Hydrogen Oxidation by Bioinspired Models of [FeFe]-Hydrogenase

Area of Science:

• Bioinorganic Chemistry
• Organometallic Chemistry
• Catalysis

Background:

• Synthetic azadithiolate-bridged diiron clusters are structural models for [FeFe]-hydrogenase active sites.
• Recent advances enabled bidirectional catalysis (H2 oxidation and H+ reduction) in these models.
• Hydrogen oxidation by synthetic hydrogenase analogues, especially diiron hexacarbonyls, is uncommon.

Purpose of the Study:

• To synthesize and investigate a series of biomimetic diiron hexacarbonyl complexes.
• To understand how varying substituents on the azadithiolate bridge influence hydrogen oxidation.
• To explore structure-activity relationships in synthetic hydrogenase analogues.

Main Methods:

• Synthesis of novel azadithiolate-bridged diiron hexacarbonyl complexes.
• Systematic variation of para-substituents (electron-withdrawing vs. electron-donating) on the ortho-methyl aniline moiety.
• Electrochemical and spectroscopic characterization to probe electronic structure changes.

Main Results:

• The para-substituents significantly impact the electronic structure of the azadithiolate bridge and the diiron cluster.
• Electron-withdrawing groups, such as -NO2, enhance the rate of H2 oxidation compared to electron-donating groups like -OCH3.
• The electronic properties of the bridge are directly correlated with catalytic activity.

Conclusions:

• Substituent effects on the azadithiolate bridge are crucial for tuning the H2 oxidation capability of diiron hexacarbonyl complexes.
• This study provides insights into the design principles for developing efficient synthetic hydrogen oxidation catalysts.
• The findings advance the biomimetic approach to understanding and replicating hydrogenase function.