Catalysis by Ir(III), Rh(III) and Pd(II) metal ions in the oxidation of organic compounds with H2O2

Catalytic activities of three transition metals, as iridium (III) chloride, rhodium (III) chloride and palladium (II) chloride, were compared in the oxidation of six aromatic aldehydes (benzaldehyde, p‐chloro benzaldehyde, p‐nitro benzaldehyde, m‐nitro benzaldehyde, p‐methoxy benzaldehyde and cinnamaldehyde), two hydrocarbons (viz. (anthracene and phenanthrene)) and one aromatic and one cyclic alcohol (cyclohexanol and benzyl alcohol) by 50% H₂O₂. The presence of traces (substrate: catalyst ratio equal to 1:62500 to 1:1961) of the chlorides of iridium(III), rhodium(III) and palladium(II) catalyze these oxidations, resulting in good to excellent yields. It was observed that in most of the cases palladium(II) chloride is the most efficient catalyst. Conditions for the highest and most economical yields were obtained. Deviation from the optimum conditions decreases the yields. Oxidation in aromatic aldehydes is selective at the aldehydeic group only and other groups remain unaffected. This new, simple and economical method, which is environmentally safe, also requires less time. Reactive species of catalysts, existing in the reaction mixture are also discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Band bending at the Si(1 1 1)–SiO2 interface induced by low-energy ion bombardment

Experiments employing photoreflectance spectroscopy have uncovered band bending due to electrically active defects at the Si(1 1 1)–SiO₂ interface after sub-keV Ar⁺ ion bombardment. The band bending of about 0.5 eV resembles that for Si(1 0 0)–SiO₂, and both interfaces exhibit two kinetic regimes for the evolution of band bending upon annealing due to defects healing. The healing takes place about an order of magnitude more quickly at the (1 1 1) interface, however, probably because of less fully saturated bonding and higher compressive stress.     

A simple and sensitive analytical method for the determination of antimony in environmental and biological samples.

The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable.     

Combining the best in triplex recognition: synthesis and nucleic acid binding of a BQQ-neomycin conjugate

Synthesis of a BQQ-neomycin conjugate is reported. The conjugate combines two ligands, one known to intercalate triplexes (BQQ) and another known to bind in the triplex groove (neomycin). The conjugate stabilizes T.A.T, as well as mixed base DNA triplex, better than neomycin, BQQ, or a combination of both. The conjugate selectively stabilizes the triplex (in the presence of physiological salt concentrations), with as little as 4 muM of the ligand leading to a DeltaTm of >60 degrees C. Competition dialysis studies show a clear preference for the drug binding to triplex DNA/RNA over the duplex/single strand structures. Modeling studies suggest a structure of neomycin bound to the larger W-H (Watson-Hoogsteen) groove with BQQ intercalated between the triplex bases.     

The structure of malabricol

A single crystal X-ray analysis has confirmed the constitution and established the stereochemistry of the triterpene, malabaricol.     

Carbon nanohorns grown from ruthenium nanoparticles

A nanoscale ruthenium/gold bimetallic cluster of clusters has been used as a molecular precursor to produce pure ruthenium nanoparticles (seeds) as catalysts for the growth of carbon nanohorns (CNHs).     

Effect of Enzyme Modification of Corn Grits on their Properties as an Adsorbent in a Skarstrom Pressure Swing Cycle Dryer

Corn grits have been tested as a desiccant in a pressure swing adsorption (PSA) system to produce dry air. Two sizes of unmodified corn grits were tested in the PSA system: 2.16 and 0.978 mm in diameter, which dried moist air to dew points of –42°C and –69°C, respectively. A modification technology has been developed for the corn grits that gives an increase in the operational adsorptive capacity in a pressure swing adsorption system, so that they remove as much moisture from air as molecular sieves at the same conditions. After modification, 2.16 mm corn grits dry moist air to a –56°C dew point and the 0.978 mm corn grits dry air to a –80°C dew point. The modification process creates surface modifications on the corn grits apparently making more adsorption sites easily available. The modification procedure increases the specific surface area of the grits and possibly decreases the crystallinity, which would make more hydroxyl groups available for adsorption of water. Possible applications of using corn grits in the pressure swing adsorption system include industrial gas dryers, sorptive cooling air conditioners, and recycling equipment for industrial solvents.