Structural and Functional Analogues of the Active Sites of the [Fe]-, [NiFe]-, and [FeFe]-Hydrogenases

Tard, Cédric; Pickett, Christopher J.

doi:10.1021/cr800542q

Cited by 1,204 publications

(1,033 citation statements)

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“…Examples of molybdenum-and iron-based catalysts have also been reported. [14][15][16] Significant advances have been realized with iron-thiolate complexes of the type [Fe 2 (m-SRS)(CO) 6Àx L x ] (R= organic group, L = electron-donor ligand, x 4), [17][18][19][20][21][22][23][24][25] which are simplified models of the Fe 2 S 2 subunit of iron-iron hydrogenase enzymes. [26] The utilization of these iron-thiolate complexes for visible light-driven H 2 production has been recently reviewed.…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic Hydrogen Production Using Models of the Iron–Iron Hydrogenase Active Site Dispersed in Micellar Solution

2013

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International audienceIron–thiolate complexes of the type [Fe2(μ-bdt)(CO)6−xP(OMe3)x] (bdt=S2C6H4=benzenedithiolate, x≤2) are simplified models of iron–iron hydrogenase enzymes. Recently, we have shown that these water-insoluble organometallic complexes, when included into micelles formed by sodium dodecyl sulfate (SDS), are good catalysts for the electrochemical production of hydrogen in aqueous solutions at pH<6. We herein report that the all-CO derivative [Fe2(μ-bdt)(CO)6] (1), owing to its comparatively low reduction potential, is also a robust molecular catalyst for visible-light-driven production of H2 in aqueous SDS solutions at pH 10.5. Irradiation at λ=455 nm of a system consisting of complex 1, Eosin Y as a sensitizer, and triethylamine as an electron donor produced up to 0.86 mL of H2 in 4.5 h, corresponding to a turnover number of 117 mol of H2 per mol of catalyst. In the presence of a large excess of sensitizer, the production of H2 lasted for more than 30 h, stressing the relative stability of complex 1 under the photocatalytic conditions used herein. Thermodynamic considerations and UV/Vis spectroscopy experiments suggest that the catalytic cycle begins with the photo-driven reduction of complex 1. The reduced intermediate reacts with a proton source to yield iron hydride. Subsequent reduction and protonation steps produce H2, regenerating the starting complex. As a result, the iron–thiolate complex 1 is a versatile proton reduction catalyst that can utilize either solar or electrical energy inputs, providing a starting point for the construction of noble metal-free molecular systems for renewable H2 production

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Section: Introductionmentioning

confidence: 99%

Photocatalytic Hydrogen Production Using Models of the Iron–Iron Hydrogenase Active Site Dispersed in Micellar Solution

2013

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“…Platinum is very efficient in catalyzing H 2 production, but the low natural abundance and high cost of this noble metal restrict its widespread utilization 9, 10. Progress has been made in identifying HER catalysts by the use of molecular complexes consisting of earth‐abundant metals, such as Fe,11, 12, 13, 14, 15 Co,9, 16, 17, 18, 19, 20 Ni,21, 22, 23, 24, 25 and Mo 26, 27. For example, Co and Fe complexes of N‐based macrocyclic ligands (e.g.…”

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confidence: 99%

Singly versus Doubly Reduced Nickel Porphyrins for Proton Reduction: Experimental and Theoretical Evidence for a Homolytic Hydrogen‐Evolution Reaction

et al. 2016

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A nickel(II) porphyrin Ni‐P (P=porphyrin) bearing four meso‐C6F5 groups to improve solubility and activity was used to explore different hydrogen‐evolution‐reaction (HER) mechanisms. Doubly reduced Ni‐P ([Ni‐P]2−) was involved in H2 production from acetic acid, whereas a singly reduced species ([Ni‐P]−) initiated HER with stronger trifluoroacetic acid (TFA). High activity and stability of Ni‐P were observed in catalysis, with a remarkable i c/i p value of 77 with TFA at a scan rate of 100 mV s−1 and 20 °C. Electrochemical, stopped‐flow, and theoretical studies indicated that a hydride species [H‐Ni‐P] is formed by oxidative protonation of [Ni‐P]−. Subsequent rapid bimetallic homolysis to give H2 and Ni‐P is probably involved in the catalytic cycle. HER cycling through this one‐electron‐reduction and homolysis mechanism has been proposed previously but rarely validated. The present results could thus have broad implications for the design of new exquisite cycles for H2 generation.

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“…These have been focused on silylenes,9 or cyclopentadienyl or arene (half)sandwich systems;10, 11, 12, 13 in these compounds protonation and proton‐coupled electron transfer are of limited relevance to the key chemical reactions of the metal complexes. In contrast, the spectroscopic data we have so obtained can be modelled by ab initio DFT calculations and we show that this provides compelling evidence for the muono‐formyl Fe‐C(Mu)=O and bridging Fe‐Mu‐Fe or terminal Fe‐Mu muonide transients, light isotopes of paramagnetic species that are implicit in hydrogen evolution and uptake 1, 2, 3, 14…”

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confidence: 88%

“…On a per catalytic site basis, the turnover frequencies of certain of these enzymes immobilized on electrodes can rival the best conventional electrocatalyst, carbon‐supported platinum 1, 2, 3. However, the high molecular mass and large geometric footprint of the native enzymes result in rather low current densities, at best ca.…”

mentioning

confidence: 99%

“…Given that hydrogen fuel or producer cells typically operate at current densities some two or three orders of magnitude greater, it is arguable whether hydrogenase‐based electrodes are likely to be useful materials in practical devices. Nevertheless, it is well established that the relatively small metallosulfur centers within these enzymes are responsible for their high catalytic activity and this has prompted extensive research on synthetic analogues of these active sites 1, 3, 4. This research is driven both by the need to provide mechanistic insights into the biological chemistry and the possibility of creating new materials for electrocatalysis based on abundant 3d metals.…”

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confidence: 99%

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Muonium Chemistry at Diiron Subsite Analogues of [FeFe]‐Hydrogenase

et al. 2016

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The chemistry of metal hydrides is implicated in a range of catalytic processes at metal centers. Gaining insight into the formation of such sites by protonation and/or electronation is therefore of significant value in fully exploiting the potential of such systems. Here, we show that the muonium radical (Mu.), used as a low isotopic mass analogue of hydrogen, can be exploited to probe the early stages of hydride formation at metal centers. Mu. undergoes the same chemical reactions as H. and can be directly observed due to its short lifetime (in the microseconds) and unique breakdown signature. By implanting Mu. into three models of the [FeFe]‐hydrogenase active site we have been able to detect key muoniated intermediates of direct relevance to the hydride chemistry of these systems.

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Structural and Functional Analogues of the Active Sites of the [Fe]-, [NiFe]-, and [FeFe]-Hydrogenases

Cited by 1,204 publications

References 356 publications

Photocatalytic Hydrogen Production Using Models of the Iron–Iron Hydrogenase Active Site Dispersed in Micellar Solution

Photocatalytic Hydrogen Production Using Models of the Iron–Iron Hydrogenase Active Site Dispersed in Micellar Solution

Singly versus Doubly Reduced Nickel Porphyrins for Proton Reduction: Experimental and Theoretical Evidence for a Homolytic Hydrogen‐Evolution Reaction

Muonium Chemistry at Diiron Subsite Analogues of [FeFe]‐Hydrogenase

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