Cyanide detecting porphyrin fluorescent sensors: Effects of electron-donating/withdrawing substituents

The detection of cyanide (CN−) and other dangerous chemicals is critical in many practical scenarios. In this study, dicyanovinylporphyrins (DCVPs) 2a to 2d with electron-donating or electron-withdrawing substituents as fluorescent sensors for CN− detection were synthesized through Lindsay's condensation reaction. The 2a to 2d absorption, fluorescence, and fluorescence lifetimes of the DCVPs were investigated in THF. To probe the reactivity of DCVPs to CN−, the electron density of β-carbon in their dicyanovinyl groups was controlled by introducing electron-donating or electron-withdrawing groups. The anion (Cl−, Br−, I−, ClO4−, HSO4−, NO3−, and CN−) sensing abilities of DCVPs 2a to 2d were investigated through fluorescence spectroscopy in THF. The DCVPs exhibited selective reduction in fluorescence intensity upon the addition of CN−ions. DCVP 2d also exhibited strong detection capabilities for CN−ions. Specifically detection limit for CN− was found to be 3.14 × 10−8 M in THF.