Macrocycle Size-Controlled Dynamic and Static Chirality in Donor–Acceptor [2]Catenanes

Abstract

Chiral [2]catenanes, a prominent class of mechanically interlocked molecules (MIMs), can exhibit either static or dynamic mechanostereochemistry. Controlling these mechanostereochemical states without altering the covalent connectivity, however, remains challenging. Herein, we report a series of chiral [2]catenanes derived from ExBox and cycloparaphenyleneperylene (CPPP), whose dynamic behavior is altered by the size of the CPPP macrocycle. We identified a sharp, size-dependent threshold: The conformational stereogenic unit of [7]CPPP is kinetically locked, whereas those of [8]CPPP and [9]CPPP are dynamic at room temperature. This conformational stereochemistry strongly biases the co-conformational stereochemistry in the catenane, effectively resulting in a single dominant diastereomer. This effective coupling of the two stereogenic units allows the conformational stereochemistry to be biased by the ion pairing of the interlocked cationic ring with a chiral anion. This research highlights the potential of mechanically interlocked architectures for controlling the dynamic mechanostereochemistry.