Dibenzopyrrolo[1,2‑a][1,8]naphthyridines: Synthesis and Structural Modification of Fluorescent L‑Shaped Heteroarenes

The L-shaped, π-extended pentacycle di­benzo­pyrrolo­[1,2-a]­[1,8]­naphthyridine and its derivatives were synthesized using two methods: fully intramolecular [2 + 2 + 2] cycloaddition and oxidative aromatization using substituted carbodiimide and modification of an electron-rich indole ring of an L-shaped skeleton via electrophilic reaction and cross-coupling. These L-shaped compounds emitted fluorescence in high quantum yield. The position of substituents affected the fluorescence color through two different mechanisms, π-conjugation and skeletal distortion, which caused the substituted L-shaped compounds to emit fluorescence in a variety of colors and to exhibit solvato-fluorochromism.