Search

Your search keyword '"Tashiro, Shohei"' showing total 247 results
Start Over Author "Tashiro, Shohei"
247 results on '"Tashiro, Shohei"'

5. Intricate Low-Symmetry Ag6L4Capsules Formed by Anion-Templated Self-Assembly of the Stereoisomers of an Unsymmetric Ligand

Author

Tashiro, Shohei, Yamada, Yoshihiko, Kringe, Lea Antonia, Okajima, Yoshiki, and Shionoya, Mitsuhiko

Abstract

Metal–organic cages and capsules exhibit space-specific functions based on their discrete hollow structures. To acquire enzyme-like asymmetric or intricate structures, they have been modified by desymmetrization with two or more different ligands. There is a need to establish new strategies that can desymmetrize structures in a simple way using only one type of ligand, which is different from the mixed-ligand approach. In this study, a strategy was developed to form interconvertible stereoisomers using the unsymmetric macrocyclic ligand benzimidazole[3]arene. Single-crystal X-ray diffraction analysis revealed that the isomers assembled with silver tetrafluoroborate afforded a conformationally heteroleptic Ag6L4capsule with an intricate structure. The six Ag ions in the capsule were desymmetrized, resulting in significantly different coordination geometries. Remarkably, the capsule encapsulates a single tetrafluoroborate anion via multipoint C–H···F–B hydrogen bonds in both the solid and solution states, suggesting that anions of appropriate size and shape can act as a template for the capsule formation. These results demonstrate that the use of isomerizable and unsymmetric ligands is the effectiveness of constructing highly dissymmetric supramolecular structures from a single ligand.

Published
2024
Full Text
View/download PDF

16. Materials breaking the rules: general discussion

Author

Addicoat, Matthew, primary, Bennett, Thomas D., additional, Brammer, Lee, additional, Craig, Gavin, additional, Das, Chinmoy, additional, Dichtel, William, additional, Doan, Huan, additional, Evans, Austin M., additional, Evans, Jack, additional, Goodwin, Andrew, additional, Horike, Satoshi, additional, Jiang, Jianwen, additional, Kaskel, Stefan, additional, Kato, Masako, additional, Kitagawa, Susumu, additional, Kobayashi, Atsushi, additional, Krause, Simon, additional, Lavenn, Christophe, additional, Lee, Jet-Sing M., additional, Phillips, Anthony E., additional, Roseveare, Thomas M., additional, Schmid, Rochus, additional, Shivanna, Mohana, additional, Sirbu, Dumitru, additional, Tashiro, Shohei, additional, Ting, Valeska P., additional, van der Veen, Monique A., additional, Wilson, Benjamin, additional, and Zhao, Pu, additional

Published
2021
Full Text
View/download PDF

20. Shape-selective one-step synthesis of branched gold nanoparticles on the crystal surface of redox-active PdII-macrocycles.

Author

Yamashita, Yutaro, Tashiro, Shohei, Ishii, Yoshiki, Uchihashi, Takayuki, Matsushita, Nobuyuki, Kubota, Ryou, and Shionoya, Mitsuhiko

Subjects
*GOLD nanoparticles, *CRYSTAL surfaces, *MOLECULAR crystals, *METAL-organic frameworks, *CRYSTAL growth, *GRAPHENE oxide
Abstract

The synthesis of branched gold nanoparticles (AuNPs) with shape- and size-specific optical properties requires effective control of the particle formation mechanism using appropriate reducing agents and protective agents that prevent particle aggregation in solution. In this context, the heterogeneous synthesis of AuNPs using solid surfaces of graphene oxides and metal–organic frameworks has attracted much attention. These materials are characterized by their ability to immobilize and stabilize the particles grown on the surface without the need for additional protective agents. However, the shape- and size-selective synthesis of AuNPs using solid surfaces remains challenging. Herein, we report the shape-selective one-step synthesis of monodisperse branched AuNPs using a metal–macrocycle framework (MMF), a porous molecular crystal of Pd II3 -tris(phenylenediamine) macrocycle. Konpeito-Shaped branched AuNPs with uniform size were obtained on the surface of MMF by mixing HAuCl4·4H2O, L -ascorbic acid and MMF microcrystals. Spectroscopic and microscopic observations confirmed that MMF promoted the reduction of gold by its reductive activity as well as acted as a solid support to electrostatically immobilize the pseudo-seed particles for further growth on the crystal surface. In addition, the MMF also served as a substrate for in situ high-speed AFM imaging due to the effective immobilization of AuNPs on the surface, allowing direct visualization of the particle growth. Since the chemical structural features of MMF allow the growth of branched AuNPs via pseudo-seeding, this approach would provide new synthetic methods for obtaining a variety of gold nanostructures. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

25. Mechanistic Studies on Photoinduced Catalytic Olefin Migration Reactions at the Pd(II) Centers of a Porous Crystal, Metal‐Macrocycle Framework.

Author

Yonezawa, Hirotaka, Shiraogawa, Takafumi, Han, Mengying, Tashiro, Shohei, Ehara, Masahiro, and Shionoya, Mitsuhiko

Subjects
MOLECULAR crystals, ALKENES, METAL catalysts, HETEROGENEOUS catalysts, CRYSTALS, PLASMODESMATA, POROUS metals
Abstract

Porous crystals with well‐defined active metal centers on the pore surface have high potential as heterogeneous metal catalysts. We have recently demonstrated that a porous molecular crystal, metal‐macrocycle framework (MMF), catalyzes olefin migration reactions by photoactivation of its PdIICl2 moieties exposed on the crystalline channel surface. Herein we report a mechanistic study of the photoinduced olefin migration reactions at the PdII active centers of MMF. Several experiments, including a deuterium scrambling study, revealed that olefin migration is catalyzed via an alkyl mechanism by in situ generated Pd−H species on the channel surface during photoirradiation. This proposed mechanism was further supported by DFT and ONIOM calculations. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

29. Light-triggered crystallization of a molecular host-guest complex

Author

Clever, Guido H., Tashiro, Shohei, and Shionoya, Mitsuhiko

Subjects
Azo compounds -- Chemical properties, Benzene -- Structure, Benzene -- Chemical properties, Organometallic compounds -- Structure, Organometallic compounds -- Chemical properties, Palladium -- Chemical properties, Polyethylene glycol -- Chemical properties, X-ray crystallography -- Usage, Chemistry
Abstract

Highly soluble, PEGylated cage derivative is used for showing the full reversibility of the light-driven encapsulation/release process. X-ray structure analysis has confirmed the guest molecules having left the cavity of the host and on the contrary joining the cages into a polymeric material by binding to their Pd(II) centers from outside.

Published
2010

30. Inducing [alpha]-helices in short oligopeptides through binding by an artificial hydrophobic cavity

Author

Dolain, Christel, Hatakeyama, Yoshiyuki, Sawada, Tomohisa, Tashiro, Shohei, and Fujita, Makoto

Subjects
Hydrophobic effect -- Analysis, Peptides -- Structure, Peptides -- Chemical properties, Chemistry
Abstract

Short peptides are induced into [alpha]-helix conformations in water through enclathration to an artificial hydrophobic cavity. Peptides with two aromatic residues have displayed high affinity for the host and these intermolecular aromatic-aromatic interactions have driven the helical folding of short peptides.

Published
2010

31. One-pot, template syntheses of a new class of metallomacrocycles with a tetraoxime cyclic skeleton

Author

Tashiro, Shohei, Minoda, Ai, Yamada, Mihoko, and Shionoya, Mitsuhiko

Subjects
Ethers -- Research, Macrocycles -- Chemical properties, Macrocycles -- Structure, Palladium catalysts -- Chemical properties, Palladium catalysts -- Structure, Porphyrins -- Research, Transition metal compounds -- Chemical properties, Transition metal compounds -- Structure, Chemistry
Published
2009

32. Soft metal-mediated base pairing with novel synthetic nucleosides possessing an O,S-donor ligand

Author

Takezawa, Yusuke, Tanaka, Kentaro, Yori, Maiko, Tashiro, Shohei, Shiro, Motoo, and Shionoya, Mitsuhiko

Subjects
Palladium -- Chemical properties, Palladium -- Atomic properties, Platinum compounds -- Chemical properties, Platinum compounds -- Atomic properties, Nucleosides -- Research, Biological sciences, Chemistry
Abstract

The syntheses of novel nucleosides, mercaptopyridone-bearing nucleoside (M) and hydroxypyridinethione-bearing nucleoside (S), possessing O,S-donor atoms as a bidentate ligand, are described. These nucleosides have efficiently formed metal-mediated base pairs with soft transition metal ions such as [Pd.sup.2+] and [Pt.sup.2+].

Published
2008

33. Ni(II)-mediated self-assembly of artificial [beta]-dipeptides forming a macrocyclic tetranuclear complex with interior spaces for in-line molecular arrangement

Author

Miyake, Ryosuke, Tashiro, Shohei, Shiro, Motoo, Tanaka, Kentaro, and Shionoya, Mitsuhiko

Subjects
Nickel -- Chemical properties, Organometallic compounds -- Chemical properties, Organometallic compounds -- Structure, Peptides -- Chemical properties, Chemistry
Abstract

The synthesis of a macrocyclic tetranuclear Ni(II) complex of artificial [beta]-dipeptides with two sets of tridentate ligands is described. The cyclic twisted-boat structure of the complex provides well-defined isolated spaces for in-line molecular arrangement of water and anion molecules.

Published
2008

34. Folding of an Ala-Ala-Ala tripeptide into a beta-turn via hydrophobic encapsulation

Author

Tashiro, Shohei, Kobayashi, Masahide, and Fujita, Makoto

Subjects
Hydrophobic effect -- Research, Molecular dynamics -- Analysis, Nuclear magnetic resonance spectroscopy -- Analysis, Polypeptides -- Structure, Polypeptides -- Properties, Polypeptides -- Spectra, Chemistry
Abstract

Study is conducted to show that even a three-residue peptide fragment, Ac-Ala-Ala-Ala-NH2 can be folded into a beta-[turn.sup.3] through encapsulation by a porphyrin-assembled synthetic host. It is suggested that peptide recognition within the large cavity of self-assembled [cages.sup.11,12] is a powerful method to produce the secondary structures of peptides even if the peptide fragment is considerably short.

Published
2006

36. Sequence-selective recognition of peptides within the single binding pocket of a self-assembled coordination cage

Author

Tashiro, Shohei, Fujita, Makoto, Tominaga, Masahide, Kawano, Masaki, Therrien, Bruno, and Ozeki, Tomoji

Subjects
Nuclear magnetic resonance -- Research, Peptides -- Spectra, Peptides -- Research, Crystals -- Structure, Crystals -- Research, Chemistry
Abstract

Sequence-selective recognition of peptides is expected to be an essential process for the site-specific recognition of protein surfaces, which leads to the control of protein functions and to the understanding of biological events at protein surfaces such as protein-protein or protein-oligopeptide interactions. The study aiming at the pinpoint recognition of protein surfaces by the self-assembled hollow receptors is presented.

Published
2005

37. Multifunctional Octamethyltetrasila[2.2]cyclophanes: Conformational Variations, Circularly Polarized Luminescence, and Organic Electroluminescence

Author

Shimada, Masaki, primary, Yamanoi, Yoshinori, additional, Ohto, Tatsuhiko, additional, Pham, Song-Toan, additional, Yamada, Ryo, additional, Tada, Hirokazu, additional, Omoto, Kenichiro, additional, Tashiro, Shohei, additional, Shionoya, Mitsuhiko, additional, Hattori, Mineyuki, additional, Jimura, Keiko, additional, Hayashi, Shigenobu, additional, Koike, Hikaru, additional, Iwamura, Munetaka, additional, Nozaki, Koichi, additional, and Nishihara, Hiroshi, additional

Published
2017
Full Text
View/download PDF

42. Multifunctional Octamethyltetrasila[2.2]cyclophanes: Conformational Variations, Circularly Polarized Luminescence, and Organic Electroluminescence

Author

Shimada, Masaki, Yamanoi, Yoshinori, Ohto, Tatsuhiko, Pham, Song-Toan, Yamada, Ryo, Tada, Hirokazu, Omoto, Kenichiro, Tashiro, Shohei, Shionoya, Mitsuhiko, Hattori, Mineyuki, Jimura, Keiko, Hayashi, Shigenobu, Koike, Hikaru, Iwamura, Munetaka, Nozaki, Koichi, and Nishihara, Hiroshi

Abstract

Both symmetrical and unsymmetrical cyclophanes containing disilane units, tetrasila[2.2]cyclophanes 1–9, were synthesized. The synand anticonformations and the kinetics of inversion between two anti-isomers were investigated by X-ray diffraction and variable-temperature NMR analysis, respectively. The flipping motion of two aromatic rings was affected by the bulkiness of the aromatic moiety (1vs 6), the phase (solid vs solution), and the inclusion by host molecules (1vs 1⊂[Ag2L]2+). The photophysical, electrochemical, and structural properties of the compounds were thoroughly investigated. Unsymmetrical tetrasila[2.2]cyclophanes 5–8displayed blue–green emission arising from intramolecular charge transfer. Compound 6emitted a brilliant green light in the solid state under 365 nm irradiation and showed a higher fluorescence quantum yield in the solid state (Φ = 0.49) than in solution (Φ = 0.05). We also obtained planar chiral tetrasila[2.2]cyclophane 9, which showed interesting chiroptical properties, such as a circularly polarized luminescence (CPL) with a dissymmetry factor of |glum| = ca. 2 × 10–3at 500 nm. Moreover, an organic green light-emitting diode that showed a maximum external quantum efficiency (ηext) of ca. 0.4% was fabricated by doping 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl with 6.

Published
2024
Full Text
View/download PDF

47. A 3.5-nm coordination nanotube

Author

Yamaguchi, Takumi, Tashiro, Shohei, Tominaga, Masahide, Kawano, Masaki, Ozeki, Tomoji, and Fujita, Makoto

Subjects
Nuclear magnetic resonance spectroscopy -- Usage, Nanotubes -- Chemical properties, Chemistry
Abstract

The self-assembly of a 3.5-nm coordination nanotube is described. The characterization of nanotubes is studied by NMR spectroscopy.

Published
2004

Catalog

Books, media, physical & digital resources
See catalog results