Negatively Curved Nanographenes

Negatively curved nanographenes are saddle-shaped polycyclic arenes, containing seven- or eight-membered rings, or even larger rings. These structures are fragments of carbon schwarzites, toroidal carbon nanotubes, and other intriguing negatively curved nanocarbons, offering valuable insights into their structure and serve as potential building blocks for their synthesis. This chapter provides an overview of recent progress in the chemistry of negatively curved nanographenes, focusing on synthetic strategies and their unique properties. A key method for their synthesis is the Scholl reaction, an intramolecular oxidative cyclodehydrogenation that enables the formation of multiple carbon–carbon bonds in a single step. Negatively curved nanographenes exhibit conformational flexibility and self-assembly behaviors that are not available to typical planar π-systems, presenting new opportunities for organic electronic materials. In addition to negatively curved nanographenes, this chapter also describes the synthesis of carbon nanobelts and nanorings with negative curvature, as well as bottom-up approaches toward carbon schwarzites.