Expedient Synthesis of Heterobifunctional Triarylmethane Stoppers for Macromolecular Rotaxanes.

Increasingly complex rotaxane-based molecular devices are interfaced with polymers and surfaces, but suitable bifunctional stoppering groups are lacking. Here, we report a two-step, high-yielding synthesis toward a new class of heterobifunctional triarylmethane stoppers. They possess hydroxyl and ester groups for further functionalization as well as halogen substituents conferring a diagnostic spectroscopic signature. Their utility was demonstrated with the synthesis of a chain-centered macromolecular rotaxane. This new stopper architecture should prove useful to connect rotaxanes with polymers and surfaces for applications in polymer mechanochemistry, single-molecule force spectroscopy, smart materials, and molecular machines.