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 H-2 evolution. We have recently focused on using the native CXXCH peptide sequence of the C-terminal segment of cytochrome c(556) 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 H-2 evolution with a turnover number of similar to 9 over 2 h at pH 8.5 in the presence of ascorbate as a sacrificial reagent. (c) 2011 Elsevier Inc. All rights reserved.