Chloride- and Hydrosulfide-Bound 2Fe Complexes as Models of the Oxygen-Stable State of [FeFe] Hydrogenase.

[FeFe] hydrogenases demonstrate remarkable catalytic efficiency in hydrogen evolution and oxidation processes. However, susceptibility of these enzymes to oxygen-induced degradation impedes their practical deployment in hydrogen-production devices and fuel cells. Recent investigations into the oxygen-stable (H) state of the H-cluster revealed its inherent capacity to resist oxygen degradation.

Stable Bimetallic Fe/{Fe(NO)} Moiety Derived from Reductive Transformations of a Diferrous-dinitrosyl Species.

A dimeric dithiolate-bridged species, [Fe(NO)(PS2)] () containing two {FeNO} units, can be isolated by treating [Fe(CO)(NO)] with PS2H (PS2H = bis(2-dimercaptophenyl)phenylphosphine). Crystallographic studies reveal the syn-configuration of NO units and the bridging thiolates in the butterfly shape of the 2Fe2S core. Addition of PPh to the solution of dinuclear leads to the formation of mononuclear {FeNO} [Fe(NO)(PS2)(PPh)] () that shows electrochemical responses similar to those of .

Surficial grafting of organoimido moieties enhances the capacity performance of oxometallic clusters.

Molybdenum trioxide (MoO) with a theoretical specific capacity of 1117 mA h g is widely considered a promising anode material for lithium-ion batteries. However, the irreversible conversion reactions, low electrical conductivity, and detrimental volume expansion upon Li intercalation between the one-dimensional layered structures of MoO hinder its practical implementation. Herein, we report a facile synthetic protocol that allows surficial modification by replacing the terminal and bridging oxo groups of molybdenum oxide clusters.

Demethylation of an artificial hydrogenase agent for prolonged CO release and enhanced anti-tau aggregation activity.

Carbon monoxide (CO) plays an important role in signaling in cells, making its use as a therapeutic tool highly intriguing. Reduced burst emissions are important to avoid the cytotoxicity and tissue damage caused by CO. Here, we developed a stable diiron carbonyl [FeFe] hydrogenase agent that enables prolonged CO release activity (half-life of over 9 h) in cells.

Organocatalytic asymmetric allylic alkylation of 2-methyl-3-nitroindoles: a route to direct enantioselective functionalization of indole C(sp)-H bonds.

We here described a direct catalytic asymmetric functionalization of 2-methylindoles using organocatalysis. An efficient asymmetric allylic alkylation reaction with respect to 2-methyl-3-nitroindoles and racemic Morita-Baylis-Hillman carbonate has been achieved by using a chiral biscinchona alkaloid catalyst, which provided the functionalized indole derivatives in good yields and enantioselectivities.

Photoinduced NO and HNO Production from Mononuclear {FeNO} Complex Bearing a Pendant Thiol.

Light triggers the formation of HNO from a metal-nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO} complexes (the Enemark-Felthan notation), [Fe(NO)(PS2)(PS2H)] (, PS2H = 2,2'-dimercapto-3,3'-bis(trimethylsilyl)diphenyl)phenylphosphine; H is a dissociable proton) with a pendant thiol and [Fe(NO)(PS2)(PS2CH)] () bearing a pendant thioether, are spectroscopically and structurally characterized. Both complexes are highly sensitive to visible light.

Energy-Efficient Hydrogen Evolution by Fe-S Electrocatalysts: Mechanistic Investigations.

The intrinsic catalytic property of a Fe-S complex toward H evolution was investigated in a wide range of acids. The title complex exhibited catalytic events at -1.16 and -1.

A reversible proton relay process mediated by hydrogen-bonding interactions in [FeFe]hydrogenase modeling.

A reversible and temperature-dependent proton-relay process is demonstrated for a Fe2 complex possessing a terminal thiolate in the presence of nitrogen-based acids. The terminal sulfur site (S(t) ) of the complex forms a hydrogen-bond interaction with N,N-dimethylanilinium acid at 183 K. The Fe2 core, instead, is protonated to generate a bridging hydride at 298 K.

Redox communication within multinuclear iron-sulfur complexes related to electronic interplay in the active site of [FeFe]hydrogenase.

The one-electron oxidations of a Fe2 complex lead to the formation of a persistent metal-stabilized thiyl radical Fe2 species, mixed-valent Fe4, and Fe8 complexes. The unpaired spin in the Fe2 radical species delocalizes over the Fe2 and the aromatic dithiolate, mostly on the terminal sulfur. The subsequent dimerization of the singly oxidized Fe2 to the Fe4 retains the partial thiyl radical character.

[FeFe] hydrogenase active site modeling: a key intermediate bearing a thiolate proton and Fe hydride.

The first di-protonated [FeFe] hydrogenase model relevant to key intermediates in catalytic hydrogen production is reported. The complex bearing the S-proton and Fe-hydride is structurally and spectroscopically characterized as well as studied by DFT calculations. The results show that the thiolate sulfur can accept protons during the catalytic routes.