Study On The Phosphine-substituted[FeFe]-Hydrogenase Models And The Related Carbon Nanotube Hybrids

In view of the fact that natural[FeFe]-hydrogenases are a kind of metalloenzyme with high-efficient catalytic proton reduction to hydrogen in nature,the chemical simulation of active site of[FeFe]-hydrogenases has attracted considerable attention in the field of bioinorganic chemistry and new energy materials.At the same time,hydrogen is considered to be the best fuel for the next generation of clean and renewable new energy.The widespread use of hydrogen fuel has important theoretical significance and potential application for solving the increasingly serious energy and environmental problems facing human beings today.In the context,this paper designed and synthesize a series of new phosphine-subsituted[FeFe]-hydrogenase mimics and related carbon nanotube hybrids.Their structures and catalytic properties are studied.Some important results are as follows:1.In this thesis,22 novel phosphine-subsituted[FeFe]-hydrogenase mimics was synthesized and were characterized by FT-IR,¹H-NMR and ³¹P{¹H}-NMR.The moleculars structure of 15 compounds are determined by single-crystal X-ray diffraction technique.The electrocatalytic hydrogen production performances of some compounds are studied.More importantly,[FeFe]-hydrogenase hybrid models containing functionalied single-walled carbon nanotubes has been successfully obtained in a covalent bond for the first time.The structure of the hybrid is characterized by FT-IR, XPS,TEM,and Raman,whose electrocatalytic hydrogen production performance is investigatedaswell.Additionally,[FeFe]-hydrogenasemodelandthe porphyrin-functionalized single-walled carbon nanoparticle were firstly combinated by ?-?conjugated physical adsorption to form a photocatalytic system,and the photocatalytic properties of which were explored.2.In the second chapter of theis thesis,the ligand substitutions of a novel all-carbonyl complexesFe₂{??-SCH₂?₂N?C₆H₄CH₂CH₂OH?}?CO?₆?1?withdifferent monophosphines ligand PR₃ is described.Six monophosphine-substituted [FeFe]-hydrogenase mimics Fe₂{??-SCH₂?₂N-?C₆H₄CH₂CH₂OH?}?CO?₅?PR₃?[R= C₆H₄Me-m,2;C₆H₅,3;C₆H₄Me-p,4;C₆H₄OMe-p,5;C₆H₄Cl-p,6;C₆H₄F-p,7]were obtained,in which the molecular structures of five of 1 and 3-6 are determined by X-ray crystallography.In addition,the electrochemical properties of 1 and 3-7 are studied by cyclic voltammetry.The result indicates that when weak acid?HOAc?was used as a proton source,complexes 1,and 3-7 are effectively active for electrocatalytic proton reduction to hydrogen?H₂?.3.In the third chapter,the above-prepared complex 1 with bridgehead hydroxyl group and the SWCNTs surface containing carboxyl unit are successfully attached through covalent bond.The first hybrid Fe₂{??-SCH₂?₂N-?C₆H₄CH₂CH₂O?O?CC₆H₄- SWCNT?}?CO?₆?1-f-SWCNT?containing[FeFe]-hydrogenase mimic and carbon nanotube.The structure of 1-f-SWCNT is characterized by IR,Raman,XPS and TEM. In addition,the electrochemical property of 1-f-SWCNT is evaluated by electrochemical linear scanning method,showing the proton can be stably and efficiently reduced to hydrogen in the condition of 0.5 M dilute sulfuric acid as a proton source.The total charge consumed during the 4-hour controlled potential electrolysis was 9.23 C,turnovernumber?TON?is 17.12 F/mmol.4.In the fourth chapter of this thesis,the aforementioned monophospine-substituted [FeFe]-hydrogenase mimic?6?and porphyrin-fuctionalized single-walled carbon nanotubes?TPP-f-SWCNT?are combined through?-?conjugatire absorption.A ternary biomimetic photocatalytic system containing of[FeFe]-hydrogenase mimic, porphyrin photoactive group and carbon nanotubes was constructed for the first time. The photoluminescence properties of the photocatalytic system was studied by UV-Vis and fluorescence spectra indicating that the photocatalytic system has the ability of photo generated charge under visible light.However,the photocatalytic performance of the catalytic system was evaluated by photocatalytic reduction of 4-nitrophenol?4-NP? to 4-aminophenol?4-AP?in the presence of NaBH₄ by means of UV-visible spectroscopy.The porphyrin-carbon nanotube-[FeFe]-hydrogenase mimic ternary photocatalytic system seem not to fulfill the photocatalytic reduction of the 4-nitrophenol?4-NP?to 4-aminophenol?4-AP?in the presence of NaBH₄.5.In the fifth chapter of this paper,six new PNP-chelate mimics Fe₂??-pdt??CO?₄ {??²-Ph₂P?₂NR}[R=?CH₂?₃Me,8;?CH₂?₃NMe₂,9;?CH₂?₃Si?OEt?₃,10;C₆H₅,11; C₆H₄OMe-p,12;C₆H₄CO₂Me-p,13]were successfully synthesized by substitution reactions of different bisphosphine ligand PNP?PNP=?Ph₂P?NR?with the all-carbonyl complex Fe₂??-pdt??CO?₆?pdt=?SCH₂?₂CH₂,A?irradiated by LED lamp. Correspoundingly,anothernewseriesofPNP-birdgemimics Fe₂??-pdt??CO?₄{??-Ph₂P?₂NR}[R=?CH₂?₃Me,14;?CH₂?₃NMe₂,15;?CH₂?₃Si?OEt?₃, 16;C₆H₅,17;C₆H₄OMe-p,18;C₆H₄CO₂Me-p,19]was successfully synthesized by substitution reactions of A with PNP through refluxing.Meanwhile,in the process of preparing the complex 11-13,three new monophosphine substituted[FeFe]-hydrogenase mimics Fe₂??-pdt??CO?₅{?¹-Ph₂P?R?}[R=NHC₆H₅,20;NHC₆H₄OMe-p,21; NHC₆H₄CO₂Me-p,22]was obtained.The crystal structures of 8,9,11-13,15,17-19 and 21 were measured by X-ray single crystal diffraction analysis.A comparative study of the electrochemical properties of the representative mimics 8 and 14 showed that the PNP-chelate mimic 8 has a high ability to electrocatalytically reduce protons to H₂ compared to the PNP bridging substitution mimetic 14.