A Single‐Anion‐Based Red‐Emitting Cationic Diiridium(III) Complex Bearing a Pyrimidine‐Based Bridging Ligand for Oxygen Sensing

Abstract

Compared with double‐anion‐based cationic diiridium complexes, the study of single‐anion‐based cationic diiridium complexes as emitters is largely unexplored. In this work, two methods were used to prepare single‐anion‐based cationic diiridium complex Ir‐Ir‐1 bearing 2‐pyrimidine‐benzimidazole as bridging ligand, both sides of which are symmetrical structures comprising 2‐phenylpyridine as cyclometalated ligand. It shows efficient red phosphorescence emission with redshift of the emission wavelength by 85 nm relative to the corresponding monoiridium complex Ir‐1 . Moreover, it exhibits long emission lifetime and high oxygen sensitivity, which were attributed to the intraligand charge‐transfer excited state. Hence, Ir‐Ir‐1 was used as a oxygen probe to monitor intracellular O 2 content by time‐resolved luminescence imaging.