Synthesis And Properties Of Hydrogenase Model Complexes Based On PNP Ligands

[FeFe]-hydrogenase has high catalytic hydrogen production activity,so its active center structure and function simulation are widely concerned.This dissertation mainly describes the synthesis,characterization,catalytic oxidation performance and oxidation sensitivity of[FeFe]-PNP active center model,and the relationship between structure and performance was discussed by DFT calculation.With(?-budt)Fe₂(CO)₆ as the parent complex,14 novel PNP ligand-substituted[FeFe]-PNP model complexes were designed and synthesized.Their structure were characterized by solution IR spectroscopy,NMR spectroscopy and X-ray single crystal diffraction,and their properties were studied by cyclic voltammetry.The application of[FeFe]-PNP complexes in catalytic oxidation was explored and extended.The complex 5-1 was applied to catalyze the hydroxylation of phenol to dihydroxybenzene.Under the optimal reaction conditions,the conversion of phenol was 42.0%,the selectivity of dihydroxybenzene was as high as 88.6%,and it had good special selectivity for catechol.The catalytic mechanism may be related to an internal base of amine.The effects of the substitution methods and the kinds of ligands on their properties have been investigated with the goal of understanding the oxidation sensitivity of the synthesized chelates and bridged complexes.The chelate complexes can be oxidized by single electron to form oxidized complexes.The single electron oxidation rate of the complex 3-1 is faster than that of complex 5-1.The sulfur bridge oxidation study of the bridged complexes shows that their oxidation depths are different with aliphatic or aromatic hydrocarbons groups attached to N.DFT calculation results show that the introduction of PNP ligand increases the electron cloud density of iron active center.The energy levels of HOMO and LUMO indicate that the complex 5-1 is more likely to lose electrons to form an oxidation state,and is most susceptible to interact with oxidant.The results provide theoretical support for the difference in electrochemical properties,catalytic activity of phenol hydroxylation and oxidation sensitivity of the chelates and bridged complexes.