We are now in the position to understand the correlation between the two gaps in Fig. . The lowest excited singlet and triplet states in our closed shell systems are dominated by configurations where one electron is transferred from the HOMO to the LUMO. The exchange energy, that in most systems is responsible for triplet states lying lower than singlets, is negligible in these alternating rings (see ESI, Section S6) and the typically tiny effect of dynamical spin polarization may enter into play inverting the ST gap. Specifically, the singlet excited state is stabilized by the interaction with the doubly excited state, where both electrons reside on the LUMO. This stabilization is not possible for the corresponding triplet states. Fig. , showing an impressive correlation between the size of the HOMO-LUMO gap and the ST gap, neatly confirms this view: the singlet stabilization is larger the smaller is the HOMO-LUMO gap and the only ring with positive ST gap is triazine (CN) 3 , with the largest HOMO-LUMO gap. The picture is further confirmed by our results for 2T-N and 2T-7N, whose ST gap, ∼ -0.2 and 0 eV, respectively, can be related to a much smaller HOMO-LUMO gap (∼ 6.9 eV) for 2T-N than for 2T-7N (∼ 9.8 eV). In the end, despite the adopted idealized geometries, the rings in Fig. show how a molecular edge with alternating electron-withdrawing and electron-donor groups is a key ingredient for the ST inversion.