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

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. The ruthenium probe exhibits highly selective and sensitive for CN– recognition in aqueous solution (60% water) with a detection limit of 0.75 μM. Changes in the color of the solution were clearly observed with the naked eye. Based on the color change of the solution, a strip was prepared and showed good detection performance CN– ion and quick response time. [Display omitted] •A stable and quick response ruthenium probe in aqueous solution (60% water) with a detection limit of 0.75 μM was synthesized.•The ruthenium complex showed good selectivity towards cyanide in a variety of anions and cations.•A visual colorimetric strip based on the ruthenium complex showed good detection performance on CN– ion with quick response time.