A new fluorescent probe for Zn²⁺ with red emission and its application in bioimaging

A new fluorescent probe, (E)-3-(3-(4-([2,2':6',2''-terpyridin]-4'-yl)phenyl)acryloyl)-7-(diethylamino)-2H-chromen-2-one (ZC-F4), composed of coumarin as the fluorophore and terpyridine as the receptor was designed and synthesized. This probe showed good selectivity and sensitivity towards Zn(2+) even at the ppb level with significant variation of emission wavelength (more than 100 nm shifts) after combination with Zn(2+). One can observe that the emission colour changed from green to red. A Job's plot test suggested a 1 : 1 stoichiometry between ZC-F4 and Zn(2+), and the theoretical calculation based on density functional theory has been carried out to gain an insight into the sensing mechanism. Furthermore, imaging of Zn(2+) in cells was also performed to test its feasibility in biology. This fluorescence probe should be a promising candidate for applications in cell-imaging, environment protection, water treatment and safety inspection.