Sensing Picric Acid with Dinuclear Triazole Chelated Iridium(III) Nanoaggregates: Insights into the AIEE Quenching Process.

We synthesized a mononuclear and two dinuclear Ir(III) complexes with a substituted triazole and two triazolyl bidentate chelators bridged through propyl and m-phenylene linkers, respectively. The complexes exhibit a considerable enhancement in emission intensity upon aggregation. The formation of nanoaggregates was confirmed through dynamic light scattering (DLS) and transmission electron microscopy (TEM) studies. The dinuclear complexes quench aggregation-induced enhanced emission in the presence of trinitrophenol (TNP/Picric Acid: PA) selectively from a batch of nitroaromatics in water, whereas the mononuclear complex is not selective. Therefore, dinuclear complexes were employed to selectively detect the explosive nitroaromatic picric acid (PA) in aqueous solution. For Ir1 and Ir2, the Stern-Volmer quenching constants (K_SV) for the detection of PA were determined to be 0.17 × 10⁶ and 0.34 × 10⁶ M^-1, with a low limit of detection (LOD) of 107 and 68 nM, respectively. The practical applicability was further evaluated through a selectivity study involving various metal ions and quenchers under identical conditions. Finally, the quenching process has been studied in detail to understand the participation of possible electron-transfer and energy-transfer processes. The analysis of the combined spectroscopic and theoretical results confirms that both electron-transfer and energy-transfer processes are operative here.