A highly selective and sensitive BODIPY-based colourimetric and turn-on fluorescent sensor for Hg2+ ions

A series of monostyryl boron dipyrromethenes appended with an NO4, NO2S2, N3O4, or N3O2S2-type ligand have been prepared and characterised. While the UV-Vis spectra of the former three compounds in CH3CN/H2O (2 : 3 v/v) do not respond towards a wide range of metal ions, the derivative with an N3O2S2-ligand exhibits a highly selective and sensitive spectral response towards Hg2+ ions. The absorption band is blue-shifted by 40 nm due to inhibition of the intramolecular charge transfer process upon metal complexation. The fluorescence is also turned on giving a strong emission band at 572 nm. The colour changes can be easily detected by the naked eye. The results suggest that this compound serves as a promising colourimetric and fluorescent sensor for Hg2+ ions in this mixed aqueous medium.