The Planar Four-Coordinated Metal-Organic Supramolecular For Enzyme Mimetic Studies

Hydrogen energy is the most promising new energy for scientists to explore the sustainable development strategy with the advantage of environmental protection,high efficiency,clean and so on.But most of them are present in water and other compounds,scientists from all over the world have conducted a comprehensive study on how to extract hydrogen in a cheap and easy way,which is also the direction of modern new energy research workers.Accompanied by the two Japanese scholars firstly found that TiO2 eletrode has the ability of hydrogen release in the sunlight,which makes the research on how to light water splitting with the sun has become one of the most attractive topic in modern research.Hydrogenase exists in the natural microbial body,which can be efficiently catalytic hydrogen evolution under mild conditions.Therefore,in order to unconsumption of fossil energy,scientists have made a lot of research according to the characteristics of mimic enzyme.The metal-organic macrocycle because of its welled-defined cavity and the catalytic site of the metal,is a kind of excellent functional hydrogen production catalyst.A bidentate ligand was obtained from the Schiff base reaction between 9-fluorenone or 4,5-diazafluoren-9-one and thiosemicarbazide.New proton reduction catalysts Ni-L1,Ni-L2,Pd-L1 and Pd-L2 were synthesized and structurally characterized by X-ray diffraction.In particular the oxidative quenching process of Ni-L2 toward fluorescein enable to prolong the lifetime of whole system.The direct generation of H2 was achieved by carrying out the photolysis of a solution containing fluorescein as the photosensitizer,triethylamine as the sacrificial and the redox catalysts.Pd-L1 exhibited excellent activity with a turnover number(TON)of 1399.7 moles of H2 per mole of the catalyst after 8 hours.By combining two thiosemicarbazone bidentate chelators in the ligand,herein,this work developed a new approach to assemble metal-organic macrocycle(Ni-L3).By pushed the essential components closer to avoid unwanted energy transfer,the modified supramolecular Aritificial Photosynthetic system exhibited excellent activity in light driven hydrogen evolution with TON reaching to 1600 per mole catalyst.Competitive inhibition behavior was found upon addition of ATP to the reaction mixture and suggested that the photolysis occurred in the cavity of Ni-L3.