Photoinduced Hydrogen Evolution Catalyzed by a Synthetic Diiron Dithiolate Complex Embedded within a Protein Matrix

The hydrogen-evolving diiron complex, (mu-S)(2)Fe-2(CO)(6) with a tethered maleirnide moiety was synthesized and covalently embedded within the cavity of a rigid beta-barrel protein matrix by coupling a maleimide moiety to a cysteine residue within the beta-barrel. The (mu-S)(2)Fe-2(CO)(6) core within the cavity was characterized by UV-vis absorption and a characteristic CO vibration determined by IR measurements. The diiron complex embedded within the cavity retains the necessary catalytic activity (TON up to 130 for 6 h) to evolve H-2 via a photocatalytic cycle with a Ru photosensitizer in a solution of 100 mM ascorbate and 50 mM Tris/HCl at pH 4.0 and 25 degrees C.