Design And Synthesis Of Diphenylamino-Substituted Cationic Ir(?) Complexes And Their Aggregation-Induced Phosphorescent Emission And Oxygen Sensing Properties

Iridium complexes have attracted much attention due to their high luminous efficiency and long phosphorescence lifetime.However,due to the effect of aggregation-induced quenching(ACQ),the application of iridium complexes in the aggregated state and the solid state has been greatly limited.Thus,the design and development of iridium complexes with aggregation-induced luminescence(AIE)properties have become a research hotspot at the present.In addition,as potential oxygen-sensitive probes(OSPs),understanding the effects of the structures of iridium complexes on their oxygen sensing properties at the molecular level is of great importance.In this paper,a series of diphenylamino-substituted cyclometalated iridium complexes were designed and synthesized.The relationship between the structures of iridium complexes and the photophysical and electrochemical properties was investigated,the aggregation-induced phosphorescent emission(AIPE)and oxygen sensing properties has been investigated systematically.The main research contents include the following four parts:(1)The iridium complexes Irl-Ir4 modified with a rotatable unit of benzene ring,diphenylamino(DPA)or carbazole group at the cyclometalating ligands were synthesized.The effects of the cyclometalated ligands on the photophysical,electrochemical properties and oxygen sensing performances of the complexes were studied in detail.The results show that the introduction of a phenyl or a carbazole moiety into the cyclometalating ligand leads to a blue shift of the emission,an increased Eg energy level and a prolonged phosphorescence lifetime;while the DPA-substituted Ir4 has a red shifted maximum emission,a decreased Eg energy level and a shorter phosphorescence lifetime.In addition,the complex Ir4 shows obvious AIPE properties in an acetonitrile/water system and high oxygen sensitivity immobilized on an ethyl cellulose(EC)film.(2)The iridium complexes Ir5-Ir8 with different substituents at the 5-position of the pyridine ring on the cyclometalated ligands were designed and synthesized.The effect of substituents on the luminescence properties and oxygen sensing properties of the complexes were systematically studied.The results show that the introduction of an electron-withdrawing group CF₃(Ir5)or CN(Ir6)leads to a blue-shifted emission,a prolonged phosphorescence lifetime and increased Eg energy levels.Both complexes demonstrate high oxygen sensitivity in CH₂Cl₂ and EC film.The iridium complexes substituted with CF₃(Ir5),CN(Ir6),F(Ir7)or CH₃(Ir8),exhibit AIPE properties in the acetonitrile/water system.Transmission electron microscopy(TEM)studies show that complexes Ir5,Ir7 and Ir8 formed spherical aggregates in the acetonitrile/water system.(3)The iridium complexes Ir7-Ir10 with a F or CH₃ group at the 5-or 6-position of the pyridine ring at the cyclometalating ligands were synthesized.The effects of the substituent position on the luminescence properties and oxygen sensing performances of the corresponding complexes were systematically studied.The results show that the complexes Ir9(6-F)and Ir10(6-CH₃)with the substituent at the 6-position have a blue-shifted emission,an increased Eg energy level,a higher quantum yield and a longer phosphorescence lifetime.The iridium complexes Ir7(5-F),Ir8(5-CH₃)and Ir10 are AIPE-active in the acetonitrile/water system.However,the 6-F modified Ir9 exhibits an ACQ phenomenon,and has the highest oxygen sensitivity in CH₂Cl₂ and EC film.(4)The iridium complexes Ir11 and Ir12 modified by triphenylamine group at the cyclometalating ligands were synthesized,and the influence of triphenylamine group on the luminescence properties and oxygen sensing performance of the complexes were studied.The results show that the triphenylamine-modified complexes Ir11 and Ir12 have a significant blue-shifted emission,a prolonged phosphorescence lifetime and enhanced oxygen sensitivity on the EC films.In addition,the complexes Ir11 and Ir12 exhibit AIPE properties and form spherical aggregates in the acetonitrile/water system.