Research On Transformation Reactions Of Inorganic Small Molecules Catalyzed By Polypyridine Transition Metal Complexe

The constantly developing industry of our society has been consuming non-renewable fossil energy The emission of enormous amount of CO₂ into the atmosphere,as a consequence,leads to serious greenhouse effect and a series of corresponding environmental problems.It is urgent to find a solution for a green and sustainable development pathway.On one hand,the CO₂ reduction reaction（CO₂RR）can convert CO₂ into high value-added chemical fuels in a carbon neutral way.On the other hand,a renewable energy source will reduce and alter the use of traditional fossil fuel.Hydrogen is a promising clean energy source with high energy density,clean combustion products,and various supplying means.In nature,there are enzymes capable of catalyzing CO₂ reduction and proton reduction.The active sites of these enzymes have been found as transition metal ions coordinating with protein residues.Synthesized transition metal complexes are able to mimic both the structures and functions of the active centers of these enzymes,and catalyze the conversion of small inorganic molecules.The polypyridine ligands can form stable complexes with 3d and 4d transition metals.Certain modification of the polypyridine ligands renders the corresponding complexes the catalytic activity of reducing CO₂ or protons under different conditions.Previous work of our group has shown the polypyridine transition metal complexes are competent catalyst for CO₂RR and proton reduction/hydrogen evolution reaction（HER）reactions.In this thesis,we designed and synthesized two series of novel polypyridine ruthenium and cobalt complexes.All complexes have been fully characterized.The electrocatalytic performance of ruthenium and cobalt complexes has been investigated toward CO₂ reduction and proton reduction.The content of this thesis includes the following two main sections:（1）Design and synthesis of a series of novel tetradentate polypyridine ligands and corresponding ruthenium complexes.The ligands and complexes were characterized using various spectroscopic methods.The electrocatalytic CO₂RR performance and mechanism by the ruthenium complexes were investigated.Controlled potential electrolysis（CPE） verified high conversion selectivity from CO₂ to CO with Faraday efficiency of 95%.The turnover frequencies（TOFs）of these complexes were evaluated by cyclic voltammetry methods.（2）Design and synthesis of a series of novel tetradentate polypyridine ligands and corresponding cobalt complexes.The ligands and complexes were characterized using various spectroscopic methods.The electrocatalytic HER performance of the cobalt complexes was investigated.Controlled potential electrolysis（CPE）verified the electrocatalytic hydrogen evolution by these Co complexes.The turnover frequencies（TOFs）of these complexes were evaluated by cyclic voltammetry methods.