Double Aromaticity and Ring Currents in All‐Carbon Rings

Abstract

Double aromaticity of neutral, planar rings of carbon atoms is demonstrated through visualisation of the induced ring currents, mapped at the ipsocentric B3LYP/6-31G(d)//B3LYP/6-31G(d) level for species C(6) to C(30), with onset of delocalised current in the in-plane pi system at C(10)/C(11). Both in-plane and conventional out-of-plane pi systems have diatropic/paratropic current in accordance with the Hückel rule, with 4 m+2 occupation of the out-of-plane pi system taking precedence, as predicted by simple nesting of Frost-Musulin diagrams. The current-density maps show characteristic double-doughnut and double-track topographies for out-of-plane and in-plane ring currents, respectively, both governed by a common framework of angular momentum rules.