A BODIPY-based colorimetric and fluorometric chemosensor for Hg(II) ions and its application to living cell imaging

A new monostyryl boron dipyrromethene derivative (MS1) appended with two triazole units indicates the presence of Hg²⁺ among other metal ions with high selectivity by color change and red emission. Upon Hg²⁺ binding, the absorption band of MS1 is blue-shifted by 29 nm due to the inhibition of the intramolecular charge transfer from the nitrogen to the BODIPY, resulting in a color change from blue to purple. Significant fluorescence enhancement is observed with MS1 in the presence of Hg²⁺; the metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Fe³⁺, K⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ cause only minor changes in the fluorescence of the system. The apparent association constant (K_a) of Hg²⁺ binding in MS1 is found to be 1.864 × 10⁵ M⁻¹. In addition, fluorescence microscopy experiments show that MS1 can be used as a fluorescent probe for detecting Hg²⁺ in living cells.