The reverse strategy also generally applies to azaphenalenes, and causes the singlet-triplet gaps to become less negative. We find several substituted cyclazines (Figure ) and pentaazaphenalenes (Figure , Table ) where the singlet-triplet gap becomes positive when we substitute with donors in HOMO coefficient positions or with acceptors in LUMO coefficient positions. Again, it is essential to consider where to substitute with donors and acceptors as the singlet-triplet inversion is highly sensitive to this choice. As others have discussed, it is likely that many previously studied substituted azaphenalene-based emitters may not possess inverted gaps, but are in fact conventional TADF emitters with small positive gaps. However, with the possibility of tuning the singlet-triplet gap to be more negative than the parent compound, our result guides the way to molecules with negative gaps which are robust enough that they are expected to persist (and be measurable) in a device environment.