Darstellung und Kristallstruktur von Rb4Br2O und Rb6Br4O

Syntheses and Crystal Structures of Rb₄Br₂O and Rb₆Br₄O In the quasi‐binary system RbBr/Rb₂O, the addition compounds Rb₄Br₂O and Rb₆Br₄O are obtained by solid state reaction of the boundary components RbBr and Rb₂O. Crystals of red‐orange Rb₄Br₂O as well as of orange Rb₆Br₄O decompose immediately when exposed to air. Rb₄Br₂O (Pearson code tI14, I4/mmm, a = 544.4(6) pm, c = 1725(2) pm, Z = 2, 175 symmetry independent reflections with I_o > 2σ(I), R₁= 0.0618) crystallizes in the anti K₂NiF₄ structure type; Rb₆Br₄O (Pearson code hR22, R3c, a = 1307.8(3) pm, c = 1646.6(5) pm, Z = 6, 630 symmetry independent reflections with I_o > 2σ(I), R₁ = 0.0759) in the anti K₄CdCl₆ structure type. Both structures contain characteristic ORb₆‐octahedra and can be understood as expanded perovskites, following the general systematics of alkaline metal oxide halides.     

Surface-induced dissociation and chemical reactions of C2D 4 + on stainless steel, carbon (HOPG), and two different diamond surfaces

Surface-induced interactions of the projectile ion C₂D₄⁺ with room-temperature (hydrocarbon covered) stainless steel, carbon highly oriented pyrolytic graphite (HOPG), and two different types of diamond surfaces (O-terminated and H-terminated) were investigated over the range of incident energies from a few eV up to 50 eV. The relative abundance of the product ions in dependence on the incident energy of the projectile ion [collision-energy resolved mass spectra, (CERMS) curves] was determined. The product ion mass spectra contained ions resulting from direct dissociation of the projectile ions, from chemical reactions with the hydrocarbons on the surface, and (to a small extent) from sputtering of the surface material. Sputtering of the surface layer by low-energy Ar⁺ ions (5–400 eV) indicated the presence of hydrocarbons on all studied surfaces. The CERMS curves of the product ions were analyzed to obtain both CERMS curves for the products of direct surface-induced dissociation of the projectile ion and CERMS curves of products of surface reactions. From the former, the fraction of energy converted in the surface collision into the internal excitation of the projectile ion was estimated as 10% of the incident energy. The internal energy of the surface-excited projectile ions was very similar for all studied surfaces. The H-terminated room-temperature diamond surface differed from the other surfaces only in the fraction of product ions formed in H-atom transfer surface reactions (45% of all product ions formed versus 70% on the other surfaces).     

Partial regularity and singular sets of solutions of higher order parabolic systems

In the present paper we provide a broad survey of the regularity theory for non-differentiable higher order parabolic systems of the type

Surface shear rheological studies of marine phytoplankton cultures-Nitzschia closterium, Thalassiosira rotula, Thalassiosira punctigera and Phaeocystis sp

The study of interfacial properties in the marine environment is important for the understanding of air-sea gas exchange processes, especially with respect to the behaviour of entrained air bubbles. Seawater contains surfactant material, much of which is thought to origin from the exudation of dissolved organic material (DOM) by phytoplankton. This study aims at investigating the influence of different phytoplankton species on the surface shear viscosity of an air-water interface. Measurements of surface shear viscosity were carried out with the ISR1 interfacial shear rheometer. Surface shear viscosities of stock cultures of Phaeocystis sp., Thalassiosira rotula, Thalassiosira punctigera and Nitzschia closterium as well as of F/2 nutrient medium and seawater were measured. The surface shear viscosity of N. closterium was investigated during different stages of its growth as well as for an unfiltered stock culture sample and its filtrate. Results reveal that the influence of phytoplankton on the surface shear viscosity is species specific. An increase in surface shear viscosity occurred for the N. closterium stock culture only. The remaining cultures showed similar behaviour to F/2 nutrient medium. The increase of surface shear viscosity during the growth of N. closterium occurred mainly during the exponential growth phase. The increases in surface shear viscosity depend on the presence of phytoplankton cells in the sample. The formation of compact mechanical structures at the air-water interface originating from the aggregation of DOM released by N. closterium as a cause for the observed increases in surface shear viscosity is discussed.     

Palladium mediated activation of C-F bonds in 2,4,6-trifluoropyrimidine: Synthesis and structure of palladium pyrimidyloxy and pyrimidinone derivatives

[PdMe₂(dcpm)] (1) reacts with 2,4,6-trifluoropyrimidine in the presence of water to give the palladium derivative [PdMe{4-C₄N₂F₂H(O)}(dcpm)] (2). When additional triethylamine is present complex [PdMe(2-OC₄N₂F₂H)(dcpm)] (4) in addition to 2 is formed. Compound 2 converts slowly into the binuclear complex [Pd{4-C₄N₂F₂H(O)}(μ-dcpm)]₂ (5). The molecular structure of 5 was determined by X-ray crystallography. The palladium-palladium distance is 2.5898(3) Å.     

Visualization of Protein‐Specific Glycosylation inside Living Cells

Protein glycosylation is a ubiquitous post‐translational modification that is involved in the regulation of many aspects of protein function. In order to uncover the biological roles of this modification, imaging the glycosylation state of specific proteins within living cells would be of fundamental importance. To date, however, this has not been achieved. Herein, we demonstrate protein‐specific detection of the glycosylation of the intracellular proteins OGT, Foxo1, p53, and Akt1 in living cells. Our generally applicable approach relies on Diels–Alder chemistry to fluorescently label intracellular carbohydrates through metabolic engineering. The target proteins are tagged with enhanced green fluorescent protein (EGFP). Förster resonance energy transfer (FRET) between the EGFP and the glycan‐anchored fluorophore is detected with high contrast even in presence of a large excess of acceptor fluorophores by fluorescence lifetime imaging microscopy (FLIM).     

Consequences of the One-Electron Reduction and Photoexcitation of Unsymmetric Bis-imidazolium Salts

Coupling of uronium salts with in situ generated N-heterocyclic carbenes provides straightforward access to symmetrical [4](2+) and unsymmetrical bis-imidazolium salts [6](2+) and [9](2+) . As indicated by cyclic and square-wave voltammetry, [6](2+) and [9](2+) can be (irreversibly) reduced by one electron. The initially formed radicals [6](.+) and [9](.+) undergo further reactions, which were probed by EPR spectroscopy and density functional calculations. The final products of the two-electron reduction are the two carbenes. Upon irradiation with UV light both [6](2+) and [9](2+) emit at room temperature in solution but with dramatically different characteristics. The different fluorescence behavior is analyzed by emission spectroscopy and interpreted by using time-dependent density functional calculations as largely due to different excited-state dynamics of [6](2+) and [9](2+) . The geometries of both radicals [6](.+) and [9](.+) and excited states {[6](2+) }* and {[9](2+) }* are substantially different from those of the parent ground-state molecules.     

Tuning the size of supramolecular M4L4 tetrahedra by ligand connectivity

Triangular triscatechol ligands are prepared in facile reaction sequences. The catechol units are either bound to the triangular backbone through their 3- or 4-position. With titanium(IV) ions, the ligands form metallosupramolecular M(4)L(4) tetrahedra which are characterized by ESI MS and proton NMR. Quantum-chemical calculations reveal that connectivity at the catechol in the 3-position results in highly condensed structures while attachment in the 4-position affords container molecules providing huge internal cavities.