Combining acid-base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase

Area of Science:

• Bioinorganic Chemistry
• Catalysis
• Enzyme Mechanisms

Background:

• Enzymes like [FeFe]-hydrogenases utilize redox cofactors for electron transfer.
• Ferredoxins provide one-electron redox capability, complementing the diiron active site in hydrogenases.
• Mimicking ferredoxin function is key to understanding and replicating hydrogenase activity.

Purpose of the Study:

• To synthesize a novel model system that replicates ferredoxin function in [FeFe]-hydrogenases.
• To investigate the catalytic activity of a model containing a redox-active ligand and a diiron active site.
• To explore the unique reactivity of the model system towards hydrogen and carbon monoxide.

Main Methods:

• Synthesis of a specific model complex, Fe(2)[(SCH(2))(2)NBn](CO)(3)(FcP*)(dppv) (1), incorporating a redox-active ligand (FcP*).
• Characterization of the model's electrochemical properties, particularly the redox potential of FcP*.
• Investigation of the catalytic activity of the oxidized model complex ([1](2+)) in hydrogen oxidation.

Main Results:

• The redox-active ligand FcP* mimics ferredoxin cofactors by oxidizing at mild potentials.
• The synthesized model complex (1) integrates a diiron center, proton relay, and a one-electron redox module.
• The oxidized model complex ([1](2+)) exhibits unique reactivity and demonstrates catalytic hydrogen oxidation in the presence of oxidant and base.

Conclusions:

• The study successfully created a functional model of [FeFe]-hydrogenase active sites using a synthetic redox cofactor.
• The findings highlight the potential of FcP* as a ferredoxin mimic for bioinorganic studies.
• The catalytic activity observed provides valuable insights into the mechanism of hydrogen oxidation by hydrogenases.