The structure of the blue luminescent delta-phase of tris(8-hydroxyquinoline)aluminium(III) (Alq(3))

The existence of the facial isomer in the delta-phase of Alq(3) is proven by X-ray structural analysis, revealing that both the different molecular structure and the weaker overlap of the pi-orbitals of hydroxyquinoline ligands belonging to neighboring Alq(3) molecules as compared to other phases (alpha,beta) are likely to be the origin of the significantly different optical properties of delta-Alq(3).