Study On Biomimetic Complexes Of Iron-containing Hydrogenases With High Catalytic Activity

Hydrogenase has received a lot of attention as a metalloenzyme that can efficiently catalyze hydrogen redox reactions under mild conditions.The research on biomimetic simulations of hydrogenase’s active center structure and catalytic hydrogen generation process has a wide range of potential applications.In this thesis,a variety of phosphine ligand-substituted[Fe Fe]and[Fe]-hydrogenase model complexes were designed and synthesized by introducing bisphosphine ligands with improved electron donating properties,resulting in improved catalytic activity.Additionally,the application field of the hydrogenase model complexes was extended to phenol hydroxylation and electrocatalytic CO₂ reduction,and the relationship between the structure and catalytic performance of the model complexes was thoroughly investigated,laying the groundwork for the design of catalyst structures in the future.The main contents are as follows:（1）Two percarbonyl diferroic complexes were developed and synthesized:（μ-pdt）Fe₂（CO）₆（1,pdt=propane-1,2-dithiol）and（μ-tdt）Fe₂（CO）₆（2,tdt=Toluene-3,4-dithiol）.and the effect of thiolate ligands on the structure and properties of[2Fe2S]clusters was further studied.Both 1 and2 have electrocatalytic hydrogen production performance under weakly acidic circumstances,and complex 2 has a better catalytic performance than 1.Under the conditions of Me OH and H₂O as proton sources,the TOF of catalyzing CO₂ reduction process of 2 containing 0.62 M Me OH is as high as 112.7 s^-1,and its catalytic efficiency is 490 times than 1,due to the rigidity and conjugation effects of the tolylylene sulfur bridges that affect the electronic properties of the diiron complexes.（2）Two basic structural models of[Fe-]hydrogenases with bisphosphine ligands,Fe（II）（CO）₂I₂-[DPPE]（3）and Fe（II）（CO）₂I₂-[DPPP]（4）,were designed and synthesized,and the catalytic phenol hydroxylation performance was investigated.Under the optimal reaction conditions,the phenol conversion rate of 6 was 19.6%,and the selectivity of DHB was 82.5%.（3）Novel[Fe Fe]-model complexes with bisphosphine ligands:（μ-budt）Fe₂（CO）₅（DPEphos）（6）and（μ-budt）Fe₂（CO）₅（Xantphos）（7）were synthesized and characterized,and the catalytic phenol hydroxylation reaction was carried out.Complex 6 outperforms complex 7 under ideal reaction conditions,with a phenol conversion rate of 57.7%and a DHB yield of 49.6%,both of which are at the forefront of the area of phenol catalytic hydroxylation.In addition,the catalytic reaction mechanism was studied by electron spin resonance.（4）Two[2Fe2S]model complexes（μ-tdt）Fe₂（CO）₅（DPEphos）（8）and（μ-tdt）Fe₂（CO）₅（Xantphos）（9）were synthesized and characterized.The infrared and ultraviolet spectra of complexes 6-9 were studied and compared,and it was discovered that the electron densities of the two complexes with the same parent structure were similar.Furthermore,all four complexes have the ability to catalyze hydrogen production under mild acid conditions,among which complex 8has the best catalytic effect.