Supertwistacene: A Helical Graphene Nanoribbon

Abstract

This work describes a synthetic chiral graphene nanoribbon, named supertwistacene <b>1</b>. It has four superbenzene (HBC) units linearly fused in a helical manner. The structure of <b>1</b>, 4.3 nm in length, with an end-to-end twist of 117°, was confirmed by single-crystal X-ray diffraction. In contrast to various twistacene compounds and their analogues, <b>1</b> has a very stable configuration. It resists thermal isomerization even when being heated at 200 °C for 16 h. Enantiopure <b>1</b> obtained by chiral HPLC shows distinct CD signals in a broad spectral range until 600 nm. In addition, two smaller congeners of <b>1</b>, the trimer <b>2</b> and the dimer <b>3</b>, were also prepared and systematically investigated. Combining theoretical and experimental studies on <b>1</b>-<b>3</b> presents a big picture on their (chir)optical and electronic characteristics.