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This paper reports the first example of C-H arylation of benzene under mild conditions, using H2 as an electron source {turnover numbers (TONs)=0.7-2.0 for 24 h}. The reaction depends on a Rh-based electron storage catalyst, and proceeds at room temperature and in aqueous solution. Furthermore, the H2 is inactive during the radical transfer step, greatly reducing unwanted side reactions.

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.

This paper reports the synthesis, structure, and mechanistic action of a Rh-based catalyst, the monohydroxide diaqua RhIII complex 1, for the direct synthesis of H2O2 from H2 and O2. Of particular ...

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 developed via a homogeneous model complex of the [NiFe]hydrogenases (H2ases) and can act as both the cathode and anode of a fuel cell.

This paper reports the first example of a reductive C(sp

This paper reports a possible mechanism of acetic acid formation from CO2, CH3I and H2 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 H2, (2) the role of the metal (Rh) centre as a point for storing electrons from H2 and (3) the importance of an electron-withdrawing ligand (quaterpyridine, qpy) that supports electron storage.

This paper reports the first example of C-H arylation of benzene under mild conditions, using H

This paper reports a possible mechanism of acetic acid formation from CO2, CH3I and H2 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 H2, (2) the role of the metal (Rh) centre as a point for storing electrons from H2 and (3) the importance of an electron-withdrawing ligand (quaterpyridine, qpy) that supports electron storage.

Three isomers of the same NiFe complex can mimic the catalytic properties of [NiFe], [FeFe], and [Fe] hydrogenase enzymes., 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.

The development of hydrogen fuel cells is greatly hindered by the unwanted generation of H2 O2 at the cathode. A non-Pt cathode catalyst is now shown to be capable of simultaneously reducing both O2 and H2 O2 , thus rendering H2 O2 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 /H2 O2 .

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 O2 and in water.

We present a mechanistic investigation for the activation of H2 and O2, induced by a simple ligand effect within [NiFe] models for O2-tolerant [NiFe]hydrogenase. Kinetic study reveals Michaelis–Menten type saturation behaviors for both H2 and O2 activation, which is the same behavior as that found in O2-tolerant [NiFe]hydrogenase. Such saturation behavior is caused by H2 complexation followed by heterolytic cleavage of H2 by an outer-sphere base, resulting in the formation of a hydride species showing hydridic character.

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.

We report the reactivity of a new MnI(cyclam) complex (cyclam: 1,4,8,11-tetraazacyclotetradecane) toward O2 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 MnI dicarbonyl complex, [MnI(cyclam)(CO)2]+ reacts with O2, but not with H2O, to form a bis(μ-oxo)Mn2III,IV complex, though a MnI tricarbonyl complex, [MnI(cyclam)(CO)3]+ does not react with either O2 or H2O. Newly synthesized MnI(cyclam) dicarbonyl complex was characterized by ESI mass spectrometry, UV–vis absorption spectroscopy, IR spectroscopy, and X-ray analysis.

We report the first example of a wholly inorganic mimic of a part of the FeMoco active centre of nitrogenases. We detail the synthesis, characterisation and reactivity of two related, transient hydride-containing inorganic clusters, a dihydride complex and a vinyl monohydride complex, which bear the [Fe2MoOS3] portion of FeMoco. The dihydride complex is capable of reducing acetylene to ethylene via the vinyl monohydride complex. In the reaction cycle, a transient low-valent complex was generated by the reductive elimination of H2 or ethylene from dihydride or vinyl monohydride complexes, respectively.

We report the first example of the characterization of a Ru-based peroxide intermediate of O2-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.

The development of hydrogen fuel cells is greatly hindered by the unwanted generation of H

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

We report the synthesis and characterization of a μ-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 (Ni–SIr)I model complex by X-ray analysis and reported reversible switching between the catalytically inactive (Ni–SIr)I and a catalytically active (Ni–SIr)II models.

We report an acid-stable Si oxide-doped Ir oxide film (IrSi oxide film), made by metal organic chemical vapour deposition (MOCVD) of an Ir(V) complex for electrochemical water-oxidation. This is a successful improvement of catalytic ability and stability depending upon the pH of Ir oxide by doping of Si oxide. The turnover frequency (TOF) of the electrochemical water-oxidation by the IrSi oxide film is the highest of any Si oxide-doped Ir oxide materials and higher even than that of Ir oxide in acidic media.

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, ...

We report the first example of a µ-η1:η1-N2 dinuclear RuII complex with a polyamine ligand and elucidate the structure by means of X-ray analysis. The N≡N stretching vibration has been observed at ...

We report the first example of reduction of O2 to H2O by a Ni(II) dihydrido species. Isotope-labeling experiments reveal a four-electron reduction of O2 by the dihydrido species. The water-soluble ...

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...

We report the first example of a Ni0 precursor that provides a contamination-free (

We report the synthesis of mononuclear nonheme manganese(V)–oxo complexes in aqueous acetonitrile solution from the reaction of manganese(III) complexes using hydrogen peroxide as an oxidant for th...

Lanthanide(III) bent-metallocene complexes with a novel photofunctionalized pentamethylcyclopentadienyl ligand having an N-phenylcarbazolyl group (CpPhCar = η5-C5Me4CH2C18H12N), [Ln(CpPhCar)2I(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 1 was efficiently sensitized by CpPhCar (e = 0.88 × 104 M−1 cm−1 at 331 nm, Φ = 0.67 at 330 nm excitation, kr = 1.68 × 103 s−1). Additionally, the solid-state structure of potassium salts of C5-ring (η5-C5R5, R = Me, H) derivatives was uncommonly characterized in CpPhCar.

A naphthyl-substituted pentamethylcyclopentadienyl ligand (Cp(Naph) = η(5)-C(5)Me(4)CH(2)C(10)H(7)) and its Sm(II) complexes [Sm(Cp(Naph))(2)(THF)(x)] (1: x = 2, 2: x = 0) have been prepared and characterised. The solvent-induced reversible conversion between the di-THF solvated purple complex 1 and the un-solvated dark green complex 2 is presented.

We report the decomposition of formic acid to hydrogen and carbon dioxide, catalysed by a NiRu complex originally developed as a [NiFe]hydrogenase model. This is the first example of H2 evolution, catalysed by a [NiFe]hydrogenase model, which does not require additional energy.

Herein, we report the first crystal structure of a monomeric p-semiquinonato d-block complex and its reactivity toward dioxygen, closely associated with a biological system of an oxygen evolving centre of photosystem II.

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 Vmax 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 O2-stability along with thermostability and pH resistance. This is the first report of the purification and characterization of a FDH from Citrobacter species.

We propose a model for the water-oxidation and recovery systems of the oxygen-evolving complex (OEC) of the photosystem II (PSII) enzyme. The whole system is constructed from two catalytic cycles, conducted as a tandem reaction: (i) a water-oxidation loop uses cerium(IV) ammonium nitrate as an oxidant to activate a dimanganese complex for water-oxidation and thereby liberate a molecule of O2 and (ii) a recovery loop begins with photoinhibition of the dimanganese complex but then uses O2 to reactivate the manganese centre. The net result is a catalytic water-oxidation catalyst that can use self-generated O2 for recovery.

A new cyanobacterium of strain O-77 was isolated from a hot spring at Aso-Kuju National Park, Kumamoto, Japan. According to the phylogenetic analysis determined by 16S rRNA gene sequence, the strain O-77 belongs to the genus Leptolyngbya, classifying into filamentous non-heterocystous cyanobacteria. The strain O-77 showed the thermophilic behavior with optimal growth temperature of 55°C. Moreover, we have purified and characterized the oxygen-evolving photosystem II (PSII) from the strain O-77. The O2-evolving activity of the purified PSII from strain O-77 (PSIIO77) was 1275 ± 255 μmol O2 (mg Chl a)(-1) h(-1). Based on the results of MALDI-TOF mass spectrometry and urea-SDS-PAGE analysis, the purified PSIIO77 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 PSIIO77 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.