Upon substituting the 3-membered ring with a strongly electron-withdrawing pull moiety (-CN, magenta in Figure ), the a2 LUMO energy is lowered by more than 3 eV, while smaller stabilizing effects are observed on the other orbitals. The Hund´s rule inversion is subsequently preserved but is lowered from S3 to S2 with E(S2-T4)=-28 meV, Figure .