Carboxamidoquinoline–coumarin derivative: A ratiometric fluorescent sensor for Cu(II) in a dual fluorophore hybrid

A novel dual fluorophore-based ratiometric Cu2+ sensor CPC was synthesized via integrating carboxamidoquinoline and coumarin fluorophores. CPC showed high selectivity for Cu2+ over other metal ions at pH 7.24 in acetonitrile–water solution. The emission produced by carboxamidoquinoline was obviously quenched upon binding Cu2+, while the emission produced by coumarin remained almost intact during the whole titration, thus acting as a stable internal standard and validating CPC as a ratiometric sensor. A Job's plot and the MS analysis implied that there was only the formation of a CPC/Cu2+ complex with 1:1 stoichiometry.