The Design,Preparation,Photophysical Properties Of Dual-emissive Iridiu (?) Complexes And Application In Oxygen Detection

Phosphorescence iridium?III?complexes have been used as new luminescent sensors for analytes,including anions,cations,molecule oxygen,amino acid,DNA and biomolecules.These complexes display changes in their emission intensities and lifetimes upon analyte binding.Compared to common metal-to-ligand charge-transfer?MLCT?emitters of d6 electron strutures,such as the ruthenium?II?and osmium?II?complexes,iridium?III?complexes exhibited more complicated emissive states mainly including intraligand charge-transfer?IL?and ligand-to-ligand charge-transfer?LLCT?.These emissive states that are very sensitive to their ligands and local environment.In some cases,the iridium?III?complexes may display luminescene from two of these states,resulting in distinct dual-emission features.In this paper we discussion dual-emissive phosphorescent iridium?III?complexes and their applications in oxygen detection:1.Design,synthesis,and photophysical properties of dual-emissive phosphorescent iridium?III?complexes.We prepared a series of iridium?III?complexes [Ir?ppy-CH₂-NR¹R²?₂?bpy-CONH?]?PF₆?using N^C ligands with respective primary,secondary and tertiary amine substitutes.The amine-free complex has also been prepared for comparison study.The photophysical properties of these complexes were investigated in detail.These complexes were characterized with 1H NMR and mass spectroscopy?MS?.The complexes modified with the secondary and tertiary amines showed dualemission properties.TD-DFT investigation suggested that an amine-to-ligand charge-transfer?NLCT?state interrupts the communication between the IL and MLCT states.Owing to the different quenching efficiency of these two states toward oxygen,these complexes can be used as ratiometric oxygen sensors.2.Ratiometric oxygen probes and cell detection applications based on dual emission iridium complexes.A series of iridium?III?complexes [Ir?ppy-CH₂-R?₂?bpy-?CONH-C₄H₉?₂?]?PF₆?whose N^C ligands were respectively modified with methyl,secondary amine,and tertiary amine have been designed,synthesized,and characterized.Complex 7 showed dual emission at room temperature;the two emission bands occurred at 520 nm and 620 nm,respectively.This complex exhibited ratiometric phosphorescence response toward oxygen.Remarkable profile change was observed under both low and high oxygen content.Living cell imaging demonstred that the complex is able to serve as ratiometric probes for intracellular hypoxia and hyperoxia.