Discrepancy Regarding the Dethreading of a Dibenzo-24-crown-8 Macrocycle through a Perfluorobutyl End in [2]Pseudorotaxanes

Here are reported the synthesis and characterization of four new dibenzo-24-crown-8 (DB24C8)-based ammonium-containing pseudorotaxanes, for which one of the two encircled axle's extremities consists of a perfluorobutyl moiety. The subsequent dethreading of the DB24C8 over the perfluorobutyl extremity was studied. Although the perfluorobutyl extremity of an ammonium-containing axle did not allow threading of DB24C8, dethreading of a perfluorobutyl extremity-containing pseudorotaxane was possible and its rate depended on both the strength of the template-to-DB24C8 complex and the nature of the axle. In particular, dethreading process may be assisted by the presence, in the threaded axle, of a poor secondary site of interaction for the DB24C8 and this assistance proved to be higher when this site is close to the DB24C8.

Automated summary

This study synthesized and characterized four new DB24C8-based ammonium-containing pseudorotaxanes, and found that the perfluorobutyl extremity of the axle allows for dethreading of DB24C8, with the rate depending on the strength of the template-to-DB24C8 complex and the nature of the axle. The dethreading process may be assisted by the presence of a poor secondary site of interaction for the DB24C8 in the threaded axle, especially when this site is close to the DB24C8.