New 7-hydroxycoumarin-based fluorescent chemosensors for Zn(II) and Cd(II)

Abstract

Five new 4- or 8-substituted-7-hydroxycoumarin derivatives (1-5) were synthesized as fluorescent sensors for metal ions. Fluorescent changes and selectivity for metal ions were compared based on the introduction of different ligands and/or testing with different substitution positions of 7-hydroxycoumarin in aqueous solution. Especially, probes 2, 3 and 5 displayed large fluorescence enhancements with Zn2+ and Cd2+. Probes 2 and 3 showed moderate selectivity for Zn2+ over Cd2+. On the other hand, probe 4 showed large fluorescence quenching effects upon the addition of Ag+ and Hg2+.