Optical detection of cyanide by palladium(II)-dithiazolopyridine probe at the parts per billion level

The ensemble of 2,6-bis(2-chlorophenyl)dithiazolo[4,5-b:5',4'-e]pyridine 1 with Pd2+ ions (1•Pd2+) was prepared for the detection of cyanide ions (CN¯) in 50% aqueous methanol. Among the tested metal ions, only Pd2+ sensitively induced the red shift of the absorption bands and the complete decrease of fluorescence emission. The detection limit toward Pd2+ was 2 ppb. The ensemble 1•Pd2+ selectively and rapidly detected a low concentration of cyanide ions by a colorimetric change (40 ppb) as well as a “turn-on” fluorescent response (5 ppb). Job’s plot revealed the complex formation with 1:1 stoichiometry. The binding and replacement mode of 1•Pd2+ and CN¯ were also confirmed by 1H NMR titrations and IR analysis. In general, a fast and selective recognition of CN¯ is reported.