An approach to water-soluble hydrogenase active site models: Synthesis and electrochemistry of diiron dithiolate complexes with 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane ligand(s) |
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| Authors: | Yong Na Kun Jin Licheng Sun |
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| Affiliation: | a State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology, Zhongshan Road 158-46, Dalian 116012, PR China
b Department of Chemistry, Royal Institute of Technology (KTH), Stockholm 10044, Sweden |
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| Abstract: | In order to improve the hydro- and protophilicity of the active site models of the Fe-only hydrogenases, three diiron dithiolate complexes with DAPTA ligand(s) (DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane), (μ-pdt)[Fe(CO)3][Fe(CO)2(DAPTA)] (1, pdt = 1,3-propanedithiolato), (μ-pdt)[Fe(CO)2(DAPTA)]2 (2) and (μ-pdt)[Fe(CO)2(PTA)][Fe(CO)2(DAPTA)] (3), were prepared and spectroscopically characterized. The water solubility of DAPTA-coordinate complexes 1-3 is better than that of the PTA-coordinate analogues. With complexes 1-3 as electrocatalysts, the overvoltage is reduced by 460-770 mV for proton reduction from acetic acid at low concentration in CH3CN. Significant decrease, up to 420 mV, in reduction potential for the Fe(I)Fe(I) to Fe(I)Fe(0) process and the curve-crossing phenomenon are observed in cyclic voltammograms of 2 and 3 in CH3CN/H2O mixtures. The introduction of the DAPTA ligand to the diiron dithiolate model complexes indeed makes the water solubility of 2 and 3 sufficient for electrochemical studies in pure water, which show that the proton reduction from acetic acid in pure water is electrochemically catalyzed by 2 and 3 at ca. −1.3 V vs. NHE. |
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| Keywords: | Bioinorganic chemistry Diiron dithiolate complexes Electrochemistry Iron-only hydrogenase Triazaphosphaadamantane ligand |
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