Circularly polarized luminescence of lanthanide complexes: From isolated individuals, discrete oligomers, to hierarchical assemblies

Circularly polarized luminescence (CPL) is the emission featured spatial orientation equivalent to circular dichroism. Owning to the unique magnetic dipole-allowed but electric-dipole-forbidden 4f & RARR; 4f transitions, chiral lanthanide complexes have been recognized as ideal candidates to achieve unprecedented luminescence dissymmetry factor (g(lum)). Their inherent electric-dipole-forbidden transition can be partly allowed, through the rational design of coordination ligands to lower the surrounding symmetry, further endowing them with relatively high quantum yields (QYs). Moreover, the blossom of supramolecular chemistry in lanthanide complexes allows for the construction of discrete oligomers and hierarchical assemblies, rendering them with enhanced chiroptical activities. Here, we deploy this review by summarizing recent advances in the chiroptical properties of lanthanide complexes, spanning multiple scales from isolated mononuclear individuals, discrete polynuclear oligomers, to infinite hierarchical assemblies. We first introduce the basic concept and several important parameters for the assessment of CPL activity. Then, isolated mononuclear lanthanide complexes coordinated with different types of antennas, along with the unique chirality transfer and induction in achiral lanthanide complexes were discussed. Next, the systematical discussion on chiroptical properties in discrete polynuclear lanthanide oligomers and infinite hierarchical lanthanide assemblies was presented. Meanwhile, the state-of-the-art applications of CPL-active lanthanide complexes were revisited. We end up this review with the conclusion and prospects, involving the rational design of ligands, directed and hierarchically precise self-assembly, and extending applications of chiral lanthanide complexes.

Automated summary

This review summarizes recent advances in the chiroptical properties of lanthanide complexes, covering multiple scales from isolated mononuclear individuals, discrete polynuclear oligomers, to infinite hierarchical assemblies. The basic concept and important parameters for the assessment of CPL activity are introduced. The discussion includes mononuclear lanthanide complexes coordinated with different types of antennas, as well as unique chirality transfer and induction in achiral lanthanide complexes. The chiroptical properties in discrete polynuclear lanthanide oligomers and infinite hierarchical lanthanide assemblies are systematically discussed, along with the state-of-the-art applications of CPL-active lanthanide complexes.