Synthesis, characterization and DFT investigation of aluminum complexes of aryl- substituted-8-hydroxyquinoline

New aryl substituted 8-hydroxyquinoline derivatives have been synthesized. The compounds were characterized by 1H, 13C-NMR spectroscopy and mass spectrometry. The aluminum complexes of these derivatives show strong green emission in the range 530–535 nm with high quantum yield compared to the parent tris (8-hydroxyquinolinato)aluminum(III) complex. The structure of the aryl-substituted 8-hydroxyquinoline aluminum complexes in the ground state have been optimized at the B3LYP/6-31G* level of theory. The parent 8-hydroxyquinoline has also been examined using this method with the same basis set. A clear correlation between the shortening of the Al-N bond and red shift in the fluorescence emission band was observed. We have also found that substitution at the 5 and 7 position of the 8-hydroxyquinoline ligand cause simultaneous energy lowering of both highest occupied molecular orbital and the lowest unoccupied molecular orbital with the 5, 7-aryl substituted derivatives exhibiting the greatest effect.

► Synthesis of new 5, 7-aryl 8-hydroquinoline derivatives.
► The new Al complexes dyes exhibit higher quantum yields than the parent compound.
► Energy gaps were calculated by DFT B3LYP methods.
► DFT B3LYP methods show that 5- and 7-substitution stabilizes both HOMO and LUMO.