Interestingly, we also find that the reverse strategy can effectively suppress the singlet-triplet gap inversion. This is done by applying donors at HOMO coefficient positions and acceptors at LUMO coeffiecients. The 5,10-diol and 5,10-diamine substituted isopyrenes thereby attain positive singlet triplet-gaps of E(S 1 -T 1 )=+189 meV and E(S 1 -T 1 )=+149 meV, respectively. Although these derivatives have double-bond delocalized structures like the parent isopyrene, the substituents remove the Hund's rule violation. This is a testament to the effectiveness of the Heilbronner strategy in manipulating singlet-triplet gaps, and underlines that it constitutes a rational design strategy.