Ratiometric & reversible fluorescent sensing of NaCN by an effective probe based on phenanthro[9,10-d]imidazole platform

Abstract A novel compound 1 based on phenanthro[9,10-d]imidazole platform has been unveiled as an effective ratiometric fluorescent probe for selective and rapid detection of NaCN. The sensing behavior was demonstrated by UV-vis, fluorescence experiments and NMR studies. This sensory system exhibited prominent visual emission color change toward CN − over other testing anions in CH 3 CN-PBS buffer (v/v, 3:1, pH 7.2) solution, with a 1:1 binding stoichiometry. Detection limit of the new cyanide-sensing probe 1 was 1.8 × 10 −9  mol L −1 , which was much lower than the World Health Organization (WHO) recommended level drinking water. The experimental results revealed that the formation of anionic species from the deprotonation of imidazole moiety by the CN − ion was responsible for the spectral changes. Calculations of the transition energies also verified such process. The spectral responses of probe could be switched back and forth alternatively by adding CN − and H + anions into the CH 3 CN-PBS buffer (v/v, 3:1, pH 7.2) solution, which indicated that compound 1 was stable and could be used in reversible manner.