| Summary: | 碩士 === 國立交通大學 === 生物科技系所 === 102 === In nature, hydrogen production is catalyzed by hydrogenases (H2ase). Hydrogenases can be classified into three types depending on different central metals, [Fe-Fe], [Fe-Ni] or [Fe] within the enzymes. The study of the active site of [Fe-Fe] hydrogenase, diiron carbonyl sulfur cluster (also named H-cluster), provides a structural basis for hydrogen generation. The aim of the research is to mimic the structure of H-cluster with different metals and apply it as a catalyst for hydrogen production. My goal is to synthesize artificial [Fe-Fe] H-cluster and covalent link to different phosphine ligands and I also replaces the iron metal centers with rhenium and study their catalytic activity for photocatalytic hydrogen production at different temperatures and different phases. In this study, we first synthesize iron-sulfur cluster ([Fe2(CO)6(μ-pdt)]) and covalent link P-ligabds ([Fe2(CO)5(μ-pdt)(P-ligand)]) and rhenium (Re)-substituted H-cluster mimics complex ([Re2(CO)6(μ-pdt)]). Then the synthesized metal-sulfur clusters were subjected to photocatalytic hydrogen production studies in organic phase and aqueous phase. In addition, different P-ligands were added into the system to study the efficiency. All the synthetic compounds were checked by MS spectra and the characteristics of the complex was analyzed by UV-Vis spectrum and cyclic voltammetry. The experimental structures here elucidated by DFT calculations, and the orbital analyses optimized the analyzed the LUMO, HUMO, charge distribution and IR spectra were performed based on the optimized geometries.
Hydrogen generation could proceed in organic phase and aqueous phase. In organic phase, formic acid is the hydrogen source. For iron-sulfur clusters, additional added P-ligand with electron donating functional group are better than electron withdrawing. And the covalent link P-ligand to iron-sulfur clusters are worse than without linking to P-ligand. And the replaced the center iron into rhenium is also worse than it. In aqueous phase system, covalent link P(p-C6H4OMe)3 to iron-sulfur cluster is the best. The mechanism of hydrogen evolution by various metal sulfur clusters will be elucidated in the future.
In DFT calculations, the ruthenium-sulfur clusters are modeled to calculate energy level of HOMO and LUMO and the IR spectroscopy. And using these data to explain the hydrogen generation results. According to the energetics, we found that the energy level increased after covalent link to P-ligand, and the band gap between HOMO-LUMO is decreased. The computational results could be further used to predict the hydrogen generation process.
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