Institut für Chemie

650 Items

Recent Submissions
IR spectro-electrochemistry of an adsorbed oxygen-tolerant [NiFe] hydrogenase on conductive surfaces

Heidary, Nina (2017)

Hydrogenases are metalloenzymes, catalyzing the reversible oxidation of molecular hydrogen into two protons and two electrons. The 'Knallgasbacterium' Ralstonia eutropha H16 (Re) is one of the few examples, harboring several [NiFe] hydrogenases that established mechanisms to enable catalytic conversion of H2 in the presence of O2. In order to exploit the catalytic potential of these oxygen-tole...

Beiträge zur bioinspirierten Katalyse

Lindenmaier, Nils (2017)

In dieser Arbeit wurden einkernige Ni- und heterodimere [NiFe]-Komplexe im Kontext der von [NiFe]-H2ase und -CODH „bioinspirierten” Katalyse synthetisiert und untersucht. Im ersten Teil der Arbeit wurde ein neuartiger Silylen-Pyridin-Hybridligand für die Koordination von Nickel(II)- und Nickel(0)-Spezies entwickelt und auf seine σ-Donor- und π-Akzeptoreigenschaften hin analysiert. Der zweite Te...

Scattering techniques for nanoparticle analysis

Breßler, Ingo (2017)

This work presents three program packages implementing different methods for nanoparticle analysis, focusing on the quantitative determination of particle size distributions required in standardization of nanoparticle reference materials. In part one, classical curve fitting is discussed. It finds optimal parameters of a scattering model composed of analytical expressions. The classical curve ...

Multinary metal oxides for solar water splitting

Wang, Fuxian (2017)

The world has experienced an exponential increase in the demand for energy primarily coming from the consumption of fossil fuels, which is accompanied by the inevitable emission of carbon dioxide, causing global warming. Developing renewable and carbon-free sources is essential to reduce carbon dioxide emission and mitigate global warming. Among the renewable energy sources, solar energy has th...

Elucidating the mechanism of action of antimicrobial peptides by means of computational approaches

de Miguel Catalina, Alejandra (2017)

Microorganism such as bacteria, viruses, fungi and some parasites, possess the inherent ability to cease the activity of an antimicrobial -for instance antibiotics, antivirals and antimalarials- against it. This property is known as antimicrobial resistance (AMR) and causes with time the ineffectiveness of standard treatments, helping infections persist and spread to other hosts. AMR is one of ...

HP-MoO2: A High-Pressure Polymorph of Molybdenum Dioxide

Lüdtke, Tobias Clemens ; Wiedemann, Dennis ; Efthimiopoulos, Ilias ; Becker, Nils ; Seidel, Stefan ; Janka, Oliver ; Pöttgen, Rainer ; Dronskowski, Richard ; Koch-Müller, Monika ; Lerch, Martin (2017)

High-pressure molybdenum dioxide (HP-MoO2) was synthesized using a multianvil press at 18 GPa and 1073 K, as motivated by previous first-principles calculations. The crystal structure was determined by single-crystal X-ray diffraction. The new polymorph crystallizes isotypically to HP-WO2 in the orthorhombic crystal system in space group Pnma and was found to be diamagnetic. Theoretical investi...

Synthesis and crystal structure of δ-TaON, a metastable polymorph of tantalum oxide nitride

Lüdtke, Tobias Clemens ; Schmidt, Alexander ; Göbel, Caren ; Fischer, Anna ; Becker, Nils ; Reimann, Christoph ; Bredow, Thomas ; Dronskowski, Richard ; Lerch, Martin (2014)

δ-TaON was prepared by reaction of gaseous ammonia with an amorphous tantalum oxide precursor. As a representative of the anatase structure (aristotype) it crystallizes in the tetragonal crystal system with lattice parameters a = 391.954(16) pm and c = 1011.32(5) pm. At temperatures between 800 and 850 °C an irreversible phase transformation to baddeleyite-type β-TaON is observed. While quantum...

Bixbyite-type phases in the system Ta-Zr-O-N

Lüdtke, Tobias Clemens ; Orthmann, Steven ; Lerch, Martin (2017)

Phase-pure tantalum/zirconium oxide nitrides and nitrides were synthesized by the ammonolysis of amorphous oxide precursors. The nitrogen-rich oxide nitrides with variable anion composition and the nitride TaZrN3 crystallize in the cubic bixbyite-type structure (space group Ia3̅). The nitrogen content of these compounds has a significant influence on the cell parameters, the atomic positions, a...

A density-functional theory approach to the existence and stability of molybdenum and tungsten sesquioxide polymorphs

Becker, Nils ; Reimann, Christoph ; Weber, Dominik ; Lüdtke, Tobias Clemens ; Lerch, Martin ; Bredow, Thomas ; Dronskowski, Richard (2016)

The sesquioxides of molybdenum and tungsten have been reported as thin films or on surfaces as early as 1971, but the preparation of bulk materials and their crystal structures are still unknown up to the present day. We present a systematic ab initio approach to their possible syntheses and crystal structures applying complementary methods and basis-set types. For both compounds, the corundum ...

Synthese und Charakterisierung neuer Oxide und Oxidnitride des Niobs

Orthmann, Steven (2017)

By different synthesis routes the first oxide nitrides in the series scandium-niobium-oxygen-nitrogen could be synthesized and characterized. ScNb4O7N3, which crystallizes in the rutile-type structure, exhibit a band gap of 2.62 eV after a short oxidation. Furthermore anion-deficit NbSc2(O,N,□)6 with fluorite-type structure could be synthesized. UV-Vis measurements point to a band gap of 3.36 e...

Synthesis and characterization of metastable transition metal oxides and oxide nitrides

Lüdtke, Tobias Clemens ; Weber, Dominik ; Schmidt, Alexander ; Müller, Alexander ; Reimann, Christoph ; Becker, Nils ; Bredow, Thomas ; Dronskowski, Richard ; Ressler, Thorsten ; Lerch, Martin (2016)

New routes to vanadium sesquioxide and tantalum oxide nitride (γ- and δ-phase) are presented. Phase pure V2O3 with bixbyite-type structure, a metastable polymorph, was obtained from vanadium fluoride hydrates at ~750 K. It crystallizes in the cubic crystal system in space group Ia3¯ with lattice parameter a=939.30(5) pm. The catalytical properties of the corresponding oxide nitride phases and t...

Proteome characterization of Escherichia coli cells evolved to tolerate elongation factor P deletion

Wang, Mingjian (2017)

Elongation factor P (EF-P) is an essential translation factor in bacteria, it has been reported that EF-P plays an important role in rescuing the translation stalling caused by the oligo-proline containing peptides stretch. The growth rate of E. coli was significantly restricted when EF-P was knocked out. However, through a continuous directed evolution in the turbidostatic model, both the wild...

Bor-Lewis-Säure-katalysierte Aktivierung von substituierten Cyclohexa-1,4-dienen: Anwendungen als Transferreagenzien in der Synthesechemie

Keeß, Sebastian (2017)

Die vorliegende Arbeit widmet sich der Entwicklung geeignet substituierter Cyclohexa-1,4-diene und deren Anwendung als sicher handhabbare Ersatzstoffe für als Reinsubstanz gefährliche Chemikalien in Lewis-Säure-katalysierten Transferreaktionen. Im ersten Teil dieser Dissertation wurde im Rahmen einer systematischen Untersuchung der Einfluss verschiedener Faktoren auf die im Jahr 2013 von Simonn...

Relativistic effects on electronic structure and nuclear magnetic resonance shifts in heavy metal systems

Greif, Anja Helene (2017)

The role of relativistic effects on the electronic structure and ligand NMR chemical shifts in diamagnetic 5d transition-metal and uranium hydrides as well as organometallic uranium complexes is investigated. New NMR trends and spectral regions for these compounds are suggested based on fully and quasi-relativistic density functional theory calculations carefully calibrated on the experimentall...

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 ...