TY - JOUR A1 - Sperlich, Eric A1 - Köckerling, Martin T1 - Cluster salts [Nb6Cl12(HIm)(6)]A(n) (with HIm=1H-imidazole and A=Mineral Acid Anion, n=1 or 2) made in and with Bronsted-basic ionic liquids and liquid mixtures JF - ChemistryOpen N2 - Four new hexanuclear niobium cluster compounds of the general formula [Nb6Cl12(HIm)(6)](A)(n) . x(solvent molecule) (HIm=1H-imidazole, A=mineral acid anion, Cl- (n=2) (1), (SO4)(2-) (n=1) (2), (CrO4)(2-) (n=1) (3), and (HAsO4)(2-) (n=1) (4)) were prepared. Their synthesis can be done in basic ionic liquids, which form on the addition of a mineral acid, which also delivers the counter anion for the final cluster compound, to an excess of the 1H-imidazole. Some addition of an auxiliary solvent, like methanol, improves the speed of crystallisation. The cluster unit comprises a hexanuclear Nb-6 unit of octahedral shape with the edges bridged by Cl atoms and the exo sites being occupied by N-bonded 1H-imidazole ligands. The cluster cation carries sixteen cluster-based electrons. Between the NH groups of the ligands of the cluster unit, the anions and the co-crystallised water (1), or 1H-imidazole and methanol molecules (2, 3, and 4) a network of hydrogen bonds exists. KW - cluster KW - ionic liquid KW - structure elucidation KW - heterocyclic ligand KW - Niobium Y1 - 2021 U6 - https://doi.org/10.1002/open.202000266 SN - 2191-1363 VL - 10 IS - 2 SP - 248 EP - 254 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Breternitz, Joachim A1 - Lehmann, Frederike A1 - Barnett, Sarah A. A1 - Nowell, Harriott A1 - Schorr, Susan T1 - Zur Rolle der Iodid-Methylammonium-Interaktion in der Ferroelektrizität in CH3NH3PbI3 T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Ihre außergewöhnlich hohen Konversionseffizienzen von über 20 % und die einfache Zellherstellung machen Hybridperowskite zu heißen Kandidaten für alternative Solarzellenmaterialien. CH3NH3PbI3 als Archetyp dieser Materialklasse besitzt außergewöhnliche Eigenschaften wie eine sehr effiziente Umwandlung von Solarenergie, wobei besonders Ferroelektrizität als mögliche Erklärung in den Fokus gerückt ist. Diese erfordert allerdings eine nicht-zentrosymmetrische Kristallstruktur als notwendige Voraussetzung. Wir stellen hier eine Erklärung des Symmetriebruchs in diesem Material auf kristallographischem, d. h. fernordnungs-basiertem, Wege vor. Während das Molekülkation CH3NH3+ intrinsisch polar ist, ist es extrem fehlgeordnet und kann deshalb nicht die einzige Erklärung darstellen. Es verzerrt allerdings das umgebende Kristallgitter und ruft dadurch eine Verschiebung der Iod-Atome von den zentrosymmetrischen Positionen hervor. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1199 KW - ferroelectricity KW - hybrid perovskites KW - inorganic chemistry KW - photovoltaic materials KW - structure elucidation Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525674 SN - 1866-8372 IS - 1 ER - TY - GEN A1 - Breternitz, Joachim A1 - Lehmann, Frederike A1 - Barnett, Sarah A. A1 - Nowell, Harriott A1 - Schorr, Susan T1 - Role of the Iodide-methylammonium interaction in the ferroelectricity of CH3NH3PbI3 T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Excellent conversion efficiencies of over 20% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1196 KW - ferroelectricity KW - hybrid perovskites KW - inorganic chemistry KW - photovoltaic materials KW - structure elucidation Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-518227 SN - 1866-8372 IS - 1 ER - TY - JOUR A1 - Breternitz, Joachim A1 - Lehmann, Frederike A1 - Barnett, Sarah A. A1 - Nowell, Harriott A1 - Schorr, Susan T1 - Zur Rolle der Iodid-Methylammonium-Interaktion in der Ferroelektrizität in CH3NH3PbI3 JF - Angewandte Chemie N2 - Ihre außergewöhnlich hohen Konversionseffizienzen von über 20 % und die einfache Zellherstellung machen Hybridperowskite zu heißen Kandidaten für alternative Solarzellenmaterialien. CH3NH3PbI3 als Archetyp dieser Materialklasse besitzt außergewöhnliche Eigenschaften wie eine sehr effiziente Umwandlung von Solarenergie, wobei besonders Ferroelektrizität als mögliche Erklärung in den Fokus gerückt ist. Diese erfordert allerdings eine nicht-zentrosymmetrische Kristallstruktur als notwendige Voraussetzung. Wir stellen hier eine Erklärung des Symmetriebruchs in diesem Material auf kristallographischem, d. h. fernordnungs-basiertem, Wege vor. Während das Molekülkation CH3NH3+ intrinsisch polar ist, ist es extrem fehlgeordnet und kann deshalb nicht die einzige Erklärung darstellen. Es verzerrt allerdings das umgebende Kristallgitter und ruft dadurch eine Verschiebung der Iod-Atome von den zentrosymmetrischen Positionen hervor. KW - ferroelectricity KW - hybrid perovskites KW - inorganic chemistry KW - photovoltaic materials KW - structure elucidation Y1 - 2019 VL - 132 IS - 1 PB - John Wiley & Sons, Inc. CY - New Jersey ER - TY - JOUR A1 - Senf, Deborah A1 - Ruprecht, Colin A1 - Kishani, Saina A1 - Matic, Aleksandar A1 - Toriz, Guillermo A1 - Gatenholm, Paul A1 - Wagberg, Lars A1 - Pfrengle, Fabian T1 - Tailormade polysaccharides with defined branching patterns BT - Enzymatic polymerization of arabinoxylan oligosaccharides JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - The heterogeneous nature of non-cellulosic polysaccharides, such as arabinoxylan, makes it difficult to correlate molecular structure with macroscopic properties. To study the impact of specific structural features of the polysaccharides on crystallinity or affinity to other cell wall components, collections of polysaccharides with defined repeating units are required. Herein, a chemoenzymatic approach to artificial arabinoxylan polysaccharides with systematically altered branching patterns is described. The polysaccharides were obtained by glycosynthase-catalyzed polymerization of glycosyl fluorides derived from arabinoxylan oligosaccharides. X-ray diffraction and adsorption experiments on cellulosic surfaces revealed that the physicochemical properties of the synthetic polysaccharides strongly depend on the specific nature of their substitution patterns. The artificial polysaccharides allow structure-property relationship studies that are not accessible by other means. KW - carbohydrates KW - enzymes KW - glycosynthases KW - structure elucidation KW - synthetic methods Y1 - 2018 U6 - https://doi.org/10.1002/anie.201806871 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 37 SP - 11987 EP - 11992 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Bringmann, Gerhard A1 - Mutanyatta-Comar, Joan A1 - Maksimenka, Katja A1 - Wanjohi, John M. A1 - Heydenreich, Matthias A1 - Brun, Reto A1 - Müller, Werner E. G. A1 - Peter, Martin A1 - Midiwo, Jacob O. A1 - Yenesew, Abiy T1 - Joziknipholones A and B : the First Dimeric Phenylanthraquinones, from the Roots of Bulbine frutescens N2 - From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated, together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P-configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M-configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 104 KW - antimalarial activity KW - chirality KW - joziknipholones KW - natural products KW - structure elucidation Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42638 ER -