Comparative study on indolium-fluorophore conjugates as dual sensors for cyanide ion in aqueous media

Abstract

Three derivatives of indolium ions containing different fluorophores - julolidine, triphenylamine and pyrene - are synthesized in excellent yields by a condensation reaction. These compounds exhibit excellent selectivity toward cyanide ion on both colorimetric and fluorescence modes. The lowest limits of detection at 0.65 µM on the colorimetric mode and 24 nM on the fluorescence mode are achieved from the triphenylamine derivative. Data from 1H NMR and mass analysis confirm that the selectivity involves the formation of adducts between cyanide and indolium derivatives. One of these compounds is used as a fluorescence sensor for quantitative analysis of cyanide ion in real water samples which shows high accuracy and precision.