We further test these findings on a few well-studied azaphenalenes, namely heptazine, cyclazine and pentaazaphenalene (Figure ). While the number of available substituent positions is more limited in these molecules, particularly in heptazine, the derivatives we are able to explore reveal the enhancement to the inverted gap can be almost 100 meV compared to the parent compounds. We thus show a range of molecules with very negative gaps in Figure . Heptazine-2,5,8-triamine (melem) is the most negative singlet-triplet gap we have on record at the EOM-CCSD level with E(S 1 -T 1 )=-265 meV. Melem has been studied in OLED devices and has achieved very high photoluminescence quantum yields, which have yet to be rationalized. If the inverted singlet-triplet gap of melem is retained in devices, it may contribute to its high photoluminescence quantum yield. However, we note that there is no oscillator strength from S 1 in melem due to its high symmetry (Table ).