Synthesis of a zigzag carbon nanobelt.

The structure-selective precise synthesis of carbon nanotubes (CNTs) has been long sought in materials science. The aromatic molecules corresponding to segment structures of CNTs, that is, carbon nanobelts (CNBs), are of interest as templates for CNT growth. Among the three types of CNB (armchair, chiral and zigzag CNBs), zigzag CNBs have been considered the most difficult type to synthesize. Here we report the synthesis, isolation and structural characterization of a zigzag CNB. The synthesis involves an iterative Diels-Alder reaction sequence followed by reductive aromatization of oxygen-bridged moieties. As predicted by theoretical calculations, this CNB was isolated as a stable compound. The structure of the zigzag CNB was fully characterized by X-ray crystallography and its wide energy gap with blue fluorescence properties was revealed by photophysical measurements. With synthetic strategies towards all three types of CNB in hand, the road to the precise synthesis of CNTs can now proceed to the next stage.