Design,Synthesis,Photophysical Properties,and Sensing Of Dual-emissive Iridium(Ⅲ)Complexes

Phosphorescence iridium（Ⅲ）complexes possess excellent photophysical properties,including high quantum efficiency,tunable emission wavelength,large Stokes shift,good photochemical stability as well as good prospects in the fields of biosensing and cell imaging.Phosphorescent probes based on iridium complexes may achieve the detection through the response of emission intensity or lifetime when the concentration or environmental parameter of the detection substance changes.At present,most phosphorescent iridium（Ⅲ）complexes are based on single-wavelength emission,but their intensity is sensitive to internal or external environment variables.These problems can be avoided by dual-emissive phosphorescent probes.In this paper,dual-emissive iridium（Ⅲ）complexes have been designed and synthesized,and their applications in detecting oxygen and zinc ions have been studied.The main research contents of the paper are as follows:1.Design,synthesis and detection of oxygen responsive fluorescent-phosphorescent dual-emission iridium（Ⅲ）complexesBy designing 5-（4-ethynylphenyl）-2,2’-bipyridine as the N^N ligand and introducing secondary and tertiary amine groups into the C^N ligand,a group of iridium complexes have been synthesized to study the dual-wavelength emission behavior.First,the photophysical properties of the complexes such as ultraviolet-visible absorption spectrum,emission spectrum,and luminescence lifetime under normal oxygen environment and anaerobic environment have been investigated.The two complexes exhibit unique singlet-triplet dual emission when 5-（4-ethynylphenyl）-2,2’-bipyridine is the N^N ligand.The short-wavelength emission peak is fluorescence emission,and the long-wavelength emission peak is phosphorescent emission.In addition,due to the excited states of fluorescence and phosphorescence,their sensitivity to oxygen quenching is quite different.Fluorescence peaks do not respond to oxygen,while phosphorescence peaks are more sensitive to oxygen,enabling single-molecule oxygen detection.2.Design,synthesis and simultaneous detection of oxygen and zinc ion of a dual-phosphorescent iridium（Ⅲ）complexWith ppy-CH₂-NH-C₄H₉ served as the C^N ligand and an amide group and di（2-picolyl）amine group served as the N^N auxiliary ligand,a phosphorescent iridium（Ⅲ）complex has been synthesized.The application of the probe to detect two substances has been studied by oxygen titration spectrum and zinc ion titration spectrum.It is characterized by two emission peaks in the emission spectrum.The high energy band has an emission peak around 500 nm which responds to oxygen,and the low energy band has an emission peak around 600 nm which responds to zinc ions,thus it can detect both oxygen and zinc ions.