Near Infrared Emission Enables Sequential Energy Transfer Cascade Artificial Light Systems And Antibacterial Applications

In nature,light harvesting plays a pivotal role in the photosynthesis process of green plants.LHSs have exhibited a wide range of applications in photochemical catalysis,antibacterial,information encryption and anticounterfeiting,etc.Now,bacterial infection has posed tremendous threats to human health.In particular,with the emergence of large numbers of unknown drug-resistant bacteria and superbugs,traditional antibiotic treatment faces a major challenge.One promising strategy to control bacterial infection by photodynamic inactivation（PDI）.The combination of artificial LHSs and photodynamic inactivation will have a broad application prospect.Two tetraphenylene（TPE）-based Pt（Ⅱ）unit metallacycles,PtTPEM1 and PtTPEM2,were designed in this thesis,and artificial LHSs were fabricated using Pt（Ⅱ）metallacycles as a platform.The main research for this thesis is divided into three sections.Part I:The TPE-based ligand L3 and the L1 and L2 have been obtained by meticulous optimization of the synthetic routes.The[3+3]metallacycles PtTPEM1 and PtTPEM2 were obtained in a nearly quantitative yield upon addition of silver trifluoromethanesulfonate（Ag OTf）to the stoichiometric mixture of L3 and L1 or L3 and L2.The structures of PtTPEM1 and PtTPEM2 were characterized by ¹H NMR,³¹P{¹H}NMR and HR-ESI-MS.Part Ⅱ:The TPE-based metallacycles PtTPEM1 and PtTPEM2 have good solubility in DMSO and is almost insoluble in water.The fluorescence of PtTPEM1 and PtTPEM2 in the DMSO solution was very weak but became stronger in the solid state,indicating good AIE character.Upon increase of the water fraction（f_w,v/v）from 20%to 40%,intensity at 550 nm was markedly increased,with an enhanced fluorescence quantum yield,owing to restriction of the intramolecular motion of TPE groups in the aggregated state.Fluorescence intensity was only slightly decreased when f_w>40%and remained constant until f_w=99%,indicating excellent fluorescence performance in the aggregated state.Part III:Based on the fact that PtTPEM1-PtTPEM2 possesses a strong fluorescence in DMSO/H₂O（99/1）mixture,we developed a cascaded artificial light-capturing system,in which an aggregation-induced emission active platinum（Ⅱ）metallacycle（PtTPEM1）was designed as the antenna,sulforhodamine 101（SR101）acted as a key conveyor,and the near-infrared emissive photosensitizer Chlorin-e6（Ce6）served as the final energy acceptor.When the ratio of PtTPEM1/SR101/Ce6 was 20:1:2,Φ_ETwas 91.3%,and AE reached 44.13.The well-dispersed Ce6 in the proximity of energy donors can not only avoid its self-quenching in a physiological environment but also contribute to the energy transfer from donor to acceptor,thereby significantly improving ¹O₂generation ability of the light-harvesting system under white light irradiation.By integrating of the platinum（Ⅱ）metallacycle and ¹O₂,the efficient synergistic antibacterial effect was achieved at low concentrations,and the dark toxicity caused by the platinum（Ⅱ）metallacycle was greatly decreased.