Photocatalytic hydrogen evolution by a diiron hydrogenase model based on a peptide fragment of cytochrome c556 with an attached diiron carbonyl cluster and an attached ruthenium photosensitizer

It is of particular interest to mimic the process of intramolecular electron relay at the active site of [FeFe]-hydrogenase in order to understand the mechanism of the catalytic activity of H2 evolution. We have recently focused on using the native CXXCH peptide sequence of the C-terminal segment of cytochrome c556 as a platform which holds a diiron carbonyl cluster via two cysteines and have attached a ruthenium photosensitizer via a histidine. The modified peptide with the two metal moieties is found to act as the photocatalyst for H2 evolution with a turnover number of ~9 over 2h at pH 8.5 in the presence of ascorbate as a sacrificial reagent. To create a [FeFe]-hydrogenase functional model, two essential components, a diiron carbonyl cluster and ruthenium photosensitizer, were attached to the CXXCH peptide platform of the cytochrome c556 sequence. The peptide–metal complex functions as a hydrogen-evolving catalyst with a turnover number of 9 over 2h in water (pH 8.5). [Display omitted]