Rotaxane

Supramolecular chemistry

Slipping

Crystal structure

Molecule

Pseudorotation

Stereochemistry

Organic chemistry

Mathematics

Molecular dynamics

Computational chemistry

Geometry

Crystallography

Chemistry

Crown ether

Steric effects

Ring (chemistry)

ChemistryOpen

A pseudo ‐rotaxane is a host−guest complex composed of a linear molecule encircled by a macrocyclic ring. These complexes can be assembled by sliding the host over the guest terminal groups. If there is a close match between the molecular volume of the flanking groups on the guest and the cavity size of the macrocycle, the slipping might occur slowly or even become completely hindered. We have previously shown that it is possible to overcome the restraints imposed by steric effects on the sliding process by integrating electrostatic attractive interactions during the slipping step. In this work, we extend our electrostatically assisted slipping approach ( EASA ) to a new host−guest system featuring a flexible macrocyclic ring and a series of asymmetric guests containing a cyclic tertiary ammonium group. Compelling evidence for pseudo ‐rotaxane formation is presented, along with thermodynamic and kinetic data. Experimental results suggests that the higher conformational flexibility of 24‐crown‐8 significantly increases the sliding rate, compared with the more rigid dibenzo‐24‐crown‐8, without affecting complex stability. Furthermore, by combining the EASA and macrocycle flexibility, we were capable to slip a large eight‐membered cyclic group across the 24‐crown‐8 annulus, setting a new limit on the ring molecular size that can pass through a 24‐membered crown ether.

An Operative Electrostatic Slipping Mechanism along Macrocycle Flexibility Accelerates Guest Sliding during <i>pseudo</i>‐Rotaxane Formation

An Operative Electrostatic Slipping Mechanism along Macrocycle Flexibility Accelerates Guest Sliding during pseudo‐Rotaxane Formation