Ir(III) Complex–based Phosphorescence and Electrogenerated Chemiluminescence Dual–probe for the Detection of Mercury Ion

Abstract

Mercury, one of the most prevalent toxic metal elements, poses severe risks for human health and environment. Thus, various molecular probes have been developed for the colorimetric and fluorometric detection of mercury. Nevertheless, it is still urgent to develop a cost effective, rapid, selective and sensitive probe for the detection of mercury(II) ion. In this study, we designed several Ir(III) complex–based phosphorescence and electrochemiluminescence dual mode chemodosimeters, which possess phenylpyridine (ppy) or phenylisoquinoline (piq) as main ligands and acetylacetone as ancillary ligands in common for the selective detection of mercury(II) ion. Acetylacetonate ancillary ligand of probe 1 reacted with mercury(II) ion selectively, inducing phosphorescence enhancement with concomitant blue shift of the emission spectra. Meanwhile, mercury(II) ion selectively quenched the phosphorescence of probe 2. In addition, we proposed a two–step sensing mechanism through the comparison of NMR spectra of the probes in the absence and presence of mercury(II) ion. Mass analysis and crystallographic determination further supported that acetylacetonate readily reacts with mercury(II) ion, followed by the dissociation of mercury–acetylacetone from Ir(III) complex. These probes further showed selective electrogenerated chemiluminescence (ECL) responses, quenching upon the addition of mercury(II) ion. ECL based chemosensors have been widely studied for their several advantages, such as the possibility of being a powerful candidate for point–of–care (POC) detection, high sensitivity and simple analytical process. Moreover, probe 9 showed the best ECL property with a good linear correlation between 0 and 40 μM of mercury(II) ion with a low limit of detection (LOD) as 170 pM.