Studies On Polybipyridine Transition Metal Complexes Catalyzed Reduction Reactions (CO₂RR And HER)

In order to alleviate the increasingly serious environmental and energy problems caused by the huge consumption of fossil energy,it is urgent to find clean and renewable energy sources.Energy conversion and storage via carbon dioxide reduction reaction(CO₂RR)not only cut down the green house gas emisson,but also produce carbon-based compounds as raw materials for bulk chemical industry.Seeking efficient CO₂RR catalysts is of great significance for the successful application of solar energy(via the generation of electric energy)to the light-driven carbon dioxide reduction process.The molecular ruthenium complexes with polypyridyl ligands that were early studied as homogeneous CO₂RR catalysts have shown prommising activity toward the carbon dioxide reduction reaction.Organic polybipyridine ligands taking the advantages of chemically stable structures and great modification potential allows the systematical investigation about the structure-activity relationship of CO₂RR catalysts.Similar to the CO₂RR process,the proton reduction to hydrogen reaction is a criticle process in the context of developing alternative energy sources of fossil fuels.The practical application of hydrogen production from water requires efficient and reliable water(proton)reduction catalyst.In nature the active centers of hydrogenases have been found to contain transition metal cations.In the preveious studies,transition metal complexes with various polybipyridine ligands have shown great potential of efficiently catalyzing CO₂RR or hydrogen evolution reaction(HER).The content of this dissertation includes design,syntheses,and characterization of novel ruthenium and nickel complexes with polybipyridine ligands,and investigation of their electrocatalytic performance and mechanisms towards CO₂RR(by Ru complexes)or HER(by Ni complexes).This dissertation consists of the following three parts of research work:(1)A series of ruthenium complexes bearing tetradentate polypyridine ligands were designed, synthesized,and characterized by organic/inorganic spectroscopic methods.Their homogeneous catalytic performance and mechanism toward carbon dioxide reduction were studied.(2)A series of ruthenium complexes bearing tridentate polypyridine ligands were designed,synthesized,and characterized by organic/inorganic spectroscopic methods.The homogeneous catalytic performance of these complexes toward carbon dioxide reduction was studied.(3)Novel bypyridine bisthiophenol(N₂S₂)ligands and corresponding nickel complexes have been designed,synthezied,and charaterized by organic/inorganic spectroscopic methods.The performance and mechanism of the complexes toward homogeneous electrocatalytic proton reduction were studied.