Five polycyclic aromatic hydrocarbons of the C 26 series having similar bonding structure yield dianions upon reduction with lithium metal. Anisotropy changes, revealed from an advanced charge distribution analysis performed on these dianions, show a correlation to the bonding structure of the dianions. Electron counting and orbital considerations rationalize this correlation in terms of aromatic/anti-aromatic behaviour that is mixed into the character of the aromatic PAH upon reduction.

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... ions made regarding relative stability based on this correlation were successfully tested against calculation and experiment. The anisotropy change is suggested as a valid index for the reduction-induced change in the aromatic character of PAHs, which is applicable for both aromatic and anti-aromatic changes.