Design, Synthesis And Applications Of Phosphorescent Iridium(Ⅲ) Complexes Containing Aldoxime Or Pyrazine Moieties

Phosphorescent transition-metal complexes have received extensive attention in biosensing and bioimaging,owing to their rich excited-state characters,high luminescence quantum yields,long emission lifetime,good photostability and biocompatibility.In this work,a series of aldoxime-modified iridium（Ⅲ）polypyridine complexes were designed as phosphorogenic probes for hypochlorite.Meanwhile,the complexes were modified with two lipophilic carbon chains of different lengths to tune their cellular distribution,especially their retention in the cell membrane resulting from the lipophilic-lipophilic interaction with the lipid bilayer.These phosphorescent probes are able to not only simultaneously sense exogenous and endogenous analytes but also to distinguish them from each other.Another polypyridinium complex containing pyridinium was also designed and synthesized,and its phosphorescence response towards external stimuli was studied.This dissertation is comprised of the following three parts:Firstly,a series of iridium（Ⅲ）complexes containing an aldoxime responsive group and carbon chains of different lengths were designed,synthesized,and characterized.Photophysical investigation revealed that the lengths of the carbon chains has negligible effect on the emission wavelengths and lifetimes.The cytotoxicity assay and flow cytometry showed that a longer carbon chain reduced the cytotoxicity of the complex.Laser-scanning confocal microscopy indicated that these probes are capable of imaging exogenous and endogenous hypochlorite in living cells.Costaining experiments involving CellMask and MitoTracker illustrated that the complexes were mainly concentrated in the mitochondria,and partially stained the cell membrane for the complex with two long carbon chains.Secondly,an amine group was modified on 2-phenylpyridine ligand improves the stability of staining of the cell membrane.Complex Ir8 was used to distinguish the endogenous and exogenous hypochlorite.Cellular imaging showed that Ir8-loaded HeLa cells exhibited phosphorescence from the cell membrane when exdogenous hypochlorite was present in the culture medium.In sharp contrast,when the cells were pretreated with elesclomol,which can induce the generation of endogenous hypochlorite,intense phosphorescence was observed from the cytoplasm.These results were further confirmed by costaining experiments.The co-staining coefficients with the CellMask and MitoTracker were 22%and 87%,respectively,in the presence of endogenous hypochlorite,and became 68%and 34%,respectively,when the cells were pretreated with elesclomol.All the results demonstrated that these phosphorescent iridium（Ⅲ）complexes can distinguish between endogenous and exogenous hypochlorite in living cells.Thirdly,a stimuli-responsive complex[Ir（pq）₂（bpzMe₂）]（PF₆）₃ was synthesized.Photophysical and electrochemical properties of the complex was investigated and the phosphorescence response of this complex toward external stimuli including electric fields and reducing agents was investigated.