CONJUGATED BODIPY-SALICYLALDEHYDE PROBES AS FLUORESCENT AND COLORIMETRIC CYANIDE SENSORS

Abstract

The development of selective cyanide detection is becoming an increasing demand because it is the one of the most toxic anion that is very harmful to human health and environment. Herein, two new colorimetric and fluorescent probes (GSB and RSB) based on boron dipyrrole-methene (BODIPY) containing salicylaldehyde group for cyanide detection are successfully prepared in 4 steps from the corresponding pyrroles in 70-80 %yield. Taking the advantage of the electrophilic property of aldehyde, nucleophilic addition of cyanide anion can convert salicylaldehyde into cyanohydrin which trigger the color, absorption and emission changes in the probes. In aqueous DMSO/water GSB and RSB undergo exclusive colorimetric changes from orange and purple to colorless upon the addition of cyanide. Moreover, GSB exhibited selective fluorescence turn-on at 504 nm while RSB displayed large blue shift from 600 to 504 nm upon the addition of cyanide. Other 13 anions gave almost no interference under physical condition. The detection limit of cyanide-sensing GSB and RSB are 0.88 and 1.79 μM, respectively which is lower than the concentration limited by World Health Organization (WHO) in drinking water (2.7 μM). A calculation from density functional theory (DFT) supports the cyanide suppress the photoinduced electron transfer (PET) mechanism along with the interruption of π-conjugation between salicylaldehyde and BODIPY core. Cell imaging studies demonstrated that GSB and RSB are compatible and capable of sensing cyanide anion in living cell.