The molecule is a ring of eighteen carbon atoms, connected by alternating triple and single bonds; thus, it is a polyyne and a cyclocarbon.

Cyclo[18]carbon is the smallest cyclo[n]carbon predicted to be relatively stable, with a computed strain energy of 72 kilocalories per mole.

[1][2] A collaboration of teams at IBM and the University of Oxford team claimed to synthesize it in solid state in 2019[3] by electrochemical decarbonylation of several sites of a cyclobutanone structure:[4] Later, researchers from Spain have used computational techniques to probe the structural and electronic properties of the molecule, and have discovered it to be an electron acceptor.

[5] According to these IBM researchers, the electronic structure of their product consists of alternating triple bonds and single bonds, rather than a cumulene-type structure of consecutive double bonds.

This supposedly makes this molecule a semiconductor.