Decorating polymer beads with 1014 inorganic-organic [2]rotaxanes as shown by spin counting

Conjugated bis(enaminones) as effective templates for rotaxane assembly and their post-synthetic modifications

The development of efficient methods for the synthesis of mechanically interlocked compounds is currently considered a major challenge in supramolecular chemistry. Twofold vinylogous fumaramides, a class of conjugated bis(enaminones), successfully achieve the assembly of hydrogen-bonded amide-based rotaxanes, with a templating ability comparable to that of their parent fumaramide-based systems, showcasing full conversions and impressive yields up to 92%. Computational calculations offer a compelling explanation for the remarkable efficiency of these bis(enaminones) in driving the synthesis of unprecedented rotaxanes. The reactivity of these interlocked species was thoroughly investigated, revealing that a one-step double stopper-exchange process can be successfully performed while preserving the mechanical bond. This approach facilitates the formation of controllable rotaxanes, including a three-station molecular shuttle, whose assembly via a clipping methodology is highly unselective. The internal translational motion of this latter species has been successfully controlled in a reversible way by means of a cycloaddition/retrocycloaddition sequence.

Control and Transferability of Magnetic Interactions in Supramolecular Structures: Trimers of {Cr7 Ni} Antiferromagnetic Rings

A synthetic strategy is demonstrated to prepare two distinct trimers of antiferromagnetically coupled {Cr7 Ni} rings, substantially varying the magnetic interactions between the spin centres. The interactions were studied using multi-frequency cw EPR: in a trimer linked via non-covalent H-bonding interactions no measurable interaction between rings was seen, while in a trimer linked via iso-nicotinate groups isotropic and anisotropic exchange interactions of +0.42 and -0.8 GHz, respectively, were observed. The latter are the same as those for a simpler hetero-dimer system, showing how the spin-spin interactions can be built in a predictable and modular manner in these systems.

Light-responsive rotaxane-based materials: inducing motion in the solid state

Light-responsive rotaxane-based solid-state materials are ideal scaffolds in order to develop smart materials due to the properties provided by the mechanical bond, such as control over the dynamics of the components upon application of external stimuli. This perspective aims to highlight the relevance of these materials, by pointing out recent examples of photoresponsive materials prepared from a rotaxanated architecture in which motion of the counterparts and/or macroscopic motion of the interlocked materials are achieved. Although further development is needed, these materials are envisioned as privileged scaffolds which will be used for different advanced applications in the area of molecular machinery.