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26 results on '"Ohba, Tadashi"'

1. Shape-Memory Platinum(II) Complexes : Intelligent Vapor-History Sensor with ON-OFF Switching Function

Author

Shigeta, Yasuhiro, Kobayashi, Atsushi, Ohba, Tadashi, Yoshida, Masaki, Matsumoto, Takeshi, Chang, Ho-Chol, and Kato, Masako

Subjects
shape-memory effects, vapochromism, chromophores, platinum, mechanochromism
Abstract

A novel platinum(II)-diimine complex, [Pt(CN)(2)(H(2)dcphen)] (1; H(2)dcphen=4,7-dicarboxy-1,10- phenanthroline), was synthesized and its vapochromic shape-memory behavior was evaluated. The as-synthesized amorphous purple solid, [Pt(CN)(2)(H(2)dcphen)]2H(2)O (1P), exhibited vapochromic behavior in the presence of alcoholic vapors through transformation to a red, crystalline, porous, vapor-adsorbed form, 1Rvapor. The obtained 1Rvapor complex released the adsorbed vapors upon heating without collapse of the porous structure. The vaporfree, porous 1Ropen could detect water or n-hexane vapor, although these vapors could not induce 1P-to-1Rvapor transformation, and 1Ropen could easily be converted to the initial 1P by manual grinding. These results indicate that 1 is a new shape-memory material that functions through formation and collapse of the porous framework with an emission change upon vapor-adsorption and grinding; this enables it to exhibit vapor history and ON-OFF switching sensing functions.

Published
2016

3. Dynamics of Photoelectrons and Structural Changes of Tungsten Trioxide Observed by Femtosecond Transient XAFS

Author

Uemura, Yohei, Kido, Daiki, Wakisaka, Yuki, Uehara, Hiromitsu, Ohba, Tadashi, Niwa, Yasuhiro, Nozawa, Shunsuke, Sato, Tokushi, Ichiyanagi, Kohei, Fukaya, Ryo, Adachi, Shin-ichi, Katayama, Tetsuo, Togashi, Tadashi, Owada, Sigeki, Ogawa, Kanade, Yabashi, Makina, Hatada, Keisuke, 1000030359484, Takakusagi, Satoru, Yokoyama, Toshihiko, 1000080176924, Ohtani, Bunsho, 1000060175164, Asakura, Kiyotaka, Uemura, Yohei, Kido, Daiki, Wakisaka, Yuki, Uehara, Hiromitsu, Ohba, Tadashi, Niwa, Yasuhiro, Nozawa, Shunsuke, Sato, Tokushi, Ichiyanagi, Kohei, Fukaya, Ryo, Adachi, Shin-ichi, Katayama, Tetsuo, Togashi, Tadashi, Owada, Sigeki, Ogawa, Kanade, Yabashi, Makina, Hatada, Keisuke, 1000030359484, Takakusagi, Satoru, Yokoyama, Toshihiko, 1000080176924, Ohtani, Bunsho, 1000060175164, and Asakura, Kiyotaka

Abstract

The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time-resolved X-ray absorption fine structure (XAFS) spectroscopy using an X-ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of photoexcitation.

Published
2016

6. Deprotonation of a dinuclear copper complex of 3,5-diamino-1,2,4-triazole for high oxygen reduction activity

Author

Kato, Masaru, Kimijima, Ken'ichi, Shibata, Mari, Notsu, Hideo, Ogino, Kazuya, Inokuma, Kiyoshi, Ohta, Narumi, Uehara, Hiromitsu, Uemura, Yohei, Oyaizu, Nobuhisa, Ohba, Tadashi, Takakusagi, Satoru, Asakura, Kiyotaka, Yagi, Ichizo, Kato, Masaru, Kimijima, Ken'ichi, Shibata, Mari, Notsu, Hideo, Ogino, Kazuya, Inokuma, Kiyoshi, Ohta, Narumi, Uehara, Hiromitsu, Uemura, Yohei, Oyaizu, Nobuhisa, Ohba, Tadashi, Takakusagi, Satoru, Asakura, Kiyotaka, and Yagi, Ichizo

Abstract

A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.

Published
2015

7. Deprotonation of a dinuclear copper complex of 3,5-diamino-1,2,4-triazole for high oxygen reduction activity

Author

1000070709633, Kato, Masaru, Kimijima, Ken'ichi, Shibata, Mari, Notsu, Hideo, Ogino, Kazuya, Inokuma, Kiyoshi, Ohta, Narumi, Uehara, Hiromitsu, Uemura, Yohei, Oyaizu, Nobuhisa, Ohba, Tadashi, Takakusagi, Satoru, Asakura, Kiyotaka, 1000040292776, Yagi, Ichizo, 1000070709633, Kato, Masaru, Kimijima, Ken'ichi, Shibata, Mari, Notsu, Hideo, Ogino, Kazuya, Inokuma, Kiyoshi, Ohta, Narumi, Uehara, Hiromitsu, Uemura, Yohei, Oyaizu, Nobuhisa, Ohba, Tadashi, Takakusagi, Satoru, Asakura, Kiyotaka, 1000040292776, and Yagi, Ichizo

Abstract

A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.

Published
2015

8. Dynamics of Photoelectrons and Structural Changes of Tungsten Trioxide Observed by Femtosecond Transient XAFS

Author

Uemura, Yohei, primary, Kido, Daiki, additional, Wakisaka, Yuki, additional, Uehara, Hiromitsu, additional, Ohba, Tadashi, additional, Niwa, Yasuhiro, additional, Nozawa, Shunsuke, additional, Sato, Tokushi, additional, Ichiyanagi, Kohei, additional, Fukaya, Ryo, additional, Adachi, Shin‐ichi, additional, Katayama, Tetsuo, additional, Togashi, Tadashi, additional, Owada, Sigeki, additional, Ogawa, Kanade, additional, Yabashi, Makina, additional, Hatada, Keisuke, additional, Takakusagi, Satoru, additional, Yokoyama, Toshihiko, additional, Ohtani, Bunsho, additional, and Asakura, Kiyotaka, additional

Published
2015
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14. Deprotonation of a dinuclear copper complex of 3,5-diamino-1,2,4-triazole for high oxygen reduction activity

Author

Kato, Masaru, primary, Kimijima, Ken'ichi, additional, Shibata, Mari, additional, Notsu, Hideo, additional, Ogino, Kazuya, additional, Inokuma, Kiyoshi, additional, Ohta, Narumi, additional, Uehara, Hiromitsu, additional, Uemura, Yohei, additional, Oyaizu, Nobuhisa, additional, Ohba, Tadashi, additional, Takakusagi, Satoru, additional, Asakura, Kiyotaka, additional, and Yagi, Ichizo, additional

Published
2015
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19. Vapour and mechanically induced chromic behaviour of platinum complexes with a dimer-of-dimer motif and the effects of heterometal ions

Author

Ohba, Tadashi, Kobayashi, Atsushi, Chang, Ho-Chol, 1000080214401, Kato, Masako, Ohba, Tadashi, Kobayashi, Atsushi, Chang, Ho-Chol, 1000080214401, and Kato, Masako

Abstract

Heterodinuclear complexes, syn-[MPt(mu-pyt)(2)(bpy)(2)](n+) (syn-[MPt], M = Pd2+, Au3+, Hpyt = pyridine-2-thiol, bpy = 2,2'-bipyridine), were synthesized as a selective geometrical isomer by stepwise complexation. X-ray analyses of the hexafluorophosphate salts of these complexes proved their dinuclear structures with short M...Pt distances (2.9084(4) angstrom for syn-[PdPt] and 2.9071(4) angstrom for syn-[AuPt]), similar to the homodinuclear complex (2.9292(2) angstrom for syn-[PtPt]). In the syn-[PdPt] crystal, two dinuclear motifs are arranged closely in a head-to-head manner with a short Pt...Pt distance (3.3757(3) angstrom), forming a dimer-of-dimer structure as in the case of syn-[PtPt], whereas the corresponding crystal of syn-[AuPt] has a discrete arrangement of the dinuclear motifs. By the isomerisation of syn-[PdPt], anti-[PdPt] with equivalent environments of the Pd2+ and Pt2+ ions was also obtained successfully. Syn-[PdPt](PF6)(2) exhibits vapochromic behaviour based on the absorption/desorption of CH3CN vapour, similar to that observed for syn-[PtPt](PF6)(2). The reversible structural transformations induced by the uptake and release of CH3CN molecules were investigated by powder and single-crystal X-ray diffraction studies. These revealed that the vapochromic behaviour was based on the interconversion between two phases, the dimer-of-dimer structure with a short Pt. Pt distance and a p-p stacked arrangement with no Pt. Pt intermolecular interaction. The introduction of the heterometal ions enabled control of the colour region: orange. red for syn-[PdPt] vs. light red. dark red for syn-[PtPt], reflecting the weaker metal-metal interaction between Pd2+ and Pt2+ ions in the dinuclear motif. In addition, these complexes were found to exhibit mechanochromic behaviour based on a crystal-to-amorphous transformation upon grinding, and the reconstruction of the crystal structures by vapour sorption.

Published
2013

24. Shape-Memory Platinum(II) Complexes: Intelligent Vapor-History Sensor with ON-OFF Switching Function.

Author

Shigeta Y, Kobayashi A, Ohba T, Yoshida M, Matsumoto T, Chang HC, and Kato M

Abstract

A novel platinum(II)-diimine complex, [Pt(CN)2 (H2 dcphen)] (1; H2 dcphen=4,7-dicarboxy-1,10- phenanthroline), was synthesized and its vapochromic shape-memory behavior was evaluated. The as-synthesized amorphous purple solid, [Pt(CN)2 (H2 dcphen)]⋅2 H2 O (1 P), exhibited vapochromic behavior in the presence of alcoholic vapors through transformation to a red, crystalline, porous, vapor-adsorbed form, 1 R⊃vapor. The obtained 1 R⊃vapor complex released the adsorbed vapors upon heating without collapse of the porous structure. The vaporfree, porous 1 R⊃open could detect water or n-hexane vapor, although these vapors could not induce 1 P-to-1 R⊃vapor transformation, and 1 R⊃open could easily be converted to the initial 1 P by manual grinding. These results indicate that 1 is a new shape-memory material that functions through formation and collapse of the porous framework with an emission change upon vapor-adsorption and grinding; this enables it to exhibit vapor history and ON-OFF switching sensing functions., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2016
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25. Dynamics of Photoelectrons and Structural Changes of Tungsten Trioxide Observed by Femtosecond Transient XAFS.

Author

Uemura Y, Kido D, Wakisaka Y, Uehara H, Ohba T, Niwa Y, Nozawa S, Sato T, Ichiyanagi K, Fukaya R, Adachi S, Katayama T, Togashi T, Owada S, Ogawa K, Yabashi M, Hatada K, Takakusagi S, Yokoyama T, Ohtani B, and Asakura K

Abstract

The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time-resolved X-ray absorption fine structure (XAFS) spectroscopy using an X-ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of photoexcitation., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2016
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26. Ln-Co-based rock-salt-type porous coordination polymers: vapor response controlled by changing the lanthanide ion.

Author

Kobayashi A, Suzuki Y, Ohba T, Noro S, Chang HC, and Kato M

Subjects
Adsorption, Crystallography, X-Ray, Ions chemistry, Models, Molecular, Organometallic Compounds chemistry, Particle Size, Porosity, Surface Properties, Cobalt chemistry, Lanthanoid Series Elements chemistry, Organometallic Compounds chemical synthesis, Polymers chemistry
Abstract

We synthesized new porous coordination polymers (PCPs) {Ln(III)[Co(III)(dcbpy)(3)]·nH(2)O} (Ln = La(3+), Nd(3+), Gd(3+); H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and characterized them by X-ray diffraction and vapor-adsorption measurements. These three Ln-Co-based PCPs have similar rock-salt types and highly symmetrical porous structure and show a reversible structural collapse-regeneration accompanied by water-vapor desorption-adsorption. Similar structural regeneration was also observed for the Gd-Co PCP upon exposure to MeOH and CH(3)CN vapors, whereas the remaining two PCPs barely responded to organic vapors.

Published
2011
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