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Faculty of Chemistry

Welcome to the Faculty of Chemistry

In order take the sustainability and environmental compatibility into account the research foci in chemistry have changed during the last years. The enormous importance of chemistry in economy, i.e. energy supply, development of new materials, pharmaceutical research and biotechnology, is unambiguous. The close collaboration of the Faculty of Chemistry with natural scientists and engineers of the University Stuttgart, as well as with scientists of the local Max-Planck-, Fraunhofer-, and Textile Chemistry and Chemical Fibers Institute, provides a considerable location advantage.

 

Abstracts of new Publications

Publication in Angewandte Chemie: A Sink for Signals: Triplex RNA motif binds cellular cGMP after expression in mammalian cells

The transmission of signals within cells is dependent on cyclic guanosine monophosphate (cGMP) as an important second messenger. Researchers led by Clemens Richert (Institut für Organische Chemie, University of Stuttgart) and Robert Feil (Interfakultäres Institut für Biochemie, University of Tübingen) developed a RNA motif that acts as a genetically encoded sink for cGMP molecules. As the motif can be repeated multiple times in a long continuous sequence, it was named “endless”.cGMP is generated in many organ systems of mammals. It plays an important role in blood vessel relaxation and the regulation of blood pressure, and aberrant cGMP signaling might be related to cardiovascular disorders. Experimental manipulation of endogenous cGMP levels should lead to a better understanding of cGMP’s multiple functions in health and disease. While it is relatively simple to elevate intracellular cGMP levels in experiments, for example, by using nitric oxide (NO), it was not yet possible to lower intracellular cGMP concentrations artificially. The newly developed cGMP-binding RNA motif “endless” is based on a triple helix. One of the three RNA segments forms a loop enclosing a binding cavity for cGMP (see Figure).
© Wiley-VCH
The functionality of “endless” was tested in smooth muscle cells obtained from blood vessels. Live cell imaging with a cGMP biosensor was used to estimate levels of free cGMP in the cytosol. In cells that expressed an artificial “endless” gene, NO-induced cGMP signals were significantly suppressed in comparison to control cells. Thus, “endless” RNA acts as a sink for cGMP and should be very useful for future research on the physiological role of cGMP.
C. Kröner, M. Thunemann, S. Vollmer, M. Kinzer, R. Feil and C. Richert
Angewandte Chemie International Edition, 2014
DOI: 10.1002/anie.2014035792014
Weitere Informationen erhalten Sie von
Prof. Clemens Richert
Institut für Organische Chemie
Universität Stuttgart
E-Mail

Publication in Chemical Science: Spectroscopic Determination of Crystal Field Splittings in Lanthanide Double Deckers

We have investigated the crystal field splitting in the archetypal lanthanide-based single-ion magnets and related complexes (NBu4)+[LnPc2]– (Ln = Dy, Ho, Er; dmf = N,N-dimethylformamide) by means of far infrared and inelastic neutron scattering spectroscopies. In each case, we have found several features corresponding to direct crystal field transitions within the ground multiplet. The observation of three independent peaks in the holmium derivative enabled us to derive crystal field splitting parameters. In addition, we have carried out CASSCF calculations. We show that exploiting the interplay of CASSCF calculation (for the composition of the states) and advanced spectroscopic measurements (for accurate determination of the energies) is a very powerful approach to gain insight into the electronic structure of lanthanide-based single-molecule magnets.
by R. Marx, F. Moro, M. Dörfel, L. Ungur, M. Waters, S.D. Jiang, M. Orlita, J. Taylor, W. Frey, L.F. Chibotaru, J. van Slageren
Chem. Sci. 2014
DOI: 10.1039/C4SC00751D (2014)
For further information please contact
Prof. Joris van Slageren
Instituto of Physical Chemistry
University of Stuttgart
E-Mail

Publication in JACS: Isolation of Neutral Mononuclear Copper Complexes Stabilized by Two Cyclic (Alkyl)(amino)carbenes

Two (cAAC)2Cu complexes, featuring a two-coordinate copper atom in the formal oxidation state zero, were prepared by reducing (Et2-cAAC)2Cu+I with metallic sodium in THF, and by a one-pot synthesis using Me2-cAAC, Cu(II)Cl2, and KC8 in toluene in a molar ratio of 2:1:2, respectively. Both complexes are highly air and moisture sensitive but can be stored in the solid state for a month at room temperature. DFT calculations showed that in these complexes the copper center has a d10 electronic configuration and the unpaired electron is delocalized over two carbene carbon atoms. This was further confirmed by the EPR spectra, which exhibit multiple hyperfine lines due to the coupling of the unpaired electron with 63,65Cu isotopes, 14N, and 1H nuclei.
by D. S. Weinberger, Nurul Amin SK, K. C. Mondal, M. Melaimi, G. Bertrand, A. C. Stückl, H. W. Roesky, B. Dittrich, S. Demeshko, B. Schwederski, W. Kaim, P. Jerabek and G. Frenking
J. Am. Chem. Soc. 2014, 136, 6235-6238
DOI: dx.doi.org/10.1021/ja502521b
For further information contact
Prof. Wolfgang Kaim
Institute of Inorganic Chemistry
University of Stuttgart
E-Mail

Distinguished Paper Award of the American Cleaning Institute for a Publication in the Journal of Surfactants and Detergents

Even though foams have been the subject of intensive investigations over the last decades, many important questions related to their properties remain open. This concerns in particular foams which are stabilized by mixtures of surfactants. The present study deals with the fundamental question: which are the important parameters one needs to consider if one wants to characterize foams properly? We give an answer to this question by providing a measuring protocol which we apply to well-known surfactant systems. The surfactants of choice are the two non-ionic surfactants n-dodecyl-β-d-maltoside (β-C12G2) and hexaethyleneglycol monododecyl ether (C12E6) as well as their 1:1 mixture. Following the suggested protocol, we generated data which allow discussion of the influence of the surfactant structure and of the composition on the time evolution of the foam volume, the liquid fraction, the bubble size and the bubble size distribution. This paper shows that different foam properties can be assigned to different surfactant structures, which is the crucial point if one wants to tailor-make surfactants for specific applications.
by Julia Boos, Wiebke Drenckhan, Cosima Stubenrauch
Journal of Surfactants and Detergents, Volume 16, (October 2013) p. 1-12
For further information please contact
Prof. Cosima Stubenrauch
Institute of Physical Chemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: A Rechargeable Hydrogen Battery Based on Ru Catalysis

Apart from energy generation, the storage and liberation of energy are among the major problems in establishing a sustainable energy supply chain. Herein we report the development of a rechargeable H2 battery which is based on the principle of the Ru-catalyzed hydrogenation of CO2 to formic acid (charging process) and the Ru-catalyzed decomposition of formic acid to CO2 and H2 (discharging process). Both processes are driven by the same catalyst at elevated temperature either under pressure (charging process) or pressure-free conditions (discharging process). Up to five charging–discharging cycles were performed without decrease of storage capacity. The resulting CO2/H2 mixture is free of CO and can be employed directly in fuel-cell technology.
by M. Sc. Shih-Fan Hsu, Dipl.-Chem. Susanne Rommel, M. Sc. Philipp Eversfield, Dr. Keven Muller, Prof. Dr. Elias Klemm, Prof. Dr. Werner R. Thiel und Prof. Dr. Bernd Plietker,*
Angew. Chemie, 2014
DOI: 10.1002/anie.201310972
Fur further information please contact
Prof. Bernd Plietker
Institute of Organic Chemistry
University of Stuttgart
E-Mail

Publication in Advanced Energy Materials: Charge Transport Anisotropy in Highly Oriented Thin Films of the Acceptor Polymer P(NDI2OD-T2)

This publication by Sabine Ludwigs and her PhD students Kim Tremel and Florian Fischer in collaboration with scientists from Strasbourg, Dresden and Potsdam investigates the morphology of the n-type semicrystalline polymer P(NDI2OD-T2) and establishes relationships to absorption characteristics and charge transport in thin films. Charge transport anisotropy of highly oriented films (obtained by high temperature rubbing & post-annealing) reveals average mobilities as high as 0.1 cm²/Vs along the polymer chains, i.e. parallel to the rubbing direction, whereas mobilities normal to the rubbing direction are approximately one order of magnitude lower. Interestingly this high anisotropy along the polymer chain is consistent with our recent findings for poly(3-hexylthiophene) (see Crossland, Ludwigs et al. Adv. Mater. 2012, 24, 839).
by K. Tremel , F.S.U. Fischer , N. Kayunkid , R. Di Pietro, R. Tkachov , A. Kiriy, D. Neher, S. Ludwigs , M. Brinkmann
Adv. Energy Mater. 2014
DOI: 10.1002/aenm.201301659
For further information please contact:
Prof. Sabine Ludwigs
Institute of Polymer Chemistry
University of Stuttgart
E-Mail

Publication in Advanced Materials: Organic Solar Cells: On the Efficiency of Charge Transfer State Splitting in Polymer: Fullerene Solar Cells

New insights in the efficiency of charge transfer state splitting in poly(3-hexylthiophene): fullerene solar cells were recently shown in a collaborative project between Potsdam, Stanford, Raleigh, Berkeley, Dresden and Stuttgart. Sabine Ludwigs and her PhD student Florian Fischer contributed to this highly interdisciplinary research project by determining energy levels both of the pure components and of the polymer blend films with their in-situ spectroelectrochemistry measurements.
by S. Albrecht, K. Vandewal, J.R. Tumbleston, F.S.U. Fischer, J.D. Douglas, J.M.J. Fréchet, S. Ludwigs, H. Ade, A. Salleo, and D. Neher
Adv. Mater. 2014, 26, 2533
DOI: 10.1002/adma.201470107
For further information please contact:
Prof. Sabine Ludwigs
Institute of Polymer Chemistry
University of Stuttgart

E-Mail

Publication in Angewandte Chemie: C4 Cumulene and the Corresponding Air-Stable Radical Cation and Dication

A neutral C4 cumulene 1 that includes a cyclic alkyl(amino) carbene (cAAC), its air-stable radical cation 1.+, and dication 12+ have been synthesized. The redox property of 1.+ was studied by cyclic voltammetry. EPR and theoretical calculations show that the unpaired electron in 1.+ is mainly delocalized over the central C4 backbone. The commercially available CBr4 is utilized as a source of dicarbon in the cumulene synthesis.
by Yan Li, Kartik Chandra Mondal, Prinson P. Samuel, Hongping Zhu, Claudia M. Orben, Saravanan Panneerselvam, Birger Dittrich, Brigitte Schwederski, Wolfgang Kaim, Totan Mondal, Debasis Koley, Herbert W. Roesky
Angew. Chem. 2014, 126, 4252-4256
DOI: 10.1002/ange.201310975
For further information please contact:
Prof. Wolfgang Kaim
Institute of Inorganic Chemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: Anomalous Diamagnetic Susceptibility in 13-Atom Platinum Nanocluster Superatoms

We are used to being able to predict diamagnetic susceptibilities χD to a good approximation in atomic increments since there is normally little dependence on the chemical environment. Surprisingly, we find from SQUID magnetization measurements that the χD per Pt atom of zeolite-supported Pt13 nanoclusters exceeds that of Pt2+ ions by a factor of 37–50. The observation verifies an earlier theoretical prediction. The phenomenon can be understood nearly quantitatively on the basis of a simple expression for diamagnetic susceptibility and the superatom nature of the 13-atom near-spherical cluster. The two main contributions come from ring currents in the delocalized hydride shell and from cluster molecular orbitals hosting the Pt 5d and Pt 6s electrons.
by Roduner, E., Jensen, C., van Slageren, J., Rakoczy, R. A., Larlus, O. and Hunger, M.
Angew. Chemie, 2014
doi: 10.1002/ange.201310637
For further information please contact:
Prof. Joris van Slageren
Institute of Physical Chemistry
University of Stuttgart
E-Mail

Publication in JACS: The Total Syntheses of Guttiferone A and 6-epi-Guttiferone A

Polyprenylated polycyclic acylphloroglucinols (PPAP) are a constantly growing class of natural products that exhibit a common bicyclo[3.3.1]nonatrione core and consist of currently more than 200 members. A subclassification among the various natural products of this class includes the position of the exocyclic acyl group, the prenylation grade of the core, and the relative configuration at C-7 within the core. About 10% of the reported structures, however, possess an additional chiral center at C-6. Herein we describe a straightforward access to guttiferone A and epi-guttiferone A, in which full control of stereoselectivity is achieved via conformational control, and a strict separation of framework decorating from framework constructing operations sets the stage for a short 13-step synthesis.
by Fiene Horeischi , Nicole Biber , and Bernd Plietker
J. Am. Chem. Soc. 2014, 136 (10), 4026
DOI: 10.1021/ja500063a
For further information please contact:
Prof. Bernd Plietker
Institute of Organic Chemistry
University of Stuttgart
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Publication in JACS: Stabilization of a Cobalt–Cobalt Bond by Two Cyclic Alkyl Amino Carbenes


by Kartik Chandra Mondal, Prinson P. Samuel, Herbert W. Roesky, Elena Carl, Regine Herbst-Irmer, Dietmar Stalke, Brigitte Schwederski, Wolfgang Kaim, Liviu Ungur, Liviu Chibotaru, Markus Herrmann and Gernot Frenking
J. Am. Chem. Soc. 2014, 136, 1770−1773
DOI: 10.1021/ja4123285
For further information please contact:
Prof. Wolfgang Kaim
Institute of Inorganic Chemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: The Electronic Ground State of [Fe(CO)3(NO)]: A Spectroscopic and Theoretical Study

During the past 10 years iron-catalyzed reactions have become established in the field of organic synthesis. For example, the complex anion [Fe(CO)3(NO)], which was originally described by Hogsed and Hieber, shows catalytic activity in various organic reactions. This anion is commonly regarded as being isoelectronic with [Fe(CO)4]2−, which, however, shows poor catalytic activity. The spectroscopic and quantum chemical investigations presented herein reveal that the complex ferrate [Fe(CO)3(NO)]cannot be regarded as a Fe−II species, but rather is predominantly a Fe0 species, in which the metal is covalently bonded to NO by two π-bonds. A metal–N σ-bond is not observed.
by M. Sc. Johannes E. M. N. Klein, Dr. Burkhard Miehlich, Dr. Michael S. Holzwarth, Prof. Dr. Matthias Bauer, Dipl.-Chem. Magdalena Milek, Dr. Marat M. Khusniyarov, Dr. Gerald Knizia, Prof. Dr. Hans-Joachim Werner, Prof. Dr. Bernd Plietker,*
Angew. Chem. Int. Ed. 2014, 53
DOI: 0.1002/anie.201309767
For further information please contact:
Prof. Bernd Plietker
Institute of Organic Chemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: Asymmetric Palladium(II)-Catalyzed Cascade Reaction Giving Quaternary Amino Succinimides by 1,4-Addition and a Nef-Type Reaction

Simple starting materials, high-value products: A dinuclear ferrocene-based PdII complex transforms mixtures of racemic N-benzoyl α-amino acids, nitroolefins, acetic anhydride, and manganese acetate into biologically interesting quaternary aminosuccinimides. The products are obtained as single diastereomers in highly enantioenriched form. Key steps of the cascade mechanism are a 1,4-addition of in situ generated azlactones to nitroolefins and a Nef-type reaction.
by M. Weber, W. Frey, R. Peters
Angew. Chem. Int. Ed. 2013, 52, 13223-13227
DOI: 10.1002/anie.201307334
For further information please contact:
Prof. Rene Peters
Institute of Organic Chemistry
University of Stuttgart
E-Mail

VIP Publication in ChemPlusChem: Influence of Chromophore Length and Acceptor Groups on the Optical Properties of Rigidified Merocyanine Dyes

Three series of rigidified tri-, penta- and heptamethine merocyanine dyes were synthesised. A piperidyl moiety was chosen as the electron-donating substituent while the electron-accepting group was varied from ketones to malononitriles and cyanoacetates. The structures of the compounds in the solid state and in solution were elucidated by X-ray diffraction and NMR spectroscopy, respectively, while optical properties were investigated by absorption and emission spectroscopy. As a general trend, the acceptor properties decrease in the series malononitrile>cyanoacetate>ketone based on the analysis of their solvatochromic behaviour. The experimental results were further supported by calculations at the B3LYP 6-311+G(d) level of theory.
by Katharina Christina Kreß, Dr. Thomas Fischer, Dr. Joachim Stumpe, Dr. Wolfgang Frey, Dr. Melanie Raith, Omid Beiraghi, Prof. Dr. S. Holger Eichhorn, Dr. Stefan Tussetschläger, Prof. Dr. Sabine Lascha
ChemPlusChem (2013)
DOI: 10.1002/cplu.201300308
For further information please contact:
Prof. Sabine Laschat
Institute of Organic Chemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: Genomic Imprinting—The Struggle of the Genders at the Molecular Level

Genomic imprinting, the parent of origin-dependent expression of genes, has been discovered as a fascinating example of the control of gene expression by epigenetic processes in the human body. It affects about 100 genes, which are often involved in growth and development. In this Review, we discuss the mechanisms leading to the generation of gender-specific imprints in form of DNA methylation marks, their preservation during growth and development of the organism, and the processes that translate parental methylation marks into monoallelic gene expression. We discuss the gender-specific dimorphic nature of imprints from an evolutionary point of view and present the prevalent model that molecular imprinting mediates a conflict of interest between the parents that occurs in viviparous animals. Finally, we summarize the relevance of parental imprinting for human health.
by Renata Z. Jurkowska, Albert Jeltsch
Angew. Chem. Int. Ed. 52, 2-15 (2013)
DOI: 10.1002/anie.201307005
For further information please contact:
Prof. Albert Jeltsch
Institute of Biochemistry
University of Stuttgart
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Publication in PNAS: Previously unknown role for the ubiquitin ligase Ubr1 in endoplasmic reticulum-associated protein degradation.

Quality control and degradation of misfolded proteins are essential processes of all cells. The endoplasmic reticulum (ER) is the entry site of proteins into the secretory pathway in which protein folding occurs and terminally misfolded proteins are recognized and retrotranslocated across the ER membrane into the cytosol. Here, proteins undergo polyubiquitination by one of the membrane-embedded ubiquitin ligases, in yeast Hrd1/Der3 (HMG-CoA reductase degradation/degradation of the ER) and Doa10 (degradation of alpha), and are degraded by the proteasome. In this study, we identify cytosolic Ubr1 (E3 ubiquitin ligase, N-recognin) as an additional ubiquitin ligase that can participate in ER-associated protein degradation (ERAD) in yeast. We show that two polytopic ERAD substrates, mutated transporter of the mating type a pheromone, Ste6* (sterile), and cystic fibrosis transmembrane conductance regulator, undergo Ubr1-dependent degradation in the presence and absence of the canonical ER ubiquitin ligases. Whereas in the case of Ste6* Ubr1 is specifically required under stress conditions such as heat or ethanol or in the absence of the canonical ER ligases, efficient degradation of human cystic fibrosis transmembrane conductance regulator requires function of Ubr1 already in wild-type cells under standard growth conditions. Together with the Hsp70 (heat shock protein) chaperone Ssa1 (stress-seventy subfamily A) and the AAA-type ATPase Cdc48 (cell division cycle), Ubr1 directs the substrate to proteasomal degradation. These data unravel another layer of complexity in ERAD.
by Stolz A., Besser S., Hottmann H., Wolf D. H.
Proc. Natl. Acad. Sci. 2013, 110(38) 15271-6.
DOI: 10.1073/pnas.1304928110
For further information please contact:
Prof. Dieter Wolf
Institute of Biochemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: Trichlorosilyl-Substituted Carbon-Centered Stable Radicals

Cyclic alkyl(amino) carbenes formed zwitterionic adducts with SiCl4, which were further converted into carbon-centered stable radicals by changing the donor-acceptor C→Si coordinate bond into a C-Si covalent bond through a KC8 reduction. As the carbon radical site was directly bonded to a SiCl3 unit, a radical center that is right next to an acceptor has been generated.
by K. C. Mondal, H. W. Roesky, A. C. Stückl, F. Ehret, W. Kaim, B. Dittrich, B. Maity, D. Koley
Angew. Chem. 125, 12020-12023 (2013)
DOI: 10.1002/ange.201300668
For further information please contact:
Prof. Wolfgang Kaim
Institut für Anorganische Chemie
Universität Stuttgart
E-Mail

Publication in the European Journal of Inorganic Chemistry: Understanding the ammonothermal method for growing GaN crystals

RN_2013_klein.jpg
Gallium nitride (GaN) is an important material for the semiconductor industry. It features a wide band gap and high thermal conductivity at room temperature, which make it a good material for optoelectronic devices and high-performance radio-frequency microdevices. In the European Journal of Inorganic Chemistry, Rainer Niewa and co-workers at the University of Stuttgart and Ludwig Maximilians University of Munich, Germany, report the existence of ammoniates of gallium halides in the ammonothermal growth of GaN and provide a rigorous characterization of these compounds.
by Shiyu Zhang, Frauke Hintze, Wolfgang Schnick, Rainer Niewa
Eur. Journal of Inorg. Chem. 31, 5387 (2013)
DOI: 10.1002/ejic.201300958, see also the press release.
Further informaton:
Prof. Rainer Niewa
Institute of Inorganic Chemistry
University of Stuttgart
Phone 0711/685-64217

E-Mail

VIP - Publication in Angewandte Chemie: A Lyotropic Chiral Smectic C Liquid Crystal with Polar Electrooptic Switching.

EA__BP_wStr_13_hell
A lyotropic analogue of the ferroelectric smectic C* phase has been found. The lyotropic smectic C* phase shows macroscopic chirality effects, such as a helical ground state and polarity-dependent electrooptic switching, thus indicating the presence of a spontaneous electric polarization. The helicity implies communication of the chiral director twist across the achiral solvent layers separating adjacent layers of the chiral mesogens.
by Johanna R. Bruckner, Dr. Jan H. Porada, Clarissa F. Dietrich, Dr. Ingo Dierking,
Prof. Frank Giesselmann

Angewandte Chemie Int. Ed. 52, 8934-8937 (2013)
DOI: 10.1002/anie.201303344
Prof. Frank Giesselmann
Institute of Physical Chemistry
University of Stuttgart
Phone 0711/685-64460

E-Mail

Publication in Angewandte Chemie: A Nucleobase Analogue that Pairs Strongly with Adenine

EA__BP_wStr_13_hell
Shaping up for an A: Adenine is the only canonical nucleobase that does not offer a third hydrogen-bonding functionality at its Watson–Crick face, making it difficult to bind with high affinity. A 6-ethynyl-2-pyridone binds more tightly and with greater sequence fidelity than thymine.
by Marco Minuth and Clemens Richert
Angewandte Chemie 125, 11074 (2013)
DOI: 10.1002/ange.201305555
Prof. Clemens Richert
Institute of Organic Chemistry
University of Stuttgart
Phone 0711/685-64311

E-Mail

BIC - New English edition published: The textbook „Bioinorganic Chemistry – Inorganic Elements in the Chemistry of Life – An Introduction and Guide“ by W. Kaim, B. Schwederski andA. Klein is available again.

The 2nd English edition of the successful textbook on Bioinorganic Chemistry has now appeared in revised and updated form, published by Wiley. The current knowledge on the role of inorganic elements in life processes is demonstrated by classical examples and by the latest developments, including materials aspects as well as environmentally, pharmaceutically and medically relevant topics.
by Wolfgang Kaim, Brigitte Schwederski, Axel Klein
For further information contact
Prof. Wolfgang Kaim
Institute of Inorganic Chemistry
University of Stuttgart
E-Mail

VIP - Publication in Angewandte Chemie: Identifying Intermediates of Sequential Electron and Hydrogen Loss from a Dicarbonylcobalt Hydride Complex

Step by step: Electron and hydrogen transfer steps are documented IR-spectroelectrochemically and structurally for the H2 producing oxidation of a dicarbonylcobalt hydride complex, modified by the sterically protecting 1,1’-bis(diisopropylphosphino)ferrocene. The series complements the mechanism discussed for water-reducing cobalt compounds with less π-accepting ligands.
by Michael J. Krafft, Martina Bubrin, Alexa Paretzki, Falk Lissner, Jan Fiedler, Stanislav Záliš and Wolfgang Kaim
Angew. Chem. Int. Ed. 52, 6781-6784 (2013)
DOI: 10.1002/anie.201301706
For further information contact
Prof. Wolfgang Kaim
Institute of Inorganic Chemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: The Inherent Single-Molecule Magnet Character of Trivalent Uranium

We describe three structurally unrelated uranium(III) coordination complexes, which all show single-molecule magnet (SMM) properties. Hence, the important conclusion from this work is that the SMM behavior of uranium(III) is not closely linked to specific symmetries or ligand surroundings, which greatly increases the potential of this ion for the development of improved SMMs.
by Fabrizio Moro, David P. Mills, Stephen T. Liddle und Joris van Slageren
Angew. Chem. Int. Ed., 52, 3430 - 3433 (2013)
DOI: 10.1002/anie.201208015
For further information contact
Prof. Joris van Slageren
Institute of Physical Chemistry
University of Stuttgart
E-Mail

Publication in Angewandte Chemie: Triazenides and NO2 as „suspect“ ligands

Depending on substituents and metal configuration the triazenides [RNNNR] can act as EPR-spectroscopically detectable triazenyl radical ligands in metal complexes. Triazenyls are related to the hitherto unused nitrogen dioxide radical ligand, [NO2]. The number of potentially noninnocent (“suspect”) ligands is thus significantly higher than previously assumed.
by Fabian Ehret, Martina Bubrin, Stanislav Záliš and Wolfgang Kaim
Angewandte Chemie, 2013
DOI: 10.1002/ange.201209260
For further information contact
Prof. Wolfgang Kaim
Institute of Inorganic Chemistry
University of Stuttgart
E-Mail

TOP 15 Paper in Chemical Science: Asymmetric Michael additions of a-cyanoacetates by soft Lewis acid / hard Brønsted acid catalysis: stereodivergency with bi- vs monometallic catalysts

The direct asymmetric conjugate addition of α-cyanoacetates to enones generating densely functionalized a-amino acid precursors with adjacent quaternary and tertiary stereocenters is described comparing mono- and bis-palladacycle catalysts. This paper features the complementary value of mono- and bimetallic catalysis in a case study using related catalyst systems. Different major diastereomers of the 1,4-addition products are formed by the use of the planar chiral mono- and bimetallic catalyst systems and provide access to epimeric amino acid derivatives. Both catalyst types require the use of a Brønsted acid (HOAc) as a co-catalyst to avoid an undesired ß-hydride elimination. Kinetic studies show that the C-C bond forming step takes place almost instantaneously with the bis-palladium complex after productive substrate coordination. This extraordinarily high reactivity for an elementary step generating a sterically demanding linkage of a quaternary and a tertiary stereocenter stresses the cooperativity of both metal centers.
by S. H. Eitel, S. Jautze, W. Frey, R. Peters
Chemical Science, 2013
DOI: 10.1039/C3SC50419K
For further information contact
Prof. Rene Peters
Institute of Organic Chemistry
University of Stuttgart
E-Mail

Publication in Advanced Materials: Hydrogen-Bond Reinforced Vanadia Nanofiber Paper of High Stiffness

In this work, it is demonstrated the self-assembly of vanadia nanofibers into a free-standing, paper-like material of extraordinary mechanical properties stiffness (45 GPa) and strength (220 GPa), as well as high mechanical flexibility (toughness 500 kJm-3). The mechanical performance of our material clearly outperforms that of paper-like films comprised of carbon nanostructures like carbon nanotubes or graphene oxide. As evidenced by our microscopic analysis, this outstanding mechanical performance results from an architecture closely resembling that of structural biomaterials like nacre. In fact, similar to its natural counterparts, the vanadia paper effectively combines a stiff inorganic component in the form of single-crystalline oxide nanofibers with a soft component constituted by a hydrogen-bonded water network between the fibers. Another common feature is the hierarchical organization of the basic components, specifically the slabs of nanofibers are laterally assembled into lamellar-like structures which in turn are vertically stacked with inclusion of a water layer in between. The aforementioned properties, complemented by the good in-plane electrical conductivity and ion intercalation capability of the vanadia paper, render this material superior to previously reported paper-like films, in terms of both its microstructure and application potential.
by Zaklina Burghard, * Andreas Leineweber, Peter A. van Aken, Thomas Dufaux, Marko Burghard, and Joachim Bill
Advanced Materials, 2013
DOI: 10.1002/adma.201300135
Prof. Joachim Bill
Institut für Materialwissenschaft
Universität Stuttgart
E-Mail

Micropumps - Nature Communications: One-piece micropumps from liquid crystalline core-shell particles

Responsive polymers are low-cost, light weight and flexible, and thus an attractive class of materials for the integration into micromechanical and lab-on-chip systems. Triggered by external stimuli, liquid crystalline elastomers are able to perform mechanical motion and can be utilized as microactuators. Here we present the fabrication of one-piece micropumps from liquid crystalline core-shell elastomer particles via a microfluidic double-emulsion process, the continuous nature of which enables a low-cost and rapid production. The liquid crystalline elastomer shell contains a liquid core, which is reversibly pumped into and out of the particle by actuation of the liquid crystalline shell in a jellyfish-like motion. The liquid crystalline elastomer shells have the potential to be integrated into a microfluidic system as micropumps that do not require additional components, except passive channel connectors and a trigger for actuation. This renders elaborate and high-cost micromachining techniques, which are otherwise required for obtaining microstructures with pump function, unnecessary.
see a movie
by  Eva-Kristina Fleischmann, Hsin-Ling Liang, Nadia Kapernaum, Frank Giesselmann,
Jan Lagerwall and Rudolf Zentel

Nature Communications, November 2012
DOI:10.1038/ncomms2193
Prof. Frank Giesselmann
Institute of Physical Chemistry
University of Stuttgart
Phone 0711/685-64478
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Highly Active Catalysts for Asymmetric Aza-Claisen Rearrangements - JACS Publication: Paramagnetic Palladacycles with PdIII Centers are Highly Active Catalysts

A combination of spectroscopic and electrochemical methods—XANES, EXAFS, X-ray, 1H NMR, EPR, Mössbauer, and cyclic voltammetry—demonstrate that the most efficient Pd catalysts for the asymmetric rearrangement of allylic trifluoroacetimidates unexpectedly possess in the activated oxidized form a PdIII center bound to a ferrocene core which remains unchanged (FeII) during the oxidative activation. These are the first recognized PdIII complexes acting as enantioselective catalysts.
by S. H. Eitel, M. Bauer, D. Schweinfurth, N. Deibel, B. Sarkar, H. Kelm, H.-J. Krüger, W. Frey, R. Peters
J. Am. Chem. Soc. 2012, 134, 4683–4693.
Prof. René Peters
Institute of Organic Chemistry
University of Stuttgart
Phone 0711/685-64330
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Template-directed solid phase synthesis: Publication in Angewandte Chemie

by Andreas Kaiser, Sebastian Spies und Clemens Richert*
For details see Angewandte Chemie, Juli 2012
DOI: 10.1002/ange.201203859
* Prof. Clemens Richert
Institute of Organic Chemistry
University of Stuttgart
Phone 0711/685-64311
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Publication in JACS: Isolation of ZnO-binding 12-mer peptides and determination of their binding epitopes by NMR spectroscopy

Organic-inorganic hybrid materials are a highly topical research field combining the scientific disciplines of materials science, nanotechnology, and biotechnology. Especially, the specific interactions of peptides with inorganic materials for surface functionalization, sensing applications, or biomineralization approaches are in the focus of interest. Peptides, built up by the combination of amino acid residues with various functional groups, are ideal candidates for the molecular recognition of an inorganic target material. Peptides from a random peptide library which interact with the polar surfaces (0001) and (000-1) of single crystalline zinc oxide (ZnO) were identified by phage display (PD). The peptides’ molecular interaction sides leading to the ZnO-binding were determined with a label-free nuclear magnetic resonance (NMR) approach. In this study, we identified the pH dependent binding sites of the peptide-ZnO interaction on the atomic level and accounted ionic and polar forces for this effect. The combined approach of PD and NMR was exemplarily shown for ZnO-binding peptides, but it can be generalized for other target substrates. To broaden the understanding of the molecular basis of the peptide binding to inorganic materials is a step further towards a rational design of specifically interacting peptides for technical applications.
by Dirk Rothenstein, Birgit Claasen, Beatrice Omiecienski, Patricia Lammel, and Joachim Bill
J. Am. Chem. Soc., 2012
DOI: 0.1021/ja302211w
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Prof. Joachim Bill
Institute of Materials Science
University of Stuttgart
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Publication in Angewandte Chemie International Edition: Synthesis of Macroporous Polystyrene by the Polymerization of Foamed Emulsions

An ideal template for the production of macroporous polystyrene can be prepared from foamed oil-in-water emulsions containing styrene, water, glycerol, and sodium dodecylsulfate. After addition of a photoinitiator the mixture is polymerized with UV light and the foam structure of the precursor is transferred to the polymer. The resulting materials display densely packed cells with windows between adjacent pores (see SEM image; scale bar: 250 µm).
by Dr. Fabian Schüler, Debora Schamel, Dr. Anniina Salonen, Dr. Wiebke Drenckhan, Prof. Dr. Michael D. Gilchrist, Prof. Dr. Cosima Stubenrauch
Angew. Chem. Int. Ed. 2012, 51
DOI: 10.1002/ange.201107806
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Prof. Cosima Stubenrauch
Institute of Physical Chemistry
Universität Stuttgart
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Publication in JACS: Water- and Ionic-Liquid-Soluble Branched Polythiophenes Bearing Anionic and Cationic Moieties

The synthesis of ionically functionalized branched polythiophenes with either carboxylic acid (anionic, P3T-COOH) or methylimidazolium (cationic, P3T-MIM) end groups is presented. Due to the large number of end groups present in the polymer, the functionalization has a major impact on the solubility of the polymers. In the case of P3T-COOH, the polymer shows a fully reversible phase transfer between organic solvents and water, depending on the pH. Remarkably, the ionic-liquid-modified polymer P3T-MIM is soluble in a room-temperature ionic liquid. The absorption properties are unaffected by the functional end groups.
by Thomas V. Richter, Christian Bühler and Sabine Ludwigs
J. Am. Chem. Soc. 134, 2012, 43
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Prof. Sabine Ludwigs
Institute of Polymer Chemistry
Universität Stuttgart
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Publication in Advanced Materials: Anisotropic Charge Transport in Spherulitic Poly(3-hexylthiophene) Films

Poly(3-hexylthiophene) (P3HT) is one of the most important semiconducting polymers for organic photovoltaics and optoelectronics. Yet, because of the structural complexity of semicrystalline polymers, comparatively little is known conclusively about the relationship between charge transport and microstructure in P3HT-containing semiconductors. This lack of information arises mainly from an inability to manufacture samples with spontaneous long-range crystalline order approaching macroscopic dimensions, that allow characterisation in a similar fashion to inorganic single crystals. We have overcome this limitation and grown well-ordered P3HT spherulites, suffi ciently large to measure charge transport within single oriented crystal domains, enabling measurements of the charge mobility both parallel and perpendicular to the characteristic π -stacked nanocrystalline lamellae and across spherulite boundaries.
by Edward J. W. Crossland , Kim Tremel , Florian Fischer , Khosrow Rahimi , Günter Reiter , Ullrich Steiner and Sabine Ludwigs
Adv. Mat. 2012
DOI: 10.1002/adma.201104284
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Prof. Sabine Ludwigs
Institute of Polymer Chemistry
Universität Stuttgart
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VIP paper in Angewandte Chemie, Int. Ed.: Na11Hg52: Complexity in a Polar Metal

The mercury puzzle: Using the new technique of electrocrystallization the sodium mercury alloy Na11Hg52 could be obtained in a phase pure form. This amalgam is a key component in the industrially important chlor-alkali process. The combination of different bonding situations in this phase results in it having the typical properties of a “bad” metal.
by Constantin Hoch* and Arndt Simon
Angewandte Chemie Int. Ed., 2012, 51, 1-5 DOI: 10.1002/anie.201108064
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Dr. Constantin Hoch
Institute of Inorganic Chemistry
University Stuttgart
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Advanced Materials Article: Virus-Templated Synthesis of ZnO Nanostructures and Formation of Field-Effect Transistors

A novel bio-inspired approach to the fabrication of nanostructured functional devices is presented. ZnO nanowires are formed by self-assembly of nanosized ZnO building blocks controlled by tobacco mosaic virus (TMV) templates at nearly ambient conditions. This process allows the integration of TMV/ZnO nanostructures into field effect transistors (FETs) with prestructured electrodes in a bottom gate/bottom contact arrangement. The FETs operate as-deposited, including the intact viral material, without any further post-treatment. Furthermore, the electronic performance of the TMV/ZnO films showed remarkable differences to ZnO, which was deposited by an identical chemical bath deposition procedure on self-assembled monolayers (SAMs) with carboxylate termination or on deoxyribonucleic acid (DNA). The FETs with the SAM/ZnO semiconductor exhibited charge carrier mobilities two orders of magnitude lower than those obtained with TMV/ZnO, and also a drastically higher threshold voltage. The DNA/ZnO material showed even inferior values. These results suggest that TMV does not only function as a structural scaffold, but also has an obvious effect on the properties of the semiconducting layer, indicating an electron injection capability of the TMV templates.
by Petia Atanasova *, Dirk Rothenstein , Jörg J. Schneider , Rudolf C. Hoffmann , Stefan Dilfer , Sabine Eiben, Christina Wege , Holger Jeske, and Joachim Bill
Advanced Materials 23, 2011, 4918
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Prof. Joachim Bill
Institute of Materials Science
University Stuttgart
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Nature Chemistry Article: The Total Synthesis of Hyperpapuanone, Hyperibone L, epi-Clusianone and Oblongifolin A

Polyprenylated polycyclic acylphloroglucines (PPAP) are a family of natural products which possess a wide range of different important biological activities which are the consequence of position and configuration of four substituents decorating one common central bicyclo[3.3.1]nonane-2,4,9-trione core. The rigid bicyclic framework with its lipophilic sidechains and its hydrophilic trione moiety represents a nature-derived lead structure that arranges the substituents R1 – R4 into a defined topographical orientation. Since the substituents are responsible for the biological activities the seven-step synthetic approach presented in this manuscript sets the stage for an iterative introduction of R1 – R4 thus generating structurally diverse trans-type B PPAP. Four natural and one non-natural trans-type B PPAPs were prepared starting from acetylacetone with overall yields ranging from 6 to 22 %. The concept of separating framework construction from decorating transformations plus the minimization of protecting group operations are the key issues for the realization of our synthetic approach
by Nicole Biber, Katrin Möws, and Bernd Plietker*
Nature Chemistry online 16.10.2011 doi:doi:10.1038/nchem.1170
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Prof. Bernd Plietker
Institute of Organic Chemistry
University Stuttgart
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Nature Communication Article: Encapsulation of Single-molecule magnets in carbon nanotubes

Next-generation electronic, photonic or spintronic devices will be based on nanoscale functional units, such as quantum dots, isolated spin centres or single-molecule magnets. The key challenge is the coupling of the nanoscale units to the macroscopic world, which is essential for read and write purposes. Carbon nanotubes with one macroscopic and two nanoscopic dimensions provide an excellent means to achieve this coupling. Although the dimensions of nanotube internal cavities are suitable for hosting a wide range of different molecules, to our knowledge, no examples of molecular magnets inserted in nanotubes have been reported to date. Here we report the successful encapsulation of single-molecule magnets in carbon nanotubes, yielding a new type of hybrid nanostructure that combines all the key single-molecule magnet properties of the guest molecules with the functional properties of the host nanotube. The findings may pave the way to the construction of spintronic or ultrahigh-density magnetic data storage devices.
by M. C. Giménez-López, F. Moro, A. La Torre, C.J. Gómez-García, P. D. Brown, J. van Slageren & A. N. Khlobystov
Nature Communications Volume:2, Article number:407 doi:10.1038/ncomms1415
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Prof. Joris van Slageren
Institute of Physical Chemistry
University Stuttgart
Phone 0711/685-64380
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Nature Chemistry Paper: A delocalised arene-bridged diuranium single molecule magnet

Single-molecule magnets (SMMs) are compounds that, below a blocking temperature, exhibit stable magnetization purely of molecular origin, and not caused by long-range ordering of magnetic moments in the bulk. They thus show promise for applications such as data storage of ultra-high density. The stability of the magnetization increases with increasing ground-state spin and magnetic anisotropy. Transition-metal SMMs typically possess high-spin ground states, but insufficient magnetic anisotropies. Lanthanide SMMs exhibit large magnetic anisotropies, but building high-spin ground states is difficult because they tend to form ionic bonds that limit magnetic exchange coupling. In contrast, the significant covalent bonding and large spin–orbit contributions associated with uranium are particularly attractive for the development of improved SMMs. Here we report a delocalized arene-bridged diuranium SMM. This study demonstrates that arenebridged polyuranium clusters can exhibit SMM behaviour without relying on the superexchange coupling of spins. This approach may lead to increased blocking temperatures.
by D. P. Mills, F. Moro, J. McMaster, J. van Slageren, W. Lewis, A. J. Blake, S. T. Liddle
Nature Chem., 3, 454 - 460 (2011) doi: http://dx.doi.org/10.1038/nchem.1028
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Prof. Joris van Slageren
Institute of Physical Chemistry
University Stuttgart
Phone 0711/685-64380
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Nature Chemistry Paper: Efficient enzyme-free copying of all four nucleobases templated by immobilized RNA

The transition from inanimate materials to the earliest forms of life must have involved multiplication of a catalytically active polymer that is able to replicate. The semiconservative replication that is characteristic of genetic information transfer requires strands that contain more than one type of nucleobase. Short strands of RNA can act as catalysts, but attempts to induce efficient self-copying of mixed sequences (containing four different nucleobases) have been unsuccessful with ribonucleotides. Here we show that inhibition by spent monomers, formed by the hydrolysis of the activated nucleotides, is the cause for incomplete extension of growing daughter strands on RNA templates. Immobilization of strands and periodic displacement of the solution containing the activated monomers overcome this inhibition. Any of the four nucleobases (A/C/G/U) is successfully copied in the absence of enzymes. We conclude therefore that in a prebiotic world, oligoribonucleotides may have formed and undergone self-copying on surfaces.
by Christopher Deck, Mario Jauker and Clemens Richert*
PUBLISHED ONLINE in Nature Chemistry: 10 JULY 2011 | DOI: 10.1038/NCHEM.1086
* Prof. Clemens Richert
Institute of Organic Chemistry
University Stuttgart
Phone 0711/685-64311
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TOP 11 among the downloads JCP in May 2011: Explicitly correlated multireference configuration interaction with multiple reference functions: Avoided crossings and conical intersections

We develop an explicitly correlated multireference configuration interaction method (MRCI-F12) with multiple reference functions. It can be routinely applied to nearly degenerate molecular electronic structures near conical intersections and avoided crossings, where the reference functions are strongly mixed in the correlated wave function. This work is a generalization of the MRCI-F12 method for electronic ground states, reported earlier by Shiozaki et al. [J. Chem. Phys. 134, 034113 (2011)]10.1063/1.3528720. The so-called F12b approximation is used to arrive at computationally efficient formulas. The doubly external part of the wave function is expanded in terms of internally contracted configurations generated from all the reference functions. In addition, we introduce a singles correction to the CASSCF reference energies, which is applicable to multi-state calculations. As examples, we present numerical results for the avoided crossing of LiF, excited states of ozone, and the H2 + OH (A2Σ+) reaction.
Toru Shiozaki and Hans-Joachim Werner
J. Chem. Phys. 134, 184104 (2011); doi:10.1063/1.3587632
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Prof. Hans-Joachim Werner
Institut für Theoretische Chemie
Phone 0711/685-64401
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New Materials with High Li-Motion: Hot article: high download number in autumn 2010 (ZAAC)

New materials with high Li-Motion were synthesized and characterized by the group of Prof. Niewa, Institute of Inorganic Chemistry, University of Stuttgart.
Daniel Bräunling, Oliver Pecher, Dmytro M. Trots, Anatoliy Senyshyn, Dmitry A. Zherebtsov, Frank Haarmann, Rainer Niewa
ZAAC 636(6), 936-946, (2010) doi: 10.1002/zaac.201000002
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