Total synthesis of decarboxyaltenusin.

The total synthesis of decarboxyaltenusin (5'-methoxy-6-methyl-[1,1'-biphenyl]-3,3',4-triol), a toxin produced by various mold fungi, has been achieved in seven steps in a yield of 31% starting from 4-methylcatechol and 1-bromo-3,5-dimethoxybenzene, where the longest linear sequence consists of five steps. The key reaction was a palladium-catalyzed Suzuki coupling of an aromatic boronate with a brominated resorcin derivative.

Reversible and Irreversible Structural Changes in Cu/ZnO/ZrO2 Catalysts during Methanol Synthesis.

The structure and chemical state of heterogeneous catalysts are closely related to their operational stability. Knowing these relationships as precisely as possible is thus essential for further catalyst development. This work focuses on the deactivation of a Cu/ZnO/ZrO2-type catalyst for methanol synthesis. Experiments were performed in a parallel setup, with which time-dependent changes in the catalyst material can be observed. Elucidation of potential deactivation pathways is described for catalyst aging at different times on stream (0, 50, 935 h). Data from X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, N2 physisorption, and transmission electron microscopy measurements reveal that sintering of Cu0 domains and restructuring within ZnO domains mainly contribute to deactivation. Subsequent reactivation by reduction (in H2/N2) reverts the observed structural changes only to a limited extent. Moreover, this work highlights the participation of ZrO2 as a promoter and reveals redispersion of zirconia after initial reduction.

Facet-, composition- and wavelength-dependent photocatalysis of Ag2MoO4.

Faceted ß-Ag2MoO4 microcrystals are prepared by controlled nucleation and growth in diethylene glycol (DEG) or dimethylsulfoxide (DMSO). Both serve as solvents for the liquid-phase synthesis and surface-active agents for the formation of faceted microcrystals. Due to its reducing properties, truncated ß-Ag2MoO4@Ag octahedra are obtained in DEG. The synthesis in DMSO allows avoiding the formation of elemental silver and results in ß-Ag2MoO4 cubes and cuboctahedra. Due to its band gap of 3.2 eV, photocatalytic activation of ß-Ag2MoO4 is only possible under UV-light. To enable ß-Ag2MoO4 for absorption of visible light, silver-coated ß-Ag2MoO4@Ag and Ag2(Mo0.95Cr0.05)O4 with partial substitution of [MoO4]2- by [CrO4]2- were prepared, too. The photocatalytic activity of all the faceted microcrystals (truncated octahedra, cubes, cuboctahedra) and compositions (ß-Ag2MoO4, ß-Ag2MoO4@Ag, ß-Ag2(Mo0.95Cr0.05)O4) is compared with regard to the photocatalytic decomposition of rhodamine B and the influence of the respective faceting, composition and wavelength.

ß-SnWO4 with Morphology-Controlled Synthesis and Facet-Depending Photocatalysis.

Faceted ß-SnWO4 microcrystals are prepared with different morphologies including tetrahedra, truncated tetrahedra, truncated octahedra, and short-spiked and long-spiked spikecubes. All of these morphologies are prepared with comparable experimental conditions via microwave-assisted synthesis of high-boiling alcohols (the so-called polyol method). The decisive parameters for controlled formation of one or the other morphology of faceted ß-SnWO4 microcrystals are studied and discussed, including microwave-assisted heating, Sn(OH)2 as the Sn2+ reservoir, the temperature of particle nucleation, the temperature of particle growth, and the concentration of the starting materials. Morphology and crystallinity are characterized by scanning electron microscopy, X-ray powder diffraction, UV-vis, and Fourier-transform infrared spectroscopy. Finally, the photocatalytic properties of all obtained faceted microcrystals-tetrahedra, truncated tetrahedra, truncated octahedra, cubes, and short-spiked and long-spiked spikecubes-are exemplarily compared with regard to the photocatalytic decomposition of rhodamine B and the influence of the respective surface crystal planes.

Pyridine-based low-temperature synthesis of CoN, Ni3N and Cu3N nanoparticles.

CoN, Ni3N and Cu3N nanoparticles were obtained by pyridine-based synthesis using CoI2, NiI2, and CuI as the starting materials as well as NH3/KNH2 as the base and nitride source. Colloidally stable suspensions of crystalline, small-sized CoN (4.5 ± 0.7 nm), Ni3N (2.7 ± 0.4 nm), and Cu3N (4.2 ± 0.7 nm) were instantaneously available from refluxing pyridine. This approach strictly avoids all oxygen sources (including starting materials and solvents), which is highly relevant with regard to the material purity and properties.