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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
Published on: September 26, 2016
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An Operative Electrostatic Slipping Mechanism along Macrocycle Flexibility Accelerates Guest Sliding during
Aldo C Catalán1, Axel A Loredo1, Ruy Cervantes1
1Department of Chemistry, Center for Research and Advanced Studies (Cinvestav), Avenida IPN 2508, 07360, Mexico City, Mexico.
Chemistryopen
|June 20, 2022
Summary
This study demonstrates electrostatically assisted slipping (EASA) to form pseudo-rotaxanes, overcoming steric hindrance. Increased macrocycle flexibility enhances guest molecule sliding rates and complex stability.
Area of Science:
- Supramolecular Chemistry
- Host-Guest Chemistry
Background:
- Pseudo-rotaxanes are host-guest complexes formed by threading a guest molecule through a macrocyclic host.
- Steric hindrance between guest and host can impede complex formation.
- Electrostatically assisted slipping (EASA) has been previously shown to overcome steric restraints.
Purpose of the Study:
- To extend the EASA approach to a new host-guest system with a flexible macrocycle and asymmetric guests.
- To investigate the influence of macrocycle flexibility on pseudo-rotaxane formation kinetics and thermodynamics.
- To establish new limits for guest molecular size that can be threaded through a macrocycle.
Main Methods:
- Assembly of pseudo-rotaxane complexes using EASA.
- Characterization of host-guest interactions and complex formation.
- Kinetic and thermodynamic analysis of the slipping process.
Main Results:
- Successful formation of pseudo-rotaxanes with a flexible 24-crown-8 macrocycle and asymmetric guests.
- Higher conformational flexibility of 24-crown-8 significantly increased the sliding rate compared to rigid dibenzo-24-crown-8.
- The EASA approach combined with macrocycle flexibility enabled threading of a large cyclic group, expanding the size limits for crown ether complexation.
Conclusions:
- Macrocycle flexibility is a key factor in accelerating pseudo-rotaxane formation kinetics without compromising stability.
- The EASA strategy is effective in overcoming steric barriers for complex assembly.
- This work advances the design and synthesis of complex supramolecular architectures by enabling the threading of larger guest molecules.
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