Anion-Driven Circularly Polarized Luminescence Inversion of Unsymmetrical Europium(III) Complexes for Target Identifiable Sensing.

Anion-responsive sign inversion of circularly polarized luminescence (CPL) was successfully achieved by NO-type nona-coordinated europium(III) (Eu) complexes [()- and ()-] composed of a less-hindered unsymmetrical N-tridentate ligand (a chiral bis(oxazoline) ligand) and three O-chelating (β-diketonate) ligands. Here, ()- exhibited a positive CPL signal ( - > 0) at the D → F transition of Eu, which can be changed to a negative sign (i.e.