ORGANISCHE PHOSPHORVERBINDUNGEN 791 HERSTELLUNG UND EIGENSCHAFTEN VON α-AMINO-ω-CARBOXYALKYLPHOSPHON-UND-PHOSPHINSÄUREN

Abstract

The synthesis, chemical and spectral properties of α-amino-ω-carboxyalkylphosphonic acids, (HO)₂P(O)CH(NH₂)(CH₂) _x CO₂H, x = 2 to 6, and of α-amino-ω-carboxyalkyl-methylphosphinic acids CH₃(HO)P(O)CH(NH₂)(CH₂) _x CO₂H, x = 2 to 6 are described and the fungicidal activity of some of these derivatives is reported.     

Temperature-Dependent Surface-Enrichment Effects of Imidazolium-Based Ionic Liquids

We present the first systematic study of the influence of temperature on the degree of surface enrichment of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs). Using angle-resolved X-ray photoelectron spectroscopy, we demonstrate that the degree of surface enrichment strongly decreases with increasing temperature for all the studied ILs. For ILs with the same cation, but different anions, [C₈C₁Im]Br, [C₈C₁Im][TfO] and [C₈C₁Im][Tf₂N], no significant differences of the temperature-induced partial loss of surface enrichment are found. Measurements for [C₄C₁Im][TfO], [C₈C₁Im][TfO] and [C₁₈C₁Im][TfO] indicate a small effect of the chain length. For [C₁₈C₁Im][TfO], a continuous decrease of alkyl surface enrichment is found with increasing temperature, with no abrupt changes at the phase-transition temperature from the smectic A to the isotropic phase, indicating that the surface enrichment is not affected by this phase transition.     

Present status of the Technological Laboratory at the LMU Munich

The Technological Laboratory of LMU is undergoing major changes. Most important of them is raising a DLC-Factory’s for diamond-like-carbon (DLC) foils production and a shutdown of the Hot-Lab Facility. Current Laboratory status and development plans are presented in this paper.     

Broadband spin‐controlled focusing via logarithmic‐spiral nanoslits of varying width

This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic spiral (LS) nanoslit, which forms a type of switchable and focus‐tunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS‐nanoslit converges incoming light of opposite handedness (to that of the LS‐nanoslit) into a confined subwavelength spot, while it shapes light with similar chirality into a donut‐like intensity profile. Benefitting from the varying width of the LS‐nanoslit, different incident wavelengths interfere constructively at different positions, i.e., the focal length shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm), which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale.

     

Di-tert-butyldiphosphatetrahedrane as a Source of 1,2-Diphosphacyclobutadiene Ligands

Reactions of di-tert-butyldiphosphatetrahedrane ( 1 ) with cycloocta-1,5-diene- or anthracene-stabilised metalate anions of iron and cobalt consistently afford complexes of the rarely encountered 1,2-diphosphacyclobutadiene ligand, which have previously been very challenging synthetic targets. The subsequent reactivity of 1,2-diphosphacyclobutadiene cobaltates toward various electrophiles has also been investigated and is compared to reactions of related 1,3-diphosphacyclobutadiene complexes. The results highlight the distinct reactivity of such isomeric species, showing that the 1,2-isomers can act as precursors for previously unknown triphospholium ligands. The electronic structures of the new complexes were investigated by several methods, including NMR, EPR and Mößbauer spectroscopies as well as quantum chemical calculations.     

Physical boundaries within aggregates – differences between amorphous,para‐crystalline,and crystalline Structures

The structural properties of finely divided inorganic materials such as metal and metalloid oxides, silicates or carbonates of both synthetic and natural origin are compared by means of electron microscopy and tomography. The structure of the outer surfaces of various compact or compacted agglomerates may suggest some striking similarities between various amorphous silica on the one hand and crystalline titania and alumina on the other however the details of the interior fine structure are completely different. Inside of the crystalline aggregates of, for example, alumina and titania distinct grain boundaries between the inter‐grown primary crystallites exist. Also physical boundaries between different solid phases and crystalline/amorphous transitions in core/shell structures can occur. No physical grain or phase boundaries were found inside of synthetic amorphous silica or para‐crystalline carbon black thus, the aggregate is the constituent particle. Synthetic amorphous silica from different production technologies (fumed/pyrogenic, precipitated, aerogel, gel) may exhibit different macro‐morphology but distinct similarities of the amorphous silica networks. Computational studies on silica and titania underline the stability of constituent particles and aggregates as observed by means of TEM after dispersing the original materials by ultra‐sonication.     

Single‐Layered Ultrasmall Nanoplates of MoS2 Embedded in Carbon Nanofibers with Excellent Electrochemical Performance for Lithium and Sodium Storage

The preparation and electrochemical storage behavior of MoS₂ nanodots—more precisely single‐layered ultrasmall nanoplates—embedded in carbon nanowires has been studied. The preparation is achieved by an electrospinning process that can be easily scaled up. The rate performance and cycling stability of both lithium and sodium storage were found to be outstanding. The storage behavior is, moreover, highly exciting from a fundamental point of view, as the differences between the usual storage modes—insertion, conversion, interfacial storage—are beneficially blurred. The restriction to ultrasmall reaction domains allows for an almost diffusion‐less and nucleation‐free “conversion”, thereby resulting in a high capacity and a remarkable cycling performance.     

Selector‐Induced Dynamic Deracemization of a Selectand‐Modified Tropos BIPHEPO‐Ligand: Application in the Organocatalyzed Asymmetric Double‐Aldol‐Reaction

Stereolabile interconverting catalysts open up the possibility of directing enantioselectivity in asymmetric synthesis by formation of diastereomeric complexes with chiral auxiliaries and deracemization. However, the stoichiometrically used auxilliaries can significantly limit the potential applications of such systems. We synthesized a new BIPHEPO tropos ligand containing achiral selectands in the backbone, which forms transient diastereomeric associates with amylose‐tris‐3,5‐dimethylphenyl carbamate as a selector and thus deracemizes. The enantiomerically enriched BIPHEPO obtained was successfully used in the organocatalytic asymmetric double aldol addition of substituted methyl ketones to form benzaldehyde. This strategy combines an on‐column deracemization with the high stereoinduction of chiral biarylphosphineoxides and opens up new possibilities in the field of self‐amplified asymmetric syntheses.     

First principles calculations of oxygen reduction reaction at fuel cell cathodes

The efficiency of solid oxide fuel cells (SOFC) depends critically on materials, in particular for the cathode where the oxygen reduction reaction (ORR) occurs. Typically, mixed conducting perovskite ABO₃-type materials are used for this purpose. The dominating surface terminations are (001) AO and BO₂, with the relative fractions depending on materials composition and ambient conditions.Here, results of recent large-scale first principles (ab initio) calculations for the two alternative polar (La,Sr)O and MnO₂ (001) terminations of (La,Sr)MnO₃ cathode materials are discussed. The surface oxygen vacancy concentration for the (La,Sr)O termination is more than 5 orders of magnitude smaller compared to MnO₂, which leads to drastically decreased estimated ORR rates. Thus, it is predicted for prototypical SOFC cathode materials that the BO₂ termination largely determines the ORR kinetics, although with Sr surface segregation (long-term degradation) its fraction of the total surface area decreases, which slows down cathode kinetics.     

On‐Surface Assembly of Hydrogen‐ and Halogen‐Bonded Supramolecular Graphyne‐Like Networks

Demonstrated here is a supramolecular approach to fabricate highly ordered monolayered hydrogen‐ and halogen‐bonded graphyne‐like two‐dimensional (2D) materials from triethynyltriazine derivatives on Au(111) and Ag(111). The 2D networks are stabilized by N???H?C(sp) bonds and N???Br?C(sp) bonds to the triazine core. The structural properties and the binding energies of the supramolecular graphynes have been investigated by scanning tunneling microscopy in combination with density‐functional theory calculations. It is revealed that the N???Br?C(sp) bonds lead to significantly stronger bonded networks compared to the hydrogen‐bonded networks. A systematic analysis of the binding energies of triethynyltriazine and triethynylbenzene derivatives further demonstrates that the X₃‐synthon, which is commonly observed for bromobenzene derivatives, is weaker than the X₆‐synthon for our bromotriethynyl derivatives.