Study On The NIR Properties Of Visible Light-sensitized ?-diketone Rare Earth Complexes

NIR emitting materials are employed in military reconnaissance,OLED,fiber-optic communications and medical diagnosis,Especially in the field of medical diagnosis.These lanthanide luminescent probes for applications in celluar imaging and analyte detection in vitro or in vivo have shorter excitation wavelength.However,one of the challenges for designing luminescent lanthanide complexes,particularly those aimed at bio-assays and bioimaging,is to shift the excitation wavelength from the UV to visible range,since living tissues are usually damaged by UV light.In order to synthesize the use of lower energy excitation wavelengths in the visible spectral region to sensitize ytterbium NIR luminescence,we designed and prepared three bis-?-diketones,featuring?ILCT?excited states,DTTA;NTDA and NDPA,have been designed and prepared for the synthesis of a series of anionic quadruple-stranded dinuclear helicates?HNEt₃?₂[M₂?DTTA?₄][M=Yb?1?,Y?2?,Gd?3?,Eu?4?,Nd?5??HNEt₃?₂=Triethylamine)];?HNEt₃?₂[M₂?NTDA?₄][M=Yb?6?,Y?7?,Gd?8?,Nd?9?];?HNEt₃?₂[M₂?NTDA?₄][M=Yb?10?,Y?11?,Gd?12?,Nd?13?],ligands and complexes have been fully characterized by analysis and near infrared investigation.Acording to the comprehensive spectral characterization and in combination with quantum chemical modelling,the ILCT feature of ligands is confirmed.At the same time,the transformation of ligand structure lead to a remarkable red shift of the absorbance edge.Upon excitation with blue light,the two ytterbium helicates show excellent NIR luminescence in the range of 900–1100 nm,with the high luminescence quantum yields.In a word,the synthesis of helicates based on ligands featuring intra-ligand charge transfer?ILCT?excited states is a valuable approach for enhancing the lanthanide ion NIR luminescence with visiblelight excitation.