Mechanochemistry with mechanical bonds – 3 studentships

Any force developed at the macroscopic scale can induce dramatic changes at the molecular scale, even breaking covalent bonds.[1] Indeed, mechanical force is a formidable source of energy that, with its ability to distort, bend and stretch chemical bonds, is unique in its ability to promote reaction pathways that are otherwise inaccessible to traditional methods of activation. A precise control of this force can be achieved when the chemical entity that is the subject of the mechanical force (a “mechanophore”) is embedded within a polymeric backbone.[2-5] Pulling both ends of a macromolecule apart creates highly directional strain with its highest intensity in the middle of the chain in a way reminiscent to a tug-of-war. The activation can be performed in solution, with the help of ultrasounds, or in the solid state, by simple stretching.

 Mechanical bonds have always fascinated chemists because of their intriguing nature and an undeniable aesthetic appeal. Since the first synthesis of a catenane in 1960, mechanical bonds have been used in a variety of contexts and their dynamic properties have been exploited to build molecular machines and new materials. The ability of their subcomponents to undergo large amplitude displacement, such as macrocycle shuttling in a rotaxane, make them ideal structures for mechanical coupling. We are currently investigating the rich array of mechanochemical behaviours displayed by catenanes and rotaxanes.[3-5] We have recently demonstrated that the activity of a mechanophore is altered when a rotaxane is used as a force actuator,[4] that rotaxanes under tension act as a lever that accelerate the dissociation of interlocked covalent bonds,[5] and that catenanes can act as mechanical protecting groups.[5]

 In this project you will use interlocked architectures (catenane/rotaxane) to promote unusual mechanochemical transformations and processes. You will investigate their activation both in solution, using ultrasounds, and in the solid-state by mechanical stretching, and explore their properties. This project could lead to the development of self-healing materials and to the creation of chemical systems able to perform complex synthetic tasks.

 You will be trained in synthetic organic, polymer, and supramolecular chemistry.