Propeller-Shaped Aluminum Complexes with an Azaperylene Core in the Ligands

Tris(8-hydroxyquinoline) aluminum(III) (Alq(3)) and its derivatives, characterized by a propeller-shaped three-dimensionally pi-conjugated structure, have been intensively studied in the few past decades on account of their potential utility in optoelectronic applications. Reported herein are the synthesis and properties of pi-extended Alq(3) complexes that contain an azaperylene core in each ligand. Intramolecular palladium-catalyzed direct C-H arylations or base-promoted arylations were employed to prepare these large Alq(3) analogues. A single-crystal X-ray diffraction analysis of one of the obtained Al complexes revealed a unique three-dimensional packing structure within the crystal, i.e., a honeycomb packing along the ab-plane and columnar pi-stacks along the c-axis. An Alq(3) analogue with azaperylene-dicarboximide ligands exhibited deep blue color in solution with an intense absorption band that extended to 780 nm (lambda(max) = 634 nm; epsilon = 58,000 M-1 cm(-1)).