Synthesis,Characterization And Electrochemical Studies Of Azadithiolate-[FeFe]-Hydrogenase Models Based On Aromatic Amine-containing Organophosphine Ligands

Hydrogenase is a type of enzyme that exists in microorganism,which can catalyze highly proton reduction and hydrogen oxidation reversibly.Howerver,the unstable hydrogenase in vitro hinders its practical application.Since the crystal structure of hydrogenase has been determined,the simulation of the model structure,function and catalytic mechanism of hydrogenase activity center has become a hotspot in the field of green chemistry.The chemist chooses[2Fe2S]cluster as the operational center for the simulation of hydrogenation enzyme to better understand the functional structure and hydrogen production mechanism of the hydrogenase activity center.Since organophosphine,isocyanide and nitrogen-containing ligands are not only a class of ligands with good electron donation,but also regulate its own electron-donating and spatial effect by changing its substituent,they are extensively used to better simulate the CN-ligand of Hydrogenase.Based on our group's stdudy on organophosphine ligands in recent years,seven organophosphorus ligands and their azadithiolate-[FeFe]-Hydrogenase models were synthesized.These synthesized hydrogenase models were characterized by IR,NMR and ESI-MS.Their electrochemical properties were also explored by cyclic voltammetry(CV).This thesis relates to three aspects:1.The synthesis of seven organophosphorus ligands:diphenylphosphine methanol(L1),N-(diphenylphosphino)methylene aniline(L2),N-(diphenylphosphino)methylene-1-naphthylamine(L3).N-[(diphenylphosphino)methylene]-N-phenylmethylene aniline(L4),N-[(diphenylphosphino)methylene]N-phenylmethylene-1-naphthylamine(L5),N-[(diphenylphosphino)methylene]-N(2-pyridylmethylene)aniline(L6),N-[(diphenylphosphino)methylene]-N-(3-pyridylmethylene)aniline(L7).2.The synthesis and characterization of seven monosubstituted azadithiolate[FeFe]-Hydrogenase models based on synthesized ligands:[(?-SCH2NHCH2S)Fe2(CO)5(L1)](1),[(?-SCH2NHCH2S)Fe2(CO)5(L2)](2),[(?-S-CH2NHCH2S)Fe2(CO)5(L3)](3),[?-SCH2NHCH2S)Fe2(CO)5(L4)](4),[(?-SCH2NHCH2S)Fe2(CO)5(L5)](5),[(?-SCH2NHCH2S)Fe2(CO)5(L6)](6),[(?-SCH2NHCH2S)Fe2(CO)5(L7)](7).The crystal structure of model 1 was also determined by X-ray single crystal diffraction.3.By cyclic voltammetry,the electrochemical properties of models 1-7 and their catalysis to proton reduction hydrogen production were studied.It was found that the first reduction peaks of models 1?7 were all positive shift after the addition of trifluoromethanesulfonic acid,indicating the protonation of the bridgehead nitrogen atoms of all models,but no protonation of nitrogen atoms on aromatic amine in organophosphine was found for all these models.By the electrocatalysis study of these models,their possible catalytic mechanism of the proton reduction hydrogen production may depend on the process of proton couple electron transfer(PCET).