Polymerization of substituted acetylenes by various rhodium catalysts: Comparison of catalyst activity and effect of additives

This research deals with comparison of the activity of various Rh catalysts in the polymerization of monosubstituted acetylenes and the effect of various amines used in conjunction with [Rh(nbd)Cl]₂ in the polymerization of phenylacetylene. A zwitterionic Rh complex, Rh⁺(nbd)[(η⁶‐C₆H₅)B^?(C₆H₅)₃] ( 3 ), was able to polymerize phenylacetylene ( 5a ), t‐butylacetylene ( 5b ), N‐propargylhexanamide ( 5c ) and n‐hexyl propiolate ( 5d ), and displayed higher activity than the other catalysts examined, that is [Rh(nbd)Cl]₂ ( 1 ), [Rh(cod)(O‐o‐cresol)]₂ ( 2 ), and Rh‐vinyl complex ( 4 ). Monomers 5a and 5c polymerized virtually quantitatively or in fair yields with all these catalysts, while monomer 5b was polymerizable only with catalyts 3 and 4 . Monomer 5d did not polymerize in high yields with these Rh complexes. The catalytic activity tended to decrease in the order of 3 > 4 > 2 > 1 . Although polymerization of 5a did not proceed at all in toluene with [Rh(nbd)Cl]₂ alone, it smoothly polymerized in the presence of various amines as cocatalysts. The polymerization rate as well as the molecular weight of polymer depended on the basicity and steric bulkiness of amines. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4530–4536, 2005     

Étude par la fluorescence aux rayons-X du changement de coordinence de l'aluminium dans les silico-alumines armorphes

Sans résumé     

Microscopic evidence for a new type of ordering of spin components in a random mixture with competing magnetic anisotropies

The Mössbauer spectroscopy was applied on a random mixture of two kinds of magnetic ions with competing anisotropies, Fe_1?xCo_xCl₂·2H₂O. The Mössbauer spectra observed in the Co(Fe)-rich antiferromagnetic (AF) phase near the tetracritical point show that, although the m₂(m₁) spin component parallel to the easy axis of pure FeCl₂·2H₂O(CoCl₂·2H₂O) has no long-range order in this phase (from the neutron diffraction experiment), the m₂(m₁) spin component contributes to the magnetic hyperfine field at ⁵⁷Fe nuclei as well as the m₁(m₂) spin component (which has a long-range order). This fact indicates that the m₂(m₁) spin components exists in the Co(Fe)-rich AF phase near the tetra-critical point at least in a time scale of ～ 10^?8s. This result predicts that the antiferromagnetic ordering in the Co(Fe)-rich AF phase is a new type one. The new phase observed in the intermediate concentration region is demonstrated as the “mixed ordering” phase.     

UV photoelectron spectra and sum rule consideration: Out-of-plane orbitals of unsaturated compounds with planar-skeleton structure

He(l) photoelectron spectra are presented for various planar unsaturated aliphatic compounds such as mono- and di-methyl substituted ethylenes, alkyl aldehydes, chloro-substituted aldehydes, ketones and alkyl acids. Each photoelectron spectrum is resolved into individual bands by considering the band shape, the relative intensity and the number of p-type localized MO's (LO's). The sum rule previously proposed on vertical ionization energies by the present authors is applied to the photoelectron bands associated with out-of-plane LO's. In each compound, a partial sum P(a″) is obtained over all the out-of-plane LO's and it is shown that the calculated P(a″) value is in good agreement with the experimental one which may be obtained by an appropriate sum of vertical ionization energies with negative signs.     

Quasielastic neutron scattering in the high-field phase of a Haldane antiferromagnet

Inelastic neutron scattering experiments on the Haldane-gap quantum antiferromagnet Ni(C5D14N2)2-N3(PF6) are performed in magnetic fields below and above the critical field H(c) at which the gap closes. Quasielastic neutron scattering is found for H>H(c), indicating topological excitations in the high-field phase.     

Properties of CuIn(SxSe1−x)2 polycrystalline thin films prepared by chemical spray pyrolysis

CuIn(S_xSe_1−x)₂ thin polycrystalline films were grown by the chemical spray pyrolysis method on the glass substrate at 280-400°C. The alloy composition in the film was studied with relation to that in the splay solution. Films were characterized by X-ray diffraction, optical absorption, Raman spectroscopy, resistivity and surface morphology. The CuInSe₂-rich alloy films grown at high substrate temperature had chalcopyrite structure, while, the CuInS₂-rich films grown at low substrate temperature exhibited sphalerite structure. Optical-gap energies were smaller than that of the bulk crystal by 0.1-0.2 eV for CuInS₂-rich films. Raman spectra exhibited both CuInSe₂-like and CuInS₂-like A₁ modes, and their relative changed systematically with alloy composition.     

Magnetic resonance experiments in NiBr2 at high frequencies and high magnetic fields

By performing magnetic resonance experiments in NiBr₂ at high frequencies and magnetic fields, we have observed a resonance line which we relate to a helimagnetic phase, and an antiferromagnetic resonance line corresponding to an antiferromagnetic phase with strong out-of-plane anisotropy and small in-plane anisotropy.     

High-pressure synthesis, crystal and electronic structures, and transport properties of a novel perovskite HgSnO3

We synthesized a novel perovskite-type oxide, HgSnO3, under high pressure and high temperature, and investigated the crystal and electronic structures as well as the transport properties. It was found that HgSnO3 possesses a trigonal-hexagonal lattice with space group R3c. The band gap of HgSnO3 estimated by diffuse reflectance spectrum measurement is relatively small (1.6 eV), irrespective of the large octahedral tilting distortion. The small band gap is caused by the increase in the bandwidth of the conduction and valence bands due to mixing between the empty Hg 6s orbitals and the antibonding Sn 5s-O 2p states and the mixing between the filled Hg 5d orbitals and the O 2p states, respectively. The electronic resistivity, Seebeck coefficient, and Hall coefficient measurements indicate that as-synthesized HgSnO3 is an n-type semiconductor.     

Efficient and rapid synthesis of phenolic analogs of 4-phenylbutanoic acid using microwave-assisted Michael addition as a key reaction

The addition of phenols to acrylonitrile in the presence of aqueous benzyltrimethylammonium hydroxide or tetramethylammonium hydroxide under microwave irradiation yielded the corresponding Michael adducts. The obtained adducts were easily transformed to phenolic analogs of 4-phenylbutanoic acids via the hydrolysis of nitrile groups.