Development of emissive aminopentaazaphenalene derivatives employing a design strategy for obtaining luminescent conjugated molecules by modulating the symmetry of molecular orbitals with substituent effects.

This communication describes the transformation of a non-emissive heterocycle into a luminophore via modulation of molecular orbitals by employing a dialkylamine-substituted pentaazaphenalene (A5AP) skeleton. It was presumed that the introduction of the amine group changed the symmetry-forbidden HOMO-LUMO (H-L) transition to an allowed one. According to optical measurements and theoretical calculations, the H-L transition was turned into the symmetry-allowed one because of the lone pair on the nitrogen atom in the dialkylamine substituent. Finally, the A5AP derivatives presented significant emission from the H-L transition.