A Rhodamine-coumarin Triazole Conjugate as a Fluorescent Chemodosimeter for Cu(II) Detection and its Application in...

A rhodamine-triazole fluorescent probe bearing a coumarin moiety RTC was synthesized using the Cu(I)-catalyzed click reaction. The rhodamine-triazole conjugate was highly selective to Cu²⁺ among other metal ions, including Ca²⁺, Co²⁺, Cu²⁺, Cd²⁺, Mg²⁺, Fe²⁺, Fe³⁺, Hg²⁺, Zn²⁺, Ni²⁺, Pd²⁺ and Pb²⁺ in physiological conditions. Upon the addition of Cu²⁺, the colorless RTC solution turned pink and exhibited a significant fluorescence emission centered at 578 nm. The binding of Cu²⁺ induced a hydrolysis reaction, leading to a release of the coumarin unit from the rhodamine probe, as confirmed by mass spectrometric data. From the fluorescence titration, the detection limit of RTC for Cu²⁺ was determined to be 21 nM (1.3 ppb). The sensor was responsive to Cu²⁺ in a wide pH range and successfully applied to monitor Cu²⁺ in HEK293T cells by confocal fluorescence imaging.