, the nucleation process is initiated and both types of particles, i.e., isotropic spherical and anisotropic gold nanotriangles, are formed simultaneously. As it was not possible to produce monodisperse nanotriangles with such a one-step procedure, the anisotropic nanoparticles needed to be separated from the spherical ones. Therefore, a new type of separation procedure using combined polyelectrolyte/micelle depletion flocculation was successfully applied. As a result of the different purification steps, a green colored aqueous dispersion was obtained containing highly purified, well-defined negatively charged flat nanocrystals with a platelet thickness of 10 nm and an edge length of about 175 nm. The NTs produce promising results in surface-enhanced Raman scattering. Y1 - 2016 U6 - https://doi.org/10.1039/c6ra04808k SN - 2046-2069 VL - 6 SP - 33561 EP - 33568 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Sinha, Shreya A1 - Saalfrank, Peter T1 - "Inverted" CO molecules on NaCl(100) BT - a quantum mechanical study JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Somewhat surprisingly, inverted ("O-down") CO adsorbates on NaCl(100) were recently observed experimentally after infrared vibrational excitation (Lau et al., Science, 2020, 367, 175-178). Here we characterize these species using periodic density functional theory and a quantum mechanical description of vibrations. We determine stationary points and minimum energy paths for CO inversion, for low (1/8 and 1/4 monolayers (ML)) and high (1 ML) coverages. Transition state theory is applied to estimate thermal rates for "C-down" to "O-down" isomerization and the reverse process. For the 1/4 ML p(1 x 1) structure, two-dimensional and three-dimensional potential energy surfaces and corresponding anharmonic vibrational eigenstates obtained from the time-independent nuclear Schrodinger equation are presented. We find (i) rather coverage-independent CO inversion energies (of about 0.08 eV or 8 kJ mol(-1) per CO) and corresponding classical activation energies for "C-down" to "O-down" isomerization (of about 0.15 eV or 14 kJ mol(-1) per CO); (ii) thermal isomerization rates at 22 K which are vanishingly small for the "C-down" to "O-down" isomerization but non-negligible for the back reaction; (iii) several "accidentally degenerate" pairs of eigenstates well below the barrier, each pair describing "C-down" to "O-down" localized states. Y1 - 2020 U6 - https://doi.org/10.1039/d0cp05198e SN - 1463-9076 SN - 1463-9084 VL - 23 IS - 13 SP - 7860 EP - 7874 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Dolya, Natalya A1 - Rojas, Oscar A1 - Kosmella, Sabine A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Kudaibergenov, Sarkyt T1 - "One-Pot" in situ frmation of Gold Nanoparticles within Poly(acrylamide) Hydrogels JF - Macromolecular chemistry and physics N2 - This paper focuses on two different strategies to incorporate gold nanoparticles (AuNPs) into the matrix of polyacrylamide (PAAm) hydrogels. Poly(ethyleneimine) (PEI) is used as both reducing and stabilizing agent for the formation of AuNPs. In addition, the influence of an ionic liquid (IL) (i.e., 1-ethyl-3-methylimidazolium ethylsulfate) on the stability of the nanoparticles and their immobilization in the hydrogel is investigated The results show that AuNPs surrounded by a shell containing PEI and IL, synthesized according to the one-pot approach, are much better immobilized within the PAAm hydrogel. Hereby, the IL is responsible for structural changes in the hydrogel as well as the improved stabilization and embedding of the AuNPs into the polymer gel matrix. KW - gold nanoparticles KW - immobilization KW - ionic liquids KW - poly(acrylamide) hydrogels Y1 - 2013 U6 - https://doi.org/10.1002/macp.201200727 SN - 1022-1352 VL - 214 IS - 10 SP - 1114 EP - 1121 PB - Wiley-VCH CY - Weinheim ER - TY - THES A1 - Fischer, Anna T1 - "Reactive hard templating" : from carbon nitrides to metal nitrides T1 - Synthese von Metallnitrid Nanostrukturen durch "Reaktives Hardtemplating" N2 - Nanostructured inorganic materials are routinely synthesized by the use of templates. Depending on the synthesis conditions of the product material, either “soft” or “hard” templates can be applied. For sol-gel processes, usually “soft” templating techniques are employed, while “hard” templates are used for high temperature synthesis pathways. In classical templating approaches, the template has the unique role of structure directing agent, in the sense that it is not participating to the chemical formation of the resulting material. This work investigates a new templating pathway to nanostructured materials, where the template is also a reagent in the formation of the final material. This concept is described as “reactive templating” and opens a synthetic path toward materials which cannot be synthesised on a nanometre scale by classical templating approaches. Metal nitrides are such kind of materials. They are usually produced by the conversion of metals or metal oxides in ammonia flow at high temperature (T > 1000°C), which make the application of classical templating techniques difficult. Graphitic carbon nitride, g-C3N4, despite its fundamental and theoretical importance, is probably one of the most promising materials to complement carbon in material science and many efforts are put in the synthesis of this material. A simple polyaddition/elimination reaction path at high temperature (T = 550°C) allows the polymerisation of cyanamide toward graphitic carbon nitride solids. By hard templating, using nanostructured silica or aluminium oxide as nanotemplates, a variety of nanostructured graphitic carbon nitrides such as nanorods, nanotubes, meso- and macroporous powders could be obtained by nanocasting or nanocoating. Due to the special semi-conducting properties of the graphitic carbon nitride matrix, the nanostructured graphitic carbon nitrides show unexpected catalytic activity for the activation of benzene in Friedel-Crafts type reactions, making this material an interesting metal free catalyst. Furthermore, due to the chemical composition of g-C3N4 and the fact that it is totally decomposed at temperatures between 600°C and 800°C even under inert atmosphere, g-C3N4 was shown to be a good nitrogen donor for the synthesis of early transition metal nitrides at high temperatures. Thus using the nanostructured carbon nitrides as “reactive templates” or “nanoreactors”, various metal nitride nanostructures, such as nanoparticles and porous frameworks could be obtained at high temperature. In this approach the carbon nitride nanostructure played both the role of the nitrogen source and of the exotemplate, imprinting its size and shape to the resulting metal nitride nanostructure. N2 - Die Nanostrukturierung anorganischer Materialien, d.h. die Kontrolle ihrer Form und Größe auf der Nanometerebene durch unterschiedliche Herstellungsverfahren, ist ein sich immer noch erweiterndes Forschungsgebiet. Eine solche Nanostrukturierung wird oft über sogenannte Templatierungsverfahren erreicht: Hier werden Formgeber (Template) mit definierter Morphologie und Größe verwendet und deren Struktur in ein neues Material abgebildet. Templatierungsverfahren können, je nach der Beschaffenheit des Templats, zwischen „weich“ und „hart“ unterschieden werden. Die Begriffe beziehen sich dabei vor allem auf die mechanische und thermische Stabilität der Template, d.h. weiche Template sind vornehmlich organischer, harte Template anorganischer Natur. Wo weiche Template in milden chemischen Verfahren eingesetzt werden, werden harte Template zur Herstellung von Materialien bei Hochtemperaturverfahren verwendet (z. B. poröse Kohlenstoffe). Allgemein dienen Template ausschließlich als Strukturgeber und gehen in keiner Weise in Form einer chemischen Reaktion in die Synthese des gewünschten Materials mit ein. Gegenstand dieser Arbeit ist ein neues Templatierungsverfahren: Die „reaktive Templatierung“. Hierbei wird das Templat - neben seiner Funktion als Strukturgeber – auch als Reagenz für die Synthese des Produktes verwendet. Dieser Synthese-Ansatz öffnet damit neue Wege für die Synthese von nanostrukturierten Materialien, die durch klassische Templatierungsansätze schwer zugänglich sind. Hierzu zählen zum Beispiel die Metallnitride. Üblicherweise werden Metallnitride über die Umsetzung von Metallen oder Metalloxiden in einem Ammoniakstrom bei Mindesttemperaturen von 1000°C gewonnen, was die Anwendung klassischer Templatierungsverfahren beinahe unmöglich macht. Darüber hinaus sind konzentrierte Lauge oder Flusssäure, welche zur Entfernung klassischer harter Template benötigt werden auch Aufschlussmittel für Metallnitride. Graphitisches Kohlenstoffnitrid, g-C3N4, ist wohl eines der meistversprechendsten Materialien um Kohlenstoff in der Materialwissenschaft zu ergänzen. Es wurden bereits viele potentielle Syntheseansätze beschrieben. Eine durch Groenewolt M. erstellte Route ist die thermisch induzierte Polykondensation von Cyanamid (NCNH2) bei 550°C. Da g-C3N4 sich zwischen 600°C und 800°C vollständig in NH3 und CxNyH-Gase zersetzt, ist es eine geeignete Festkörper-Stickstoffquelle für die Herstellung von Metalnitriden. Daher boten sich nanostrukturierte graphitische Kohlenstoffnitride als geeignete reaktive Template oder Nanoreaktoren zur Herstellung von nano-strukturierten Metalnitriden an. Die Templatierung der g-C3N4-Matrix wurde über klassische Harttemplatierungsverfahren erreicht. So konnte eine Vielzahl nano-strukturierter g-C3N4 Materialien synthetisiert werden wie zum Beispiel Nanostäbchen, Nanoröhren, mesoporöse oder makroporöse graphitische Kohlenstoffnitride. Diese haben sich interessanterweise, als metalfreie Katalysatoren für die Aktivierung von Benzol in Friedel-Crafts-Acylierung und -Alkylierung erwiesen. Durch die Infiltrierung der nano-strukturierten g-C3N4-Materialien mit diversen Metal-Präkursoren und nachfolgendem Tempern bei 800°C unter Schutzgas, konnten entsprechende nano-strukturierte Metalnitride, als Nanoabdrücke der vorgegebenen Kohlenstoffnitrid Nanostrukturen hergestellt werden. So konnten TiN, VN, GaN, AlGaN und TiVN Nanopartikel synthetisiert werden, macroporöse TiN/Kohlenstoff Komposite sowie TiN Hohlkugeln. Die so hergestellten Materialien erwiesen sich als effektive basische Katalysatoren für Aldol-Kondensations Reaktionen. KW - Kohlenstoffnitride KW - Metallnitride KW - nano KW - Templatierung KW - Carbonitrides KW - metal nitrides KW - reactive templating KW - confinement KW - nano Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-19777 ER - TY - JOUR A1 - Weber, Nancy A1 - Tiersch, Brigitte A1 - Unterlass, Miriam M. A1 - Heilig, Anneliese A1 - Tauer, Klaus T1 - "Schizomorphic" Emulsion Copolymerization Particles JF - Macromolecular rapid communications N2 - Cryo-electron microscopy, atomic force microscopy, and light microscopy investigations provide experimental evidence that amphiphilic emulsion copolymerization particles change their morphology in dependence on concentration. The shape of the particles is spherical at solids content above 1%, but it changes to rod-like, ring-like, and web-like structures at lower concentrations. In addition, the shape and morphology of these particles at low concentrations are not fixed but very flexible and vary with time between spheres, flexible pearlnecklace structures, and stretched rods. KW - amphiphilic particles KW - emulsion polymerization KW - morphology Y1 - 2011 U6 - https://doi.org/10.1002/marc.201100491 SN - 1022-1336 VL - 32 IS - 23 SP - 1925 EP - 1929 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Vishnevetskaya, Natalya S. A1 - Hildebrand, Viet A1 - Niebuur, Bart-Jan A1 - Grillo, Isabelle A1 - Filippov, Sergey K. A1 - Laschewsky, Andre A1 - Mueller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - "Schizophrenic" Micelles from Doubly Thermoresponsive Polysulfobetaine-b-poly(N-isopropylmethacrylamide) Diblock Copolymers JF - Macromolecules : a publication of the American Chemical Society Y1 - 2017 U6 - https://doi.org/10.1021/acs.macromol.7b00356 SN - 0024-9297 SN - 1520-5835 VL - 50 SP - 3985 EP - 3999 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Paz, Cristian A1 - Becerra, Jose A1 - Silva, Mario A1 - Cabrera-Pardo, Jaime A1 - Burgos, Viviana A1 - Heydenreich, Matthias A1 - Schmidt, Bernd T1 - (-)-8-Oxohobartine a New Indole Alkaloid from Aristotelia chilensis (Mol.) Stuntz JF - Records of Natural Products N2 - The fruit of Aristotelia chilensis is considered a "super fruit" due to its high concentration of polyphenols displaying exceptional antioxidant capacities ORAC. From maqui berries have been reported several anthocyanins and glycosylated flavonoids, those benefits increase the attention to restudy the plant. From the leaves of A. chilensis several indole alkaloids have been reported, we in addition to aristoteline, aristone, aristoquinoline and 3-fromylindole report the spectroscopic elucidation of 8-oxo-9-dehydromakomakine (1), hobartine (2) and a new alkaloid named 8-oxohobartine (3). Compound 1 to 3 did not show bactericidal activity against E. coli and S. aureus till 200 mu g. KW - Aristotelia chilensis KW - indole alkaloids KW - 8-oxohobartine Y1 - 2016 SN - 1307-6167 VL - 10 SP - 68 EP - 73 PB - ACG Publications CY - Gebze-Kocaeli ER - TY - JOUR A1 - Paz, Cristian A1 - Becerra, Jose A1 - Silva, Mario A1 - Burgos, Viviana A1 - Heydenreich, Matthias A1 - Schmidt, Bernd A1 - Thu Tran, A1 - Vetter, Irina T1 - (-)-Pentylsedinine, a New Alkaloid from the Leaves of Lobelia tupa with Agonist Activity at Nicotinic Acetylcholine Receptor JF - Natural product communications : an international journal for communications and reviews N2 - Lobelia tupa, also called devil's tobacco, is a native plant from the center-south of Chile which has been used by the native people of Chile as a hallucinogenic and anesthetic plant. A new piperidine alkaloid, called pentylsedinine, which comprises five carbons in the side chain, was isolated from the aerial part of L. tupa, along with lobeline and lobelanidine. The structure was established on the basis of 1D and 2D NMR spectroscopy. While lobeline is a neutral antagonist at alpha 3 beta 2/alpha 3 beta 4 nAChR and alpha 7 nAChR, both lobelanidine and pentylsedinine act as partial agonists at nAChR KW - Lobelia tupa KW - Piperidine alkaloid KW - nAChR KW - Pentylsedinine Y1 - 2015 SN - 1934-578X SN - 1555-9475 VL - 10 IS - 8 SP - 1355 EP - 1357 PB - NPC CY - Westerville ER -