Search results for: Taka-aki Okamura

Items from 1 to 20 out of 102 results

article

One Ligand Fits All: Formation and Stabilization of a Single‐Ligand Arenethiolato Cobalt(II) Complex via Metal‐π Coordination from a Bulky Acylamino Group

Yusuke Tomita, Taka‐aki Okamura, Kiyotaka Onitsuka

European Journal of Inorganic Chemistry > 2022 > 36 > n/a - n/a

Metalloproteins activate inert molecules under mild conditions by exploiting the low‐coordinated metal centers formed in protein pockets. The creation of biomimetic metal centers using bulky ligands is an attractive strategy in bioinorganic chemistry. Herein, we report a highly bulky arenethiolato ligand containing acylamino groups that forms a neutral single‐ligand Co(II) complex. X‐ray analysis...

article

Conformational Switch of Arylopeptide: Helix–Helix Transition Based on Side Chain Solvation

Yuki Ishido, Naoya Kanbayashi, Taka‐aki Okamura, Kiyotaka Onitsuka

Macromolecular Rapid Communications > 42 > 14 > n/a - n/a

Front Cover: In article number 2100250, Naoya Kanbayashi, Kiyotaka Onitsuka, and co‐workers present a reversible conformational switch of a non‐natural polypeptide with an aromatic ring in its peptide backbone, referred to as an “arylopeptide”, between two distinct helical structures. On this cover, the structural change of arylopeptide in the solvent is shown. In addition, a continuation of the spiral...

article

Conformational Switch of Arylopeptide: Helix–Helix Transition Based on Side Chain Solvation

Yuki Ishido, Naoya Kanbayashi, Taka‐aki Okamura, Kiyotaka Onitsuka

Macromolecular Rapid Communications > 42 > 14 > n/a - n/a

Controlling the structural transition between well‐defined architectures found in living system is essential in polymer chemistry as well as material science. Herein, the reversible conformational switch of a non‐natural polypeptide with an aromatic ring (2,6‐naphthalene spacer) on its peptide backbone, referred to as an arylopeptide, between two distinct well‐defined helical structures (extended...

article

Frontispiz: Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Yuki Kataoka, Naoya Kanbayashi, Naoka Fujii, Taka‐aki Okamura, more

Angewandte Chemie > 132 > 26 > n/a - n/a

Helikale Polymere Die Synthese eines neuartigen Typs π‐gestapelter Polymere wird von N. Kanbayashi, K. Onitsuka et al. in der Zuschrift auf S. 10372 beschrieben. Die Struktur wird durch spektroskopische Analysen und AFM‐Messungen bestätigt.

article

Frontispiece: Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Yuki Kataoka, Naoya Kanbayashi, Naoka Fujii, Taka‐aki Okamura, more

Angewandte Chemie International Edition > 59 > 26 > n/a - n/a

Helical Polymers The synthesis of a novel type of π‐stacked polymer is described by N. Kanbayashi, K. Onitsuka et al. in their Communication on page 10286. Its structure was established by spectroscopic analysis and AFM measurements.

article

Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Yuki Kataoka, Naoya Kanbayashi, Naoka Fujii, Taka‐aki Okamura, more

Angewandte Chemie International Edition > 59 > 26 > 10286 - 10291

π‐Stacked polymers, which consist of layered π‐electron systems in a polymer, can be expected to be used in molecular electronic devices. However, the construction of a stable π‐stacked structure in a polymer is considerably challenging because it requires sophisticated designs and precise synthetic methods. Herein, we present a novel π‐stacked architecture based on poly(quinolylene‐2,3‐methylene)...

article

Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Yuki Kataoka, Naoya Kanbayashi, Naoka Fujii, Taka‐aki Okamura, more

Angewandte Chemie > 132 > 26 > 10372 - 10377

article

Crystal Structures of Expanded Poly(l‐leucine) Isomers Containing Bis(pyridine)silver(I) Moieties: Precise Formation of Secondary Structure Depending on the Side Chain

Taka‐aki Okamura

Chemistry – A European Journal > 24 > 51 > 13437 - 13440

Precise construction of a three‐dimensional molecular structure is key for functional macromolecules, such as enzymes or proteins. Previously, a new concept, “expanded poly(α‐amino acid)s” containing rigid spacers, was proposed for strategic construction of chiral helices. Herein, expanded poly(l‐leucine) isomers containing bis(pyridine)silver(I) moieties were synthesized, and their crystal structures...

article

Synthesis and solution structure of desoxotungsten(IV) and monooxotungsten(VI) benzenedithiolate complexes containing two intramolecular NH⋯S hydrogen bonds

Taka-aki Okamura, Yui Omi, Kiyotaka Onitsuka

Inorganica Chimica Acta > 2017 > 467 > C > 379-384

Desoxotungsten(IV) and monooxotungsten(VI) benzenedithiolate complexes containing two intramolecular NH⋯S hydrogen bonds, (NEt₄)[W^IV{OSi(^tBu)Ph₂}(1,2-S₂-3-^tBuCONHC₆H₃)₂] (1) and (NEt₄)[W^VIO{OSi(^tBu)Ph₂}(1,2-S₂-3-^tBuCONHC₆H₃)₂] (2), were synthesized by silylation of the parent mono- and di-oxo compounds. The geometrical isomers, trans- and cis-1, were present at room temperature without any interconversion...

article

Unexpected Reaction Promoted by NH+···O=Mo Hydrogen Bonds in Nonpolar Solvents

Taka‐aki Okamura, Takayoshi Yamada, Yuki Hasenaka, Satoshi Yamashita, more

European Journal of Inorganic Chemistry > 2016 > 18 > 2952 - 2961

A new synthetic method using [Mo^IV(S‐tBu)₄], 1,2‐benzenedithiol containing bulky hydrophobic acylamino substituents, 3,6‐[(4‐tBuC₆H₄)₃CCONH]₂C₆H₂‐1,2‐(SH)₂ (LH₂), a tertiary amine [R₃N = Et₃N or 2,6‐lutidine (Lu)], and an equimolar amount of water afforded (R₃NH)₂[Mo^IVO(L)₂] [(R₃NH)₂[1]]. Each compound formed a strong NH⁺···O=Mo hydrogen bond between the tertiary ammonium cation and the terminal oxo...

chapter

Inorganic–Organic Calcium Carbonate Composite of Synthetic Polymer Ligands with an Intramolecular NH···O Hydrogen Bond

Norikazu Ueyama, Kazuyuki Takahashi, Akira Onoda, Taka-aki Okamura, more

Topics in Current Chemistry > Biomineralization II > 155-193

Amide NH prelocating in the vicinity of a carboxylic acid group shifts the pK _a of carboxylic acid to a lower value. A carboxylate anion is stabilized by NH⋯O hydrogen bond under hydrophobic conditions. In the case of Ca carboxylate complex, the decrease of the pK _a value increases a formation constant involving the protonation process of carboxylic acid. In addition, the NH⋯O...

article

Planar‐Chiral Cyclopentadienyl‐Ruthenium‐Catalyzed Regio‐ and Enantioselective Asymmetric Allylic Alkylation of Silyl Enolates under Unusually Mild Conditions

Naoya Kanbayashi, Arisa Yamazawa, Koichiro Takii, Taka‐aki Okamura, more

Advanced Synthesis & Catalysis > 358 > 4 > 555 - 560

We report the asymmetric allylic alkylation of allylic chlorides with silyl enolates as a carbon nucleophile using a planar‐chiral cyclopentadienyl‐ruthenium (Cp′Ru) catalyst. The reaction proceeds under unusually mild conditions to give the desired branched products with complete regioselectivity and high enantioselectivity, and reactive functional groups, such as aldehyde, can be tolerated. In this...

article

Synthesis, structure and sorption property of metal complexes with mixed multicarboxylate and imidazole-containing ligands

Li Luo, Peng Wang, Qing Liu, Taka-aki Okamura, more

Microporous and Mesoporous Materials > 2016 > 219 > C > 199-208

Zinc(II) and nickel(II) frameworks [Zn₂(L)(BTC)(NO₃)]·H₂O·2CH₃CN (1), [Ni₂(L)(H₂O)₃(HBTC)₂]·3.6H₂O (2), [Ni(L)(H₂O)₂](BPDC)·2H₂O (3), [Ni(L)(H₂O)(BPDC)]·4H₂O (4) and [Ni₂(L)(MeOH)₄(BPDC)₂]·2H₂O (5) were synthesized by reactions of corresponding metal salts with 3,3′,5,5′-tetra(1H-imidazol-1-yl)-1,1′-biphenyl (L) and multicarboxylic acids of 1,3,5-benzenetricarboxylic acid (H₃BTC), 4,4′-biphenyldicarboxylic...

article

A series of divalent metal complexes with mixed 5-(imidazol-1-ylmethyl)isophthalic acid and N-donor ligands: Synthesis, characterization and property

Hai-Wei Kuai, Taka-aki Okamura, Wei-Yin Sun

Polyhedron > 2014 > 72 > Complete > 8-18

Eight complexes with different 3d metal centers and auxiliary ligands, [Cu(L)(py)] (1), [Cu(L)(bpy)]·1.5H ₂ O (2), [Mn(L)] (3), [Mn(L)(pybim)]·3H ₂ O (4), [Ni(L)(bpy)]·2H ₂ O (5), [Ni(L)(phen)]·2H ₂ O (6), [Ni(L)(bpe)(H ₂ O)]·2H ₂ O (7) and [Zn(L)(bpy)]·2H ₂ O (8) [H ₂ L=5-(imidazol-1-ylmethyl)isophthalic acid, py=pyridine, bpy=2,2′-bipyridine,...

article

Asymmetric Auto‐Tandem Catalysis with a Planar‐Chiral Ruthenium Complex: Sequential Allylic Amidation and Atom‐Transfer Radical Cyclization

Naoya Kanbayashi, Kazuhiro Takenaka, Taka‐aki Okamura, Kiyotaka Onitsuka

Angewandte Chemie > 125 > 18 > 4997 - 5001

Ru zeigt, was es kann: Eine asymmetrische Auto‐Tandemreaktion mit einem planar‐chiralen Cyclopentadienyl‐Ruthenium‐Komplex als Katalysator verbindet Allylchloride und α‐Halogenamide zu nützlichen diastereomeren‐ und enantiomerenangereicherten γ‐Lactamen mit mehreren Stereozentren. Die Umsetzung verläuft als Eintopfsequenz aus allylischer Amidierung und radikalischer Atomtransfercyclisierung. PG=Schutzgruppe.

article

Asymmetric Auto‐Tandem Catalysis with a Planar‐Chiral Ruthenium Complex: Sequential Allylic Amidation and Atom‐Transfer Radical Cyclization

Naoya Kanbayashi, Kazuhiro Takenaka, Taka‐aki Okamura, Kiyotaka Onitsuka

Angewandte Chemie International Edition > 52 > 18 > 4897 - 4901

Ru does it all: A novel example of an asymmetric auto‐tandem reaction catalyzed by a planar‐chiral cyclopentadienyl–ruthenium complex is described. The reaction of allylic chloride with α‐haloamides provides synthetically useful, diastereomerically and enantiomerically enriched γ‐lactams with multiple stereogenic centers through one‐pot sequential allylic amidation/atom‐transfer radical cyclization...

article

Metal complex with terpyrindine derivative ligand as highly selective colorimetric sensor for iron(III)

Peng Wang, Taka-aki Okamura, Hong-Ping Zhou, Wei-Yin Sun, more

Chinese Chemical Letters > 2013 > 24 > 1 > 20-22

A new metal complex [MnL ₂ ](NO ₃ ) ₂ ·CH ₃ CN (1) was synthesized by reaction of 4′-4-(1,2,4-triazol-1-yl)-phenyl-2,2′:6′,2″-terpyridine (L) with manganese nitrate. The structure of the complex was determined by X-ray crystallography. The results of UV–vis studies showed that the complex exhibits colorimetric sensing ability for Fe ³⁺ , which can be observed...

article

Structural diversity of terpyridine-based metal complexes with varied dicarboxylate auxiliary ligands

Peng Wang, Li Luo, Taka-aki Okamura, Hong-Ping Zhou, more

Polyhedron > 2012 > 44 > 1 > 18-27

Six new metal complexes, [Zn ₂ L ₂ (1,2-bdc) ₂ ] (1), [CuZnL ₂ (1,2-bdc) ₂ ] (2), {[Cu ₂ L(1,3-bdc) ₂ ]·2H ₂ O} _n (3), {[Cu ₂ L ₂ (1,4-bdc)](NO ₃ ) ₂ ·2H ₂ O} _n (4), [Cu ₂ L ₂ (1,4-bdc)(SCN) ₂ ]·2H ₂ O (5) and {[ZnL(dc)]·H ₂ O} _n (6),...

article

Coordination polymers constructed by diverse metal centers and the rigid ligand 3,5-di(1H-imidazol-1-yl)pyridine: Synthesis, structure and properties

Li Luo, Yue Zhao, Yi Lu, Taka-aki Okamura, more

Polyhedron > 2012 > 38 > 1 > 88-96

Six new coordination polymers, [Cu(L) ₂ (H ₂ O) ₂ ](NO ₃ ) ₂ (1), [Cu(L) ₂ ](ClO ₄ ) ₂ (2), [Cd(L) ₂ (H ₂ O) ₂ ](ClO ₄ ) ₂ (3), [Cd(L)(OAc) ₂ (H ₂ O)] (4), [Cu ₃ (L) ₄ (H ₂ O) ₂ (SO ₄ )](SO ₄ ) ₂ ·30H ₂ O (5), and [Ni(L)(H...

article

Metal-organic frameworks with N-(4-pyridylmethyl)iminodiacetate ligand: Synthesis, structure and sorption properties

Chao Hou, Qing Liu, Yi Lu, Taka-aki Okamura, more

Microporous and Mesoporous Materials > 2012 > 152 > Complete > 96-103

Three novel metal-organic frameworks based on the N-(4-pyridylmethyl)iminodiacetate (pmida ²⁻ ), namely {[Cd(pmida)H ₂ O]·1.8 H ₂ O]} _n (1), {[Cd(pmida)(H ₂ O)]·2H ₂ O} _n ^· (2) and {[Zn(pmida)(H ₂ O)]·2H ₂ O} _n (3), have been prepared and characterized by single crystal X-ray diffraction, IR, powder X-ray diffraction...

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INFONA - science communication portal

Search results for: Taka-aki Okamura

One Ligand Fits All: Formation and Stabilization of a Single‐Ligand Arenethiolato Cobalt(II) Complex via Metal‐π Coordination from a Bulky Acylamino Group

Conformational Switch of Arylopeptide: Helix–Helix Transition Based on Side Chain Solvation

Conformational Switch of Arylopeptide: Helix–Helix Transition Based on Side Chain Solvation

Frontispiz: Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Frontispiece: Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene) Stabilized by Intramolecular Hydrogen Bonds

Crystal Structures of Expanded Poly(l‐leucine) Isomers Containing Bis(pyridine)silver(I) Moieties: Precise Formation of Secondary Structure Depending on the Side Chain

Synthesis and solution structure of desoxotungsten(IV) and monooxotungsten(VI) benzenedithiolate complexes containing two intramolecular NH⋯S hydrogen bonds

Unexpected Reaction Promoted by NH+···O=Mo Hydrogen Bonds in Nonpolar Solvents

Inorganic–Organic Calcium Carbonate Composite of Synthetic Polymer Ligands with an Intramolecular NH···O Hydrogen Bond

Planar‐Chiral Cyclopentadienyl‐Ruthenium‐Catalyzed Regio‐ and Enantioselective Asymmetric Allylic Alkylation of Silyl Enolates under Unusually Mild Conditions

Synthesis, structure and sorption property of metal complexes with mixed multicarboxylate and imidazole-containing ligands

A series of divalent metal complexes with mixed 5-(imidazol-1-ylmethyl)isophthalic acid and N-donor ligands: Synthesis, characterization and property

Asymmetric Auto‐Tandem Catalysis with a Planar‐Chiral Ruthenium Complex: Sequential Allylic Amidation and Atom‐Transfer Radical Cyclization

Asymmetric Auto‐Tandem Catalysis with a Planar‐Chiral Ruthenium Complex: Sequential Allylic Amidation and Atom‐Transfer Radical Cyclization

Metal complex with terpyrindine derivative ligand as highly selective colorimetric sensor for iron(III)

Structural diversity of terpyridine-based metal complexes with varied dicarboxylate auxiliary ligands

Coordination polymers constructed by diverse metal centers and the rigid ligand 3,5-di(1H-imidazol-1-yl)pyridine: Synthesis, structure and properties

Metal-organic frameworks with N-(4-pyridylmethyl)iminodiacetate ligand: Synthesis, structure and sorption properties

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