A highly selective turn-on fluorescence chemosensor for Hg(II) and its application in living cell imaging

A new coumarin derivative (MS1) containing an imine moiety and a hydroxyl moiety exhibits an enhanced fluorescence in the presence of Hg2+ ions. Other metal ions Al3+, Ca2+, Co2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Ni2+, Pb2+, and Zn2+ produced only minor changes in the fluorescence values of MS1. The binding ratio of MS1-Hg2+ complexes was determined from the Job plot to be 1:1. The binding constant (Ka) of Hg2+ binding to MS1 was found to be 6.85 × 103 M−1. The maximum fluorescence enhancement caused by Hg2+ binding to MS1 was observed in the pH range of 6.5-9.0. Confocal fluorescence microscopy imaging using RAW 264.7 cells showed that MS1 could be used as an effective fluorescent probe for detecting Hg2+ in living cells.