Eu3+ chelate with phenanthroline derivative gives selective emission responses to Cu(II) ions

Two novel ternary europium(III) complexes (Eu-1 and 2) based on modified phenanthroline ring have been successfully synthesized and give characteristic purple–red emissions. The complex with 4-substituted carboxyl group has been proved to act as a selective luminescence quencher for copper(II) ions, as shown by the “on/off” switch phenomenon and the smart responsive changes in the UV–vis region (detection limit up to 0.5 μM). The preliminary data imply that Eu-1 could be applicable as a potential fluorescent sensor for detection of copper(II) ions.