Comparative study of electronic structure and optical properties of a series of Pt(II) complexes containing different electron-donating and -withdrawing groups: A DFT study

We report a quantum-chemistry study of electronic structures and spectral properties of a series of Pt(II) complexes containing different substituents (-CH₃ (1), -OCH₃ (2), -NO₂ (3), -CF₃ (4), and -COOH (5)). 1 and 2 have been previously synthesized in experiment, while 3-5 are artificial complexes that we suggest can be used to investigate the electron-withdrawing effect on charge injection, transport, absorption, and phosphorescence properties. The results reveal that the stronger electron-donating and -withdrawing groups show stronger absorption intensity, while the phosphorescence efficiency is generally higher for complexes containing electron-donating substituents. 1 and 2 are easier for hole injection, while 3-5 are easier for electron injection. The enhanced electron injection abilities of 3-5 will confine more excitons in the light-emitting layer (EML) and may not result in lower electroluminescence (EL) efficiency than 1 and 2. These results suggest that the three artificial complexes may be new emitters in organic light-emitting diodes (OLEDs).