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     

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.     

Field-induced three- and two-dimensional freezing in a quantum spin liquid

Field-induced commensurate transverse magnetic ordering is observed in the Haldane-gap compound Ni(C(5)D(14)N(2))2N(3)(PF(6)) by means of neutron diffraction. Depending on the direction of applied field, the high-field phase is shown to be either a three-dimensional ordered Néel state or a short-range ordered state with dominant two-dimensional spin correlations. The structure of the high-field phase is determined, and properties of the observed quantum phase transition are discussed.     

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.     

Synthesis and charge/discharge properties of polyacetylenes carrying 2,2,6,6-tetramethyl-1-piperidinoxy radicals

The 2,2,6,6-tetramethyl-1-piperidinoxy (TEMPO)-containing acetylenic monomers HC[triple bond]CC(6)H(3)-p,m-(CONH-4-TEMPO)(2) (1), HC[triple bond]CC(6)H(3)-p,m-(COO-4-TEMPO)(2) (2), (S,S,S,S)-HC[triple bond]CC(6)H(3)-p,m-[CO-NHCH{COO-(4-TEMPO)}CH(2)COO-(4-TEMPO)](2) (3), (S,S)-HC[triple bond]CC(6)H(4)CO-NHCH{COO-(4-TEMPO)}CH(2)COO-(4-TEMPO) (4), HC[triple bond]CC(6)H(4)-p-OCO-4-TEMPO (5), HC[triple bond]CCH(2)C(CH(3))(CH(2)OCO-4-TEMPO)(2) (6), HC[triple bond]CCH(2)NHCO-4-TEMPO (7), and HC[triple bond]CCH(2)OCO-4-TEMPO (8) were polymerized to afford novel polymers containing the TEMPO radical at high densities. Monomers 1, 3-6, and 8 provided polymers with average molecular weights of 10 000-136 500 in 62-99 % yield in the presence of a rhodium catalyst, whereas monomers 2 and 7 gave insoluble polymers in 100 % yield. The formed polymers were thermally stable up to approximately 274 degrees C according to thermogravimetric analysis (TGA). All the TEMPO-containing polymers demonstrated reversible charge/discharge processes, whose discharge capacities were 21.3-108 A h kg(-1). In particular, the capacity of poly(1)-, poly(4)-, and poly(5)-based cells reached 108, 96.3, and 89.3 A h kg(-1), respectively, which practically coincided with their theoretical values.     

High-pressure synthesis and correlation between structure, magnetic, and dielectric properties in LiNbO(3)-type MnMO3 (M=Ti, Sn)

LiNbO(3)-type MnMO(3) (M = Ti, Sn) were synthesized under high pressure and temperature; their structures and magnetic, dielectric, and thermal properties were investigated; and their relationships were discussed. Optical second harmonic generation and synchrotron powder X-ray diffraction measurements revealed that both of the compounds possess a polar LiNbO(3)-type structure at room temperature. Weak ferromagnetism due to canted antiferromagnetic interaction was observed at 25 and 50 K for MnTiO(3) and MnSnO(3), respectively. Anomalies in the dielectric permittivity were observed at the weak ferromagnetic transition temperature for both the compounds, indicating the correlation between magnetic and dielectric properties. These results indicate that LiNbO(3)-type compounds with magnetic cations are new candidates for multiferroic materials.     

Effect of ASP2151, a herpesvirus helicase-primase inhibitor, in a guinea pig model of genital herpes

ASP2151 is a herpesvirus helicase-primase inhibitor with antiviral activity against varicella zoster virus and herpes simplex virus types 1 (HSV-1) and 2 (HSV-2). Here, we examined the potency and efficacy of ASP2151 against HSV in vitro and in vivo. We found that ASP2151 was more potent in inhibiting the replication of HSV-1 and HSV-2 in Vero cells in the plaque reduction assay and had greater anti-HSV activity in a guinea pig model of genital herpes than did acyclovir and valacyclovir (VACV), respectively. Oral ASP2151 given from the day of infection reduced peak and overall disease scores in a dose-dependent manner, resulting in complete prevention of symptoms at the dose of 30 mg/kg. The 50% effective dose (ED(50)) values for ASP2151 and VACV were 0.37 and 68 mg/kg, respectively, indicating that ASP2151 was 184-fold more potent than VACV. When ASP2151 was administered after the onset of symptoms, the disease course of genital herpes was suppressed more effectively than by VACV, with a significant reduction in disease score observed one day after starting ASP2151 at 30 mg/kg, whereas the therapeutic effect of VACV was only evident three days after treatment at the highest dose tested (300 mg/kg). This indicated that ASP2151 possesses a faster onset of action and wider therapeutic time window than VACV. Further, virus shedding from the genital mucosa was significantly reduced with ASP2151 at 10 and 30 mg/kg but not with VACV, even at 300 mg/kg. Taken together, our present findings demonstrated the superior potency and efficacy of ASP2151 against HSV.     

Deprotonation‐Induced Aromaticity Enhancement and New Conjugated Networks in meso‐Hexakis(pentafluorophenyl)[26]hexaphyrin

meso‐Hexakis(pentafluorophenyl)‐substituted neutral hexaphyrin with a 26π‐electronic circuit can be regarded as a real homolog of porphyrin with an 18π‐electronic circuit with respect to a quite flat molecular structure and strong aromaticity. We have investigated additional aromaticity enhancement of meso‐hexakis(pentafluorophenyl)[26]hexaphyrin(1.1.1.1.1.1) by deprotonation of the inner N? H groups in the macrocyclic molecular cavity to try to induce further structural planarization. Deprotonated mono‐ and dianions of [26]hexaphyrin display sharp B‐like bands, remarkably strong fluorescence, and long‐lived singlet and triplet excited‐states, which indicate enhanced aromaticity. Structural, spectroscopic, and computational studies have revealed that deprotonation induces structural deformations, which lead to a change in the main conjugated π‐electronic circuit and cause enhanced aromaticity.