On the stability and optical spectra of Alq negative ion in solution and thin films

In this Letter, we report on the optical and magnetic properties of the negative ion of Aluminium tris(8-hydroxyquinolate) (Alq) in solution and thin film. The negative ion is stable in solution and as a thin film only in vacuum. The negative ion is non-luminescent and unstable in ambient air/oxygen. The absorption spectrum of the negative ion consists of an intense band at 336 nm with a molar extinction coefficient of 1.42×104 M−1 cm−1. The negative ion is paramagnetic with an effective paramagnetic moment of 0.9 μB per Alq− molecule. However, there is no detectable ESR signal even at 130 K.