Synthesis of Quinolino[4,3‐j]phenanthridines and their Photophysical Characterization

Abstract

Quinolino[4,3‐j]phenanthridines were synthesized from para‐terphenyl‐2,2′′‐diamines, which were obtained by cross‐coupling reactions. The diamines were converted into amides and ortho‐cyclized to quinolino[4,3‐j]phenanthridines using Morgan‐Walls reactions. Prolonged reaction times were required in these electrophilic substitution reactions to overcome the respective deactivated intermediates formed after the first ortho fusion. Optophysical properties were determined by UV/Vis and fluorescence spectroscopy and calculated by quantum chemical calculations. The compounds exhibit rather small HOMO/LUMO gaps and a remarkable bathochromic shift of luminescence upon protonation, what makes these compounds promising candidates for optoelectronic applications.