Fluorescence Sensors for Bismuth (III) Ion from Pyreno[4,5-d]imidazole Derivatives

Three pyreno[4,5-d]imidazole derivatives are synthesized and evaluated as fluorescent sensors for bismuth (III) ion. The target compounds are prepared in 55-86% yields from a condensation reaction between pyrene-4,5-dione and aromatic aldehydes. The compound bearing a phenolic group can selectively detect bismuth (III) ion via fluorescence enhancement with a detection limit of 1.20 μm in CH₃ CN-DMSO mixture and 3.40 μm in 10% pH5 aqueous in CH₃ CN-DMSO mixture. The sensing mechanism involving a formation of coordination complex is investigated by UV-VIS and fluorescence titrations, ¹ H-NMR and the decomplexation of the bismuth complex by sulfide ion. The application of this sensor for quantitative analysis of spiked bismuth (III) ion in real water samples from two different sources is demonstrated.