Zwei Galliumfluorid-Ammoniakate: Ga(NH3)F3 und Ga(NH3)2F3

Two Gallium Fluoride Ammine Complexes: Ga(NH₃)F₃ and Ga(NH₃)₂F₃ Two gallium trifluoride ammines, Ga(NH₃)F₃ and Ga(NH₃)₂F₃, are obtained as single crystals through oxidation of gallium metal with NH₄HF₂ (Ga : NH₄HF₂ = 1 : 1.5) and NH₄F (Ga : NH₄F = 1 : 3.5), respectively, at 450 °C and 400 °C. Ga(NH₃)F₃ crystallizes with the non-centrosymmetric space group Abm2 (a = b = 544.6(2) pm, c = 986.6(4) pm) forming two-dimensional layers of [Ga(NH₃)F₅] octahedra. The addition of another NH₃ molecule in Ga(NH₃)₂F₃ (orthorhombic, Immm, a = 700.0(3) pm, b = 724.7(2) pm, c = 393.1(1) pm) leads to one-dimensional rods of [Ga(NH₃)₂F₄] octahedra running parallel [001] which are stacked in the [010] direction. Infrared spectra suggest hydrogen bonding (N–H…F) in Ga(NH₃)F₃, for Ga(NH₃)₂F₃ an unequivocal statement is not possible.     

Zwitterionic [(4‐n‐Alkyl‐1,4‐bisazoniacyclohex‐1‐yl)methyl]pentafluorosilicates: A New Class of Surface‐Active Compounds with a Hexacoordinate Silicon Atom

A series of [(4‐n‐alkyl‐1,4‐bisazoniacyclohex‐1‐yl)methyl]pentafluorosilicates (alkyl = hexyl, heptyl, octyl, nonyl, decyl; compounds 14 – 18 ) were synthesized and studied for their surface activity. The zwitterionic pentafluorosilicates with hexacoordinate Si atoms 14 – 18 were prepared by reaction of the respective [(4‐n‐alkylpiperazin‐1‐yl)methyl]trimethoxysilanes [obtained by treatment of (MeO)₃SiCH₂Cl with the respective n‐alkylpiperazine in the presence of NEt₃] with HF in water/ethanol. Surface tension measurements with solutions of 14 – 18 in 0.01 M hydrochloric acid proved that these compounds are surfactants, the increase of the n‐alkyl chain length resulting in an increase of surface activity ( 14 → 18 ). The equilibrium surface tension vs concentration isotherms for 14 – 17 (solutions of “surface‐chemically pure” samples in 0.01 M hydrochloric acid) were analyzed quantitatively.     

Synthesis and Structural Characterization of Cationic Complexes with Hexacoordinate Silicon(IV) and Three Bidentate 1‐Oxopyridine‐2‐olato(1–) Ligands

The cationic complexes with hexacoordinate silicon(IV), tris[1‐oxopyridine‐2‐olato(1–)]silicon(IV) trifluoromethanesulfonate ( 4 ), 4 · ¹/₂ C₅H₅NO₂, tris[1‐oxopyridine‐2‐olato(1–)]silicon(IV) ethyl sulfate–ethanol ( 5 · EtOH), and tris[1‐oxopyridine‐2‐olato(1–)]silicon(IV) isopropyl sulfate ( 6 ), were synthesized. The identities of 4 , 4 · ¹/₂ C₅H₅NO₂, 5 · EtOH, and 6 were established by elemental analyses (C, H, N, S), mass‐spectrometric studies (FAB MS) as well as solid‐state (²⁹Si) and solution (¹H, ¹³C, ¹⁹F, ²⁹Si) NMR experiments. In addition, 4 · ¹/₂ C₅H₅NO₂ was structurally characterized by single‐crystal X‐ray diffraction.     

Polypropylene-Clay Nanocomposites: Comparison of Different Layered Silicates

In former studies of the preparation of polypropylene(PP)-clay nanocomposites, different types of layered silicates were used. However, the obtained results were not comparable due to different preparation conditions and types of silicates. The aim of this work was the investigation of the influence of different layered silicates on the properties of the resulting nanocomposites. FT-IR-spectra, SAXS, TEM micrographs, elemental analysis, mechanical properties and surface tension measurements were used for the comparison of the four different layered silicates under investigation.     

Generation of Supraclusters and Nanoclusters Using Laser Desorption/Ionisation Mass Spectrometry

Laser desorption/ionisation of discrete molecular clusters combined with time-of-flight (TOF) or Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry affords spectra in which extensive higher mass clusters are observed. The size of the largest cluster aggregates (or supraclusters) is of the same order of magnitude as nanoclusters. The spectra obtained using TOF mass spectrometry sometimes exhibit post-source decay fragmentation, depending upon the operational conditions employed during data acquisition, which, although providing useful data on the ligand dissociation dynamics, complicate spectral interpretation. Complementary FTICR mass spectra are free of such features. The identities of the supra/nanoclusters generated from the molecular cluster precursors have not been conclusively established but are mostly coordinatively unsaturated. Density functional molecular orbital calculations have identified the possible structures of the comparatively simple electronically unsaturated system, [Ru₃(CO)₆]^–, that provides a clue to the aggregation mechanism.     

Comparing the Self-Assembly of Sexiphenyl-Dicarbonitrile on Graphite and Graphene on Cu(111)

A comparative study on the self-assembly of sexiphenyl-dicarbonitrile on highly oriented pyrolytic graphite and single-layer graphene on Cu(111) is presented. Despite an overall low molecule–substrate interaction, the close-packed structures exhibit a peculiar shift repeating every four to five molecules. This shift has hitherto not been reported for similar systems and is hence a unique feature induced by the graphitic substrates.     

A hydrogel-based versatile screening platform for specific biomolecular recognition in a well plate format

Precise determination of biomolecular interactions in high throughput crucially depends on a surface coating technique that allows immobilization of a variety of interaction partners in a non-interacting environment. We present a one-step hydrogel coating system based on isocyanate functional six-arm poly(ethylene oxide)-based star polymers for commercially available 96-well microtiter plates that combines a straightforward and robust coating application with versatile bio-functionalization. This system generates resistance to unspecific protein adsorption and cell adhesion, as demonstrated with fluorescently labeled bovine serum albumin and primary human dermal fibroblasts (HDF), and high specificity for the assessment of biomolecular recognition processes when ligands are immobilized on this surface. One particular advantage is the wide range of biomolecules that can be immobilized and convert the per se inert coating into a specifically interacting surface. We here demonstrate the immobilization and quantification of a broad range of biochemically important ligands, such as peptide sequences GRGDS and GRGDSK-biotin, the broadly applicable coupler molecule biocytin, the protein fibronectin, and the carbohydrates N-acetylglucosamine and N-acetyllactosamine. A simplified protocol for an enzyme-linked immunosorbent assay was established for the detection and quantification of ligands on the coating surface. Cell adhesion on the peptide and protein-modified surfaces was assessed using HDF. All coatings were applied using a one-step preparation technique, including bioactivation, which makes the system suitable for high-throughput screening in a format that is compatible with the most routinely used testing systems.