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1,662 results on '"Shinokubo, Hiroshi"'

51. Synthesis and electron-transport properties of a stable antiaromatic NiII norcorrole with the smallest meso-substituent

Author

Ukai, Shusaku, Koo, Yun Hee, Fukui, Norihito, Seki, Shu, and Shinokubo, Hiroshi

Abstract

meso-Dimethylnorcorrole Ni^II complex exhibited enough stability under ambient conditions despite the distinct antiaromaticity. The small methyl substituents realized a dense and long-range π-stacking in its solid state, which resulted in the superior electron-transporting ability to previously reported Ni^II norcorroles.

Published
2020

59. d-Mannose-appended 5,15-diazaporphyrin for photodynamic therapy

Author

Ali, Lamiaa M. A., primary, Miyagawa, Kazuya, additional, Fukui, Norihito, additional, Onofre, Mélanie, additional, El Cheikh, Khaled, additional, Morère, Alain, additional, Clément, Sébastien, additional, Gary-Bobo, Magali, additional, Richeter, Sébastien, additional, and Shinokubo, Hiroshi, additional

Published
2022
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69. Ni(II) 10-Boracorrole: An Antiaromatic Porphyrinoid Containing a Boron Atom at the meso-Position

Author

Omori, Hiroto and Shinokubo, Hiroshi

Abstract

A Ni(II) 10-boracorrole (2) was obtained from the transmetalation of the corresponding 10-silacorrole with BBr3. The antiaromaticity of 2 was examined by 1H NMR spectroscopy and theoretical calculations. The antiaromatic character of 2 is reflected in a very narrow HOMO–LUMO gap that results in weak and broad absorption bands in the NIR region up to 1800 nm. Furthermore, titration experiments revealed a high Lewis acidity of 2 toward pyridines. Theoretical calculations on 2 indicated the presence of p−π^* conjugation, which significantly stabilizes the energy level of its LUMO., ファイル公開：2020-08-12

Published
2019

70. Synthesis of meso-Alkyl-Substituted Norcorrole–Ni^II Complexes and Conversion to 5-Oxaporphyrins (2.0.1.0)

Author

Liu, Si‐Yu, Tanaka, Hiroko, Nozawa, Ryo, Fukui, Norihito, and Shinokubo, Hiroshi

Subjects
carbohydrates (lipids), fungi, polycyclic compounds
Abstract

The synthesis of antiaromatic Ni^II–norcorroles having primary, secondary, and tertiary alkyl groups at the reactive meso‐positions was attempted. Reductive coupling of a Ni^II–dipyrrin precursor provided Ni^II–meso‐dihexylnorcorrole, which underwent substantial degradation on silica gel. Introduction of tert‐butyl groups was unsuccessful due to the difficult preparation of the corresponding dipyrrin precursor. Meanwhile, Ni^II–norcorroles with isopropyl and cyclohexyl groups were isolated as stable molecules under ambient conditions. Furthermore, we found that oxidation of Ni^II–meso‐dialkylnorcorroles with hydrogen peroxide in the presence of sodium carbonate gave Ni^II–5‐oxaporphyrins(2.0.1.0). In contrast, oxidation of Ni^II–meso‐dimesitylnorcorrole under the same reaction conditions gave 10‐oxaporphyrin(1.1.1.0). The contrasting reactivity can be attributed to the steric congestion around the meso‐positions., ファイル公開：2020-06-07

Published
2019

78. Site-selective halogenation on meso-mesityl substituents of 10,20-dimesityl-5,15-diazaporphyrins with an AuX3/AgOTf combination

Author

Longevial, Jean-François, Miyagawa, Kazuya, Shinokubo, Hiroshi, Longevial, Jean-François, Miyagawa, Kazuya, and Shinokubo, Hiroshi

Abstract

We have developed site-selective bromination on the mesityl substituents of 10,20-dimesityl-5,15-diazaporphyrins. Treatment of 10,20-dimesityl-5,15-diazaporphyrin and its nickel(II) complex with a combination of AuBr3/AgOTf induced selective bromination on the mesityl groups. These brominated products can be employed for late-stage modification of the aryl substituents.

Published
2021

79. Stepwise N‐Methylation of Ruthenium and Cobalt 5,15‐Diazaporphyrins: Post‐Functionalization of Porphyrinoid Catalysts.

Author

Nishijo, Mayu, Mori, Shiho, Nishimura, Tsubasa, Shinokubo, Hiroshi, and Miyake, Yoshihiro

Subjects
RUTHENIUM, RUTHENIUM catalysts, LEWIS acidity, CATALYSTS, CATALYTIC activity, ELECTRONIC structure
Abstract

Post‐functionalization of porphyrinoid catalysts provides a powerful tool for fine‐tuning their electronic structure. We have succeeded in the stepwise methylation of the peripheral nitrogen atoms in ruthenium and cobalt 5,15‐diazaporphyrins. The axial coordination of an anion to the metal center accelerates the second methylation through charge neutralization. N‐Methylation of the diazaporphyrin complexes effectively controls their electron deficiency, Lewis acidity, and catalytic activity. [ABSTRACT FROM AUTHOR]

Published
2022
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80. Protonation‐Induced Antiaromaticity in Octaaza[8]circulenes: Cyclooctatetraene Scaffolds Constrained with Four Amidine Moieties.

Author

Akahori, Shuhei, Kaga, Atsushi, Kim, Jinseok, Yorimitsu, Hideki, Kim, Dongho, Shinokubo, Hiroshi, and Miyake, Yoshihiro

Subjects
ORGANIC chemistry, MOIETIES (Chemistry), PROTON transfer reactions, ANTIAROMATICITY, AMIDINES, X-ray diffraction, PYRIDINE
Abstract

The switching of cyclic π‐conjugation pathways using external stimuli is an attractive research topic in the field of organic chemistry. Here, we synthesized C4h‐symmetric octaaza[8]circulenes with four peripherally arranged amidine moieties that exhibit enhanced antiaromaticity upon protonation. Titration experiments with methanesulfonic acid revealed the formation of the tetraprotonated forms of the octaaza[8]circulenes in solution. Single‐crystal X‐ray diffraction analyses and theoretical calculations indicated that the contribution of the 8π antiaromatic character of the octaaza[8]circulenes is enhanced by the delocalization of charge through the protonation of the pyridine rings. [ABSTRACT FROM AUTHOR]

Published
2022
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85. Indeno[1,2,3,4-pqra]Perylene : A Medium-Sized Aromatic Hydrocarbon Exhibiting Full-Range Visible-Light Absorption

Author

Kato, Masaki, Fukui, Norihito, and Shinokubo, Hiroshi

Abstract

We report the synthesis and properties of indeno[1,2,3,4-pqra]perylene, which was prepared by the fusion of one anthracene unit with one naphthalene unit via three carbon-carbon bonds. The synthetic route through two-fold C−H arylation enabled not only the synthesis of unsubstituted indenoperylene, but also rapid access to its arylated derivatives on the gram scale. Indenoperylene is a medium-sized aromatic hydrocarbon with the composition C24H12 that is isomeric to coronene. Nevertheless, its absorption covers the entire visible region owing to its small HOMO-LUMO gap. Furthermore, indenoperylene exhibits high stability despite the absence of peripheral substituents. We propose that the unique electronic structure of indenoperylene originates from the coexistence of an electron-withdrawing subunit (benzoaceanthrylene) and an electron-donating subunit (perylene). The electronic properties of indenoperylene were modulated via post-functionalization through regioselective bromination. The current research demonstrates that indenoperylene is a promising candidate as a main skeleton for near-infrared-responsive and redox-active materials.

Published
2022

86. Azabuckybowl-Based Molecular Tweezers as C60 and C70 Receptors

Author

Takeda, Motoki, Hiroto, Satoru, Yokoi, Hiroki, Lee, Sangsu, Kim, Dongho, and Shinokubo, Hiroshi

Abstract

We designed and synthesized molecular tweezers consisting of nitrogen-embedded buckybowl subunits. The judicious choice of the covalent linkers modulated their binding strength with C60 or C70 in solution. Titration studies by optical and 1H NMR analyses revealed a 1:1 composition of the resulting complexes. X-ray diffraction analysis elucidated their solid-state structures, in which two azabuckybowl units surround one fullerene molecule. The large association constants stabilize the complexes toward redox reactions and the purification process on silica-gel column chromatography. The linker enabled tuning of the cavity size for binding of fullerenes, achieving complementary fullerene hosts for C60 and C70: the carbazole-bridged dimer preferentially associates with C70 over C60, while the phenanthrene-bridged dimer interacts with C60 more strongly than C70. Electrochemical analysis in combination with density functional theory calculations indicated the existence of intermolecular charge-transfer interactions between the buckybowl units and the fullerenes. Nonlinear optical measurements showed that the two-photon absorption cross sections of the molecular tweezers are enhanced upon association with fullerenes., ファイル公開：2019-05-23

Published
2018

87. A directly fused tetrameric porphyrin sheet and its anomalous electronic properties that arise from the planar cyclooctatetraene core

Author

Nakamura, Yasuyuki, Aratani, Naoki, Shinokubo, Hiroshi, Takagi, Akihiko, Kawai, Tomoji, Matsumoto, Takuya, Zin Seok Yun, Deok Yun Kim, Tae Kyu Ahn, Donghi Kim, Atsuya Muranaka, Kobayashi, Nagao, and Osuka, Atsuhiro

Subjects
Porphyrins -- Atomic properties, Imidazole -- Atomic properties, Chemistry
Abstract

The synthesis and characterizations of a square-planar porphyrin sheet are reported, which is, the first-example of two-dimensionally pie-extended porphyrinic systems caused by symmetric direct fusion of four porphyrins. The porphyrin sheet forms stable 1:2 complexes with guest protons that are located just above the cyclooctatetraene (COT) core, whereas the imidazolyl protons bound to the zinc(II) porphyrin local cores are observed slightly upfield positions.

Published
2006

96. Transformation of zirconocene-olefin complexes into zirconocene allyl hydride and their use as dual nucleophilic reagents: reactions with acid cholride and 1,4-diketone

Author

Fujita, Kazuya, Yorimitsu, Hideki, Shinokubo, Hiroshi, and Oshima, Koichiro

Subjects
Nucleophilic reactions -- Analysis, Chemistry
Abstract

Zirconocene-olefin complexes Cp2Zr(H2C=CHR), prepared in benzene-THF at 0 degree Celsius, react with acid chlorides to provide homoallylic alcohols. The key is equilibrium between the zirconocene-olefin complexes and the corresponding zirconocene allyl hydride complexes via allylic C-H bond cleavage of the coordinatin alkenes.

Published
2004

97. A Supramolecular Polymer Constituted of Antiaromatic NiII Norcorroles.

Author

Ukai, Shusaku, Takamatsu, Aiko, Nobuoka, Masaki, Tsutsui, Yusuke, Fukui, Norihito, Ogi, Soichiro, Seki, Shu, Yamaguchi, Shigehiro, and Shinokubo, Hiroshi

Subjects
SUPRAMOLECULAR polymers, STACKING interactions, ELECTRONIC materials, ELECTRONIC structure, MONOMERS, PORPHYRINS
Abstract

For the creation of next‐generation organic electronic materials, the integration of π‐systems has recently become a central theme. Such functional materials can be assembled by supramolecular polymerization when aromatic π‐systems are used as monomers, and the properties of the resulting supramolecular polymer strongly depend on the electronic structure of the monomers. Here, we demonstrate the construction of a supramolecular polymer consisting of an antiaromatic π‐system as the monomer. An amide‐functionalized NiII norcorrole derivative formed a one‐dimensional supramolecular polymer through π‐π stacking and hydrogen‐bonding interactions, ensuring the persistency of the conducting pathway against thermal perturbation, which results in higher charge mobility along the tightly bound linear aggregates than that of the aromatic analogue composed of ZnII porphyrins. [ABSTRACT FROM AUTHOR]

Published
2022
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98. TiCl (sub)4 -n-Bu (sub)4 NX (X= I, Br, and Cl) combination-induced coupling of alpha,beta-unsaturated ketones with aldehydes

Author

Zhenfu Han, Uehira, Shigeki, Shinokubo, Hiroshi, and Oshima, Koichiro

Subjects
Chemistry, Organic -- Research, Chlorine -- Physiological aspects, Titanium -- Physiological aspects, Iodine -- Physiological aspects, Bromine -- Physiological aspects, Aldehydes -- Physiological aspects, Ketones -- Physiological aspects, Halides -- Physiological aspects, Biological sciences, Chemistry
Abstract

Research has been conducted on the three-component coupling reaction between vinyl ketones, aldehydes and halides. The development of this reaction with TiCl (sub)4 -n-Bu (sub)4 NX (X= I, Br, and Cl) combined reagents has been examined and described.

Published
2001

99. Triethylborane-induced bromine atom-transfer radical addition in aqueous media: study of the solvent effect on radical addition reactions

Author

Yorimitsu, Hideki, Shinokubo, Hiroshi, Matsubara, Seijiro, and Oshima, Koichiro

Subjects
Chemistry, Organic -- Research, Bromine -- Physiological aspects, Radicals (Chemistry) -- Physiological aspects, Solution (Chemistry) -- Physiological aspects, Lactones -- Physiological aspects, Acetates -- Physiological aspects, Olefins -- Physiological aspects, Biological sciences, Chemistry
Abstract

Research has been conducted on the bromine atom-transfer radical addition of alpha-bromoacetate with 1-alkene in water. Results indicate that the reaction in water occurs at ambient temperature in the presence of triethylborane producing 4-bromoalkanoate which is converted into gamma-lactone or gamma-lactam.

Published
2001

100. Selective halogen-magnesium exchange reaction via organomagnesium ate complex

Author

Inoue, Atsushi, Kitagawa, Kazuya, Shinokubo, Hiroshi, and Oshima, Koichiro

Subjects
Organometallic chemistry -- Research, Halogens -- Usage, Magnesium (Metal) -- Usage, Chemical reactions -- Analysis, Biological sciences, Chemistry
Abstract

Results demonstrate that magnesium ate complex facilitates the facile-halogen-magnesium exchange in aryl- and alkenyl- halides at low temperatures. Data indicate that the reaction can be used for preparing organomagnesium reagents and fine-tuned by selecting proper ligands on magnesium.

Published
2001

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