Synthesis of a pH-Sensitive Hetero[4]Rotaxane Molecular Machine that Combines [c2]Daisy and [2]Rotaxane Arrangements

The synthesis of a novel pH‐sensitive hetero[4]rotaxane molecular machine through a self‐sorting strategy is reported. The original tetra‐interlocked molecular architecture combines a [c2]daisy chain scaffold linked to two [2]rotaxane units. Actuation of the system through pH variation is possible thanks to the specific interactions of the dibenzo‐24‐crown‐8 (DB24C8) macrocycles for ammonium, anilinium, and triazolium molecular stations. Selective deprotonation of the anilinium moieties triggers shuttling of the unsubstituted DB24C8 along the [2]rotaxane units. Molecular muscles: The self‐sorting strategy between a naked dibenzo‐24‐crown‐8 (DB24C8), a DB24C8‐based hermaphrodite molecule, and a molecular axle that contains both an ammonium or an anilinium template allows for the efficient synthesis of a hetero[4]rotaxane molecular machine. Deprotonation of the anilinium stations allows shuttling of the DB24C8 units along the axle, which is linked to the daisy scaffold (see figure).