361 results match your criteria: "Technische Universitat Graz[Affiliation]"
Chemistry
December 2016
Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Straße 1-3, 26211, Oldenburg, Germany.
Silylated germylene-PMe adducts exchange their phosphane moiety smoothly for an N-heterocyclic carbene or isocyanide species to form their respective base adducts. Reaction of the silylated germylene-PMe adducts with monosubstituted alkynes produce germylene adducts with the alkyne inserted into a Ge-Si bond. A computational study of this process provides evidence for the initial formation of a germirene, which rearranges to a vinylgermylene species.
View Article and Find Full Text PDFJ Chem Phys
November 2016
Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom.
Alkali metal atoms and small alkali clusters are classic heliophobes and when in contact with liquid helium they reside in a dimple on the surface. Here we show that alkalis can be induced to submerge into liquid helium when a highly polarizable co-solute, C, is added to a helium nanodroplet. Evidence is presented that shows that all sodium clusters, and probably single Na atoms, enter the helium droplet in the presence of C.
View Article and Find Full Text PDFOrganometallics
August 2016
Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 9, 8010 Graz, Austria.
In order to estimate the reactivity of disilylated germylene phosphine adducts, a cyclic version of this compound class was reacted with a number of different reagents. Reactions with the chalcogens sulfur, selenium, and tellurium led to dimers of the heavy ketone analogues. Reactions with water and ethyl bromide proceeded to give the respective oxidized germanol and germyl bromide.
View Article and Find Full Text PDFMolecules
August 2016
Institut für Chemie, Karl Franzens Universität Graz, Stremayrgasse 9, 8010 Graz, Austria.
Polysilanes are known to exhibit the interesting property of σ-bond electron delocalization. By employing optical spectroscopy (UV-vis), it is possible to judge the degree of delocalization and also differentiate parts of the molecules which are conjugated or not. The current study compares oligosilanes of similar chain length but different substitution pattern.
View Article and Find Full Text PDFDalton Trans
August 2016
Institut für Physikalische and Theoretische Chemie, Technische Universität Graz, Stremayrgasse 9/II, A-8010, Graz, Austria.
A series of dinuclear metal(ii)-acetato complexes: [Ni2(μ-L(Cl)O)(μ2-OAc)2](PF6)·3H2O (1), [Ni2(μ-L(Cl)O)(μ2-OAc)2](ClO4)·CH3COCH3 (2), [Cu2(μ-L(Cl)O)(μ2-OAc)(ClO4)](ClO4) (3), [Cu2(μ-L(Cl)O)(OAc)2](PF6)·H2O (4), [Zn2(μ-L(Cl)O)(μ2-OAc)2](PF6) (5) and [Mn2(L(Cl)-O)(μ2-OAc)2](ClO4)·H2O (6), where L(Cl)O(-) = 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenolate, were synthesized. The complexes were structurally characterized by spectroscopic techniques and single crystal X-ray crystallography. Six-coordinate geometries with doubly bridged acetato ligands were found in Ni(ii), Zn(ii) and Mn(ii) complexes 1, 2, 5 and 6, whereas with Cu(ii) complexes a five-coordinate species was obtained with 4, and mixed five- and six-coordinate geometries with a doubly bridged dimetal core were observed in 3.
View Article and Find Full Text PDFZ Med Phys
March 2017
Universitätsklinik für Strahlentherapie-Radioonkologie, Comprehensive Cancer Center Graz, Medizinische Universität Graz, Austria. Electronic address:
In four-dimensional time-dependent computed tomography (4D-CT) of the lungs, irregularities in breathing movements can cause errors in data acquisition, or even data loss. We present a method based on sending a synthetic, regular breathing signal to the CT instead of the real signal, which ensures 4D-CT data sets without data loss. Subsequent correction of the signal based on the real breathing curve enables an accurate reconstruction of the size and movement of the target volume.
View Article and Find Full Text PDFChemistry
June 2016
Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky Str. 9-11, 26111, Oldenburg, Germany.
The ionization of 1,1-dihydridocyclopentasilane 7 has been found to yield the cyclic polysilanylsilyl cation 8 instead of the expected hydrogen-substituted silylium ion 6. The silyl cation 8 is stabilized by the formation of an intramolecular Si-H-Si bridge, which also provides the thermodynamic driving force for its formation. In general, the preference for the formation of Si-H-Si bridges can be used to scavenge and identify transient intermediates in the Lewis acid induced rearrangement of polysilanes.
View Article and Find Full Text PDFLab Chip
April 2016
Institut für Analytische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
We present a microfluidic platform that contains a micro flow reactor for on-chip biomolecule labelling that is directly followed by a separation bed for continuous free-flow electrophoresis and has an integrated hydrogel-based near-infrared fluorescent pH sensor layer. Using this assembly, labelling of protein and peptide mixtures, their separation via free-flow isoelectric focusing and the determination of the isoelectric point (pI) of the separated products via the integrated sensor layer could be carried out within typically around 5 minutes. Spatially-resolved immobilization of fluidic and sensing structures was carried out via multistep photolithography.
View Article and Find Full Text PDFSci Rep
February 2016
Intelligent Autonomous Systems Lab, Technische Universität Darmstadt, 64289, Germany.
A recurrent spiking neural network is proposed that implements planning as probabilistic inference for finite and infinite horizon tasks. The architecture splits this problem into two parts: The stochastic transient firing of the network embodies the dynamics of the planning task. With appropriate injected input this dynamics is shaped to generate high-reward state trajectories.
View Article and Find Full Text PDFCryst Growth Des
January 2016
Dipartimento di Chimica, Materiali e Ingegneria Chimica "G. Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy.
Analyst
November 2015
Institut für Analytische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
We demonstrate the fabrication, characterization and application of microfluidic chips capable of continuous electrophoretic separation via free flow isoelectric focussing (FFIEF). By integration of a near-infrared (NIR) fluorescent pH sensor layer under the whole separation bed, on-line observation of the pH gradient and determination of biomolecular isoelectric points (pI) was achieved within a few seconds. Using an optical setup for imaging of the intrinsic fluorescence of biomolecules at 266 nm excitation, labelling steps could be avoided and the native biomolecules could be separated, collected and analysed for their pI.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2015
Institut für Chemie, Organische & Bioorganische Chemie, Universität Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz (Austria).
N-Dealkylation methods are well described for organic chemistry and the reaction is known in nature and drug metabolism; however, to our knowledge, enantioselective N-dealkylation has not been yet reported. In this study, exclusively the (S)-enantiomers of racemic N-ethyl tertiary amines (1-benzyl-N-ethyl-1,2,3,4-tetrahydroisoquinolines) were dealkylated to give the corresponding secondary (S)-amines in an enantioselective fashion at the expense of molecular oxygen. The reaction is catalyzed by the berberine bridge enzyme, which is known for CC bond formation.
View Article and Find Full Text PDFDalton Trans
November 2015
Institut für Physikalische and Theoretische Chemie, Technische Universität Graz, Stremayrgasse 9, A-8010 Graz, Austria.
The syntheses and structural characterization of three new monodimensional azido-bridged manganese(ii) complexes with empirical formulae [Mn(N3)2(aminopyz)2]n (1), [Mn(N3)2(4-azpy)2]n (2) and [Mn(N3)2(4-Bzpy)2]n (3) (pyz = pyrazine (1,4-diazine)), 4-azpy = 4-azidopyridine and 4-Bzpy = 4-benzoylpyridine) are reported. 1 is a monodimensional compound with double EO azido bridges, 2 is an alternating monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EE and 3 is a monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EO-diEO-di-EO-di-EE. The magnetic properties of 1-3 are reported.
View Article and Find Full Text PDFLangmuir
September 2015
Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstraße 6, D-37077 Göttingen, Germany.
Gold nanoparticle (AuNP) network structures featuring particles from the two-phase Brust-Schiffrin synthesis and linear RAFT oligomers of styrene with two and multiple trithiocarbonate (TTC) groups along their backbone have been investigated in detail. Insights into the internal structures of these particle networks could be obtained from small-angle X-ray scattering experiments, showing that primary AuNPs are cross-linked by the employed molecular linker. The extent of AuNP network formation was investigated by means of dynamic light scattering and UV/visible extinction spectroscopy, showing an abrupt attenuation of network formation after a critical degree of polymerization of the cross-linker is exceeded.
View Article and Find Full Text PDFOrganometallics
August 2015
Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Strasse 9-11, D-26129 Oldenburg, Federal Republic of Germany.
The rearrangement of tris(trimethylsilyl)silyltrimethylgermane to give tetrakis(trimethylsilyl)germane was investigated as a typical example for Lewis acid catalyzed Wagner-Meerwein-type rearrangements of polysilanes and polygermasilanes. Direct Si NMR spectroscopic evidence is provided for several cationic intermediates during the reaction. The identity of these species was verified by independent synthesis and NMR characterization, and their transformation was followed by NMR spectroscopy.
View Article and Find Full Text PDFInorg Chem
July 2015
‡Institut für Chemie, Universität Graz, Stremayrgasse 9, 8010 Graz, Austria.
Complexes featuring lanthanide silicon bonds represent a research area still in its infancy. Herein, we report a series of Cp-free lanthanide (+II) complexes bearing σ-bonded silyl ligands. By reactions of LnI2 (Ln = Yb, Eu, Sm) either with a 1,4-oligosilanyl dianion [K-Si(SiMe3)2SiMe2SiMe2Si(SiMe3)2-K)] (1) or with 2 (Me3Si)3SiK (3) the corresponding neutral metallacyclopentasilanes ({Me2Si(Me3Si)2Si}2)Ln·(THF)4 (Ln = Yb (2a), Eu (2b), Sm (2c)), or the disilylated complexes ({Me3Si}3Si)2Ln·(THF)3 (Ln = Yb (4a), Eu (4b), Sm (4c)), were selectively obtained.
View Article and Find Full Text PDFChem Phys Lett
June 2015
Institut für Festkörperphysik, Technische Universität Graz, Petersgasse 16, 8010 Graz, Austria.
The origins of specific polymorphic phases within thin films are still not well understood. The polymorphism of the molecule dioctyl-terthiophene is investigated during the presence of a silicon-oxide surface during the crystallisation process. It is found that a monolayer of molecules forms two-dimensional crystals on the surface.
View Article and Find Full Text PDFOrganometallics
April 2015
Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 9, 8010 Graz, Austria.
The reaction of a cyclic disilylated bromostibine with magnesium yields a rare example of a magnesium stibide that can be silylated with trimethylchlorosilane. Reaction of the thus-obtained trisilylated stibine with potassium -butoxide gives a potassium stibide in a clean reaction. Attempts to obtain an antimony-containing oligosilanide did not lead to the expected compound but to another potassium stibide, which presumably forms from the initially formed silanide by a 1,2-silyl shift.
View Article and Find Full Text PDFOrganometallics
April 2015
Institut für Anorganische Chemie and Institut für Physikalische und Theoretische Chemie, Technische Universität Graz, Stremayrgasse 9, 8010 Graz, Austria.
By reactions of magnesium oligosilanides with SbCl, a number of oligosilanylated antimony compounds were obtained. When oligosilanyl dianions were used, either the expected cyclic disilylated halostibine was obtained or alternatively the formation of a distibine was observed. Deliberate formation of the distibine from the disilylated halostibine was achieved by reductive coupling with CK.
View Article and Find Full Text PDFInorg Chem
April 2015
‡Institut für Chemie, Universität Graz, Stremayrgasse 9, 8010 Graz, Austria.
Complexes featuring lanthanide (Ln)-Si bonds represent a highly neglected research area. Herein, we report a series of open-shell Ln(II+) and Ln(III+) complexes bearing σ-bonded silyl and base-stabilized N-heterocyclic silylene (NHSi) ligands. The reactions of the Ln(III+) complexes Cp3Ln (Ln = Tm, Ho, Tb, Gd; Cp = cyclopentadienide) with the 18-crown-6 (18-cr-6)-stabilized 1,4-oligosilanyl dianion [(18-cr-6)KSi(SiMe3)2SiMe2SiMe2Si(SiMe3)2K(18-cr-6)] (1) selectively afford the corresponding metallacyclopentasilane salts [Cp2Ln({Si(SiMe3)2SiMe2}2)](-)[K2(18-cr-6)2Cp](+) [Ln = Tm (2a), Ho (2b), Tb (2c), Gd (2d)].
View Article and Find Full Text PDFOrganometallics
December 2014
Institut für Chemie, Karl Franzens Universität Graz, Stremayrgasse 9 and Heinrichstraße 28, 8010 Graz, Austria.
Reactions of EtP adducts of bissilylated germylenes and stannylenes with gold, silver, and copper cyanides led to cyanogermyl or -stannyl complexes of the respective metals. In the course of the reaction the phosphine moved to the metal, while the cyanide migrated to the low-coordinate group 14 element. The respective gold complexes were found to be monomeric, whereas the silver and copper complexes exhibited a tendency to dimerize in the solid state.
View Article and Find Full Text PDFInorganica Chim Acta
October 2014
Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 9, A-8010 Graz, Austria.
In order to evaluate the influence of germanium atoms in oligo- and polysilanes, a number of oligosilane compounds were prepared where two or more silicon atoms were replaced by germanium. While it can be expected that the structural features of thus altered molecules do not change much, the more interesting question is, whether this modification would have a profound influence on the electronic structure, in particular on the property of σ-bond electron delocalization. The UV-spectroscopic comparison of the oligosilanes with germanium enriched oligosilanes and also with oligogermanes showed a remarkable uniform picture.
View Article and Find Full Text PDFChem Commun (Camb)
January 2015
Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 9, 8010 Graz, Austria.
A disilylated germylene phosphine adduct was obtained by reaction of tris(trimethylsilyl)silyl potassium with PMe3 and GeCl2·dioxane. The adduct reacted with tolane to give a germacyclopropene, while reactions with phenylacetylene occurred by insertion into the Si-Ge bonds giving vinylgermylene adducts. Release of the mono- or divinylgermylenes by base abstraction led to insertion into Si-Si bonds and formation of silagermetes.
View Article and Find Full Text PDFChemistry
July 2014
Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 9, 8010 Graz (Austria).
In the presence of PMe3 or N-heterocyclic carbenes, the reaction of oligosilanylene dianions with GeCl2⋅dioxane gives germylene-base adducts. After base abstraction, the free germylenes can dimerize by formation of a digermene. An electrochemical and theoretical study of a bicyclic tetrasilylated digermene revealed formation of a comparably stable radical anion and a more reactive radical cation, which were characterized further by UV/Vis and ESR spectroscopy.
View Article and Find Full Text PDFOrganometallics
December 2013
Technische Universität Graz, Stremayergasse 16, A-8010 Graz, Austria.
The molecular structures of axial and equatorial conformers of -CHSiHX (X = Cl, Br, I) as well as the thermodynamic equilibrium between these species was investigated by means of gas electron diffraction, dynamic nuclear magnetic resonance, temperature-dependent Raman spectroscopy, and quantum-chemical calculations applying CCSD(T), MP2, and DFT methods. According to the experimental and calculated results, all three compounds exist as a mixture of two chair conformers of the six-membered ring. The two chair forms of symmetry differ in the axial or equatorial position of the X atom.
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