Chirality and Chiroptics of Lanthanide Molecular and Supramolecular Assemblies

Chiroptical probes based on circular dichroism (CD) and circularly polarized luminescence (CPL) are crucial for understanding chirality in nature. Lanthanide chiroptical complexes are considered as promising candidates for the more sensitive CPL because of their unique optical properties, such as the magnetic dipole-allowed but electric-dipole-forbidden f-f transitions, large pseudo-Stokes shift, and long luminescence lifetime. However, due to the non-directional nature of lanthanide ions which allows variable coordination numbers, the design of their chiral complexes, especially at the supramolecular level, remains a challenge. Recent developments demonstrate the assemblies of chiroptical helices, cages, wheels, knots, and frameworks, which opens up future potential for applications such as in sensing and chiral guest recognition. This review provides the basics of coordination chemistry and photophysics of lanthanide ions, introduces chiroptical characterization, and summarizes the progress on the development of chiroptical lanthanide molecular and supramolecular systems. Perspectives on future development and applications are also discussed.