Di–thioether amide–Pd2+ complex based-methionine fluorescent chemosensor with selectivity over cysteine and histidine

Determination of methionine (Met) has garnered increasing attention in various fields because methionine is a biomarker for various diseases. However, chemosensors for Met are very limited compared to those for other amino acids, and many Met chemosensors show low selectivity towards Met over cysteine (Cys) and histidine (His). In this study, a di–thioether amide–Pd2+ complex, 1-Pd2+, based on a 7-diethylaminocoumarin scaffold, was prepared as a sensitive and selective fluorescent chemosensor for Met. The limit of detection (LOD) for Met of 1-Pd2+ was determined to be 1.0 μM and the chemosensor exhibited a high selectivity towards Met over various amino acids including Cys and His. 1-Pd2+ worked well in a broad pH range of 4.0–8.0 and was applied to determine the concentration of Met in tap water samples. In addition, ligand 1 was demonstrated to be a selective and sensitive fluorescent chemosensor for Pd2+. The LOD for Pd2+ of 1 was determined to be 1.7 μM and it exhibited a high selectivity for Pd2+ over various other metal ions.