Photofunctional Ionic Iridium Complexes:Design,Synthesis And Their Applications

Phosphorescent transition metal complexes are an important kind of organic semiconductors because of their excellent photophysical properties and have been widely used in organic optoelectronic field.Among them,cyclometalated iridium(?)complex is one of the most excellent phosphorescent materials with relatively short phosphorescent lifetime and high quantum efficiency compared with other transition metal complexes.For iridium(?)complex,the ligand can regulate the excited-state properties,and the adjustment of the photophysical properties can be easily achieved by changing or madulating the ligand structures.These complexes have been applied successfully in the field of OLEDs,LECs,bioimaging,sensor and photocatalysis.According to the difference of charges,iridium(?)complexes can be classified into neutral and ionic ones.The synthesis of neutral iridium complexes generally requires high reaction temperature and complicated purification procedures.However,the synthesis of ionic iridium(?)complex is simple and their excited state can be easily tuned by modifying the cyclometalated or ancillary ligands.In addition,the ionic iridium(?)complexes carry charge,and there is an electrostatic force between ionic complex component and the counterions,which is sensitive to external stimuli,especially electric field.In this thesis,we aim to develop some new and effective strategies to tune the photophysical properties of ionic iridium(?)complexes and realize their various optical applications.1.A phosphorescent iridium(?)complex with formamide for the luminescence determination of low-level water content in organic solventsA phosphorescent water probe based on an iridium(?)complex with 5-formamide-1,10-phenanthroline ligand has been designed and synthesized.The phosphorescence can be quenched by the addition of fluoride anion and it also can be recovered by adding trace water into the detecting solution.This phosphorescent water probe shows low limit of detection(LOD)and limit of quantitation(LOQ).Utilizing the long phosphorescent lifetime,time-resolved photoluminescence experiment was performed for trace water detection,which could effectively eliminate the short-lived fluorescent background and improve the sensitivity and signal-to-noise ratio of the probe in complex system.2.Ionic iridium(?)complexes with anthraquinone groups for photodynamic therapyThe electron-withdrawing anthraquinone group was successfully introduced into the four ionic iridium(?)complexes to regulate their excited-state energy levels.Among them,the quantum efficiency of Ir1 was the highest,and those of other complexes were extremely low.We found that Ir1 as triplet photosensitizer can show high singlet oxygen generation efficiency in both solution and living cells.MTT data showed that its phototoxicity was relatively low.In addition,Ir1 showed specific staining of mitochondria and the costaining coefficient is up to 95.4%.Finally,excellent photodynamic therapy effect has been achieved with Ir1 as the photosensitizer.3.Luminescent ion pairs with tunable emission colors for light-emitting devices and electrochromic switchesA class of tunable emissive materials based on luminescent ion-paired iridium(?)complexes(IP1-IP6)has been developed.The polymer films doped with IP6 was used to fabricate LEDs,which show yellow,orange and white emission.The emission color of the IPs in solutions can be regulated by electric field.At last,a solid-film electrochromic switch device was fabricated successfully using IPs,and the process of color changing was fast and reversible.These results indicated that luminescent ion pairs based on ionic iridium(?)complex will be promising candidates for optoelectronic applications.