Vibrational analysis of different crystalline phases of the organic electroluminescent material aluminium tris(quinoline-8-olate) (Alq3)

Abstract

The isomerism of the Alq₃ molecule was investigated by applying infrared (IR) spectroscopy to two different crystalline phases of aluminium tris(quinoline-8-olate) (α-Alq₃ and δ-Alq₃). Significant differences between the two phases were found in the IR spectra, which can be explained in terms of the different symmetries of the facial and meridional isomer. Additionally, intermolecular interactions of the Alq₃-molecules due to crystallinity were taken into account. The results suggest that α-Alq₃ consists of the meridional isomer, while the recently discovered blue luminescent δ-phase is composed of the facial isomer of the Alq₃ molecule.