Ba14Cu2In4N7, a new subnitride with isolated nitridocuprate groups and indium clusters

Single crystals of Ba₁₄Cu₂In₄N₇, tetradecabarium dicopper tetraindium heptanitride, were synthesized by slow cooling from 1023 K at 7 MPa of N₂ using an Na flux. The compound crystallizes in the monoclinic space group P2/m with Z = 2, and contains ⁰[CuN₂] nitrido­cuprate units and distorted ⁰[In₄] clusters. One Ba atom, not connected to any N atoms, is surrounded by 12 other Ba atoms in a barium cuboctahedron. The structural formula is expressed as (Ba)Ba₂₇N₆[CuN₂]₄[In₄]₂.     

Chromatographic Properties of Monolithic Silica Capillary Columns for Polar and Nonpolar Compounds in Reversed-Phase HPLC

Retention properties of monolithic silica C₁₈ columns were examined for polar and nonpolar compounds. Monolithic silica columns were prepared from two kinds of starting materials, tetramethoxysilane (abbreviated as TMOS) or a mixture of TMOS and methyltrimethoxysilane (abbreviated as Hybrid), and modified with dimethyloctadecylchlorosilane (C₁₈). Retention factors of various compounds on Hybrid-C₁₈ are about twice as much as that on TMOS-C₁₈. The two types of columns showed very similar retention selectivity with few exceptions. TMOS-C₁₈ showed slight preference toward planar polynuclear aromatic hydrocarbons (PAHs) compared to bulky aromatic hydrocarbons, while Hybrid-C₁₈ showed opposite tendency. Some TMOS-C₁₈ columns showed peak tailing for PAHs, and also for basic compounds in an acidic mobile phase, while Hybrid-C₁₈ and majority of TMOS-C₁₈ columns resulted in good peak shape for these compounds.     

Primary processes in the photoreduction of 1-chloro- and 1,8-dichloro-anthraquinones in ethanol studied by laser spectroscopy

The hydrogen-atom abstraction of the title compounds from ethanol was found to originate from the T₁ state in spite of the mixed nπ*-ππ* or ππ* character of the lowest triplet state (T₁). No evidence for electron transfer from ethanol to the T₁ state of α-halogenoanthraquinones was obtained.     

Complexed bridging ligand,Cu(bptap)2, as a ferromagnetic coupler

A novel complexed bridging ligand [Cu(bptap)2] which acts as a ferromagnetic coupler forms one dimensional chain consisting of tri-copper(II) [Cu2(Cu(bptap)2)]4+ units in which adjoining copper(II) ions are ferromagnetically coupled.     

Synthesis of Silicon Carbide Fibers by Sol-Gel Processing

Silica-phenolic resin hybrid fibers with carbon-to-silicon atomic ratios of 2.6 to 5.4 have been prepared from ethanol solutions of tetraethoxysilane, phenolic resins, water, and hydrochloric acid with a tetraethoxysilane-H₂O−HCl molar ratio of 1:2:0.01 by sol-gel processing. The hybrid fibers have been heated at 1500°C in Ar for carbothermal reduction to convert them into silicon carbide fibers. The effects of the holding time at 1500°C and the carbon-to-silicon atomic ratio of the hybrid fibers on the free carbon content in the silicon carbide fibers have been investigated. It has been found that the conversion is complete by the heat-treatment for more than 2 h. The silicon carbide fibers with a free carbon content of ca. 2 wt% have been obtained from the hybrid fibers with the ratios of 2.6 to 4.3.     

Chemical modification of butyl rubber. III. Butyl rubber with D-maltose derivative as pendant groups

A new type of amphiphilic elastomer was synthesized, which consisted of butyl rubber and a D-maltose derivative as a backbone and side groups, respectively. The synthesis was accomplished by the sequence of the three following reactions: (1) Hydroxyl groups of D-maltonolactone were protected by a trimethylsilyl group. (2) The resulting maltonolactone derivative was subjected to a reaction with chemically modified butyl rubber having pendant amino groups. (3) The protecting trimethylsilyl groups on the maltose residues were removed by treating with tetra-n-butylammonium fluoride. This new amphiphilic elastomer behaved as a thermoplastic elastomer and showed good mechanical properties. The saccharide seg-ments aggregated in the hydrophobic butyl rubber matrix to form a microphase-separated structure, as confirmed by differential scanning calorimetry, transmission electron mi-croscopy, small-angle x-ray scattering, and dynamic mechanical measurements. The ag-gregated saccharide domains are estimated to function both as crosslinking sites and rein-forcing fillers in the rubber matrix. © 1995 John Wiley & Sons, Inc.     

Studies on the biosynthesis of corrinoids and porphyrinoids. I. The labeling of oxygen of vitamin B12

Recently the amide-oxygen has been suggested to participate in the formation of the corrin ring of vitamin B12. To confirm this hypothesis, 17O-labeled aminolevulinic acid (ALA) was prepared and administered to Propionibacterium shermanii. The isolated vitamin B12 showed only broad 17O signals in the oxygen-17 nuclear magnetic resonance (17O-NMR) spectrum. However, distinct isotope-shifted peaks were observed in the 13C-NMR spectrum of vitamin B12 isolated after incorporation of [1-13C:1,4-18O2]ALA. Of these shifted peaks, one peak (C27) showed very low intensity. This indicates that dilution of 18O occurred at the acetyl chain of the A ring of vitamin B12. This result supports the assumption that the lactone formation of the A ring promotes the ring contraction, as proposed by Eschenmoser.     

Magnetic anisotropy and molecular assembling in d complex cation–f complex anion type coordination compounds

The system [Fe(bpca)₂][Er(NO₃)₄(H₂O)₂] (1) (Hbpca = bis(2-pyridil-carbonyl) amine) is a complex cation–complex anion type coordination compound consisting of distinct d and f units, interlinked by hydrogen bonds. Particularly, the association of f-type complex anions in dimers is remarked and discussed. The energy decomposition analyses based on DFT calculations offered supplementary insight into the coordination effects at the lanthanide ions and the hydrogen bond driven supramolecular association of the complex units. Special ab initio procedures and subsequent modeling afforded the computation of anisotropic magnetization tensors of the [Er(NO₃)₄(H₂O)₂]^? f-type units. The computed results are in line with the experimental data for compound 1.     

Evaluation of 13C-phenylalanine and 13C-tyrosine breath tests for the measurement of hepatocyte functional capacity in patients with liver cirrhosis.

Liver disease is associated with an abnormal elevation of the plasma concentrations of the aromatic amino acids phenylalanine and tyrosine. The liver is the main site of aromatic amino acid metabolism, particularly the hydroxylation of phenylalanine to tyrosine and further tyrosine degradation. In the present study, we have examined the usefulness of the L-[1-13C]phenylalanine breath test (13C-PheBT) and L-[13C]tyrosine breath test (13C-TyrBT) for the detection of hepatic damage in patients with liver cirrhosis. First, the time courses of 13CO2 excretion after the administration of L-[1-13C]phenylalanine and L-[1-13C]tyrosine were compared. The peak times (the time expressed in minutes at which 13CO2 excretion was maximal) were 20 min in both breath tests, but 13C-TyrBT gave a higher peak than 13C-PheBT. Next, the parameters of 13C-PheBT and 13C-TyrBT were compared with biochemical liver function test values. These parameters were well correlated with several liver blood test values conventionally regarded as measures of hepatocyte functional reserve. Therefore, 13C-PheBT and 13C-TyrBT may be useful to assess the degree and progression of hepatic dysfunction.