Tribenzo[27]crown-9: A new ring for dibenzylammonium rods

[GRAPHICS] Dibenzylammonium (DBA(+)) ions thread through the cavity of tribenzo[27]crown-9 (TB27C9) to generate [2]pseudorotaxanes that are stabilized principally by hydrogen bonding interactions. The stabilities and complexation kinetics associated with these pseudorotaxanes depend markedly on the nature of the substituents situated on the phenyl rings of the DBA(+) ions. For example, the complex formed between TB27C9 and the DBA(+) ion bearing electron withdrawing p-CO2Me substituents is stronger than that obtained from TB27C9 and the "parent", unsubstituted DBA(+) ion itself. Furthermore, the "parent" complex equilibrates much more rapidly with its uncomplexed components than do the complexes generated from TB27C9 and substituted DBA(+) ions.