Blue emitting phosphorescent platinum(II) complexes with cyclometalated 4,5-dimethylimidazolylidene ligands

• Published in: Journal of organometallic chemistry 2023-11, Vol.1000, p.122785, Article 122785
• Main Authors: Stipurin, Sergej, Strassner, Thomas
• Format: Article
• Language: English
• Subjects: Cyclometalated; NHC; OLED; Phosphorescence; Platinum
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2023.122785

•Phosphorescent platinum(II) complexes with cyclometalated imidazolylidenes.•β-Diketonates and bis(pyrazolyl)borate ligands as auxiliary ligands.•Photoluminescence quantum yields of up to 92% were determined.•The lowest emission maximum was found to be at 448 nm.•Quantum chemical calculations gave insight into the emissive states. Three different imidazolylidene ligand precursors with methyl groups in 4- and 5-position were synthesized and selected to build a series of nine cyclometalated platinum(II) complexes. Next to the carbene ligands, β-diketonate and bis(pyrazolyl)borate motifs were used as auxiliary ligands. All complexes were fully characterized by standard techniques, five of them also by solid-state structure determinations. All of the synthesized platinum complexes show phosphorescence at room temperature in a PMMA matrix with quantum yields of up to 92% in the green-blue to pure blue area (CIE color coordinates of 0.154; 0.119) of the visible spectrum. Quantum chemical calculations (PBE0/6-311G*) as well as electrochemical experiments provided additional insight into the properties of these compounds. The synthesis and characterization of nine C^C* platinum(II) complexes with 4,5-dimethylimidazolylidene ligands including five solid-state structures is presented. A phosphorescent emission in the deep blue area of the spectrum with quantum yields of up to 92% is observed. Luminescence and electrochemical properties are rationalized by density functional theory calculations. [Display omitted]