Four kinds of five-coordinate mononuclear aluminum complexes based on salen ligands, salen $(^tBu)AlX(4, 5, 6, and 7)$, were synthesized to develop blue luminescent and hole-blocking materials for phosphorescence-based organic EL devices. The synthesized complex 4 exhibited photoluminescence (PL) maximum at 470 nm in solid. The tuning of the solubility and fluorescent property of the aluminum complexes were attempted by introducing $^tBu$ groups to phenyl portion of salen ligand and modifying conjugation length and electron density of the ancillary ligand X, respectively. In PL spectra, the emission maxima of 5, 6, and 7 were gradually blue-shifted to about 10 nm ~ 20 nm compared with that of 4.
Three kinds of novel dinuclear aluminum complexes containing salen ligands, ${Salen(^tBu)AlOPh}_2C(CH_3)_2(8, 9, and 10)$, were synthesized. The synthesized dinuclear complexes emit deep blue light and have higher thermal stability than that of mononuclear complexes. It is expected that these complexes can be good candidates as blue emitting materials and hole-blocking materials.
