Molecular Shuttles Get Organized

With their ability to switch between two states, the mechanically interlocked molecules known as molecular shuttles hold much promise as components for data storage or nanoscale devices. But organizing these structures so that they might be used practically has been a challenge. Chemists led by Stephen J. Loeb and Robert W. Schurko of the University of Windsor, in Ontario, saw an opportunity to transfer molecular shuttles from the solution state, where their motion tends to be random and incoherent, to a more defined role as a structural component of a solid metal-organic framework (Nat. Chem. 2015, DOI: 10.1038/nchem.2258). They created the molecular shuttle from a dimeric moiety containing a pair of linked benzimidazole units. A crown ether encircling this moiety slides between the benzimidazole groups. Carboxylate groups at the ends of the dimeric moiety coordinate with Zn₄O clusters to assemble into an extended metal-organic framework. Solid-state NMR experiments show that the crown ether shuttles can move to and fro throughout the rigid skeleton, establishing that such molecular shuttles can function even when they are densely organized. This achievement, the researchers note, “is a crucial step toward the generation of solid-state nanoscale devices based on mechanically interlocked molecules.”