铁铁氢化酶模型配合物的合成及其电催化产氢行为研究

Synthesis and Electro-catalytic Hydrogen Evolution of Iron(I)/(II) Complexes as Functional Models for the Active Site of [FeFe] Hydrogenases

通过十二羰基三铁与2,3-二巯基吡嗪在四氢呋喃中反应将刚性共轭桥引入到铁铁氢化酶活性中心模型配合物中,化学模拟合成了[μ-SC_4N_2H_2S-μ]Fe_2(CO)_6(配合物I)。研究了配合物I的PMe3配体取代过程,得到双核铁配合物[μ-SC_4N_2H_2S-μ]Fe_2(CO)_5(PMe_3)(II)和单核铁配合物[μ-SC_4N_2H_2S-μ]Fe(CO)_2(PMe_3)_2(III)。电化学循环伏安研究表明吸电子共轭桥连结构能有效降低[2Fe_2S]模型配合物中心铁原子上的电子云密度及其还原电位。配合物I相应的第一还原电位出现在-1.18V(vs.Fc/Fc^+),是目前已见报道中最正的。同时,配合物I、II、III在不同的还原电位下均具有电催化质子还原产氢的活性。其中,配合物III在-2.28V(vs.Fc/Fc^+)下的电催化活性最高。

In order to tune the reduction potential of [2Fe2S] model for the active site of [FeFe] hydrogenases,com- plex [μ-SC4N2H2S-μ]Fe2（CO）6 （I） with the conjugated and electron withdrawing bridge was synthetized by the reac- tion of Fe3 （CO）12 and pyrazine-2, 3-dithiol in tetrahydrofuran at refluxing temperature. The diiron complex [μ-SC4N2H2S-μ]Fe2（CO）5（PMe3） （II） and a monometallic complex [μ-SC4N2H2S-μ]Fe（CO）2（PMe3）2 （III） were ob- tained in the PMe3 ligand replacements. All the complexes were fully characterized by IR, 1H, 31p, 13C NMR and mass spectroscopy. The IR analysis data suggested that the electron withdrawing bridge, pyrazine, led to decreased electron density at the iron centers, which was consistent with the electrochemical studies. The cyclic voltammograms indicated that complex I exhibited a low primary reduction potential at -1.18V vs. Fc/Fc＋ with a 270mV positive shift related to that of the benzene-1,2-dithiolate （bdt） bridged analogue [ （μ-bdt）Fe3（CO）6]. Under the weak acid conditions,all the complexes could electrochemically catalyze the proton reduction. The mononuclear ferrous complex III showed rela- tively higher activity during the formation of hydrogen, confirming its potential as a catalyst for hydrogen production.