Mut zur Lücke : Mg/ZnO‐Nanopartikel mit heller, stabiler Photolumineszenz in kolloidalen Dispersionen wie im Festkörper bilden sich durch Dotierung von Mg2+‐Ionen in ZnO‐Nanopartikel durch sonochemische Synthese. Ihre Bandlücken und Lumineszenzeigenschaften verändern sich mit der Defektkonzentration in den ZnO‐Nanopartikeln. Diese Konzentration hängt vom molaren Mg/Zn‐Verhältnis ab (siehe Bild).
Getting the sizes sorted out : In recent years, there have been increasing numbers of reports about self‐assembled nano‐ or microtubular structures because of their potential uses in a variety of technical applications, which are largely determined by the tube sizes. This Focus Review highlights microsized self‐assembled organic tubular structures formed in aqueous solutions and organic solvents.
Heads or tails? The evolution of structural and electronic properties of tin–phthalocyanine films has been analyzed for sub‐monolayer to multilayer coverage using low‐temperature scanning tunneling microscopy. Two molecular conformations are observed: randomly dispersed for the first layer, and islands with a single conformation in subsequent layers.
Catalytic convenience : The use of iridium or ruthenium catalysts for C? H bond activation has led to the addition reaction of trifluoromethylated compounds to alkenes (see scheme). This atom‐economical reaction occurs under neutral reaction conditions and without the formation of undesired defluorinated by‐products, even at high temperature.
Sweets for my sweet ! Efficient synthesis of the deoxysugar part of versipelostatin (VST) was achieved by direct and stereoselective glycosidation of the reduced VST aglycon. Comparison of the synthetic and natural VST products using NMR indicate that VST has a β‐d‐digitoxose‐(1,4)‐α‐l‐oleandrose‐(1,4)‐β‐d‐digitoxose trisaccharide. A biological assay indicates that the deoxyoligosaccharide unit of the synthetic glycoside is important for biological activity.
Easy come, easy go? Transport resistances on particle surfaces are important for mass transfer in nanoporous materials and bulk diffusion in crystals. Interference microscopy and IR micro‐imaging are shown to be excellent tools for determining such transport resistances. By studying short‐chain‐length alkane guest molecules in crystals of the metal–organic framework compound Zn(tbip) a data collection of surface permeabilities is established.
Bridging or pendant? Palladium and rhodium complexes deriving from an ambiphilic phosphine–borane ligand are shown to adopt a bridging P→M? Cl→B coordination mode in the solid state. DFT calculations provide more insight into the Cl→B interaction and suggest the possible interconversion of the bridging and B‐pendant forms in solution.
Changing channels : The novel dynamic gas‐separation mechanism is demonstrated by a GC study for a flexible single crystal [Cu2(bza)4(pyz)]n, 1 . The single‐crystal host 1 , because of its flexibility, can separate various gases by adjusting its channel structure according to the features of the guest gaseous molecules.
On the tube : The coupling of diazonium ions onto single‐walled carbon nanotubes is shown to proceed through a radical chain reaction by kinetic analysis of the absorption peak drop (see picture). Radical species are also revealed by ESR. Metallic (m) nanotubes play a special catalytic role in the functionalization of semiconducting (sc) nanotubes.
This review covers the literature concerning the modification of polysaccharides through controlled radical polymerizations (NMP, ATRP and RAFT). The different routes to well‐defined polysaccharide‐based macromolecules (block and graft copolymers) and graft‐functionalized polysaccharide surfaces as well as the applications of these polysaccharide‐based hybrids are extensively discussed.
Three of a kind : Vicinal tricarbonyl compounds undergo C? C cleavage mediated by ferric ions (see scheme). The observed cleavage of ninhydrin and dehydroascorbic acid has relevance for amino acid detection and the metabolism of vitamin C.
To Bi or not to Bi? The synthesis of phosphorus nanorods of two differing morphologies is reported, in both the presence and absence of a bismuth catalyst. Not only do these materials represent a new class of elemental nanorods but they also give valuable insight into the complex allotropy of phosphorus.
Large deuterium isotope effects of both signs have been observed on the 13C nuclear shielding in proton-chelating tautomeric forms of β-thioxoketones, and small isotope effects of both signs have been found in related forms of Schiff's bases of salicylaldehydes. These effects are interpreted in terms of shifts in the tautomeric equilibria on deuterium substitution of the enolic proton. The observation of deuterium isotope effects is suggested as a useful method for the detection of fast tautomeric equilibria in systems of the following type. . 相似文献
How low can you go? An FeII4 square was prepared by self‐assembly and exhibits both thermally induced and photoinduced spin crossover from a system with four high‐spin (HS) centers to one with two high‐spin and two low‐spin (LS) centers. The spin‐crossover sites are located on the same side of the square, and the spin transition and magnetic interactions (see picture) are synergistically coupled.
