Negatively curved molecular nanocarbons containing multiple heptagons are enabled by the Scholl reactions of macrocyclic precursors

Embedding heptagons in polycyclic aromatic frameworks gives rise to negatively curved molecular nanocarbons, which not only are key fragments of long-sought-after carbon schwarzites but also bring new opportunities to explore unprecedented nanocarbons with interesting properties. This study demonstrates the Scholl reactions of macrocyclic precursors as a general strategy for synthesizing negatively curved molecular nanocarbons containing different numbers of heptagons. The π-backbones containing multiple heptagons are significantly curved and rigid, as revealed by density functional theory calculations and X-ray crystallography. Some of these negatively curved π-backbones are interlocked through both face-to-face and edge-to-face π-π interactions in the crystals. Such unusual π-π interactions have enabled a p-type organic semiconductor, although its hole mobility in the field effect transistors is limited by the amorphous nature of the vacuum-deposited films.