A Dansyl‐Appended Koneramine as a Robust and Reversible Fluorescent Probe for Copper(II) Detection

A dansyl‐appended koneramine ligand (L Dn H) was designed as a photofunctional probe for Cu 2+ sensing. The ligand and its Zn(II), Cd(II), Cu(II), and Co(II) complexes were synthesized and fully characterized. L Dn H exhibits strong green fluorescence, which was preferentially quenched by Cu 2+ ions over a wide range of competing cations. Fluorescence titrations established 1:1 stoichiometry and revealed a high Stern–Volmer constant ( K SV = 3.40 × 10 5 M −1 ), with a detection limit (LOD = 0.27 μM) well below the US EPA guideline. Importantly, the probe demonstrated excellent reversibility through Cu 2+ /EDTA cycles, enabling reusability. Density functional theory calculations supported the experimental findings by providing insight into the electronic properties and stability of the complex. These findings establish L Dn H as a robust, reusable Cu 2+ sensor, while demonstrating the potential of koneramine scaffolds in the design of fluorescent probes.