Equilibrium geometries of PCT systems were taken from the digital repository of the original paper by Stawski et al., and then reoptimized at the CAM-B3LYP/def2TZVPP level of the theory. The HOMA values were calculated using the consistently calculated parameters provided by Andrzejak et al. The BDF π (r) function, defined as a difference between the one-electron density of delocalized (EDDB π ) and localized π-bonds (EDLB π ), was calculated using the electron density partitioning scheme introduced by Szczepanik. . To visualize and dissect ring-current densities (in accordance with the Fowler-Steiner selection rules) and the calculated chemical shifts we used the anisotropy of the induced current density (AICD) method. All the calculations were performed using the Gaussian G16 C.01 software; ; input files are available upon request from D.W.S.). annulene dianion with the corresponding relative energies found by scanning the potential energy surface at the CAM-B3LYP/def2-TZVPP theory level. The partial atomic π-charges were dissected within the framework of the electron density of delocalized bonds (EDDB) method. The BDF π (r) function was visualized at the isovalue surface τ iso = 0.005; (b) The Kekulé resonance structures for PCT 2-