Pyridinium-fused pyridinone: a novel "turn-on" fluorescent chemodosimeter for cyanide

Abstract

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 (1)H NMR titration, HR-MS, and DFT calculations. Upon the addition of 10 equivalents CN(-) to a solution of PI in THF/H2 O (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(-), CH3 COO(-) , 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) M, which is lower than the maximum permission concentration in drinking water (1.9 μM) set by the World Health Organization (WHO).

Keywords: chemodosimeter; cyanide anions; fluorescence; pyridinium; pyridinone; sensors.