In this Letter, we report on the optical and magnetic properties of the negative ion of Aluminium tris(8-hydroxy-quinolate) (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 x 10(4) M-1 cm(-1). The negative ion is paramagnetic with an effective paramagnetic moment of 0.9 mu(B) per Alq(-) molecule. However, there is no detectable ESR signal even at 130 K. (C) 2002 Elsevier Science B.V. All rights reserved.