Zur anisotropen Dilatation von Fe3S4-Kristallen im elektrostatischen Feld

Synthetic crystals of Fe₃S₄ (greigite, spinel type, lattice constant 9.87 ÅU) extend by about 0.05 ÅU in an electrostatic field (field strength 860 volts · cm⁻¹) along the [111] axis in preference to any other directions. This property to be easily deformed makes it difficult to develop this crystallite (grain size about 300 ÅU) to a single crystal. It transforms into hexagonal pyrrhotite when cultivating it for crystal growth.     

Production of $$^{178}$$ 178 Hfm2 and a simple chemical separation method for Hf recovery

Journal of Radioanalytical and Nuclear Chemistry - The nuclear isomer $$^{178}$$ Hfm2 enables various investigations owing to its unique properties. To study exotic nuclear reactions induced by...     

Mikrochemie

Ohne Zusammenfassung     

Host-guest interaction between swelling clay minerals and poorly water-soluble drugs. 1: Complex formation between a swelling clay mineral and griseofulvin

The formation of a complex between a swelling clay mineral and griseofulvin (GF), a poorly water-soluble drug, was examined. A strong host-guest interaction between the neutral drug molecules and the clay mineral was observed not only in the solid state but also in aqueous dispersion. The powder X-ray diffraction patterns revealed the disappearance of a crystalline phase of GF through host-guest interaction for samples having low GF contents. The complex formation was confirmed to be due to monolayer adsorption on the basis of quantitative thermochemical analyses. The strong interaction between GF and the clay was also detected when the complex powder was dispersed in an aqueous medium on the basis of the intensity changes of from free GF solution in CD and fluorescence spectra as compared with those observed for the free GF solution.     

Dithienoazepine-Based Near-Infrared Dyes: Janus-Faced Effects of a Thiophene-Fused Structure on Antiaromatic Azepines

We here disclose that the incorporation of thiophene rings into a seven-membered 8π azepine in a fused fashion produces a useful antiaromatic core for near-infrared (NIR) dyes. In contrast to dibenzazepine derivatives with bent structures, dithieno-fused derivatives with electron-accepting groups adopt flat conformations in the ground state. The dithieno-fused derivatives exhibited broad absorption spectra that cover the visible region as well as sharp emission bands in the NIR region, which are considerably red-shifted relative to those of the dibenzo-fused congeners. Theoretical study revealed two contradictory effects of the less-aromatic thiophene-fused structure, i.e., the enhancement of the antiaromaticity of the adjacent azepine ring and the relief of the antiaromaticity through the contribution of a quinoidal resonance form. The combination of the dithienoazepine core with cationic electron-accepting groups produced a NIR fluorescent dye with an emission at 878 nm in solution.     

Nonenzymatic enantioselective monoacetylation of prochiral 2-protectedamino-2-alkyl-1,3-propanediols utilizing a chiral sulfonamide-Zn complex catalyst

[structure: see text] Treatment of a chiral sulfonamide with Et(2)Zn gave quantitatively its Zn complex and then the structure was determined by X-ray crystallographic analysis. Reaction of prochiral N-Boc-2-amino-2-alkyl-1,3-propanediols with Ac(2)O in the presence of 5 mol % of chiral sulfonamide-Zn complex catalyst afforded the corresponding chiral monoacetyl products in 70-92% yields with 70-88% ee values. The proposed mechanism for the catalytic monoacetylation of a prochiral 1,3-propanediol was presented on the basis of CSI-MS analysis.     

Helicene‐Grafted Silica Nanoparticles Capture Hetero‐Double‐Helix Intermediates during Self‐Assembly Gelation

A mixture of a pseudoenantiomeric ethynylhelicene (M)‐tetramer and a (P)‐pentamer forms a hetero‐double‐helix in a solution, which self‐assembles and gelates solvents. When gelation was conducted in the presence of chiral silica (P)‐nanoparticles grafted with (P)‐helicene, the resulting hetero‐double‐helix intermediate was adsorbed on the (P)‐nanoparticles, and was removed from the solution by aggregation and precipitation. The resulting precipitates contained only the hetero‐double‐helix, not random coil or clusters of the hetero‐double‐helix. (P)‐Nanoparticles did not extract the hetero‐double‐helix from the self‐assembly gels. The hetero‐double‐helix was then isolated by liberating it from the precipitates in 2‐bromopropionic acid, and was crystallized from the solution. The crystalline hetero‐double‐helices were isolated for several other combinations of pseudoenantiomeric ethynylhelicene oligomers.     

Macroscopic observations of molecular recognition: discrimination of the substituted position on the naphthyl group by polyacrylamide gel modified with β-cyclodextrin

Macroscopic molecular recognition observations were realized using polyacrylamide-based gels modified with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), 1-naphthylmethyl (1Np), and 2-naphthylmethyl (2Np) moieties, which are denoted as αCD(x)-gel, βCD(x)-gel, 1Np(y)-gel, and 2Np(y)-gel, where x and y indicate the mol % of CD and Np moieties, respectively. The αCD(5)-gel did not adhere to either the 1Np(5)-gel or 2Np(5)-gel, whereas the βCD(5)-gel interacted with both to form alternating or checkered assemblies. Although the difference in the association constants of β-CD for the model polymers was small, the βCD(x)-gel successfully discriminated between 1Np(y)-gel and 2Np(y)-gel at the appropriate x and y.