Enantioselective Synthesis of Homochiral Hierarchical Nd8Fe3-Oxo Cluster from Racemic Nd9Fe2-Oxo Cluster

Abstract

Enantioselective synthesis of homochiral rare earth clusters is still a great challenge. In this work, we developed an efficient “cluster to cluster” approach, that is, a pair of enantiomerical R/S-{Nd₈Fe₃}-oxo clusters were successfully obtained from the presynthesized racemic {Nd₉Fe₂}-oxo cluster. R/S-hydrobenzoin ligands trigger the transformation of the pristine clusters by an SN₂-like mechanism. Compared to the pristine cluster with an achiral core, the new cluster exhibits hierarchical chirality, from ligand chirality to interface chirality, then to helix chirality, and finally to supramolecular double helix chirality. The spectral experiments monitored the transformation and confirmed distinctly structure-related optical activity. The enantiomeric pure cluster also exhibits a potential asymmetric catalytic activity.