Studying the Mechanical Reversibility of a Click-Chemistry Linkage by AFM-Based Single-Molecule Force Spectroscopy

Valentin Foidart, Narangerel Ganbaatar, and Anne-Sophie Duwez

Nanochemistry and Molecular Systems, Department of Chemistry, University of Liege, Belgium
vfoidart@uliege.be


These last two decades, click-chemistry has been vastly used in synthetic chemistry and polymer science, and is now expanding into biology.1 It is attractive because of the ease in formation of molecular connections it provides. The click bond is considered to be irreversible, as it stable towards most thermal and chemical treatments. Its mechanical reversibility is still an open question. A few years ago, Du Prez and co-workers proposed a versatile click chemistry platform based on the reactivity of a 1,2,4-triazoline-3,5-dione (TAD) component.2 They have demonstrated that the unique reactivity of TAD reagents lead to both ultrafast (< 1 min) covalent linking and dynamic properties. The results showed that TAD can be reliably clicked onto a range of enes and dienes partners. Among them, the cycloaddition between TAD and anthracene has shown to be thermally reversible at ambient temperature.3 Here, we have investigated the mechanical reversibility of this TAD-anthracene system by AFM-based single-molecule force spectroscopy.

The experimental system is composed of a gold-coated tip and surface. A polycaprolactone polymer is grafted to the tip thanks to a gold-sulphur interaction and linked to the anthracene on the other side. The MDI-TAD molecule is linked to a citronellol which is anchored on the surface with a gold-sulphur bond. Contrary to what is expected for a classical covalent bond, our study showed that the TAD-anthracene click bond appears to break at much lower forces.  
 

  1. Mondal, P., Jana, G., Behera, P. K., Chattaraj, P.K., Singha, N. K. A New Healable Polymer Material Based on Ultrafast Diels-Alder ‘Click’ Chemistry Using Triazolinedione and Fluorescent Anthracyl Derivatives: A Mechanistic Approach. Polym. Chem. 2019, 10 (37), 5070-5079.
  2. Billiet, S., De Bruycker, K., Driessen, F., Goossens, H., Van Speybroeck, V., Winne, J. M., Du Prez, F. E, Nat. Chem. 2014 (6), 815.
  3. De Bruycker, K., Billiet, S., Houck, H. A., Chattopadhyay, S. Winne, J. M., Du Prez, F. E. Triazolinediones as Highly Enabling Synthetic Tools. Chem. Rev. 2016, 116 (6), 3919-3974.