Language：Others   Publishing type：Research paper (scientific journal)  

Four requirements for the reductive C(sp³)–C(sp³) homo-coupling of benzyl/allyl halides in aqueous solution by using H₂ as an electron source are described.

DOI： 10.1039/d1ra08596d

Repository Public URL： https://hdl.handle.net/2324/7173466

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/chem.202102735

Language：Others   Publishing type：Research paper (scientific journal)  

This paper reports a possible mechanism of acetic acid formation from CO , CH I and H in aqueous media and the central role played by a water-soluble Rh-based electron storage catalyst. In addition to water-solubility, we also report the crystal structures of two presumed intermediates. These findings together reveal (1) the advantage of water, not only as a green solvent, but also as a reactive Lewis base to extract H from H , (2) the role of the metal (Rh) centre as a point for storing electrons from H and (3) the importance of an electron-withdrawing ligand (quaterpyridine, qpy) that supports electron storage. 2 3 2 2 2 +

DOI： 10.1039/d1cc01611c

Language：English   Publishing type：Research paper (scientific journal)  

The study of hydrogenase enzymes (H2ases) is necessary because of their importance to a future hydrogen energy economy. These enzymes come in three distinct classes: [NiFe] H2ases, which have a propensity toward H2 oxidation; [FeFe] H2ases, which have a propensity toward H2 evolution; and [Fe] H2ases, which catalyze H- transfer. Modeling these enzymes has so far treated them as different species, which is understandable given the different cores and ligand sets of the natural molecules. Here, we demonstrate, using x-ray analysis and nuclear magnetic resonance, infrared, Mössbauer spectroscopies, and electrochemical measurement, that the catalytic properties of all three enzymes can be mimicked with only three isomers of the same NiFe complex.

DOI： 10.1126/sciadv.aaz8181

Repository Public URL： https://hdl.handle.net/2324/7173462

Language：English   Publishing type：Research paper (scientific journal)  

We report an Ir complex as an anode catalyst capable of switching between a hydrogenase-type fuel-cell mode and a photosystem II-type solar-cell mode. This catalyst is connected to carbon-black-supported platinum as a cathode catalyst, which reduces dioxygen in a manner analogous to cytochrome c oxidase. Together, they make a system capable of switching between the two modes.

DOI： 10.1002/cctc.201700995

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Abstract

Chemists have long sought to regulate the reactivity of H₂, to yield hydride ions, hydrogen atoms, or electrons on demand. One source of inspiration for achieving this control is [NiFe]hydrogenase ([NiFe]H₂ase), which reacts with H₂ to form various hydrogen active species such as Ni^III hydride species, Ni^II hydride species, and Ni^I low‐valent species. Chemists have attempted to synthesize these hydrogen active species not only as models for the active species of [NiFe]H₂ase, but also as electron transfer catalysts. However, the synthesis of Ni^I complex directly from H₂ has not been reported. This paper reports the first example of a single‐step synthesis of a Ni^I complex, via reaction of a Ni^II complex with H₂, stable for over 3 months at room temperature and we further demonstrate a reductive coupling of acridinium ions as part of a reaction cycle.

DOI： 10.1002/chem.202302297

Language：English   Publishing type：Research paper (scientific journal)  

Language：Others   Publishing type：Research paper (scientific journal)  

This paper reports the synthesis, structure, and mechanistic action of a Rh-based catalyst, the monohydroxide diaqua Rh complex 1, for the direct synthesis of H O from H and O . Of particular interest is the elucidation of the crystal structures of 1, the low-valent Rh complex 2, the dinuclear Rh complex 3, and the peroxide Rh complex 4 that appear in the catalytic cycle. In order to clarify the mechanistic action of the Rh-based catalyst, the catalytic reaction was investigated with 1 in water, but the possible intermediates 2-4 were isolated in organic solvents. First, we describe the synthesis, characterization, and behavior of the functioning, Rh-based catalyst. We then describe this catalytic direct synthesis of H O from H and O with 1 (turnover number (TON) = 3.8 for 3 h). III I II III 2 2 2 2 2 2 2 2

DOI： 10.1021/acs.organomet.0c00565

Language：Others   Publishing type：Research paper (scientific journal)  

We present a novel fuel cell heterogeneous catalyst based on rhodium, nickel and sulfur with power densities 5-28% that of platinum. The NiRhS heterogeneous catalyst was developedviaa homogeneous model complex of the [NiFe]hydrogenases (H ases) and can act as both the cathode and anode of a fuel cell. 2

DOI： 10.1039/d0cc04789a

Language：English  

Oxidative damage of DNA by reactive oxygen species (ROS) is responsible for aging and cancer. Although many studies of DNA damage by ROS have been conducted, there have been no reports of the oxidation of RNA components, such as guanosine monophosphate, by metal-based species in water. Here, we report the first case of oxidation of guanosine monophosphate to 8-oxoguanosine monophosphate by a metal-based oxygen bound species, derived from O
₂
and in water.

DOI： 10.1002/asia.201801267

Language：English  

The development of hydrogen fuel cells is greatly hindered by the unwanted generation of H₂O₂ at the cathode. A non-Pt cathode catalyst is now shown to be capable of simultaneously reducing both O₂ and H₂O₂, thus rendering H₂O₂ a useful part of the feed stream. The applicability of this unique catalyst is demonstrated by employing it in a fuel cell running on H₂/CO and O₂/H₂O₂.

DOI： 10.1002/anie.201810270

Language：English   Publishing type：Research paper (scientific journal)  

We report the reactivity of a new Mn-I(cyclam) complex (cyclam: 1,4,8,11-tetraazacyclotetradecane) toward O-2 and H2O as a model for the photoinhibited species of oxygen-evolving complex (OEC). The reactivity varies according to the number of CO ligands. A Mn-I dicarbonyl complex, [Mn-I(cyclam)(CO)(2)](+) reacts with O-2, but not with H2O, to form a bis(mu-oxo) Mn-2(III,IV) complex, though a Mn-I tricarbonyl complex, [Mn-I(cyclam)(CO)(3)](+) does not react with either O-2 or H2O. Newly synthesized Mn-I(cyclam) dicarbonyl complex was characterized by ESI mass spectrometry, UV-vis absorption spectroscopy, IR spectroscopy, and X-ray analysis.

DOI： 10.1246/cl.170869

Language：English   Publishing type：Research paper (scientific journal)  

We report the mechanistic investigation of catalytic H2 evolution from formic acid in water using a formate-bridged dinuclear Ru complex as a formate hydrogen lyase model. The mechanistic study is based on isotope-labeling experiments involving hydrogen isotope exchange reaction.

DOI： 10.1080/14686996.2017.1379857

Language：English   Publishing type：Research paper (scientific journal)  

We present a mechanistic investigation for the activation of H-2 and O-2, induced by a simple ligand effect within [NiFe] models for O-2-tolerant [NiFe]hydrogenase. Kinetic study reveals Michaelis-Menten type saturation behaviors for both H-2 and O-2 activation, which is the same behavior as that found in O-2-tolerant [NiFe]hydrogenase. Such saturation behavior is caused by H-2 complexation followed by heterolytic cleavage of H-2 by an outer-sphere base, resulting in the formation of a hydride species showing hydridic character.

DOI： 10.1021/acs.organomet.7b00471

Language：English   Publishing type：Research paper (scientific journal)  

The ability to catalyze the oxidation of both H-2 and CO in one reaction pot would be a major boon to hydrogen technology since CO is a consistent contaminant of H-2 supplies. Here, we report just such a catalyst, with the ability to catalyze the oxidation of either or both H-2 and CO, based on the pH value. This catalyst is based on a NiIr core that mimics the chemical function of [NiFe] hydrogenase in acidic media (pH 4-7) and carbon monoxide dehydrogenase in basic media (pH 7-10). We have applied this catalyst in a demonstration fuel cell using H-2, CO, and H (2)/CO (1/1) feeds as fuels for oxidation at the anode. The power density of the fuel cell depends on the pH value in the media of the fuel cell and shows a similar pH dependence in a flask. We have isolated and characterized all intermediates in our proposed catalytic cycles.

DOI： 10.1002/anie.201704864

Language：English   Publishing type：Research paper (scientific journal)  

Structure and Reactivity of a Ru-based Peroxide Complex as a Reactive Intermediate of O-2-Promoted Activation of a C-H Bond in a Cp* Ligand
We report the first example of the characterization of a Ru-based peroxide intermediate of O-2-promoted activation of a C-H bond of the pentamethylcyclopentadienyl (Cp*) ligand. The peroxide complex activates the C-H bond to form a tetramethylfulvene complex. We propose a proton-coupled electron-transfer (PCET) mechanism of the C-H bond activation based on the structures and properties of the peroxide and tetramethylfulvene complexes.

DOI： 10.1246/cl.160909

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C6DT01655C

Language：English   Publishing type：Research paper (scientific journal)  

We report the first example of a non-precious metal molecular catalyst for a fuel cell cathode. A nickel dihydrido complex is capable of reducing dioxygen to water through a four-electron pathway, as evidenced by an isotope-labeling experiment and electrochemical measurements.

DOI： 10.1246/cl.150988

Language：English   Publishing type：Research paper (scientific journal)  

Synthesis and Structure of a Water-soluble mu-eta(1):eta(1)-N-2 Dinuclear Ru-II Complex with a Polyamine Ligand
We report the first example of a mu-eta(1):eta(1)-N-2 dinuclear Run complex with a polyamine ligand and elucidate the structure by means of X-ray analysis. The N N stretching vibration has been observed at 1994 cm(-1) by Raman spectroscopy, which is the lowest value of all the known N-2-coordinated Run complexes. This low value strongly suggests the N N. bond is primed for activation.

DOI： 10.1246/cl.151004

Language：English   Publishing type：Research paper (scientific journal)  

We report the first example of reduction of O-2 to H2O by a Ni(II) dihydrido species. Isotope-labeling experiments reveal a four-electron reduction of O-2 by the dihydrido species. The water-soluble Ni(II) dihydrido species was characterized by X-ray analysis, electrospray ionization mass spectrometry, and IR, H-1-INMR, ESR, and UV-vis spectroscopies.

DOI： 10.1246/cl.150935

Language：English   Publishing type：Research paper (scientific journal)  

We report the synthesis and characterization of a m-hydroxo NiRu complex as a model for the active site of (Ni-SIr)(I) of [NiFe]hydrogenase. This is the first example of the (Ni-SIr)(I) model with a bridging hydroxo ligand between dimetal centers and an available coordination site on Ni center cis to the bridging hydroxo ligand. We have determined the structure of the (NieSIr)(I) model complex by X-ray analysis and reported reversible switching between the catalytically inactive (NieSIr)(I) and a catalytically active (NieSIr)(II) models. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jorganchem.2014.09.025

Language：English   Publishing type：Research paper (scientific journal)  

Here, we report the first Fe-based model for metabolism linking between the dioxygen reduction of respiration and the water oxidation of photosynthesis. The reaction mechanism was investigated by X-ray analysis, UV-vis spectroscopy, and mass spectrometry.

DOI： 10.1246/cl.150468

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c5cc04286k

Language：English   Publishing type：Research paper (scientific journal)  

We report the first example of a Ni-0 precursor that provides a contamination-free (<1&#37;) nickel film by metal-organic chemical vapor deposition (MOCVD) using N-2 as the carrier gas. The structure and physical properties of the Ni-0 precursor and subsequent film are described.

DOI： 10.1246/cl.150155

Language：Others  

A [NiFe]hydrogenase model that catalyses the release of hydrogen from formic acid.

DOI： 10.1039/C4CC05911E, 10.1039/c4cc05911e

Language：English   Publishing type：Research paper (scientific journal)  

Membrane-bound formate dehydrogenase (FDH) was purified to homogeneity from a facultative anaerobic bacterium Citrobacter sp. S-77. The FDH from Citrobacter sp. S-77 (FDHS77) was a monomer with molecular mass of approximately 150 kDa. On SDS-PAGE, the purified FDHS77 showed as three different protein bands with molecular mass of approximately 95, 87, and 32 kDa, respectively. Based on the N-terminal amino acid sequence analysis, the sequence alignments observed for the 87 kDa protein band were identical to that of the large subunit of 95 kDa, indicating that the purified FDHS77 consisted of two subunits; a 95 kDa large subunit and a 32 kDa small subunit. The purified FDHS77 in this purification did not contain a heme b subunit, but the FDHS77 showed significant activity for formate oxidation, determined by the V-max of 30.4 U/mg using benzyl viologen as an electron acceptor. The EPR and ICP-MS spectra indicate that the FDHS77 is a molybdenum-containing enzyme, displaying a remarkable O-2-stability along with thermostability and pH resistance. This is the first report of the purification and characterization of a FDH from Citrobacter species. (c) 2014, The Society for Biotechnology, Japan. All rights reserved.

DOI： 10.1016/j.jbiosc.2014.03.011

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

We report the synthesis of mononuclear nonheme manganese(V)-oxo complexes in aqueous acetonitrile solution from the reaction of manganese(M) complexes using hydrogen peroxide as an oxidant for the first time. A crystal structure of chloro derivative of manganese(V)-oxo complex and its reactivity toward 3,5-di-tert-butyl-catechol are also reported.

DOI： 10.1246/cl.140376

Language：English   Publishing type：Research paper (scientific journal)  

A new cyanobacterium of strain 0-77 was isolated from a hot spring at Aso-Kuju National Park, Kumamoto, Japan. According to the phylogenetic analysis determined by 165 rRNA gene sequence, the strain 0-77 belongs to the genus Leptolyngbya, classifying into filamentous non-heterocystous cyanobacteria. The strain 0-77 showed the thermophilic behavior with optimal growth temperature of 55 degrees C. Moreover, we have purified and characterized the oxygen-evolving photosystem II (PSII) from the strain 0-77. The O-2-evolving activity of the purified PSII from strain 0-77 (PSII077) was 1275 +/- 255 mu mol O-2 (mg ChI a)(-1) h(-1). Based on the results of MALDI-TOF mass spectrometry and urea-SDS-PAGE analysis, the purified PSII077 was composite of the typical PSII components of CP47, CP43, PsbO, D2, D1, PsbV, PsbQ, PsbU, and several low molecular mass subunits. Visible absorption and 77 K fluorescence spectra of the purified PSII077 were almost identical to those of other purified PSIIs from cyanobacteria. This report provides the successful example for the purification and characterization of an active PSII from thermophilic, filamentous non-heterocystous cyanobacteria. (C) 2014, The Society for Biotechnology, Japan. All rights reserved.

DOI： 10.1016/j.jbiosc.2014.01.009

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Lanthanide(III)bent-metallocene complexes with a novel photofunctionalized pentamethylcyclopentadienyl ligand having an N-phenylcarbazolyl group (Cp-PhCar = eta(5)-C5Me4CH2-C18H12N), [Ln(Cp-PhCar)(2)I(THF)] (Ln = Tb (1), Gd (2)), were prepared and their molecular structures and luminescence properties were investigated. The f-f emission from the terbium metal center of I was efficiently sensitized by Cp-PhCar (epsilon = 0.88 x 10(4) M-1 cm(-1) at 331 nm, Phi = 0.67 at 330 nm excitation, k(r) = 1.68 x 10(3) s(-1)). Additionally, the solid-state structure of potassium salts of C-5-ring (eta(5)-C5R5, R = Me, H) derivatives was uncommonly characterized in Cp-PhCar.

DOI： 10.1021/om1003094

Language：English  

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