Aggregation-Induced Emission-Active Iridium(III) Complexes for Sensing Picric Acid in Water

Abstract

Herein, two new iridium(III) complexes, namely Ir2 and Ir3, with a phenyl or triphenylamine (TPA) moiety at the 4-position of the phenyl ring at 2-phenylbenzothiazole, have been synthesized, and their emission properties have been studied systematically compared with the non-substituted complex Ir1. These three complexes exhibit aggregation-induced emission (AIE) in H2O/CH3CN. The TPA-substituted complex Ir3 shows the highest AIE activity. All complexes can be used as sensors to detect picric acid (PA) in water. The Stern–Volmer constant (KSV) of Ir3 for the detection of PA was determined to be 1.96 × 106 M−1, with a low limit of detection of 2.52 nM. Proton nuclear magnetic resonance spectra, high-resolution mass spectrometry analysis, and density function theory calculations confirm that the emission quenching mechanism of Ir3 is caused by photo-induced electron transfer. Furthermore, the efficient detection of PA in natural water proves that Ir1–Ir3 can be used as promising sensors in the natural environment. These results suggest that the AIE-active iridium(III) complexes can be used to detect PA under environment-friendly conditions.