Symmetry breaking of highly symmetrical nanoclusters for triggering highly optical activity.

Developing new approaches to fulfill the enantioseparation of nanocluster racemates and construct cluster-based nanomaterials with optical activity remains highly desired in cluster science, because it is an essential prerequisite for fundamental research and extensive applications of these nanomaterials. We herein propose a strategy termed "active-site exposing and partly re-protecting" to trigger the symmetry breaking of highly symmetrical nanoclusters and to render cluster crystals optically active. The vertex PPh(3) of the symmetrical Ag(29)(SSR)(12)(PPh(3))(4) (SSR = 1, 3-benzenedithiol) nanocluster was firstly dissociated in the presence of counterions with large steric hindrance, and then the exposed Ag active sites of the obtained Ag(29)(SSR)(12) nanocluster were partly re-protected by Ag(+), yielding an Ag(29)(SSR)(12)-Ag(2) nanocluster with a symmetry-breaking construction. Ag(29)(SSR)(12)-Ag(2) followed a chiral crystallization mode, and its crystal displayed strong optical activity, derived from CD and CPL characterizations. Overall, this work presents a new approach (i.e., active-site exposing and partly re-protecting) for the symmetry breaking of highly symmetrical nanoclusters, the enantioseparation of nanocluster racemates, and the achievement of highly optical activity.