At 6 nm across, this sizable supramolecular cage is one of the largest ever built. A team led by Xiaopeng Li at Shenzhen University not only built these large cages but then coaxed them to self-assemble into helical nanowires (J. Am. Chem. Soc. 2021, DOI: 10.1021/jacs.1c00625).
Spiral packing is well known in the natural world. Spiral arrangements in plants, like those on the surface of a pineapple fruit, are related to Fibonacci number sequences. These botanical patterns are known as parastichy. Reproducing natural parastichy patterns in spiraling molecules, or inventing molecules that exhibit new types of parastichy, has proved tricky for chemists—until now.
Li and his collaborators started by building giant spheres from zinc porphyrin and diplatinum ligands. These giant cages first self-assemble into spheres, which spontaneously pack together into long, helical nanowires. These spirals of spheres exhibit a unique parastichy.
The team transferred the helical nanowires to different surfaces for analysis. The wires are conductive and stable, and might find future use in electronic devices. But Li hopes the work will also lead to a deeper understanding of complex self-assembly.