Coumarin-derived cu²⁺-selective fluorescence sensor: Synthesis, mechanisms, and applications in living cells

A novel coumarin-based fluorogenic probe bearing the 2-picoIyI unit (1) was developed as a fluorescent chemosensor with high selectivity and suitable affinity in biological systems toward Cu²⁺ over other cations tested. The fluorescence on-off mechanism was studied by femtosecond time-resolved fluorescence (TRF) upconversion technique and ab initio calculations. The receptor can be applied to the monitoring of Cu²⁺ ion in aqueous solution with a pH span 4-10. To confirm the suitability of 1 for biological applications, we also employed it for the fluorescence detection of the changes of intracellular Cu²⁺ in cultured cells. The results indicate that 1 should be useful for the fluorescence microscopic imaging and the study on the biological functions of Cu²⁺.