Protonengekoppelte Reduktion des katalytischen [4Fe‐4S]‐Zentrums in [FeFe]‐Hydrogenasen

[FeFe]-hydrogenases catalyze the uptake and release of molecular hydrogen (H2) at a unique iron-sulfur cofactor. The absence of electrochemical overpotential in the H2 release reaction makes [FeFe]-hydrogenases a prime example of efficient biocatalysis. However, the molecular proceedings of hydrogen turnover are not understood yet. In this study, we characterize the initial one-electron reduction of [FeFe]-hydrogenases by infrared spectro-electrochemistry and present evidence for proton-coupled electron transport in the formation of the reduced state Hred´. Charge compensation stabilizes the excess electron at the [4Fe-4S] cluster and maintains a conservative configuration of the diiron site. The role of Hred´ in hydrogen turnover and possible implications on the catalytic mechanism are discussed. We suggest that the regulation of electronic properties in the periphery of metal cofactors is key to orchestrate multi-electron processes.