Hemicyanine-based colorimetric chemosensors: different recognition mechanisms for CN- sensing.

Simple hemicyanine dyes were synthesized by a classical condensation reaction. The structures of these dyes were characterized by (1)H NMR spectroscopy, elemental analysis, and FAB-Mass spectrometry. The sensing behavior of the hemicyanines towards a selection of anions was investigated by UV-vis absorption spectroscopy. These structurally simple dyes displayed a rapid response and high selectivity for cyanide ion over other common anions in the DMSO/H(2)O solution. Different sensing mechanism of the dyes to cyanide ion were confirmed by (1)H NMR studies, together with theoretical calculations based on DFT and PPP-MO methods. These dyes show no colorimetric response for other anions investigated.