A5065013616- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Metalloenzymes and iron-sulfur proteins
- Electrocatalysts for Energy Conversion
- Crystallography and molecular interactions
- Metal-Catalyzed Oxygenation Mechanisms
- Ammonia Synthesis and Nitrogen Reduction
- Hydrogen Storage and Materials
- Asymmetric Hydrogenation and Catalysis
- CO2 Reduction Techniques and Catalysts
- Metal complexes synthesis and properties
- Magnetism in coordination complexes
- Lanthanide and Transition Metal Complexes
- Advanced battery technologies research
- Organometallic Complex Synthesis and Catalysis
- Metal-Organic Frameworks: Synthesis and Applications
- Porphyrin and Phthalocyanine Chemistry
- Photosynthetic Processes and Mechanisms
- Carbon dioxide utilization in catalysis
- Catalysis for Biomass Conversion
- Chemical Reactions and Isotopes
- Oxidative Organic Chemistry Reactions
- Catalytic Processes in Materials Science
- Microbial Fuel Cells and Bioremediation
- Polyoxometalates: Synthesis and Applications
Kyushu University
2016-2025
Graduate School USA
2014-2021
SPring-8
2017
Japan Science and Technology Agency
2005-2014
Lawrence Berkeley National Laboratory
1996-2014
University of California, Berkeley
1996-2014
Nagoya University
2002-2013
Kanazawa University
1999-2011
Suzuki (Japan)
2011
Osaka University
2001-2008
We have successfully achieved the electron-transfer (ET) state of 9-mesityl-10-methylacridinium ion, produced by a single step photoinduced electron transfer, which has much longer lifetime (e.g., 2 h at 203 K) and higher energy (2.37 eV) than that natural system without loss due to multistep processes.
Chemists have long sought to mimic enzymatic hydrogen activation with structurally simpler compounds. Here, we report a functional [NiFe]-based model of [NiFe]hydrogenase enzymes. This complex heterolytically activates form hydride that is capable reducing substrates by either ion or electron transfer. Structural investigations were performed range techniques, including x-ray diffraction and neutron scattering, resulting in crystal structures the finding hydrido ligand predominantly...
Models of the active site in [NiFe]hydrogenase enzymes have proven challenging to prepare. We isolated a paramagnetic dinuclear nickel-ruthenium complex with bridging hydrido ligand from heterolytic cleavage H 2 by NiRu aqua water under ambient conditions (20°C and 1 atmosphere pressure). The structure hexacoordinate Ni(μ-H)Ru was unequivocally determined neutron diffraction analysis, it comes closest an effective analog for core proposed form enzyme.
Ruthenium aqua complexes [(eta(6)-C(6)Me(6))Ru(II)(L)(OH(2))](2+) {L = bpy (1) and 4,4'-OMe-bpy (2), 2,2'-bipyridine, 4,4'-dimethoxy-2,2'-bipyridine} iridium [Cp*Ir(III)(L)(OH(2))](2+) {Cp* eta(5)-C(5)Me(5), L (5) (6)} act as catalysts for hydrogenation of CO(2) into HCOOH at pH 3.0 in H(2)O. The active hydride cannot be observed the with ruthenium complexes, whereas catalysts, [Cp*Ir(III)(L)(H)](+) (7) (8)}, have successfully been isolated after complexes. key to success isolation is change...
An acid-stable hydride complex [Cp*IrIII(bpy)H]+ {1, Cp* = η5-C5Me5, bpy 2,2'-bipyridine} serves as the active catalyst for highly chemoselective synthesis of α-amino acids by reductive amination α-keto with aqueous NH3 and HCOO- in water at pH 5−8. pH-dependent catalytic 15N- 2H-double-labeling has also been accomplished using 15NH3 DCOONa, which are ideal amine ion sources, respectively.
Abstract Current greenhouse gas emissions suggest that keeping global temperature increase below 1.5 degrees, as espoused in the Paris Agreements will be challenging, and to do so, achievement of carbon neutrality is utmost importance. It also clear no single solution can meet neutral challenge, so it essential for scientific research cover a broad range technologies initiatives which enable realization free energy system. This study details broad, yet targeted themes being pioneered within...
The paper reports on the development of a new class water-soluble organometallic catalysts for pH-dependent transfer hydrogenation. An aqua complex [(η6-C6Me6)RuII(bpy)(H2O)]2+ (1, bpy = 2,2'-bipyridine) acts as catalyst precursor hydrogenation and -insoluble ketones with HCOONa hydrogen donor in water biphasic media. Irrespective solubility toward water, rate shows sharp maximum around pH 4.0 (in case media, value aqueous phase is adopted). In absence reducible ketones, function pH, 1...
This paper reports the isolation and structural determination of a water-soluble hydride complex [Cp*Ir(III)(bpy)H](+) (1, Cp* = eta(5)-C(5)Me(5), bpy 2,2'-bipyridine) that serves as robust highly active catalyst for acid-catalyzed transfer hydrogenations carbonyl compounds at pH 2.0-3.0 70 degrees C. The 1 was synthesized from reaction precatalyst [Cp*Ir(III)(bpy)(OH(2))](2+) (2) with hydrogen donors HCOOX (X H or Na) in H(2)O under controlled conditions (2.0 < 6.0, 25 C) which avoid...
This paper reports a pH-dependent hydrogenation of water-soluble carbonyl compounds by hydrogen transfer from HCOONa as source (transfer hydrogenation) promoted [Cp*IrIII(H2O)3]2+ (1, Cp* = η5-C5Me5) catalyst precursor in water. Complex 1 has been characterized X-ray structure analysis, 1H NMR, and potentiometric titration experiments. The active catalyst, dinuclear μ-hydride complex [(Cp*IrIII)2(μ-H)(μ-OH)(μ-HCOO)]+ (2), isolated IR, electrospray ionization mass spectrometry (ESI-MS). rate...
This paper reports pH-dependent transfer hydrogenation, reductive amination, and dehalogenation of water-soluble substrates with the organometallic aqua complexes [Cp*IrIII(H2O)3]2+ (1, Cp* = η5-pentamethylcyclopentadienyl), [(Cp∧py)IrIII(H2O)2]2+ (2, Cp∧py η5-(tetramethylcyclopentadienyl)methylpyridine), [Cp*IrIII(bpy)(H2O)]2+ (3, bpy 2,2'-bipyridine) as catalyst precursors formate ions HCOONa HCOONH4 hydrogen donors. Because difference in electron-donating ability Cp*, Cp∧py, ligands,...
A six-coordinate bis(μ-oxo)nickel(III) complex, [Ni2(μ-O)2(Me3-tpa)2]2+ (1), was synthesized by the reaction of [Ni2(μ-OH)2(Me3-tpa)2]2+ (2) with 1 equiv hydrogen peroxide in methanol at −90 °C, where Me3-tpa = tris(6-methyl-2-pyridylmethyl)amine. The 6-methyl groups have a significant influence on formation and stabilization high-valent bis(μ-oxo)dinickel(III) species. 2 large excess (>10 equiv) afforded novel bis(μ-superoxo)dinickel(II) [Ni2(μ-O2)2(Me3-tpa)2]2+ (3), thus, demonstrates...
Hydrogenation of carbon dioxide (P(H2/CO2) = 5.5/2.5 MPa) into formic acid (HCOOH) under acidic conditions (pH 2.5–5.0) in water has been achieved by using water-soluble ruthenium aqua catalysts [(η6-C6Me6)RuII(L)(OH2)]SO4 (L 2,2′-bipyridine or 4,4′-dimethoxy-2,2′-bipyridine).
This review discusses the development of aqueous phase, homogeneous, transfer hydrogenation catalysis. Transfer catalysts, based on Ru, Ir and Rh, reduce organic substrates in water by assisting hydrogen from simple donor species. These catalysts are expected to have significant benefits when compared with phase including greater activity, selectivity smaller environmental impact. They will therefore be make a contribution homogeneous catalysis 'green chemistry'. Here, we comprehensively...
The growing need for hydrogen-based fuel cells has driven research into hydrogenase (H2ase)—a natural enzyme that catalyses the extraction of electrons from H2 in water under ambient conditions. Unfortunately, exact mechanism by which H2ase achieves this feat remained a matter some controversy until now, with many mechanisms being inconsistent experimental data. Recently, however, we have been able to produce successful catalytic mimic replicates key aspects it. This paper begins an overview...
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA Bis(μ-oxo)dicopper(III) Complex with Aromatic Nitrogen Donors: Structural Characterization and Reversible Conversion between Copper(I) SpeciesHideki Hayashi, Shuhei Fujinami, Shigenori Nagatomo, Seiji Ogo, Masatatsu Suzuki, Akira Uehara, Yoshihito Watanabe, Teizo KitagawaView Author Information Department of Chemistry, Faculty Science Kanazawa University, Kakuma-machi Kanazawa, Ishikawa 920-1192, Japan Institute for Molecular Myodaiji,...
Molecular recognition, via non-covalent processes such as hydrogen bonding, π−π, and hydrophobic interactions, is an important biological phenomenon for guests, drugs, proteins, other molecules with, example, host DNA/RNA. We have studied a novel molecular recognition process using guests that encompass aromatic aliphatic amino acids [l-alanine, l-glutamine (l-Gln), l-histidine, l-isoleucine (l-Ile), l-leucine (l-Leu), l-phenylalanine (l-Phe), l−proline, l-tryptophan (l-Trp), l-valine...
NAD+ (oxidized form of NAD:nicotinamide adenine dinucleotide)-reducing soluble [NiFe]-hydrogenase (SH) is phylogenetically related to NADH (reduced NAD+):quinone oxidoreductase (complex I), but the geometrical arrangements subunits and Fe-S clusters are unclear. Here, we describe crystal structures SH in oxidized reduced states. The cluster arrangement similar that complex I, orientation not, which supports hypothesis evolved as prebuilt modules. active site includes a six-coordinate Ni,...
Hydrogen peroxide is an environmentally friendly oxidizing agent but current synthetic methods are wasteful. This a result of the high flammability H2/O2 mixtures and/or requirement for cocatalysts. In this paper, we report synthesis H2O2 by means homogeneous catalyst, which allows safe, one-pot in water, using only H2 and O2. catalyst capable removing electrons from H2, storing them reduction O2, then permitting protonation reduced oxygen to H2O2. The turnover number (TON) 910 under (95/5)...
The first isolation and spectroscopic characterization of the mononuclear hydroperoxo−iron(III) complex [Fe(H2bppa)(OOH)]2+ (2) stoichiometric oxidation substrates by iron−oxo intermediate generated its decomposition have been described. purple species 2 obtained from reaction [Fe(H2bppa)(HCOO)](ClO4)2 with H2O2 in acetone at −50 °C gave characteristic UV−vis (λmax = 568 nm, ε 1200 M-1 cm-1), ESR (g 7.54, 5.78, 4.25, S 5/2), ESI mass spectra (m/z 288.5 corresponding to ion,...
The series of water-soluble palladacyclic aqua complexes [(tBu-SCS)PdII(H2O)]+ ([1]+, tBu-SCS = C6H3-2,6-(CH2StBu)2), [(iPr-SCS)PdII(H2O)]+ ([2]+, iPr-SCS C6H3-2,6-(CH2SiPr)2), [(PCP)PdII(H2O)]+ ([3]+, PCP C6H3-2,6-(OPiPr2)2), and [(PC)PdII(H2O)2]+ ([4]+, PC 4-MeC6H3-2-(OPiPr2)) have been synthesized from the reaction corresponding chloro with silver salts in water to optimize catalytic activity for pH-dependent C−C coupling reactions by changing supporting ligands S-supporting (SCS)...
A 3,5-di-tert-butyl-1,2-semiquinonato (DTBSQ) adduct of Mn(II) was prepared by a reaction between Mn(II)(TPA)Cl(2) (TPA = tris(pyridin-2-ylmethyl)amine) and DTBSQ anion isolated as tetraphenylborate salt. The X-ray crystal structure revealed that the complex is formulated manganese(II)-semiquinonate [Mn(II)(TPA)(DTBSQ)](+) (1). electronic spectra in solution also indicated semiquinonate coordination to Mn. exposure 1 acetonitrile dioxygen afforded 3,5-di-tert-butyl-1,2-benzoquione...
A new class of efficient catalyst, the Rh(I) complex [(η5-C5Me5)RhI(bpy)] (1; bpy = 2,2′-bipyridine), for C–F bond hydrogenolysis fluoroaromatics (C6F5CF3, C6F6, C6F5H, and C6F5CH3) is presented. The best turnover number 380 C6F6 afforded by using 0.1 mol % 1, 0.8 MPa H2, 2 equiv Et2NH in CH3CN at 25 °C. successful isolation cleavage product [(η5-C5Me5)RhIII(bpy)(C6F5)](F) as a plausible intermediate catalytic 1 also described.
Dioxygen-tolerant [NiFe] hydrogenases catalyze not only the conversion of H2 into 2 H(+) and e(-) but also reduction O2 to H2O. Chemists have sought mimic such bifunctional catalysts with structurally simpler compounds facilitate analysis improvement. Herein, we report a new [NiFe]-based catalyst for via an adduct. Structural investigations reveal first example side-on iron(IV) peroxo complex.