Radical Cyclic [3]Daisy Chains

Mechanically interlocked molecules (MIMs) that undergo control-lable internal motions of their component parts in more than one dimension are rare entities in the molecular world. Cyclic [2]daisy chains ([c2]DCs) are a class of MIMs that have been identified as prototypes for molecular muscles. It remains, however, a challenge to synthesize [cn]DCs with n > 2 selectively and efficiently. Herein, we report the design and synthesis of [c3]DCs employing radical and anionic templates. Two mechanically interlocked [c3]DCs with 18 positive charges were obtained in >90% yields. One [c3]DC displayed good air stability in its radical cationic form, while the other underwent reversible co-conformational switching between open macrocyclic and closed trisarm-shaped forms under electrochemical control. These findings provide not only two-dimensional MIMs with attractive electronic and switchable properties, but also a starting point for the design of extended molecular arrays, which could become the forerunners of adjustable molecular nets and breathable molecular membranes.

Automated summary

This study reports the design and synthesis of mechanically interlocked [c3]DCs using radical and anionic templates. Two [c3]DCs with 18 positive charges were obtained with over 90% yields, showcasing good air stability and reversible co-conformational switching under electrochemical control, respectively. These findings not only provide two-dimensional MIMs with attractive electronic and switchable properties, but also lay the groundwork for the design of extended molecular arrays with potential applications in adjustable molecular nets and breathable molecular membranes.