Chiral Memory via Chiral Amplification and Selective Depolymerization of Porphyrin Aggregates

Chiral memory at the supramolecular level is obtained via a new approach using chiral Zn porphrins and achiral Cu porphyrins. In a sergeant-and-soldiers experiment, the Zn sergeant transfers its own chirality to Cu soldiers and, after chiral amplification, the sergeant is removed from the coaggregates by axial ligation with a Lewis base. After this extraction, the preferred helicity observed for the aggregates containing achiral Cu porphyrins reveals a chiral memory effect that is stable and can be erased and partially restored upon subsequent heating and cooling.