A Reversible Proton Relay Process Mediated by Hydrogen‐Bonding Interactions in [FeFe]Hydrogenase Modeling

Chu, Kai‐Ti; Liu, Yu‐Chiao; Huang, Yu‐Huei; Hsu, Chia-Min; Lee, Gene‐Hsiang; Chiang, Ming‐Hsi

doi:10.1002/chem.201501114

Cited by 9 publications

(4 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This distance remained well within the sum of van der Waals radii. A similar H-bonding interaction between the S t of 1 – and N , N -dimethylanilinium acid was recently characterized at 183 K . This observed H-bonding interaction supports the hypothesis that the S t site of 1μH acts as the proton acceptor during catalysis.…”

Section: Resultssupporting

confidence: 81%

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

et al. 2018

Self Cite

View full text Add to dashboard Cite

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 -1.57 V (vs Fc/Fc) in the presence of trifluoromethanesulfonic acid (HOTf) and trifluoroacetic acid (TFA), respectively. The processes corresponded to the single reduction of the Fe-hydride-S-proton and Fe-hydride species, respectively. When anilinium acid was used, the catalysis occurred at -1.16 V, identical with the working potential of the HOTf catalysis, although the employment of anilinium acid was only capable of achieving the Fe-hydride state on the basis of the spectral and calculated results. The thermodynamics and kinetics of individual steps of the catalysis were analyzed by density functional theory (DFT) calculations and electroanalytical simulations. The stepwise CCE or CE (C, chemical; E, electrochemical) mechanism was operative from the HOTf or TFA source, respectively. In contrast, the involvement of anilinium acid most likely initiated a proton-coupled electron transfer (PCET) pathway that avoided the disfavored intermediate after the initial protonation. Via the PCET pathway, the heterogeneous electron transfer rate was increased and the overpotential was decreased by 0.4 V in comparison with the stepwise pathways. The results showed that the PCET-involved catalysis exhibited substantial kinetic and thermodynamic advantages in comparison to the stepwise pathway; thus, an efficient catalytic system for proton reduction was established.

show abstract

Section: Resultssupporting

confidence: 81%

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

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…The presence of the terminally coordinated thiolate (the S t site) in 1μH * – – 3μH * – provided an opportunity to examine the capability of the S t site for proton attachment, as occurred in [(μ,κ 2 -bdt)(μ-PPh 2 )(μ-H)Fe 2 (CO) 5 ]. , The reaction of 1μH * – – 3μH * – with 1 equiv of HOTf at 193 K afforded the S-protonated product [(μ,κ 2 -xdtH)(μ-H)(μ-CO)Fe 2 (CO) 5 ] ( 1μHSH *– 3μHSH *, the CEEC state), which was characterized by in situ FTIR spectroscopy. The species 1μHSH * was extremely unstable even at this temperature.…”

Section: Resultsmentioning

confidence: 99%

Protonation/Reduction of Carbonyl-Rich Diiron Complexes and the Direct Observation of Triprotonated Species: Insights into the Electrocatalytic Mechanism of Hydrogen Formation

et al. 2016

Self Cite

View full text Add to dashboard Cite

Both the reduced and the protonated states of diiron dithiolate complexes, which are key intermediate species for the electrocatalytic production of hydrogen, have been spectroscopically and theoretically investigated in this study. Five important states in the process of H 2 evolution have been characterized. In the presence of a superacid, protonation occurs onto the Fe−Fe vector of [(μ-xdt)Fe 2 (CO) 6 ] (xdt: pdt, 1,3-propanedithiolate; edt, 1,2-ethanedithiolate; bdt, 1,2-benzenedithiolate) to yield the cationic μ-H species (the C state). A single reduction at 193 K leads to the neutral species (the CE state), with similar structures for the pdt and edt bridgeheads. The CE species of the bdt analogue is unstable under the same conditions. An open structure resulting from the rupture of one Fe−S bond is suggested by DFT calculations. Subsequently, a second reduction induces a dramatic structural rearrangement in which the CEE state possesses an open structure exhibiting a μ-H and a μ-CO group. Protonation onto the terminal sulfur site of the CEE state affords the CEEC state, which readily converts to the parent hexacarbonyl complex accompanied by the liberation of H 2 at higher temperatures. In the presence of excess acid, the CEECC state is achieved and the third proton is coordinated to the Fe center. The S-proton and Fe-hydride have been characterized by 1 H and 2 D NMR spectroscopy. Electrocatalytic hydrogen production involving the CEEC and CEECC states has been investigated by DFT calculations. In combination with the spectroscopic results, this information allows us to construct the possible catalytic routes and study the plausible role of the triply protonated species least explored in biomimetic catalysis.

show abstract

“…Our findings provide an answer for what makes de novo catalyst design so challenging. While the critical role of pendant bases for rapid H 2 turnover rates at the catalytic cofactor (i.e., the adt bridgehead ligand) is well established in the design of synthetic catalysts (68,69), longer-range proton relay systems are now being increasingly recognized and implemented as essential attributes into the designs of synthetic Ni-or Febased catalysts (18,38,(70)(71)(72)(73)(74). Of particular note are recent enzyme-inspired efforts by Shaw and coworkers, who modified a Ni-based Dubois-type catalyst (18) with amino acid-based proton relay systems (e.g., arginine and tyrosine).…”

Section: Discussionmentioning

confidence: 99%

The roles of long-range proton-coupled electron transfer in the directionality and efficiency of [FeFe]-hydrogenases

Lampret

Duan

Hofmann

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

As paradigms for proton-coupled electron transfer in enzymes and benchmarks for a fully renewable H2 technology, [FeFe]-hydrogenases behave as highly reversible electrocatalysts when immobilized on an electrode, operating in both catalytic directions with minimal overpotential requirement. Using the [FeFe]-hydrogenases from Clostridium pasteurianum (CpI) and Chlamydomonas reinhardtii (CrHydA1) we have conducted site-directed mutagenesis and protein film electrochemistry to determine how efficient catalysis depends on the long-range coupling of electron and proton transfer steps. Importantly, the electron and proton transfer pathways in [FeFe]-hydrogenases are well separated from each other in space. Variants with conservative substitutions (glutamate to aspartate) in either of two positions in the proton-transfer pathway retain significant activity and reveal the consequences of slowing down proton transfer for both catalytic directions over a wide range of pH and potential values. Proton reduction in the variants is impaired mainly by limiting the turnover rate, which drops sharply as the pH is raised, showing that proton capture from bulk solvent becomes critical. In contrast, hydrogen oxidation is affected in two ways: by limiting the turnover rate and by a large overpotential requirement that increases as the pH is raised, consistent with the accumulation of a reduced and protonated intermediate. A unique observation having fundamental significance is made under conditions where the variants still retain sufficient catalytic activity in both directions: An inflection appears as the catalytic current switches direction at the 2H+/H2 thermodynamic potential, clearly signaling a departure from electrocatalytic reversibility as electron and proton transfers begin to be decoupled.

show abstract

A Reversible Proton Relay Process Mediated by Hydrogen‐Bonding Interactions in [FeFe]Hydrogenase Modeling

Cited by 9 publications

References 27 publications

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

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

Protonation/Reduction of Carbonyl-Rich Diiron Complexes and the Direct Observation of Triprotonated Species: Insights into the Electrocatalytic Mechanism of Hydrogen Formation

The roles of long-range proton-coupled electron transfer in the directionality and efficiency of [FeFe]-hydrogenases

Contact Info

Product

Resources

About