Ruthenium-based phosphorescent probe for selective and naked-eye detection of cyanide in aqueous media

Abstract A simple molecular phosphorescent Ru(II) probe P1 has been synthesized by the reaction of 5-aldehyde-2,2′-bipyridine with ruthenium(II) chlorides under mild conditions. The probe upon interaction with different cation and anion showed high selectivity and sensitivity for cyanide ion (CN‒) through phosphorescence “turn-on” response in aqueous solution (60% water) with a detection limit of 0.75 μM. The significant phosphorescence enhancement (~ 30-fold) is attributed to the nucleophilic addition of cyanide ion to the aldehyde groups of the ruthenium complex in 3 : 1 stoichiometry, in which a naked-eye sensitive orange red color of solution changed to a yellow. The generation of cyanohydrin species through nucleophilic addition has been confirmed by 1H NMR, FT-IR and mass spectra. Based on the color change of the solution, a visual colorimetric strip was prepared, which also showed good detection performance on cyanide ion with quick response time. The prominent efficiency of the Ru(II) probe proved the potential possibility of application in biosystems relating with cyanide ion.