Dynamic Covalent Self‐Assembly Based on Oxime Condensation

Oxime, whose dynamic nature was reported to be switchable between ON/OFF by tuning the acidity, is employed in a novel type of dynamic covalent approach that is amenable to use in water for self‐assembly of purely organic molecules with complex topology. In strongly acidic conditions, the dynamic nature of oxime is turned ON, allowing occurrence of error‐checking and therefore a catenane and a macrocycle self‐assembled in high yields. In neutral conditions, oxime ceases to be dynamic, which helps to trap the self‐assembled products even when the driving forces of their formation are removed. We envision that this switchable behaviour might help, at least partially, to resolve a commonly encountered drawback of dynamic covalent chemistry, namely that the intrinsic stability of the self‐assembled products containing dynamic bonds, such as imine or hydrazone, are often jeopardized by their reversible nature. An off and on relationship: In strongly acidic aqueous solutions, the oxime bond is dynamic and allows both a catenane and a macrocycle to self‐assemble in relatively high yields. The dynamic nature of oxime linkage could be turned OFF almost fully in neutral conditions, making the self‐assembled catenane kinetically inert in both solid state and solution at elevated temperatures or during chromatography and counteranion exchange.