A study on the aromaticity of [n]phenacenes and [n]helicenes (n = 3–9)

We studied the global and local aromaticity of [n]phenacenes and [n]helicenes for n = 3–9 using the topological resonance energy and the magnetic resonance energy methods. The local aromaticity of the individual rings was studied using the bond resonance energy, the circuit resonance energy, and the ring current methods. Our results were compared with the results obtained by others who used the para-delocalization index, the harmonic oscillator model of aromaticity, and the nucleus-independent chemical shift indices. We found that sextet rings in the Clar structure are the main source of aromatic stabilization.