Synthesis and characterization of tris-(8-hydroxyquinoline)aluminum

A comprehensive understanding of the characteristics of the organic electroluminescent (EL) material tris-(8-hydroxyquinoline)aluminum (Alq3) is meaningful for organic light-emitting devices (OLEDs). Thin films of Alq3 are among the most efficient EL molecular films known to date. Alq3 sample was synthesized and purified. The purity of Alq3 is up to 98.5%. The electronic structure and interaction in Alq3 molecule have been studied. The results of a joint experimental investigation based on a combination of X-ray diffraction (XRD) spectra, hydrogen nuclear magnetic resonance (HNMR) spectra, infrared absorption (IRA) spectra, mass spectra (MS), X-ray emission (XRE) spectra and fluorescence spectra of Alq3 have been obtained. The analysis on HNMR spectra of Alq3 demonstrated that the coordinate interaction between Al3+ and O ion is more intensive than that between Al3+ and N ion. The AlO bond is covalent bond in Alq3 molecule. Alq3 has two types of geometrical isomers, namely mer isomer and fac isomer. IRA spectra of Alq3 indicate a very intensive chelation of aromatic ring. From the MS spectra the ratio of charge to mass of Alq3 was obtained. Fluorescence data confirmed the existence of a fluorescent species formed between Al ion and 8-hydroxyquinolinol.