Manganese‐Corrole Complexes as Versatile Catalysts for the Ring‐Opening Homo‐ and Co‐Polymerization of Epoxide

Manganese‐corrole complexes in combination with a co‐catalyst [PPN]X ([PPN]⁺=bis(triphenylphosphoranylidene)iminium) were found to be new versatile catalysts for the polymerization of epoxides, copolymerization of epoxides with CO₂, and copolymerization of epoxides with cyclic anhydrides affording a wide range of polymeric materials. This work should allow the synthesis of new types of improved innovative (co)polymers with original properties and would clearly increase the number of applications for polyesters, polycarbonates, and polyethers.     

Facile Synthesis of Dibenzopentalene Dianions and Their Application as New π‐Extended Ligands

Reduction of phenyl(silyl)ethynes with potassium followed by quenching with iodine gave dibenzopentalenes in moderate yields. The intermediates of the reactions, dipotassium dibenzopentalenides, were isolated. The first dibenzopentalene–transition‐metal complex was successfully synthesized. The ruthenium atoms are located above the six‐membered rings. However, X‐ray diffraction analysis and theoretical calculations revealed that the aromatic nature of the five‐membered rings was retained. The cyclic voltammetry of the Ru complex revealed two oxidation waves with relatively large separation.     

Preparation and properties of a fullerene/polysiloxane hybrid from chemically modified fullerene and polymethoxysiloxane

An organic–inorganic hybrid was prepared by simply mixing a fullerene derivative with polymethoxysiloxane. First, C₆₀ was subjected to a radical addition reaction with 4,4′-azobis(4-cyanovaleric acid) to provide a C₆₀ derivative. Polymethoxysiloxane was prepared by a controlled hydrolytic condensation of tetramethoxysilane. These two compounds were mixed and heated to provide hybrid bulk body. The hybrid bulk body showed high mechanical strength and elastic modulus compared with polymethoxysiloxane or the C₆₀/polymethoxysiloxane hybrid. The formation of a dense siloxane network was established by a homogeneous mixing of the C₆₀ derivative with polymethoxysiloxane.     

Production of 99Mo/99mTc by photonuclear reaction using a natMoO3 target

Journal of Radioanalytical and Nuclear Chemistry - Amount estimation of production of 99Mo required for medical applications was carried out by utilizing an electron linear accelerator with...     

Syntheses of β-amidovinyltellurides and oxazoles by addition reactions of alkynes with benzenetellurinyl trifluoromethanesulfonate in acetonitrile

Benzenetellurinyl trifluoromethanesulfonate in conjunction with acetonitrile readily effected amidotellurinylation reactions with alkynes. Most of the addition reactions proceeded in a trans fashion to form the (E)-β-acetamidovinyl phenyl telluroxides. Subsequently, it was found that the prevailing Markovnikov adducts from terminal alkynes immediately isomerized to (Z)-isomers which were isolated as the corresponding vinyltellurides. On the other hand, the adducts derived from internal alkynes thermally underwent a spontaneous intramolecular cyclization to be transformed eventually into oxazoles.     

Double-Heterostructure Indium-Tin Oxide/InGaAsP/AlGaAs Lasers

The fabrication and characterization of double-heterostructure (DH) laser that utilizes an indium-tin oxide (Ito) transparent cladding and top contact layer. The first room-temperature lasing operation has been obtained form ITO/InGaAsP/AlGaAs DH laser diode at threshold current density of 12.1 kA/cm². The interfacial recombination velocity of ITO/InGaAsP Interface was estimated to be 4.9 × 10⁴ cm/s from a simple model to account for high threshold current, and optical measurements of spontaneous emission and lasing spectra from top stripe window and facet were done.     

Studies on the syntheses of polymetalloxanes and their properties as a precursor for amorphous oxide. IV. Properties of SiO2–TiO2 oxide fibers from polytitanosiloxane

From polytitanosiloxanes (PTS), SiO₂–TiO₂ oxide fibers with fairly good tensile strength were prepared, and their mechanical and thermal properties were investigated. The precursor fibers PTS-0.5 and PTS-1.0 were obtained by dry spinning of a highly viscous PTS solution which were formed as the reaction mixture of silicic acid (SA) with bis(2,4-pentanedionato)titanium diisopropoxide (PTP) in the molar ratios (SA/PTP) of 0.5 and 1.0. The precursor fibers PTS-0.5 were too brittle to measure their tensile strength, whereas PTS-1.0 and the heat-treated fibers were found to have tensile strength of 130 (precursor), 540 (500°C), and 450 (900°C) MPa, respectively. Heat-treatment of the fibers PTS-1.0 at above 1000°C forms anatase and rutile of titanium dioxide. The crystallization is resulted from the unreacted PTP which is not incorporated into the polymer network.     

Presence of β-Turn Structure in Recombinant Spider Silk Dissolved in Formic Acid Revealed with NMR

Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned ¹H, ¹³C, and ¹⁵N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the ¹⁵N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed.