Attachment of a Hydrogen‐Bonding Carboxylate Side Chain to an [FeFe]‐Hydrogenase Model Complex: Influence on the Catalytic Mechanism |
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| Authors: | Weiming Gao Dr Junliang Sun Dr Torbjörn Åkermark Dr Mingrun Li Dr Lars Eriksson Dr Licheng Sun Prof Björn Åkermark Prof |
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| Institution: | 1. Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 10691 Stockholm (Sweden), Fax: (+46)?8‐154908;2. Division of Structural Chemistry, Arrhenius Laboratory, Stockholm University, 10691 Stockholm (Sweden);3. Applied Electrochemistry, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), 10044 Stockholm (Sweden);4. Department of Chemistry, Royal Institute of Technology (KTH), 10044 Stockholm (Sweden) |
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| Abstract: | Azapropanedithiolate (adt)‐bridged model complexes of FeFe]‐hydrogenase bearing a carboxylic acid functionality have been designed with the aim of decreasing the potential for reduction of protons to hydrogen. Protonation of the bisphosphine complexes 4 – 6 has been studied by in situ IR and NMR spectroscopy, which revealed that protonation with triflic acid most likely takes place first at the N‐bridge for complex 4 but at the Fe? Fe bond for complexes 5 and 6 . Using an excess of acid, the diprotonated species could also be observed, but none of the protonated species was sufficiently stable to be isolated in a pure state. Electrochemical studies have provided an insight into the catalytic mechanisms under strongly acidic conditions, and have also shown that complexes 3 and 6 are electro‐active in aqueous solution even in the absence of acid, presumably due to hydrogen bonding. Hydrogen evolution, driven by visible light, has been observed for three‐component systems consisting of Ru(bpy)3]2+, complex 1 , 2 , or 3 , and ascorbic acid in CH3CN/D2O solution by on‐line mass spectrometry. |
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| Keywords: | electrochemistry electron transfer enzyme model iron‐hydrogenase proton reduction |
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