Getting (Nano)Tubular With Porphyrins

Nanotubes can exhibit exotic electronic properties when their atoms are willing to share delocalized electrons, but growing pristine tubes with prescribed orbital overlaps is a challenge. Researchers led by Harry L. Anderson of the University of Oxford now report a technique that uses porphyrin molecules to form well-defined, π-conjugated nanotubes (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201502735). The Oxford team first formed porphyrin dimers, the molecules lying flat next to one another, with each macrocycle featuring a zinc atom at its core. When the researchers added hexapyridyl template molecules, the dimers became the staves of a barrel. Six arms extended from the center of each template, and each arm anchored to one zinc atom. When two of these templates stacked themselves in the center of six porphryin staves, the hexapyridyl molecules pulled the dimers into a cylinder such that each porphyrin was π-conjugated with its neighbors. Although these tubes were only as tall as the dimers were long, the team believes it can synthesize longer structures that could be used to better understand the tubes’ electronic properties.