Noncovalent control of shapeshifting molecules

Dynamic covalent rearrangements of fluxional carbon cages, such as bullvalenes and barbaralanes, impart ‘shapeshifting’ molecular properties.^1,2 This seminar will describe how this constitutional adaptation can be directed by noncovalent bonding interactions and the consequences for molecular recognition and catalysis.³ We show that the amount of certain minor isomers in these shapeshifting equilibria can be enhanced by shape-selective crystallisation^3a or by intra-^3b and intermolecular^3c noncovalent interactions. Suitably functionalised barbaralanes undergo rapid inversion of their C-sp3 stereochemistry,^3c and this phenomenon can be exploited as part of the design of ligands with adaptive chirality, which can be exploited in counterion-controlled enantioselective catalysis.