High-Fidelity Stereochemical Memory in a Fe^II₄L₄ Tetrahedral Capsule

A new class of FeII4L4 capsules, based upon a tritopic trialdehyde subcomponent, is reported. One such capsule was prepared diastereoselectively through the incorporation of a chiral amine residue. This amine was displaced by an achiral one, while maintaining the stereochemistry of the cage framework (99% ee); this cage retained its stereochemistry even after 4 days at 90 °C. Mechanistic studies indicate the memory displayed by this capsule to be the result of effective stereochemical communication between the metal centers mediated by the rigid 3-fold-symmetric faces, in combination with a stepwise substitution mechanism.