Corannulene

Corannulene (C20H10) is a bowl-shaped polycyclic aromatic hydrocarbon (PAH). It is the smallest curved PAH and is commonly described as a fragment of the Buckminsterfullerene C60, reflecting its role as a precursor in fullerene chemistry. Its structure can be viewed as a central pentagonal ring fused to five surrounding rings, giving a fivefold-symmetric bowl that slopes upward away from the central plane.

Because of its curvature, corannulene is nonplanar and has C5v symmetry. The curved geometry influences its electronic structure, aromatic stabilization, and frontier molecular orbitals, making it a useful model system for studying curvature effects in PAHs. The bowl shape also leads to a relatively low barrier for bowl-to-inversion, with estimates around 11–12 kcal/mol, allowing interconversion at room temperature and imparting fluxional behavior on laboratory timescales.

Corannulene serves as a key building block in studies of curved aromatic systems and as a starting point for the synthesis of larger curved PAHs and end-cap fragments related to fullerenes. Its derivatives are explored in host–guest chemistry and materials science, where the curved surface can influence binding interactions, metal coordination, and the assembly of supramolecular structures.