Cd²⁺ Triggered the FRET “ON”: A New Molecular Switch for the Ratiometric Detection of Cd²⁺ with Live-Cell Imaging and Bound X‑ray Structure

On the basis of the Förster resonance energy transfer mechanism between rhodamine and quinoline–benzothiazole conjugated dyad, a new colorimetric as well as fluorescence ratiometric probe was synthesized for the selective detection of Cd2+. The complex formation of the probe with Cd2+ was confirmed through Cd2+-bound single-crystal structure. Capability of the probe as imaging agent to detect the cellular uptake of Cd2+ was demonstrated here using living RAW cells.