AIPE-active cationic Ir(III) complexes for efficient detection of 2,4,6-trinitrophenol and oxygen

A cationic Ir(III) complex, Ir2, with a diphenylamino (DPA)-substituted 2-phenylbenzothiazole derivative as the cyclometalating ligand was designed and synthesized. Ir2 shows obvious aggregation-induced phosphorescent emission (AIPE) in H₂O/CH₃CN, compared with a non-DPA-substituted Ir1. The AIPE-active Ir2 demonstrates efficient detection of 2,4,6-trinitrophenol, providing a higher quenching constant (K_SV = 2 644 330 M^-1vs. 73 583 M^-1 for Ir1) and a lower limit of detection (LOD = 2.23 nM vs. 50.17 nM for Ir1). High-resolution mass spectrometry analysis and density functional theory calculations demonstrate that photoinduced electron transfer may be responsible for the emission quenching. Immobilized in an ethyl cellulose film, Ir2 exhibits high oxygen sensitivity (KappSV = 0.0572 Torr^-1vs. 0.0090 Torr^-1 for Ir1) and excellent reversibility in 10 cycles. This work reveals that the DPA group plays an important role in tuning the AIPE properties and increasing the performances of the luminescent probes.