Study Of Three-step Sequential Energy Transfer Artificial Light-harvesting Systems Based On Platinum Metallacycles

In response to the oil and energy crisis and improve the use of solar energy,which is particularly important for sustainable energy development,many artificial light capture systems have been constructed,inspired by the fact that the light-harvesting systems in photosynthesis can efficiently collect solar energy and convert it into chemical energy.Currently,most of the constructed light-harvesting systems are based on one-step or two-step sequential energy transfer process,and it is still a challenge to develop a bionic artificial light harvesting system with multi-step sequential energy transfer process in an aqueous medium.In this thesis,the artificial light-harvesting systems with three-step continuous energy transfer were developed using supramolecular platinum metallacycles with aggregation-induced emission(AIE)activity as light capture antennas,eosin Y(ESY)and sulfonated rhodamine 101(SR101)as key energy carriers,and the near-infrared emitting photosensitizer Chlorin e6(Ce6)as the final energy receptor.A unique strategy to improve the energy transfer efficiency of the light harvesting system is proposed by modulating hydrophilic-hydrophobic interactions.This thesis is divided into three parts.Ⅰ.Design and synthesis of metal-organic platinum metallacycle MTPEPt1 with AIE properties,hydrophilic chains and adamantane groups.(1)Compound 1 was synthesized by monosubstitution with p-toluenesulfonyl chloride using hexaglycol as the initial raw material.compound 1 was substituted with adamantane carbonyl chloride to form compound 2.3,5-dibromophenol was again substituted with compound 2 to form compound 3.Compound 4was deprotected with tetrabutylammonium fluoride to form compound 5.(3)Compound 5reacted with trans-platinum iodide compound 7 to form ligand L1.(4)Ligands L2,L3 and the comparative compound MTPEPt2 were synthesized according to the reported literature.Ⅱ.The AIE properties of MTPEPt1,MTPEPt2,and L2 in the methanol-water system were investigated.MTPEPt1 had significant luminescence properties in 99% aqueous solution and was used as an energy donor in aqueous solution,ESY,SR101,and Ce6 served as energy acceptors,an artificial light-harvesting platform with three-step sequential energy transfer process has been successfully constructed.The close contact between donor and acceptor at each energy level and the excellent spectral overlap ensure an efficient continuous three-step energy transfer.As a result,the excitation energy is sequentially and efficiently delivered to Ce6 along MTPEPt1-ESY-SR101-Ce6.The performance of the artificial light-harvesting system with a three-step sequential energy transfer process is superior compared to the system of MTPEPt1-SR101,MTPEPt1-Ce6 or MTPEPt1-SR101-Ce6.Ⅲ.A strategy to adjust the light-harvesting property has been shown for the first time by regulating the hydrophilic and hydrophobic interactions.The β-CD@ MTPEPt1 was obtained by host-guest interactions between adamantane groups and β-cyclodextrin(β-CD),improving the water solubility of the supramolecular metal ring MTPEPt1 and reducing the aggregate size.MTPEPt2 without side chain groups has a larger aggregate size than MTPEPt1.β-CD@MTPEPt1-ESY-SR101-Ce6 light-harvesting system has higher energy transfer efficiency at all levels and higher antenna effect than that of MTPEPt1-ESY-SR101-Ce6light-harvesting system.