Electronic Structures of Platinum(II) Complexes with 2-Arylpyridine and 1,3-Diketonate Ligands: A Relativistic Density Functional Study on Photoexcitation and Phosphorescent Properties

The electronic structures of heteroleptic cyclometalated platinum(II) complexes a–f with 2-arylpyridine derivatives and 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dione which are candidate materials for phosphorescent organic electroluminescent diodes (OLEDs) were theoretically investigated using relativistic density functional theory (DFT) calculations including spin–orbit effects. The electronic excitation bands and phosphorescent emission wavelengths of the complexes were theoretically calculated and compared with the corresponding experimental results. It was theoretically confirmed that the color of the phosphorescent emission is controlled by the π–π* electronic excited state localized on each 2-arylpyridine derivative ligand. Our calculations also gave good predictions for spectral red shifts originating from excimer formations for a–f.