Pyridinium-Fused Pyridinone: A Novel "Turn-on" Fluorescent Chemodosimeter for Cyanide

A new chemodosimeter based on pyridinium-fused pyridinone iodide (PI) has been obtained through a "clean reaction" method. This compound can detect CN^- in aqueous solution with a high selectivity and rapid response. The detection of CN^- occurs through the nucleophilic attack of CN^- on the C=N bond, which induces the destruction of the π-conjugation on the pyridinium ring. Support of this detection mechanism was obtained by ¹H NMR titration, HR-MS, and DFT calculations. Upon the addition of 10 equivalents CN^- to a solution of PI in THF/H₂O (1:1, v/v), a 57-fold enhancement in fluorescence intensity was observed at the maximum emission wavelength of 457 nm. Meanwhile, the maximum absorption wavelength was also blue-shifted from 447 nm to 355 nm. Other common anions such as BF₄^-, PF₆^-, F^-, Cl^-, Br^-, I^-, H₂PO₄^-, ClO₄^-, CH₃COO^-, NO₂^-, N₃^-, and SCN^- had little effect on the detection of CN^-. The response time of PI for CN^- was less than 5 seconds. The detection limit was calculated to be 5.4×10^-8 Μ, which is lower than the maximum permission concentration in drinking water (1.9 μM) set by the World Health Organization (WHO). Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.