Detection of sulfide ion and gaseous H2S using a series of pyridine-2,6-dicarboxamide based scaffolds.

Pyridine-2,6-dicarboxamide based scaffolds with different appendages act as chemosensors for the selective detection of S2- ion, as well as gaseous H2S, in primarily aqueous media. Out of nine synthesized chemosensors, one with benzothiazole ring appendages was found to be highly selective for S2- ion and gaseous H2S. A series of spectroscopic studies confirmed that sulfide ion abstracts amidic N-H groups thus leading to the in situ generation of HS- ion, which remain bound to the pincer cavity of the resultant anionic chemosensor, and it was found that acetic acid could be used to reverse this process. It was essential for a chemosensor to feature a pincer cavity to recognize sulfide ion, whereas the sensing mechanism involved the deprotonation of the amidic N-H groups. We also illustrate the detection of sulfide ions and gaseous H2S in live cells and paper-strip sensing applications.