Institut für Chemie

636 Items

Recent Submissions
High throughput modules for performance and mechanism assessment of flame retardants in polymeric materials

Rabe, Sebastian (2017)

Due to the ever-increasing number of additives, adjuvants, synergists, and fillers, together with variations in concentration, particle size distribution and other modifications, methods for accelerated assessment of flame retarded polymeric materials are strongly needed. This work presents two novel approaches to assess the rapid screening of flame retardants in polymeric materials. Furthermor...

Synthese von fluoreszierenden 7-Azatryptophan-Derivaten und deren Einbau in Modellpeptide

Noichl, Benjamin Philipp (2017)

In nature, proteins evolve to ensure the survival of living organisms in their natural environments. To equip them with new features and functions, classical protein engineering, based on canonical twenty amino acids, could lead to the improvement of these proteins by mutagenesis. Proteins sequences containing exclusively naturally occurring amino acids (i.e. canonical 20) are often unsuitable ...

Record activity and stability of dealloyed bimetallic catalysts for proton exchange membrane fuel cells

Han, Binghong ; Carlton, Christopher E. ; Kongkanand, Anusorn ; Kukreja, Ratandeep S. ; Theobald, Brian R. ; Gan, Lin ; O'Malley, Rachel ; Strasser, Peter ; Wagner, Frederick T. ; Shao-Horn, Yang (2015)

We demonstrate the unprecedented proton exchange membrane fuel cell (PEMFC) performance durability of a family of dealloyed Pt-Ni nanoparticle catalysts for the oxygen reduction reaction (ORR), exceeding scientific and technological state-of-art activity and stability targets. We provide atomic-scale insight into key factors controlling the stability of the cathode catalyst by studying the infl...

Unprecedented silicon(II)-> calcium complexes with N-heterocyclic silylenes

Blom, Burgert ; Klatt, Günter ; Gallego, Daniel ; Tan, Gengwen ; Drieß, Matthias (2015)

The first N-heterocyclic silylene (NHSi) complexes of any s-block element to date are reported for calcium: [(eta(5)-C5Me5)(2)Ca<--:Si(O-C6H4-2-Bu-t){((NBu)-Bu-t)(2)CPh}] (6) and [(eta(5)-C5Me5)(2)Ca<--:Si((NBuCH)-Bu-t)(2)] (7). Complexes 6 and 7 are isolable in a facile way upon reaction of the corresponding free N-heterocyclic silylenes (NHSis) with [(eta(5)-C5Me5)(2)Ca] (2). Complexes 6 and ...

Nuclear resonance vibrational spectroscopy reveals the FeS cluster composition and active site vibrational properties of an O-2-tolerant NAD(+)-reducing [NiFe] hydrogenase

Lauterbach, Lars ; Wang, Hongxin ; Horch, Marius ; Gee, Leland B. ; Yoda, Yoshitaka ; Tanaka, Yoshihito ; Zebger, Ingo ; Lenz, Oliver ; Cramer, Stephen P. (2015)

Hydrogenases are complex metalloenzymes that catalyze the reversible splitting of molecular hydrogen into protons and electrons essentially without overpotential. The NAD(+)-reducing soluble hydrogenase (SH) from Ralstonia eutropha is capable of H-2 conversion even in the presence of usually toxic dioxygen. The molecular details of the underlying reactions are largely unknown, mainly because of...

Reliable palladium nanoparticle syntheses in aqueous solution: the importance of understanding precursor chemistry and growth mechanism

Kettemann, Frieder ; Wuithschick, Maria ; Caputo, Gianvito ; Krähnert, Ralph ; Pinna, Nicola ; Rademann, Klaus ; Polte, Jörg (2015)

Reliable protocols for the synthesis of palladium nanoparticles (Pd-NPs) in aqueous solution are rarely found and the corresponding growth mechanisms often remain unknown. Furthermore, syntheses of Pd-NPs always demand the use of stabilizing agents which are often unfavorable for catalytic applications. In this contribution, the importance of the palladium precursor chemistry as a prerequisite ...

Surface enhanced vibrational spectroscopic evidence for an alternative DNA-independent redox activation of endonuclease III

Moe, Elin ; Sezer, Murat ; Hildebrandt, Peter ; Todorovic, Smilja (2015)

Surface enhanced vibrational spectro-electrochemistry of endonuclease III provides direct evidence that the [4Fe-4S] cluster is responsible for the enzyme redox activity, and that this process is not exclusively DNA-mediated, as currently proposed. We report the first surface enhanced resonance Raman spectrum of a [4Fe-4S](2+) cluster containing enzyme.

From molecular copper complexes to composite electrocatalytic materials for selective reduction of CO2 to formic acid

Tran Ngoc Huan ; Andreiadis, Eugen S. ; Heidkamp, Jonathan ; Simon, Philippe ; Derat, Etienne ; Cobo, Saioa ; Royal, Guy ; Bergmann, Arno ; Strasser, Peter ; Dau, Holger ; Artero, Vincent ; Fontecave, Marc (2015)

The development of new energy storage technologies is central to solving the challenges facing the widespread use of renewable energies. An option is the reduction of carbon dioxide (CO2) into carbon-based products which can be achieved within an electrochemical cell. Future developments of such processes depend on the availability of cheap and selective catalysts at the electrode. Here we show...

Photoresponsive self-assemblies based on fatty acids

Fameau, Anne-Laure ; Arnould, Audrey ; Lehmann, Maren ; von Klitzing, Regine (2015)

Photoresponsive surfactant system based on fatty acids has been developed by the introduction in aqueous solution of a photoacid generator (PAG). Self-assembly transitions are triggered by UV irradiation due to a pH change induced by the presence of PAG.

gamma-(S)-Trifluoromethyl proline: evaluation as a structural substitute of proline for solid state F-19-NMR peptide studies

Kubyshkin, Vladimir ; Afonin, Sergii ; Kara, Sezgin ; Budisa, Nediljko ; Mykhailiuk, Pavel K. ; Ulrich, Anne S. (2015)

gamma-(4S)-Trifluoromethyl proline was synthesised according to a modified literature protocol with improved yield on a multigram scale. Conformational properties of the amide bond formed by the amino acid were characterised using N-acetyl methyl ester model. The amide populations (s-trans vs. s-cis) and thermodynamic parameters of the isomerization were found to be similar to the corresponding...

Microporous polymer network films covalently bound to gold electrodes

Becker, Daniel ; Heidary, Nina ; Horch, Marius ; Gernert, Ulrich ; Zebger, Ingo ; Schmidt, Johannes ; Fischer, Anna ; Thomas, Arne (2015)

Covalent attachment of a microporous polymer network (MPN) on a gold surface is presented. A functional bromophenyl-based self-assembled monolayer (SAM) formed on the gold surface acts as co-monomer in the polymerisation of the MPN yielding homogeneous and robust coatings. Covalent binding of the films to the electrode is confirmed by SEIRAS measurements.

Enhancing the stability of spontaneously self-assembled vesicles - the effect of polymer architecture

Bressel, Katharina ; Gradzielski, Michael (2015)

The formation of stable vesicles with a controlled size and high stability is an important matter due to their wide application in pharmaceutical and detergency formulations and as drug delivery vehicles. One can control the size of spontaneously formed vesicles in mixtures of zwitterionic and anionic surfactants by the admixture of small amounts of an amphiphilic copolymer of the PEO-PPO-PEO t...

Using nickel manganese oxide catalysts for efficient water oxidation

Menezes, Prashanth W. ; Indra, Arindam ; Levy, Ophir ; Kailasam, Kamalakannan ; Gutkin, Vitaly ; Pfrommer, Johannes ; Drieß, Matthias (2015)

Nickel-manganese oxides with variable Ni : Mn ratios, synthesised from heterobimetallic single-source precursors, turned out to be efficient water oxidation catalysts. They were subjected to oxidant-driven, photo- and electro-catalytic water oxidation showing superior activity and remarkable stability. In addition, a structure-activity relation could be established.

Mechanistic aspects of the gas-phase coupling of thioanisole and chlorobenzene to dibenzothiophene catalyzed by atomic Ho+

Zhou, Shaodong ; Schlangen, Maria ; Schwarz, Helmut (2015)

Mechanistic aspects of the novel gas-phase generation of dibenzothiophene via coupling of thioanisole and chlorobenzene, employing atomic Ho+ as a catalyst, have been investigated using Fourier-transform ion cyclotron resonance mass spectrometry in conjunction with density functional theory (DFT) calculations.

Reductive cleavage of P-4 by iron(I) centres: synthesis and structural characterisation of Fe-2(P-2)(2) complexes with two bridging P-2(2-) ligands

Yao, Shenglai ; Szilvási, Tibor ; Lindenmaier, Nils ; Xiong, Yun ; Inoue, Shigeyoshi ; Adelhardt, Mario ; Sutter, Jörg ; Meyer, Karsten ; Drieß, Matthias (2015)

The selective transformation of white phosphorus with a beta-diketiminato iron(I) toluene complex under mild reaction conditions is reported which furnishes a new dinuclear iron(III) Fe-2(P-2)(2) complex with two bridging P-2(2-) ligands. Its reduction with potassium results in the formation of the first delocalised mixed-valent bis-diphosphido iron(II,III) complex which is isostructural with t...

The influence of poly(ethylene glycol) on the micelle formation of alkyl maltosides used in membrane protein crystallization

Müh, Frank ; DiFiore, Dörte ; Zouni, Athina (2015)

With the aim of better understanding the phase behavior of alkyl maltosides (n-alkyl-beta-D-maltosides, C(n)G(2)) under the conditions of membrane protein crystallization, we studied the influence of poly(ethylene glycol) (PEG) 2000, a commonly used precipitating agent, on the critical micelle concentration (CMC) of the alkyl maltosides by systematic variation of the number n of carbon atoms in...

A unified survey of Si-H and H-H bond activation catalysed by electron-deficient boranes

Oestreich, Martin ; Hermeke, Julia ; Mohr, Jens (2015)

The bond activation chemistry of B(C6F5)(3) and related electron-deficient boranes is currently experiencing a renaissance due to the fascinating development of frustrated Lewis pairs (FLPs). B(C6F5)(3)'s ability to catalytically activate Si-H bonds through eta(1) coordination opened the door to several unique reduction processes. The ground-breaking finding that the same family of fully or par...

Surface enhanced resonance Raman detection of a catalytic intermediate of DyP-type peroxidase

Todorovic, Smilja ; Hildebrandt, Peter ; Martins, Ligia O. (2015)

We report herein the vibrational spectroscopic characterisation of a catalytic intermediate formed by the reaction of H2O2 with DyP-type peroxidase immobilised on a biocompatible coated metal support. The SERR spectroscopic approach is of general applicability to other peroxidases which form relatively stable catalytic intermediates.

Ultrafast coherent oscillations reveal a reactive mode in the ring-opening reaction of fulgides

Slavov, C. ; Bellakbil, Nabil ; Wahl, J. ; Mayer, Kerstin ; Rück-Braun, Karola ; Burghardt, I. ; Wachtveitl, Josef ; Braun, M. (2015)

The ultrafast ring-opening reaction of photochromic fulgides proceeds via conical intersections to the ground state isomers involving activation barriers in the excited state. The coherent oscillations observed in the femtosecond transient absorption signal of a methyl-substituted indolylfulgide were analysed in the framework of vibrational wavepackets to expose a dominant low-frequency mode at...

Temperature-induced molecular transport through polymer multilayers coated with PNIPAM microgels

Vikulina, Anna S. ; Aleed, Sarah T. ; Paulraj, Thomas ; Vladimirov, Yury Andreevich ; Duschl, Claus ; von Klitzing, Regine ; Volodkin, Dmitry (2015)

Polyelectrolyte multilayers serve as effective reservoirs for bioactive molecules which are stored and released from the multilayers for cellular applications. However, control over the release without significantly affecting the multilayers and biomolecules is still a challenge. On the other hand, externally stimulated release would make the multilayers promising for the development of stimuli...