Polymer-mediated extraction of 8-quinolinolato metal chelates for the determination of metal ions in water with graphite furnace atomic absorption spectrometry

Water-insoluble 8-quinolinolato metal chelates were formed and were stably solubilized in the aqueous solution of a water-soluble polymer, poly (N-isopropylacrylamide)(PNIPAAm), at room temperature. When the solution was heated at 50 degrees C, PNIPAAm precipitated and then formed a gum-like aggregate (polymer phase) having a very small volume. Accompanying the polymer precipitation, hydrophobic 8-quinolinolato chelates with cobalt(II), iron(III), nickel(II), and copper(II) ions were efficiently incorporated into the polymer phase. At 0.5% (w/v) of PNIPAAm and 8.0 mM of 8-quinolinol, the recoveries in the incorporation of four metal chelates were quantitative. The fluorescence spectra of a probe suggests that the hydrated polymer in the aqueous solution provides hydrophobic portions which can incorporate hydrophobic metal chelates. The polymer phase was easily taken out from the solution and was dissolved with a small amount of acetonitrile. The resulting solution could be directly introduced into a graphite furnace of atomic absorption spectrometry. The signal intensities for the absorbance of cobalt after concentrating the chelate were 100-fold greater than those before the concentration.     

Kinetics of the dimerization of silylenes to disilenes

The activation parameters of the dimerization of t-butylmesitylsilylene (2a), dimesitylsilylene (2b) and bis(2,4,6-triisopropylphenyl)silylene (2c) to the corresponding disilenes were estimated by monitoring the time-dependent changes in their UV-Vis absorption spectra. The activation energy increased in the order: 2a < 2b < 2c. This article is part of a Special Issue dedicated to M. Kira.     

Self-assembly of oligosilanes: Synthesis and structure of 3,5-dehydroxyphenyl substituted oligosilanes

Disilanes and hexasilanes with terminal hydrogen-bond substituents, i.e., 3,5-dihydroxyphenyl groups, were synthesized. The structures were analyzed by X-ray diffraction and it was shown that the resulting molecular orientations were controlled by the hydrogen-bond network.     

Highly regioselective diels-alder reactions of 2-trimethylsilylmethyl- and 2-trimethylstannylmethyl-1,3-butadiene

2-Trimethylsilylmethyl and 2-trimethylstannylmethyl-1,3-butadiene undergo facile cycloaddition with dienophiles, and show high regioselectivity with unsymmetrical dienophiles.     

Anti-diabetes effect of Zn(II)/carnitine complex by oral administration

A novel bis(L-carnitinato)Zn(II) complex, Zn(car)(2)Cl(2), was prepared, and its insulinomimetic and antidiabetic activities were examined. The complex showed a tendency to lower the high blood glucose levels of KK-A(y) mice with type 2 diabetes mellitus when given by oral administration at a dose of 20 mg Zn/kg body weight for 16 d. In addition, the complex improved glucose tolerance ability when examined by the oral glucose tolerance test (1 g glucose/kg body weight).     

Convection-aided collection of metal ions using chelating porous flat-sheet membranes

Chelating porous membranes were prepared by radiation-induced graft polymerization of an epoxy-group-containing monomer onto a polyethylene flat sheet and subsequent conversion of the epoxy group to an iminodiacetate group as a chelate-forming group. The chelating group density on the resultant porous flat-sheet membrane of 1.0 mol/kg was comparable to that of commercially available chelating beads. The pure water permeability of the membrane was 40% that of the trunk porous membrane, which was used for microfiltration. During the permeation of a copper chloride solution through the membrane, diffusional mass-transfer resistance of copper ion was negligible, since the ion was transported by convective flow through the pore. The tensile strength and elongation at break of the membranes were measured as a function of dose of electron-beam irradiation, the degree of grafting, and the chelating group density to determine an applicable range for practical use.     

Beta-1,3-glucan polysaccharide can act as a one-dimensional host to create novel silica nanofiber structures

We have demonstrated that the creation of novel silica nanofibers with a uniform diameter is possible by utilizing beta-1,3-glucan polysaccharide as a one-dimensional host for monoalkoxysilane; the finding establishes that beta-1,3-glucan can act not only as a novel one-dimensional host for metal alkoxide polycondensation but also as an interface between inorganic nanofibers and functional organic molecules.     

Preparation, reactions and stereochemistry at silicon of (2,3,4,5-tetraphenyl-1-silacyclopentadiene)iron tricarbonyls

Twelve derivatives of (2,3,4,5-tetraphenyl-1-silacyclopentadiene)iron tricarbonyls were prepared. These complexes undergo a variety of substitution at silicon. The exo leaving groups showed enhanced reactivity in such reactions. The stereochemistry of substitution also differs significantly from that established for optically active silanes.