Highly selective and anions controlled fluorescent sensor for Hg ²⁺ in aqueous environment

A highly selective PET fluorescent sensor B1 for Hg ²⁺ containing a BODIPY fluorophore and a NS ₂O ₂ penta-chelating receptor has been synthesized and characterized. Its absorption maximum wavelength (498 nm) and emission maximum wavelength (512 nm) are both in the visible range. The fluorescence quantum yields of the B1 and Hg ²⁺-bound states of BHg1 are 0.008 and 0.58 in 70% aqueous ethanol solution, respectively. The pKa of 1.97 is the lowest in metal ions PET chemo sensors reported up till now as we know. Thus, B1 can detect the Hg ²⁺ in a wide pH span, which indicates that it has more potential and further practical applications for biology and toxicology. Furthermore, BHg1 also displays response to some anions such as Cl ^-(Br ^-), CO ₃ ², SCN ^- and CH ₃COO ^-, which is attributed to the significant coordinating ability of these anions to Hg ²⁺.