Patrick W. Fowler and Henry S. Rzepa
Phys. Chem. Chem. Phys., 2006,8, 1775-1777
DOI:
10.1039/B601655C,
Communication
A simple proof is given that the Hückel aromaticity rules generalise to cycles with an arbitrary number of half-twists, T; addition/removal of half-twists two at a time preserves all eigenvalues and degeneracies, so that closed-shell aromatic systems occur at π-electron counts 4N + 2, and antiaromatic at 4N for even T, and vice versa for odd T.
