Syntheses of ladder-type oligonaphthalene derivatives and their photophysical and electrochemical properties.

Ladder-type oligophenylene derivatives are important compounds for light-emitting devices. However, the closely related ladder-type oligonaphthalene derivatives have received little attention due to the lack of synthetic accessibility. We hereby report the syntheses of these novel conjugated systems by means of an intramolecular cationic cyclization protocol. Utilizing a one-pot-multiple-component reaction, the acyclic precursors to these ladder-type oligomers up to pentamer can be synthesized from small fragments in just two or three steps. Photophysical and electrochemical studies revealed that the electron delocalization in these compounds is considerably enhanced relative to that found in the regular unplanarized oligonaphthalene derivatives. However, such an effect is much weaker than that found in fully planar rylene derivatives.