A Strong Supramolecular Mechanophore with Controlled Mechanical Strength

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Mechanochemistry

Background:

• Supramolecular mechanophores generally possess lower mechanical strengths (~100 pN) compared to covalent bonds (nN scale).
• Existing supramolecular systems often lack the robustness required for demanding applications.
• The dissociation kinetics of cucurbit[7]uril (CB[7])-hexanoate-isoquinoline (HIQ) complexes provided inspiration for enhanced mechanical properties.

Purpose of the Study:

• To investigate the potential of charge-dipole repulsion for creating strong supramolecular mechanophores.
• To explore the mechanical strength and tunability of the CB[7]-HIQ complex as a mechanophore.
• To develop supramolecular systems that bridge the gap between covalent and supramolecular material advantages.

Main Methods:

• Utilized charge-dipole repulsion within the cucurbit[7]uril (CB[7])-hexanoate-isoquinoline (HIQ) complex.
• Investigated the mechanical strength of the CB[7]-HIQ complex in its activated carboxylate (-COO⁻) state.
• Examined the influence of pH on the mechanical strength of the CB[7]-HIQ complex, comparing -COO⁻ and carboxylic acid (-COOH) states.

Main Results:

• The CB[7]-HIQ complex in the -COO⁻ state demonstrated a high mechanical strength of approximately 700 pN.
• This strength is comparable to that of weak covalent bonds, such as Au-S bonds or thiol-maleimide adducts.
• The mechanical strength was found to be pH-tunable, with a minimum value of ~150 pN in the -COOH state.

Conclusions:

• Charge-dipole repulsion is an effective strategy for designing strong supramolecular mechanophores.
• The CB[7]-HIQ complex offers tunable mechanical properties suitable for advanced applications.
• This work facilitates the development of hybrid supramolecular architectures combining covalent and supramolecular benefits.