A molecular bowl sumanene

Nonplanar polyaromatic carbon molecules including fullerenes and carbon nanotubes have been attracting great interest due to their potential as materials, catalysts, etc. In this context, bowl-shaped polyaromatic hydrocarbons (pi bowls) are considered to be key materials in the science of nonplanar pi-conjugated carbon systems. Among pi bowls, we focused on a molecular bowl sumanene (C21H12)'' featuring a C-3v symmetric structural motif present in fullerenes or carbon nanotube molecules. In this article, we present the research on sumanenes to date, including their synthesis, structural characterization, derivatization, complexation, and their potential uses as electrical materials. The characteristic structural feature of a sumanene depends on three sp(3) hybridized carbon atoms at the benzylic positions. Facile functionalization via selective formation of benzylic anions gives stereoselective substituted compounds, the pi-extended derivatives, and the deeper pi bowls. Furthermore, the dynamically flexible aspect based on bowl-to-bowl inversion is also described. The crystal with a columnar bowl-in-bowl stacking exhibits a high electron transport ability with anisotropy. Complexation with a cyclopentadienyl iron cation results in the first selective formation of the concave-bound complex as a pi-bowl complex.