Rhodamine-based fluorescent and colorimetric sensor for zinc and its application in bioimaging

[Display omitted] •A rhodamine-based turn-on fluorescence probe bearing bis-1,2,3-triazole moiety was synthesized and characterized by 1H NMR, 13C NMR and HRMS.•Highly selective toward Zn2+ ions over other metal ions including Cd2+.•Bis-triazolyl rhodamine sensor was used in imaging Zn2+ in cultured HeLa cells. A rhodamine derivative ZP1, appended with two 1,2,3-triazole moieties via a diaminopropyl linker, is a chromogenic and fluorogenic sensor for Zn2+. In the presence of Zn2+, a colorless solution of ZP1 becomes pink with a maximum absorption of 555nm and a large fluorescence enhancement (140-fold) at 579nm (Φ=0.12). ZP1 is highly selective with Zn2+, among other metal ions including Cd2+, with a binding constant (Ka) of 7.4×103M−1 and a detection limit of 1μM (65ppb). Similar rhodamine derivatives with a shorter linker or with a single triazolyl group cannot function as a Zn2+ chemosensor. ZP1 is membrane-permeable and could react with intracellular Zn2+ in cultured HeLa cells.