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449 results on '"Shimizu, Katsuya"'

159. Synthesis, X-Ray Crystal Structures and Antimicrobial Activities of Transition-Metal Complexes with Hinokitiol Ligand

Author

Nomiya, Kenji, Shimizu, Katsuya, and Kimura, Takao

Subjects
temperature-dependent magnetic susceptibilities, X-ray powder diffraction, copper(II) complex with hinokitiol, antimicrobial activities, crystal and molecular structures, polymorphism
Abstract

There exist at least three different polymorphs in the copper(II) complex [Cu(hino)_2] with a hinokitiol ligand (Hhino; 4-isopropyltropolone). In addition to deep-green plate crystals la and deep-green rod crystals Ib, whose crystal structures have been recently reported, novel green needle crystals Ic of [Cu(hino)_2] were found, the crystal structure of which was here determined by single-crystal X-ray analysis. Since only one crystal structure has been reported for the copper(II) complex [Cu(trop)_2] with a tropolone ligand (Htrop), the polymorphism found in the crystals of [Cu(hino)_2] would be due to the presence of the isopropyl group on the tropolone ring. The synthetic conditions giving the three polymorphs in good yields were found and the crystals were characterized with elemental analysis, FT-IR, TG/DTA and X-ray powder diffraction (XPD) measurements, as well as solution molecular weight measurements for la. The solid-state magnetic behaviors or the temperature-dependent magnetic susceptibilities were measured with Supercon-ductivity Quantum Interference Devices (SQUID): la showed a weak ferromagnetic interaction, Ib showed a paramagnetic nature with S = 1/2, while Ic showed a weak antiferro-magnetic interaction. The antimicrobial activities for selected bacteria, yeasts and molds were also measured in the water-suspension system' la and Ib showed no activity, while 1c showed modest activities, and these activities were compared with those of the neutral Hino and the anionic hino ligands.

Published
2005

185. Pressure-Induced Metallization of Yttrium Trihydride, YH3

Author

Chi Zhenhua, Shimizu Katsuya, Matsuoka Takahiro, Kagayama Tomoko, and Nguyen Huyen

Subjects
Superconductivity, Phase transition, Materials science, High-temperature superconductivity, Hydrogen, Transition temperature, Analytical chemistry, General Physics and Astronomy, chemistry.chemical_element, Yttrium, law.invention, chemistry, Electrical resistance and conductance, Electrical resistivity and conductivity, law
Abstract

As is well established, there occurs x -dependent metal-insulator transition in yttrium hydride YH x upon additional hydrogen loading. Recently, a theoretical prediction indicated the occurrence of relatively high temperature superconductivity with the transition temperature, T c of 40 K at 17.7 GPa in the fcc phase in stoichiometric YH 3 . We have succeeded in synthesis the insulating transparent YH 3 samples by the hydrogenation from pure yttrium metal by surrounded fluid H 2 at high pressure. Measurement of the electrical resistivity at high pressure and low temperature demonstrated an electronic phase transition from insulator to metal at around 70 GPa in the fcc phase.

Published
2012

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