Generation and manipulation of chiroptical activities in coinage-metal clusters

Chiral metal clusters with atomically precise structure are considered as promising candidates for disclosing the chirality origin and potential chiroptical applications compared with metal nanoparticles. Recently, researchers have successfully made great improvement for the preparation of chiral metal clusters, but for chiroptically active metal clusters is still challenging, because most left- and right-handed clusters always coexist in a system. Furthermore, proper modulation of optical activity at the nanoscale is useful for exploring the various mechanisms. Therefore, controlling the chiroptical properties of clusters arouse intense research enthusiasm. In this Review, methodology for the preparation of chiral coinage-metal clusters was elaborated, and the achiral-to-chiral transformations of specific coinage-metal clusters were mainly highlighted. Furthermore, coinage-metal cluster racemates hinder the in-dept understanding of chiroptical properties and thus the enantioenriched or even homochiral clusters attract great attention. We reviewed the novel strategies for separating enantiomers or deracemization of coinage-metal clusters. Benefiting from the successful preparation of chiroptically active clusters, the manipulation of their optical activity, which gives a great contribution to correlate chiroptical properties with structural characteristics, was also mentioned here. We hope this Review can inspire new concept to expand the preparation and application of chiral coinage-metal clusters.