Room temperature phosphorescence of a palladium(II) complex sensitized by unsymmetric perylene bisimide

A novel palladium(II) complex (Phpy)Pd(Pery-q) based on cyclopalladated 2-phenylpyridine coordinated to 5-unsymmetric perylene bisimide-8-hydroxyquinoline was synthesized and characterized by 1H NMR, MS-ESI, elemental analysis and IR spectra. The complex displayed room temperature phosphorescence (RTP) in CH2Cl2 solution with a lifetime of ca. 14.2 μs, arising from the sensitized intraligand charge transfer (3ILCT) of the appended 8-hydroxyquinoline and was dependent on the ligand orbital perturbed by the metal. Its long-lived emission is affected by aggregation in poly(N-vinylcarbazole) (PVK) film and solid state. The incorporation of an unsymmetric perylene bisimide unit into the 5-substituted-8-hydroxyquinoline ligand prevented thermally activated processes involving non-emissive metal-centered (MC) levels and sensitized (Phpy)Pd in terms of access to the 3ILCT state. The singlet state of perylene bisimide assisted by heavy metal results in the existence of intersystem crossing to 3ILCT of the 8-hydroxyquinoline ligand, thus radiatively decaying to the ground state of (Phpy)Pd(Pery-q).