TY - JOUR
T1 - The reactivity of molecular oxygen and reactive oxygen species with [FeFe] hydrogenase biomimetics
T2 - Reversibility and the role of the second coordination sphere
AU - Wang, Vincent C.C.
AU - Esmieu, Charlène
AU - Redman, Holly J.
AU - Berggren, Gustav
AU - Hammarström, Leif
N1 - Funding Information:
This work was financially supported by the Swedish research Council (contract no. 621-2014-5670) and ERC (contract no. 714102, to G. B.). We acknowledge postdoc grants to V. W. and C. E. from the Wenner-Gren Foundations. We are very grateful to Jakob Thyr and Prof. Tomas Edvinsson, who made initial efforts on Raman spectroscopy and provided inspiration on IR measurements. We also thank Dr Patrícia Raleiras for conducting spin counting experiments and MSc. Robin Tyburski for supporting DFT calculations through his funding.
Publisher Copyright:
This journal is © The Royal Society of Chemistry.
PY - 2020
Y1 - 2020
N2 - The development of oxygen-tolerant H2-evolving catalysts plays a vital role for a future H2 economy. For example, the [FeFe] hydrogenase enzymes are excellent catalyst for H2 evolution but rapidly become inactivated in the presence of O2. The mechanistic details of the enzyme's inactivation by molecular oxygen still remain unclear. Here, two H2-evolving diiron complexes [Fe2(μ-SCH2NHCH2S)(CO)6] (1adt) and [Fe2(μ-SCH2CH2CH2S)(CO)6] (2pdt), inspired by the active site of [FeFe] hydrogenase, were investigated for their reactivity with molecular oxygen and reactive oxygen species. A one-electron reduced and oxygenated 1adt species was identified and characterized spectroscopically, which can be directly generated by reacting with molecular oxygen and chemical reductants at room temperature but it is unstable and gradually decomposes. Interestingly, the whole process is reversible and the addition of protons can facilitate the deoxygenation process and prevent further degradation at room temperature. This new identification of intermediate species serves as a model for studying the reversible inactivation and degradation of oxygen-sensitive [FeFe] hydrogenases by O2, and provides chemical precedence for such processes. In comparison, the complex lacking the nitrogen bridgehead, 2pdt, exhibits reduced reactivity towards O2 in the presence of reductants, highlighting that the importance of the second coordination sphere on modulating the oxygenation processes. These results provide new directions to design molecular electrocatalysts for proton reduction operated at ambient conditions and the re-engineering of [FeFe] hydrogenases for improving oxygen tolerance.
AB - The development of oxygen-tolerant H2-evolving catalysts plays a vital role for a future H2 economy. For example, the [FeFe] hydrogenase enzymes are excellent catalyst for H2 evolution but rapidly become inactivated in the presence of O2. The mechanistic details of the enzyme's inactivation by molecular oxygen still remain unclear. Here, two H2-evolving diiron complexes [Fe2(μ-SCH2NHCH2S)(CO)6] (1adt) and [Fe2(μ-SCH2CH2CH2S)(CO)6] (2pdt), inspired by the active site of [FeFe] hydrogenase, were investigated for their reactivity with molecular oxygen and reactive oxygen species. A one-electron reduced and oxygenated 1adt species was identified and characterized spectroscopically, which can be directly generated by reacting with molecular oxygen and chemical reductants at room temperature but it is unstable and gradually decomposes. Interestingly, the whole process is reversible and the addition of protons can facilitate the deoxygenation process and prevent further degradation at room temperature. This new identification of intermediate species serves as a model for studying the reversible inactivation and degradation of oxygen-sensitive [FeFe] hydrogenases by O2, and provides chemical precedence for such processes. In comparison, the complex lacking the nitrogen bridgehead, 2pdt, exhibits reduced reactivity towards O2 in the presence of reductants, highlighting that the importance of the second coordination sphere on modulating the oxygenation processes. These results provide new directions to design molecular electrocatalysts for proton reduction operated at ambient conditions and the re-engineering of [FeFe] hydrogenases for improving oxygen tolerance.
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U2 - 10.1039/c9dt04618f
DO - 10.1039/c9dt04618f
M3 - Article
C2 - 31854399
AN - SCOPUS:85078341173
VL - 49
SP - 858
EP - 865
JO - Dalton Transactions
JF - Dalton Transactions
SN - 1477-9226
IS - 3
ER -