Thermally activated delayed fluorescence in neutral and cationic stages of aza-nanographene decorated with 6.6.6 defects.

Heteroatom-doped polycyclic aromatic hydrocarbons (PAHs) show substantially modified electron distribution caused by the presence of either an electron-rich or electron-poor element that significantly influences the optical properties of final molecules. A novel synthetic approach with a PBr3 coupling agent, applied to precisely designed monomers and followed by intramolecular fusion, incorporates a tetraaza-dibenzo[g,p]chrysene decorated with two 6.6.6 defects into a nanographene-like system. The final derivative shows an efficient green fluorescence emission (λ PF = 530 nm) accompanied by phosphorescence (λ phos = 565 nm). The emission is tuned with simple protonation and shifted bathochromically to λ PF = 620 nm and λ phos = 640 nm. Both forms show thermally activated delayed fluorescence (TADF) with PLQYs of 93% for the green band and 50% for the red one, showing a unique ability to sustain the TADF behaviour after protonation.