Highly selective colorimetric/fluorometric chemodosimeters for cyanide ions in aqueous solution based on Michael addition to C-atom possessing different polar substituents

Two simple chemosensors, 3-(4-aminophenyl)-2-cyanoacrylic acid (1) and 3-(3-aminophenyl)-2-cyanoacrylic acid (2), exhibited visual colour and fluorescence changes selectively with cyanide ions in aqueous solution. Their anion sensing properties were investigated using UV-vis, fluorescence and H-1 & C-13 NMR spectral studies and theoretical studies. The mechanism of sensing involves Michael addition of CN- to C=C bond. The addition reaction was found to occur relatively easier with p-NH2C6H4 group (Taft's sigma* 0.16) substituted C=C bond than that with m-NH2C6H4 group (sigma* 0.58) substituted compound. The detection limits were calculated to be 33 pM and 0.2 nM for the receptors 1 and 2, respectively, which are lower than the maximum permissible concentration of cyanide ion in drinking water (1.9 mu M) set by the World Health Organization (WHO). (C) 2014 Elsevier Ltd. All rights reserved.