Controlling the Chirality of Metallo-Cages by Manipulating the Stereochemistry of the Metal Centers

Abstract

Precise control over the chirality of metallo-cages by manipulating the stereochemistry of metal centers is important in many practical applications, but is extremely challenging. In this study, two isostructural metallo-cuboctahedra (1-Zn^II₁₂L1₈ and 2-Cd^II₁₂L1₈) have been assembled using ligand L1 and two kinds of metal ions (Zn^II and Cd^II) with similar coordination lability. The chiral-induction by the same guests (D-/L-camphorsulfonate, D-/L-SCS) results in a completely opposing stereochemical output of 1 and 2: D-SCS induced host–guest complex of [D-SCS⊂Δ₁₂–1] and [D-SCS⊂Λ₁₂–2], respectively, with reverse handedness. The distinct stereochemical configuration of metallo-cuboctahedra can be manipulated by participant metal ions that exhibit similar dynamics. Furthermore, a subtle variation of the ligand peripheral substituent group facilitates spontaneous resolution of metallo-cuboctahedra 3-Zn^II₁₂L2₈ from a racemic mixture as (R₂₄, Λ₁₂)-3/(S₂₄, Δ₁₂)-3 enantiopure entities. The dynamic stereochemistry of M^II₁₂L₈ cuboctahedra described in this work allows a chiral manipulation based on the nature of metal centers and ligands, enabling the design and control of the chirality of metallo-cages.