Cyclic conjugation in dianions: effect of cycles on the thermodynamic stability of polycyclic conjugated dianions

Within the theory of cyclic conjugation it is possible to determine the effect of each individual cycle on the thermodynamic stability (enthalpy) of a polycyclic conjugated molecule. Numerous calculations of this effect, reported so far, pertain to uncharged conjugated hydrocarbons in which the bonding MOs are doubly occupied and the antibonding MOs are empty. We now communicate, for the first time, energy effects of cycles in conjugated dianions, compare them with available experimental data and establish a few general regularities. (C) 1998 Elsevier Science B.V.