Irreversible Interlock of Molecular Rings

Another observation which is difficult to explain is the irreversible formation of a catenane from two preformed monomer rings. As already discussed, catenane 13 is in equilibrium with monomer ring 14. If the labile coordinate bond can be frozen after the catenane is assembled, one can obtain a complete catenane that never dissociates into two rings. 

Experimentally, sodium nitrate was added to an aqueous solution of molecular ring 16, and the solution was heated at 100 °C. Then, the equilibrium between 16 and its catenated dimer 15 is pushed by the polar media toward the catenane. After self-assembling in a high yield, catenane 15 was isolated as a CIO4 salt in a high yield (Eq. 3). It was confirmed that catenane 15 thus obtained did not dissociate into two rings in aqueous solution because its framework had been locked. 

4 Electronic Effects in the Self-Assembly of Pd(n)-Linked Catenanes 

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