Extraction—spectrophotometric determination of traces of thallium in lead,cadmium, indium and zinc metals with tri-n-octylamine

A sensitive spectrophotometric method is described for the determination of thallium in lead, cadmium, indium and zinc metals. Optimal conditions have been established for the extraction and determination of thallium. Thallium is extracted as its bromo complex with tri-n-octylamine and then converted to an iodo complex, the absorbance of which is measured at 400 nm. As little as 1 p.p.m. of thallium in lead, cadmium and zinc metals, and 2 p.p.m. of thallium in indium metal can be determined.     

EXAFS/FT-IR characterization of tetra-iridium carbonyl clusters bound to tris-(hydroxymethyl)phosphine grafted silica surface catalytically active for propene oxidation to acetone

Structure and catalytic activity of Ir₄(CO)₁₂ bound to tris-(hydroxymethyl)phosphine (THP) grafted silica (THP/SiO₂) was investigated by means of EXAFS, FT-IR and kinetic studies. It was found that Ir₄(CO)₁₂ was uniformly attached on THP/SiO₂ by substitution of CO by THP (Ir₄/THP/SiO₂). The tetra-iridium carbonyl cluster framework was remained during the substitution of THP ligands and two THP ligands coordinated to the iridium carbonyl clusters to form Ir₄(CO)₁₀(THP/SiO₂)₂. species. When Ir₄/THP/SiO₂ was evacuated at 373 K, bridge CO was desorbed and Debye-Waller factor of Ir---Ir contribution derived from EXAFS analysis was increased which suggested that the cluster framework was distorted by the evacuation at 373 K. The resulting sample evacuated at 373 K was an active catalyst for hydroformylation of ethene and partial oxidation of propene, while the Ir₄/THP/SiO₂ without evacuation exhibited poor catalytic activities. The propene oxidation reaction proceed on the Ir₄/THP/SiO₂ evacuated at 323–353 K under subatmospheric pressures to give acetone as a product in high selectivity. The ethene hydroformylation proceed on the evacuated Ir₄/THP/SiO₂ at lower temperatures compared with other conventional iridium catalysts. EXAFS characterization and kinetic studies suggested that the catalytic activities were associated with the structural distortion of the iridium cluster framework due to surface attachment by the bidentate phosphine substitution.     

Direct evidence for root growth of vertically aligned single-walled carbon nanotubes by microwave plasma chemical vapor deposition

The root growth mode of extremely dense and vertically aligned single-walled carbon nanotubes (SWNTs) synthesized by microwave plasma chemical vapor deposition was clarified by a new method, marker growth, which does not require transmission electron microscopy. SWNT layers were grown intermittently on a substrate, and a line between the layers was used as a marker to identify the growth mode. Micro-Raman spectroscopy revealed that the SWNT layers have the same diameter distribution.     

O-Alkylations of pyridoxine and pyridoxamine

O-Alkylations of pyridoxine 1 and pyridoxamine 5 were carried out in acetone in the presence of sodium ethoxide and potassium iodide to give 5-alkoxy-6-methyl-3,4-(bishydroxymethyl)pyridines 2a-j and 5-alkoxy-4-aminomethyl-6-methyl-3-hydroxyrnethylpyridines 6a-e .     

Photochemistry of Flavins in Micelles: Specific Effects of Anionic Surfactants on the Monomerization of Thymine Cyclobutane Dimers Photosensitized by Tetra-O-acyl Riboflavins*

It was found that tetra-o-acyl riboflavins efficiently photosensitize the monomerization of the cis, syn-cyclobutane dimers of 1,3-dimethylthymine and 1,3-dimethyluracil in aqueous solution in the presence of such anionic surfactants as sodium dodecyl sulfate and sodium hexadecyl sulfate at concentrations higher than their critical micelle concentration, while little monomerization of the dimers was photosensitized by the flavins in the absence of the surfactants and even in the presence of cationic and nonionic surfactants.     

Trace element abundances in stone artifacts and related materials from Japan by neutron activation analysis. An approach to archaeological provenience studies

Instrumental neutron activation analysis was carried out for trace elements in green tuff cylindrical beads (KUDATAMA) and obsidians unearthed from the sites with special reference to their archaeological provenience studies. An approach based on the characteristic index elements, the correlation diagrams of some of the elements interested, and the abundance patterns of some of rare earth elements is valid for clarifying the different source regions.     

Soluble and Planar 2,9-Diazaperopyrenes through Reductive Aromatization of Perylene Diimides: Tunable Emission and Aggregation Behaviors

Reductive aromatization of perylene diimides with acid anhydrides in the presence of Mn or Zn metals provides soluble and planar 2,9-diazaperopyrenes with ester groups at 1,3,8,10-positions. The pivaloxy groups at the peripheral positions can be transformed into a variety of aryl groups through nickel-catalyzed cross-coupling of ester groups. Emission colors of diazaperopyrenes are tunable by the peripheral substituents. The peripheral substituents also affect the aggregation behaviors of 2,9-diazaperopyrenes in the solution and solid states.     

Synthesis of Distorted 1,8,13-Trisilyl-9-hydroxytriptycenes by Triple Cycloaddition of Ynolates to 3-Silylbenzynes

1,8,13-Trialkyl(aryl)silyl-9-hydroxytriptycenes (trisilyltriptycenes) were synthesized by the triple addition of ynolates and 3-silylbenzynes with high regioselectivity. Benzene rings in the resulting triptycenes were highly distorted where the dihedral angles between the substituents were as high as 35°. The distortion energy induced step-by-step halogenation reactions to yield halogenated triptycenes, including chiral triptycenes. The 1,8,13-trihalogenated triptycenes were then converted to 1,8,13-functionalized triptycenes.