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858 results on '"Okada, Keiji"'

7. Spin-dependent electron transfer dynamics in a platinum-complex–donor–acceptor triad studied by transient-absorption detected magnetic field effect.

Author

Miura, Tomoaki, Miyaji, Kio, Horikoshi, Takafumi, Suzuki, Shuichi, Kozaki, Masatoshi, Okada, Keiji, and Ikoma, Tadaaki

Subjects
MAGNETIC field effects, ELECTRON donors, CHARGE exchange, DYNAMICS, CELLULOSE acetate, LIGHT absorption
Abstract

For realization of efficient organic light-energy conversion systems, controlling the lifetime of photogenerated charge separated states in donor (D)–acceptor (A) molecules is of much importance; the spin dynamics is one of the important controlling factors. We previously reported that the covalently-linked 1,3-bis(2-pyridylimino)-isoindolate platinum (BPIPt)–dimethoxytriphenylamine (D)–naphthaldiimide (A) triad molecule (BPIPt–DA) exhibits a triplet-born long-lived charge separated state (BPIPt–D•+A•−), the lifetime of which is significantly increased from 4 µs to 10 µs by an applied magnetic field of 270 mT in room temperature tetrahydrofuran (THF). The purpose of the present study is to clarify detailed dynamics of spin-dependent generation and the decay of BPIPt–D+A−. For this purpose, we measured transient optical absorption (TA) and the TA-detected magnetic field effect (MFE) as functions of temperature and dispersion media. In THF at 183 K, MFE-detected transient spectra of the intermediate BPIPt•−–D•+A state are observed. We have successfully quantified the recombination loss at this state by a kinetic simulation of MFE without using any reference molecules. The lifetime of the final BPIPt–D•+A•− state in a cellulose acetate polymer matrix at room temperature is significantly prolonged to 20 µs at 0 mT and 96 µs at 250 mT compared to those in THF. From the comparison of temperature dependences of the two media, effects of molecular motions on the electronic coupling and the spin relaxation are discussed. [ABSTRACT FROM AUTHOR]

Published
2019
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22. Aurophilic Interactions in Multi‐Radical Species: Electronic‐Spin and Redox Properties of Bis‐ and Tris‐[(Nitronyl Nitroxide)‐Gold(I)] Complexes with Phosphine‐Ligand Scaffolds

Author

Kira, Sayaka, primary, Miyamae, Takayuki, additional, Yoshida, Kohei, additional, Kanzaki, Yuki, additional, Sugisaki, Kenji, additional, Shiomi, Daisuke, additional, Sato, Kazunobu, additional, Takui, Takeji, additional, Suzuki, Shuichi, additional, Kozaki, Masatoshi, additional, and Okada, Keiji, additional

Published
2021
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26. Inhibition of Ligand Binding Ability of Three Porphyrins by an Organic Effector

Author

Nishimura, Tomoaki, Sasaki, Yoshito, Tachi, Yoshimitsu, Suzuki, Shuichi, Okada, Keiji, Kozaki, Masatoshi, Nishimura, Tomoaki, Sasaki, Yoshito, Tachi, Yoshimitsu, Suzuki, Shuichi, Okada, Keiji, and Kozaki, Masatoshi

Abstract

A stimulus-responsive receptor 1 was designed and prepared to control the ligand-binding ability of three active sites, two zinc tetraphenylporphyrin units (P1) and one zinc diethynyldiphenylporphyrin unit (P2), with one effector molecule 2. Bulky hexarylbenzene units are incorporated as shielding panels in the middle of the flexible side arms of 1....

Published
2020

27. Condensed Phenoxazine Dimer and Its Radical Cation

Author

Miyamae, Takayuki, Haraguchi, Makoto, Tachi, Yoshimitsu, Suzuki, Shuichi, Kozaki, Masatoshi, Okada, Keiji, Miyamae, Takayuki, Haraguchi, Makoto, Tachi, Yoshimitsu, Suzuki, Shuichi, Kozaki, Masatoshi, and Okada, Keiji

Abstract

A condensed phenoxazine dimer was synthesized and characterized. X-ray crystallographic analysis of the dimer shows a double-butterfly structure, in which the nitrogen atoms are located above and below the molecular plane....

Published
2020

29. Influence of forest windbreaks on paddy field environments and rice growth in Sorachi, Hokkaido

Author

Sameshima, Ryoji, Ishiwata, Kousuke, Okada, Keiji, and Kutomi, Yuta

Subjects
Cool summer damage prevention effect, Wind reduction, 減風, Water temperature, 冷害防止効果, 水温, Yield of paddy rice, 水稲収量
Abstract

In paddy rice production areas in Hokkaido, forest windbreaks were established to improve environmental conditions and protect rice plants from damage during cool summer weather. We measured meteorological variables, water temperature and rice growth at four sites at distances of 3H, 5H, 10H and 17H (H is the windbreak height of 18 m) leeward from a forest windbreak that stretches east-southeast to west-northwest. The 17H site was a reference site where the windbreak had little infl uence. The following effects of the windbreak were observed in sites 3H, 5H and 10H. Wind speed was reduced when the wind direction was between the south and west, which was the most frequent wind directio in June and July in this area, including in cool summer years. Air temperature increased/decreased during the daytime/nighttime, respectively, but daily average air temperature was little changed. Daily mean water temperature increased in June but decreased in July. A possible reason of this was that higher water temperatures in June hastened leaf expansion resulting in a smaller amount of radiation being transmitted to water surface in July. Although plant height and radiation interception increased earlier, their maximum values showed little difference from the reference site. There was no significant difference in the yield among the sites. Although no damage from cool summers occurred in our study years, our results show the possible mechanisms by which windbreaks can reduce damage to rice from cool summer weather. Windbreaks did not warm air or water temperatures in the booting stage in middle to late July and offered little protection effect then. However, it is known that cool water temperatures before panicle initiation, corresponding to the June period, increases the susceptibility of panicles to low temperatures in the booting stage, causing sterility. Higher water temperatures in June due to windbreaks would, therefore, reduce sterility in cool summers.

Published
2018

30. Exchange interaction of 5,5'-(m-and p-phenylene)bis(10-phenyl-5,10-dihydrophenazine) dications and related analogues

Author

Terada, Eriko, Okamoto, Toshihiro, Kozaki, Masatoshi, Masaki, Miyuki Eiraku, Shiomi, Daisuke, Sato, Kazunobu, Takui, Takeji, and Okada, Keiji

Subjects
Heterocyclic compounds -- Chemical properties, Phenothiazine -- Chemical properties, Electron paramagnetic resonance spectroscopy -- Usage, Biological sciences, Chemistry
Abstract

The EPR spectra of dications at 123K in a butyronitrile matrix that showed the population of a tripled state are discussed. Theoretical analysis of the exchange interaction of the dications and the rented (m-and p-phenylene)bisphenothiazine dications at the perpendicular geometry are also provided.

Published
2005

40. Characterization of spirochetes isolated from ticks (Ixodes tanuki, Ixodes turdus, and Ixodes columnae) and comparison of the sequences with those of Borrelia burgdorferi sensu lato strains

Author

Fukunaga, Masahito, Hamase, Akiko, Okada, Keiji, Inoue, Hirofumi, Tsuruta, Yasuto, Miyamoto, Kenji, and Nakao, Minoru

Subjects
Borrelia -- Genetic aspects, Ribosomal RNA -- Analysis, Amino acid sequence -- Observations, Biological sciences
Abstract

Phylogenetic analysis of the 16S rRNA of the spirochetes isolated from Ixodes tanuki, I. turdus and I. columnae shows that the spirochetes are genetically distinct from the other known Borrelia strains. The isolates from Ixodes tanuki, I. turdus and I. columnae have been designated as Hk501, Ya501 and Am501 respectively. The isolates have their own tick vectors with enzootic cycles, and are different from each other and the Borrelia species causing Lyme disease. A comparison of the 16S rRNA indicates that Am501 is related to Hk501.

Published
1996

41. Synthesis and Properties of Nitrogen-Containing Pyrenes

Author

Omura, Yuta, Tachi, Yoshimitsu, Okada, Keiji, Kozaki, Masatoshi, Omura, Yuta, Tachi, Yoshimitsu, Okada, Keiji, and Kozaki, Masatoshi

Abstract

We developed a short-step synthesis of 2,4,10-triazapyrenes involving two sequential C–H substitutions: Pd-catalyzed cross-coupling reactions via C–H arylation followed by intramolecular Cucatalyzed C–H functionalization. This method was successfully applied to the preparation of 4,10-diaza-, 1,4,10-triaza-, and 1,3,4,10-tetraazapyrenes....

Published
2019

44. Pathological characteristics of thyroid glands from Japanese Black Cattle living in the restricted area of the Fukushima Daiichi Nuclear Power Plant accident

Author

Sasaki, Jun, primary, Uehara, Megumi, additional, Sato, Itaru, additional, Satoh, Hiroshi, additional, Deguchi, Yoshitaka, additional, Chida, Hiroyuki, additional, Natsuhori, Masahiro, additional, Murata, Takahisa, additional, Ochiai, Kenji, additional, Otani, Kumiko, additional, Okada, Keiji, additional, and Ito, Nobuhiko, additional

Published
2019
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