Benzene Chain Made Stable Enough For First Electronics Test

A new synthesis of hexacene, a linearly fused chain of six benzene rings, for the first time leads to crystals stable enough to study in an electronic device (Nat. Chem., DOI: 10.1038/nchem.1381). The work could facilitate long-awaited evaluations of the electronics potential of hexacene and its longer chain relatives, which some researchers have likened to one-dimensional strips of the versatile material graphene. Prior syntheses of hexacene were tedious and low-yielding or did not produce hexacene crystals, which possess the molecular packing needed for optimal electronic properties. A team led by Motonori Watanabe and Tahsin J. Chow of Taiwan’s Academia Sinica made hexacene by heating a carbonyl precursor in a nitrogen atmosphere. They obtained blue-green hexacene powder, which they report is stable for more than a month in the dark. The team created hexacene crystals through vapor deposition and determined that the molecules pack in a herringbone pattern, like hexacene’s shorter cousin pentacene. Mounted in a transistor, hexacene crystals perform better on a key predictor of efficiency, hole mobility, than does pentacene. Higher acenes are worth pursuing for their electronics potential even though they’ve been branded unstable thus far, Chow says.