Ratiometric fluorescent determination of palladium based on the C-N bond cleavage of allyl quaternary ammonium

An allyl quaternary ammonium modified phenanthroimidazole derivative (AL-PPI) has been designed and synthesized for ratiometric detection of palladium. The probe AL-PPI shows high sensitivity and selectivity toward Pd-0, with the limit of detection (LOD) of 8.46 nM in ethanol and 11.5 nM in CTAC aqueous solution, respectively. The sensing mechanism is based on Pd-0-catalyzed C-N bond cleavage of the N-allylpyridinium moiety in AL-PPI. The fluorescence of AL-PPI can be quenched by Pd2+. However, by using tris(2-thiophenyl)phosphine (TFP) as the reductant and ligand, AL-PPI shows a ratiometric fluorescence response toward Pd2+. With the aid of TFP, the LOD of AL-PPI for Pd2+ is 4.29 nM. When encapsulated in CTAC micelles, the fluorescence quantum yield of AL-PPI is enhanced dramatically, which may facilitate its application in quantitative detection of palladium in practical samples.

Automated summary

An allyl quaternary ammonium modified phenanthroimidazole derivative (AL-PPI) has been developed for the ratiometric detection of palladium, showing high sensitivity and selectivity towards Pd-0. The sensing mechanism is based on the Pd-0-catalyzed C-N bond cleavage of the N-allylpyridinium moiety in AL-PPI. With the assistance of TFP, the LOD of AL-PPI for Pd2+ is significantly improved, making it a promising tool for quantitative detection of palladium in real samples.