Synthesis, crystallography, photoluminescence and electroluminescence of three polymorphs of dibenzoylmethane gallium complex

Three polymorphs of tris(dibenzoylmethane) gallium were characterized by optical microscopy, absorption, photoluminescence (PL) and used for electroluminescent devices (EL). PL spectrum of the thin film is composed of both γ-type yellow emission and β-type blue emission, but only γ-type yellow EL emission was observed, indicating the polymorphic counterpart β-type with weaker π–π interactions was defeated in competition for EL generation. A comparison of the three polymorphic crystal structures reveals that a zigzag channel from intermolecular π–π interaction at a distance of 3.6–3.7 Å to intramolecular bond–bond conjugation may dominate the charge transport and be responsible for the yellow EL emission.