A novel red-emission sulfonamidoquinoline-based sensor with visible excitation for sensing group IIB cations

A novel red-emission sulfonamidoquinoline-based derivative (2-PyTSQ) with visible excitation was synthesized as an off-on type fluorescent sensor for distinguishing group IIB cations from common metal ions. When excited at 422 nm, 2-PyTSQ displayed the longer wavelength emission (>600 nm) with a remarkable fluorescence enhancement upon Zn2+, Cd2+, or Hg2+ coordination in aqueous solution, respectively. A 2:1 stoichiometry was found for the complexes formed by 2-PyTSQ and these cations. And the binding constants (logKs) gradually decreased from 9.45 to 8.96 as ionic radius of group IIB cations increased. Moreover, fluorescence imaging studies revealed that 2-PyTSQ was a cell-permeable and Cd2+-responsive reagent in yeast cells.