Highly selective, colorimetric probes for cyanide ion based on β-formylBODIPY dyes by an unprecedented nucleophilic addition reaction

Two beta-formylBODIPYs with strong daylight excitable fluorescence and highly selective visual and colorimetric responses to cyanide anion (CN-) have been prepared. NMR titration experiments have been performed to study the sensing mechanism for these two dyes. Surprisingly, cyanide anion is nucleophilic addition to the alpha-position of BODIPY core (the azafulvene framework) in aqueous system instead of the expected classical nucleophilic addition to the formyl moiety of the probes. This nucleophilic addition of cyanide anion to the azafulvene framework causes the interruption of the pi-conjugation of the BODIPY system, which brings a significant blue-shift (up to 10(4) nm) of the absorption maxima. A broadened and decreased absorption as well as ratiometrical fluorescence response (with maxima shifts from 523 to 670 nm) were observed with the titration of cyanide anion to probe 1b. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Two beta-formylBODIPYs show strong daylight excitable fluorescence and highly selective responses to cyanide anion. Surprisingly, cyanide anion undergoes nucleophilic addition to the alpha-position of the BODIPY core instead of the expected formyl moiety, causing interruption of pi-conjugation and significant blue-shift of absorption maxima.