The assembly/disassembly of a dicopper(l) helicate with a bis-bidentate imine-quinoline ligand is driven by the Cu-II/Cu-I redox change and is signaled by a fluorescent probe bearing a -COO- group (coumarine 343). The probe coordinates the Cu-II center of the monomeric complex, which quenches its emission (fluorescence off), and is released upon reduction and formation of the Cu-I helicate (fluorescence on).