Synthesis And Characterization Of Electrophosphorescent Platinum(Ⅱ) Complexes

Platinum(Ⅱ) complexes, as phosphorescent materials, is attracting more and more attention and research, because of its excellent performance which is comparable with iridium complexes. In order to obtain high efficient red Pt(Ⅱ) complexes, this paper focuses on the following two points as design elements:(1) Choosing suitable ligand for the Pt(Ⅱ) complexes to get plane coordinate geometry, and increasing the structural rigidity of the ligands to improve the luminous efficiency. (2) Introducing large substituents to the ligands to suppress the interaction of Pt(Ⅱ) complexes, and reduce the generation of the excimer. Their structures and properties are confirmed by NMR, X-RD, UV-Visible absorbance spectroscopy and other methods. Specific work content is as follows:(1) Pt(Ⅱ) complexes were synthesized by 2,4-diphenyl-quinoline and its derivatives as aromatic ligand, and acetylacetone as auxiliary ligand. The steric hindrance was increased by changing the substituent of quinoline groups, especially the introduction of dendritic tert-butyl carbazole. Thus the molecular spacing was regulated reasonably, and intermolecular interaction was inhibited. Eventually, the quantum efficiency of Pt(Ⅱ) complexes were improved to 0.15.(2) Pt(Ⅱ) complexes were synthesized by 2-(9-butyl-carbazole) and its derivatives as aromatic ligand, and acetylacetone as auxiliary ligand. Photoluminescence spectra was shifted to red by introducing various electron-donating group to the 4-position of quinolone. The substituent’s ability, of regulating the emission, is as follows:alkyl amines>arylamines>halogen>benzene. Meanwhile, the intensity of conjugate was increased by the introduction of 9-butyl-carbazole, which ensure the entire molecule maintains planar configuration, so that the quantum efficiency of Pt(Ⅱ) complexes were improved to 0.17.(3) To explore the structure of Pt(Ⅱ) complexes’intermediate, Pt(Ⅱ) complexes were synthesized by 1,2-diphenyl-benzimidazole or 1,2-diphenyl-imidazole with K2PtCl4. Experiment results confirmed that there were two different intermediates, which were CΛN bidentate Pt(Ⅱ) chloride with mononuclear, instead of the dimmer structure as same as iridium intermediates. The formation of Pt-C bond is the essential difference between the two intermediates, it’s also the key to prepare the complexes.