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Kinetic Control of Threading and Dethreading in Linked Rotaxanes via Hydrogen Bonding
Hiromichi V Miyagishi1,2, Satoki Yamaguchi1, Susumu Tsuda3
1Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1, Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
Chemistry, an Asian Journal
|March 13, 2025
Summary
Neutral hydrogen bonding can control macrocyclic motion in mechanically interlocked molecules (MIMs). This study shows H-bond acceptors slow down MIM kinetics, acting as a brake to control molecular movement.
Area of Science:
- Supramolecular Chemistry
- Chemical Kinetics
- Materials Science
Background:
- Mechanically Interlocked Molecules (MIMs) are advanced molecular architectures with dynamic components.
- Controlling the kinetics of macrocyclic motion is crucial for MIM functionality.
- Neutral hydrogen bonding (H-bonding) offers selective and reversible interactions but its application in controlling MIM kinetics is underexplored.
Purpose of the Study:
- To investigate the influence of neutral H-bonding on the kinetics of threading and dethreading in linked rotaxanes.
- To explore the use of H-bond acceptor solvents and additives to modulate macrocyclic mobility in MIMs.
Main Methods:
- UV-vis spectroscopy to monitor reaction rates.
- Nuclear Magnetic Resonance (NMR) titrations to confirm interactions.
- Fourier Transform Infrared (FT-IR) spectroscopy for structural analysis.
- Eyring analysis to determine activation parameters.
Main Results:
- H-bond acceptor solvents (DMSO, DMF) significantly reduced threading/dethreading rates.
- H-bonding between aniline moieties and solvents acted as a kinetic brake.
- Enthalpic losses during H-bond cleavage increased activation barriers.
- Addition of H-bond acceptors (DMSO, TBPO) modulated kinetic rates.
Conclusions:
- Neutral H-bonding can effectively control the kinetics of macrocyclic motion in rotaxanes.
- Solvent and additive engineering via H-bonding provides a strategy for kinetic control in MIMs.
- This work demonstrates a pathway for designing dynamic MIM systems with tunable mobility.
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