In organic chemistry, spherical aromaticity is formally used to describe an unusually stable nature of some spherical compounds such as fullerenes and polyhedral boranes.
In 2000, Andreas Hirsch and coworkers in Erlangen, Germany, formulated a rule to determine when a spherical compound would be aromatic.
[1] In 2011, Jordi Poater and Miquel Solà expanded Hirsch's rule to open-shell spherical compounds, which have unfilled outer shells but are still aromatic.
This corresponds to the outer shell being half-filled,[2] and is similar to Baird's rule.
For example buckminsterfullerene with one additional electron, (C601–) is aromatic, with S = 11/2 and a bond-length alternation of 0.2 pm.