Cyclo[6]carbon is an allotrope of carbon with molecular formula . The molecule is a ring of six carbon atoms, connected by alternating double bonds. It is, therefore, a member of the cyclo[''n'']carbon family.
There have been a few attempts to synthesize cyclo[6]carbon, e.g. by pyrolysis of mellitic anhydride,[1] but without success until 2023, when it was successfully synthesized by atom manipulation of hexachlorobenzene.
Calculations suggest that the alternative cyclic cumulene structure, called cyclohexahexaene, is the potential energy minimum of the cyclo[6]carbon framework.[2]