Encapsulating [FeFe]-hydrogenase model compounds in peptide hydrogels dramatically modifies stability and photochemistry

A [FeFe]-hydrogenase model compound (µ-S(CH2)3S)Fe2(CO)4(PMe3)2 [1] has been encapsulated in a Low Molecular Weight (LMW) hydrogelator (Fmoc-Leu-Leu). Linear infrared absorption spectroscopy, gel melting and ultrafast time-resolved infrared spectroscopy experiments reveal significant contrasts in chemical environment and photochemistry between the encapsulated molecules and solution phase systems. Specifically, the gel provides a more rigid hydrogen bonding environment, which restricts isomerisation following photolysis while imparting significant increases in stability relative to a similarly aqueous solution. Since understanding and ultimately controlling the mechanistic role of ligands near Fe centers is likely to be crucial in exploiting artificial hydrogenases, these gels may offer a new option for future materials design involving catalysts.