title: Photocatalytic hydrogen production using models of the iron-iron hydrogenase active site dispersed in micellar solution.
abstract: Iron-thiolate complexes of the type [Fe2 (μ-bdt)(CO)6-x P(OMe3 )x ] (bdt=S2 C6 H4 =benzenedithiolate, x≤2) are simplified models of iron-iron hydrogenase enzymes. Recently, we have shown that these water-insoluble organometallic complexes, when included into micelles formed by sodium dodecyl sulfate (SDS), are good catalysts for the electrochemical production of hydrogen in aqueous solutions at pH<6. We herein report that the all-CO derivative [Fe2 (μ-bdt)(CO)6 ] (1), owing to its comparatively low reduction potential, is also a robust molecular catalyst for visible-light-driven production of H2 in aqueous SDS solutions at pH 10.5. Irradiation at λ=455 nm of a system consisting of complex 1, Eosin Y as a sensitizer, and triethylamine as an electron donor produced up to 0.86 mL of H2 in 4.5 h, corresponding to a turnover number of 117 mol of H2 per mol of catalyst. In the presence of a large excess of sensitizer, the production of H2 lasted for more than 30 h, stressing the relative stability of complex 1 under the photocatalytic conditions used herein. Thermodynamic considerations and UV/Vis spectroscopy experiments suggest that the catalytic cycle begins with the photo-driven reduction of complex 1. The reduced intermediate reacts with a proton source to yield iron hydride. Subsequent reduction and protonation steps produce H2 , regenerating the starting complex. As a result, the iron-thiolate complex 1 is a versatile proton reduction catalyst that can utilize either solar or electrical energy inputs, providing a starting point for the construction of noble metal-free molecular systems for renewable H2 production.
authors.affiliation: UMR 6521, CNRS, Université de Bretagne Occidentale, 6 Avenue Le Gorgeu, CS 93837, 29238 Brest (France).
authors.forename: Christophe
authors.initials: C
authors.lastname: Orain
authors.forename: François
authors.initials: F
authors.lastname: Quentel
authors.forename: Frederic
authors.initials: F
authors.lastname: Gloaguen
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D002384:Catalysis; D020134:Catalytic Domain; D006859:Hydrogen / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008823:Micelles; D055668:Photochemical Processes; D012996:Solutions
chemical_list: D007506:Iron-Sulfur Proteins; D008823:Micelles; D012996:Solutions; D006859:Hydrogen; C118830:iron hydrogenase; D006864:Hydrogenase
keywords: dyes/pigments; hydrogen; iron; photochemistry; water chemistry