Cyclopropanation Using Electrons Derived from Hydrogen: Reaction of Alkenes and Hydrogen without Hydrogenation.

Have you ever imagined reactions of alkenes with hydrogen that result in anything other than hydrogenation or hydrogenative C-C coupling? We have long sought to develop not only hydrogenation catalysts that activate H as hydride ions but also electron transfer catalysts that activate H as a direct electron donor. Here, we report the reductive cyclopropanation of alkenes using an iridium electron storage catalyst with H as the electron source without releasing metal waste from the reductant. We discuss the catalytic mechanism with selectivity to give the -isomer.

Disassembly and reassembly of the non-conventional thermophilic C-phycocyanin.

C-phycocyanin (CPC), which contains open-chain tetrapyrroles, is a major light-harvesting red-fluorescent protein with an important role in aquatic photosynthesis. Recently, we reported a non-conventional CPC from Thermoleptolyngbya sp. O-77 (CPC) that contains two different structures, i.

Storing electrons from H for transfer to CO, all at room temperature.

We present an Ir complex that extracts electrons from H at room temperature and stores them as a H-derived energy carrier (HEC) at room temperature. Furthermore, we demonstrate that this complex reduces CO to a metal-CO species at room temperature, and present the first electrospray ionisation mass spectrum for this compound.

H-driven reduction of CO to formate using bacterial plasma membranes.

Bacterial membranes shield the intracellular compartment by selectively allowing unwanted substances to enter in, which in turn reduces overall catalytic efficiency. This report presents a model system using the isolated plasma membranes of Citrobacter sp. S-77 that harbor oxygen-stable [NiFe]hydrogenase and [Mo]formate dehydrogenase, which are integrated into a natural catalytic nanodevice through an electron transfer relay.

Single-Step Synthesis of Ni from Ni with H.

Chemists have long sought to regulate the reactivity of H , to yield hydride ions, hydrogen atoms, or electrons on demand. One source of inspiration for achieving this control is [NiFe]hydrogenase ([NiFe]H ase), which reacts with H to form various hydrogen active species such as Ni hydride species, Ni hydride species, and Ni low-valent species. Chemists have attempted to synthesize these hydrogen active species not only as models for the active species of [NiFe]H ase, but also as electron transfer catalysts.

Selective formate production from H and CO using encapsulated whole-cells under mild reaction conditions.

Biocatalytic CO reduction into formate is a crucial strategy for developing clean energy because formate is considered as one of the promising hydrogen storage materials for achieving net-zero carbon emissions. Here, we developed an efficient biocatalytic system to produce formate selectively by coupling two enzymatic activities of H oxidation and CO reduction using encapsulated bacterial cells of Citrobacter sp. S-77.

Safe, One-Pot, Homogeneous Direct Synthesis of HO.

Hydrogen peroxide is an environmentally friendly oxidizing agent but current synthetic methods are wasteful. This is a result of the high flammability of H/O mixtures and/or the requirement for cocatalysts. In this paper, we report the synthesis of HO by means of a homogeneous catalyst, which allows a safe, one-pot synthesis in water, using only H and O.

Light-driven oxidation of CH to C chemicals catalysed by an organometallic Ru complex with O.

CH conversion is one of the most challenging chemical reactions due to its inertness in terms of physical and chemical properties. We have achieved photo-induced C-H bond breaking of CH and successive C-O bond formation to form CHOH concomitant with HCHO by an organometallic Ru complex with O.

Reductive C(sp)-C(sp) homo-coupling of benzyl or allyl halides with H using a water-soluble electron storage catalyst.

This paper reports the first example of a reductive C(sp)-C(sp) homo-coupling of benzyl/allyl halides in aqueous solution by using H as an electron source {turnover numbers (TONs) = 0.5-2.3 for 12 h}.

H activation by hydrogenase-inspired NiFe catalyst using frustrated Lewis pair: effect of buffer and halide ion in the heterolytic H-H bond cleavage.

Hydrogen is a clean fuel alternative to fossil fuels, and it is vital to develop catalysts for its efficient activation and production. We investigate the reaction mechanism of H activation in an aqueous solution by the recently developed NiFe complex (Ogo . 2020, 6, eaaz8181) using density functional theory (DFT) calculation.

Hydrogen evolution, electron-transfer, and hydride-transfer reactions in a nickel-iron hydrogenase model complex: a theoretical study of the distinctive reactivities for the conformational isomers of nickel-iron hydride.

Hydrogen fuel is a promising alternative to fossil fuel. Therefore, efficient hydrogen production is crucial to elucidate the distinctive reactivities of metal hydride species, the intermediates formed during hydrogen activation/evolution in the presence of organometallic catalysts. This study uses density functional theory (DFT) to investigate the isomerizations and reactivities of three nickel-iron (NiFe) hydride isomers synthesized by mimicking the active center of NiFe hydrogenase.

Non-conventional octameric structure of C-phycocyanin.

C-phycocyanin (CPC), a blue pigment protein, is an indispensable component of giant phycobilisomes, which are light-harvesting antenna complexes in cyanobacteria that transfer energy efficiently to photosystems I and II. X-ray crystallographic and electron microscopy (EM) analyses have revealed the structure of CPC to be a closed toroidal hexamer by assembling two trimers. In this study, the structural characterization of non-conventional octameric CPC is reported for the first time.

C-H Arylation of Benzene with Aryl Halides using H and a Water-Soluble Rh-Based Electron Storage Catalyst.

This paper reports the first example of C-H arylation of benzene under mild conditions, using H as an electron source {turnover numbers (TONs)=0.7-2.0 for 24 h}.

Synthesis of acetic acid from CO, CHI and H using a water-soluble electron storage catalyst.

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.

[NiFe], [FeFe], and [Fe] hydrogenase models from isomers.

The study of hydrogenase enzymes (Hases) is necessary because of their importance to a future hydrogen energy economy. These enzymes come in three distinct classes: [NiFe] Hases, which have a propensity toward H oxidation; [FeFe] Hases, which have a propensity toward H evolution; and [Fe] Hases, 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.

Biochemical and structural characterization of a thermostable Dps protein with His-type ferroxidase centers and outer metal-binding sites.

The DNA-binding protein from starved cells (Dps) is found in a wide range of microorganisms, and it has been well characterized. However, little is known about Dps proteins from nonheterocystous filamentous cyanobacteria. In this study, a Dps protein from the thermophilic nonheterocystous filamentous cyanobacterium Thermoleptolyngbya sp.

Selective Oxidation of H and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study.

One of the challenges in utilizing hydrogen gas (H) as a sustainable fossil fuel alternative is the inhibition of H oxidation by carbon monoxide (CO), which is involved in the industrial production of H sources. To solve this problem, a catalyst that selectively oxidizes either CO or H or one that co-oxidizes H and CO is needed. Recently, a NiIr catalyst [NiCl(X)IrCl(η-CMe)], (X = dimethyl-3,7-diazanonane-1,9-dithiolate), which efficiently and selectively oxidizes either H or CO depending on the pH, has been developed ( , 56, 9723-9726).

Computational Study on the Light-Induced Oxidation of Iridium-Aqua Complex to Iridium-Oxo Complex over WO(001) Surface.

An iridium aqua complex [Ir(η-CMe){bpy(COOH)}(HO)] under visible light irradiation has been experimentally reported to form an iridium-oxo (Ir-oxo) complex [Ir(η-CMe){bpy(COOH)}(O)], which oxidizes HO to O. However, the mechanism for the formation of this Ir-oxo complex remains unclear, due to the difficulties in observing the unstable Ir-oxo complex and computing light-induced systems having different numbers of electrons. In this study, we perform density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to investigate more in detail our previously proposed deprotonation and light-induced oxidation reactions composing the formation of the Ir-oxo complex.

Homogeneous catalytic reduction of polyoxometalate by hydrogen gas with a hydrogenase model complex.

The homogeneous catalytic reduction of a polyoxometalate (POM) by hydrogen gas in aqueous media was investigated for the first time by using a [NiRu] hydrogenase model complex (I) under very mild conditions. By bubbling hydrogen gas into the buffer solution containing I and the Dawson-type POM (II), the color of the solution turned from pale yellow to dark blue, suggesting the reduction of II. The catalytic and kinetic studies revealed that I acted as an efficient catalyst to yield one-electron-reduced Dawson-type POM (II) with a low energy barrier for activating dihydrogen and reducing II a hydride complex of I.

Dual Catalytic Cycle of H and HO Oxidations by a Half-Sandwich Iridium Complex: A Theoretical Study.

While hydrogenase and photosystem II enzymes are known to oxidize H and HO, respectively, a recently reported iridium aqua complex [Ir(η-CMe){bpy(COOH)}(HO)] is able to oxidize both of the molecules and generate energies as in the fuel and solar cells ( Ogo ChemCatChem 2017 , 9 , 4024 - 4028 ). To understand the mechanism behind such an interesting bifunctional catalyst, in the present study, we perform density functional theory (DFT) calculations on the dual catalytic cycle of H and HO oxidations by the iridium aqua complex. In the H oxidation, we found that the H-H bond is easily cleaved in a heterolytic fashion, and the resultant iridium hydride complex is significantly stabilized by the presence of HO molecules, due to dihydrogen bond.

Glyceraldehyde-3-phosphate dehydrogenase from sp. S-77 is post-translationally modified by CoA (protein CoAlation) under oxidative stress.

Protein CoAlation (S-thiolation by coenzyme A) has recently emerged as an alternative redox-regulated post-translational modification by which protein thiols are covalently modified with coenzyme A (CoA). However, little is known about the role and mechanism of this post-translational modification. In the present study, we investigated CoAlation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from a facultative anaerobic Gram-negative bacterium sp.

Redox-dependent conformational changes of a proximal [4Fe-4S] cluster in Hyb-type [NiFe]-hydrogenase to protect the active site from O.

Citrobacter sp. S-77 [NiFe]-hydrogenase harbors a standard [4Fe-4S] cluster proximal to the Ni-Fe active site. The presence of relocatable water molecules and a flexible aspartate enables the [4Fe-4S] to display redox-dependent conformational changes.

Oxidation of Guanosine Monophosphate with O via a Ru-peroxo Complex in Water.

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 and in water.

Multifunctional Catalysts for H O -Resistant Hydrogen Fuel Cells.

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