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

Abstract

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.