Effect of the Position of a Phenyl Group on the Luminescent and TNP-Sensing Properties of Cationic Iridium(III) Complexes

Three cationic Ir(III) complexes 1, 2, and 3 were successfully synthesized and characterized by tuning the position of a phenyl group at the pyridyl moiety in 2-phenylpyridine. All three complexes exhibit typical aggregation-induced phosphorescence emission (AIPE) properties in CH3CN/H2O. The AIPE property was further utilized to achieve highly sensitive detection of 2,4,6-trinitrophenol (TNP) in aqueous media with low limits of detection (LOD) of 164, 176, and 331 nM, respectively. This suggests that the different positions of the phenyl group influence the effectiveness of 1, 2, and 3 in the detection of TNP. In addition, 1, 2, and 3 showed superior selectivity and anti-interference for the detection of TNP and the potential to detect TNP in practical applications. Taking 1 as an example, the changes in the luminescent lifetime and UV-Vis absorption spectra of 1 before and after the addition of TNP, indicate that the quenching process is a combination of static and dynamic quenching. Additionally, the proton nuclear magnetic resonance spectra and spectral studies show that the detection mechanism is photo-induced electron transfer (PET).