FG Anorganische Chemie - Festkörper- und Materialchemie

30 Items

Recent Submissions
Formation, crystallization, and stabilization of mesoporous templated iron-oxide films

Kraffert, Katrin (2018)

The high structural and chemical diversity of iron-oxygen phases enables widespread applications in environment, medicine, and catalysis. Important for these high performance applications are the controlled morphology, i.e. high surface area, of the material as well as the defined crystal phase that should be stable for the chosen reaction conditions. Thus, a fundamental understanding of the fo...

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...

Isolation of a germanium(II) cation and a germylene iron carbonyl complex utilizing an imidazolin-2-iminato ligand

Ochiai, Tatsumi ; Franz, Daniel ; Wu, Xiao-Nan ; Inoue, Shigeyoshi (2015)

The novel amino(imino)germylene 1 was prepared by the conversion of HNIPr (NIPr = bis(2,6-diisopropylphenyl) imidazolin-2-imino) with 1 equiv. of Ge[N(SiMe3)(2)](2). Germylene 1 reacts with B (C6F5)(3) to afford the borate salt 2(+)[MeB(C6F5)(3)](-) in a methyl-abstraction and ring-closing reaction. The conversion of 2 with Fe-2(CO)(9) furnishes the germylene iron carbonyl complex 3 with a trig...

Novel anion conductors - conductivity, thermodynamic stability and hydration of anion-substituted mayenite-type cage compounds C(12)A(7):X (X = O, OH, Cl, F, CN, S, N)

Eufinger, Jens-Peter ; Schmidt, Alexander ; Lerch, Martin ; Janek, Jürgen (2015)

Mayenite (Ca12Al14O33) is a highly interesting functional material not only in view of its unique crystal structure as a cage compound but also for its variety of possible applications. Its ability to incorporate foreign ions into the cage structure opens the possibility to create new types of solid electrolytes and even electrides. Therefore, the conductivity of various anion substituted mayen...

Phosphinosilylenes as a novel ligand system for heterobimetallic complexes

Breit, Nora C. ; Eisenhut, Carsten ; Inoue, Shigeyoshi (2016)

A dihydrophosphinosilylene iron complex [LSi{Fe(CO)(4)}PH2] has been prepared and utilized in the synthesis of novel heterobimetallic complexes. The phosphine moiety in this phosphinosilylene complex allows coordination towards tungsten leading to the iron-tungsten heterobimetallic complex [LSi{Fe(CO)(4)}PH2{W(CO)(5)}]. In contrast, the reaction of [LSi{Fe(CO)(4)}PH2] with ethylenebis(triphenyl...

Applications of N-heterocyclic imines in main group chemistry

Ochiai, Tatsumi ; Franz, Daniel ; Inoue, Shigeyoshi (2016)

The imidazolin-2-imino group is an N-heterocyclic imino functionality that derives from the class of compounds known as guanidines. The exocyclic nitrogen atom preferably bonds to electrophiles and its electron-donating character is markedly enhanced by efficient delocalization of cationic charge density into the five-membered imidazoline ring. Thus, this imino group is an excellent choice for ...

Metastable transition metal oxides, oxide nitrides, and nitrides

Lüdtke, Tobias Clemens (2017)

In the present cumulative work the successful synthesis of new compounds of transition metals, with focus on metastable oxides and oxide nitrides of the vanadium and chromium group, is reported. δ-TaON, a new polymorph of tantalum oxide nitride, besides the known β- and γ-phases, was extensively characterized by means of X-ray diffraction on powder samples, Rietveld refinement, anion compositi...

Diffusion pathways and activation energies in crystalline lithium-ion conductors

Wiedemann, Dennis ; Islam, Mazharul M. ; Bredow, Thomas ; Lerch, Martin (2017)

Geometric information about ion migration (diffusion pathways) and knowledge about the associated energy landscape (migration activation barriers) are essential cornerstones for a comprehensive understanding of lithium transport in solids. Although many lithium-ion conductors are discussed, developed, and already used as energy-storage materials, fundamental knowledge is often still lacking. In...

Band gap engineering: the role of anions

Anke, Björn (2017)

The degradation of harmful organic pollutants with the help of semiconductors is regarded as one of the crucial solutions for waste water treatment. The main disadvantage of extensively used photocatalysts such as SnO2, ZnO, and TiO2 is their activity under UV illumination due to their wide band gap (~ 3.2 eV). Therefore they can only absorb 5 – 7 % of the solar spectrum. In order to overcome t...

Unravelling ultraslow lithium-ion diffusion in γ-LiAlO2

Wiedemann, Dennis ; Nakhal, Suliman ; Rahn, Johanna ; Witt, Elena ; Islam, Mazharul M. ; Zander, Stefan ; Heitjans, Paul ; Schmidt, Harald ; Bredow, Thomas ; Wilkening, Martin ; Lerch, Martin (2016)

Lithium aluminum oxide (γ-LiAlO2) has been discussed and used for various applications, e.g., as electrode coating, membrane, or tritium breeder material. Although lithium-ion diffusion in this solid is essential for these purposes, it is still not sufficiently understood on the microscopic scale. Herein, we not only summarize and assess the available studies on diffusion in different crystalli...

Synthesis and structural characterization of semiconductors based on kesterites

Ritscher, Anna (2016)

The here-presented thesis provides detailed investigations on the structural characteristics of the chalcogenide Cu2ZnSnS4 (CZTS). This semiconductor material is a promising candidate for absorber layers in solar cells due to its desirable properties for thin film photovoltaic applications. Yet, compared to current used chalcopyrite-based devices, efficiencies are significantly lower. This coul...

Beiträge zur Nachhaltigkeit von chemischen Verfahren

Weidauer, Maik (2016)

Der Erste Teil der Arbeit beschäftigt sich mit der Synthese und Anwendung von Eisenkomplexen in der eisenkatalysierten oxidativen Kupplung von Magnesiumorganylen mit Hilfe von Distickstoffmonoxid als Oxidationsmittel. Als Plattform für die Komplexe dienten tripodale Liganden auf Basis von Tris((1H-pyrrol-2-yl)methyl)aminen und 2,2‘,2‘‘-Nitrilotris(methylen)trisphenolen. Im Zuge der Ligandensynt...

Lithium diffusion pathways in metastable ramsdellite-like Li2Ti3O7 from high-temperature neutron diffraction

Wiedemann, Dennis ; Nakhal, Suliman ; Franz, Alexandra ; Lerch, Martin (2016-10)

Ramsdellite-like Li2Ti3O7 is an excellent, strongly anisotropic lithium-ion conductor with various proposed applications in energy storage and lithium processing. Diffusion pathways have not yet been thoroughly studied, in spite of their importance for these purposes; even the precise crystal structure of this material is a subject of ongoing discussion. Herein, we use variable-temperature neut...

,, ... und ehrt mir ihre Kunst!“ – Evaluierung historischer und neuer Synthesewege zu 1,5-Dihydroxy-6-oxo-1,6-dihydropyridin-2-carbonsäure und 1,3-Dihydroxy-2-oxo-3-pyrrolin-4-carbonsäure

Wiedemann, Dennis ; Grohmann, Andreas (2009)

The historical and recent literature describing synthetical pathways to the title compds. is comprehensively summarized and evaluated. Routes via 2,5-dioxoadipic acid or 2,5-dihydroxymuconic acid as intermediates could not be followed reproducibly. 3-Hydroxy-2-oxo-2H-pyran-6-carboxylic acid and Et 3-hydroxy-2-oxo-3-pyrroline-4-carboxylate (I) were fully characterized by spectroscopic methods an...

3d-and 4d-metal(II) complexes of a tris(pyridyl)ethane-derived N-4 ligand – a structural study and reactivity remarks

Wiedemann, Dennis ; Grohmann, Andreas (2014)

A series of complexes of the new N-4 chelate ligand L (L = 1-{6-[1,1-bis(pyridin-2-yl) ethyl] pyridin-2-yl}-N, N-dimethylmethanamine) with intermediate to late divalent transition metal ions M was obtained by the reaction between L and the respective chloride salt or similar precursor in methanol: [MCl2L] (M = Mn, Fe, Co, Ni, Zn; Ru) and [CuClL]Cl. The stereochemical characteristics of the chel...