Finally, we apply both push and pull substituent strategies in tandem. This way, the gap between the occupied and unoccupied a2-type orbitals is reduced considerably relative to the b2 orbitals, and the resulting push-pull calicene becomes a true inverted-gap molecule with an inversion between the S1 and T1 states with E(S1-T1)=-9 meV; further results in Table . Across all four compounds, the natural transition orbitals of the states violating Hund's rule closely resemble the a2 orbitals shown in Figure (see Figure ).