Theoretical Studies of Mono-Cyclometalated Ir(III) Complexes with Phenylpyrazole Based Ligands and Phosphines

Abstract

New blue emitting mixed ligand iridium(III) complexes comprising one cyclometalating, two phosphines trans to each other such as Ir(dppzc)(PPhMe2)(2)(H)(L) (L = Cl, CN) [dppzc = 1,3-Diphenyl-1H-pyrazole-4-carboxaldehyde] were studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. We investigate the electron-withdrawing capabilities of ancillary ligands using the DFT and TD-DFT calculations on the ground and excited states of the complexes. From these results, we discussed how the ancillary ligand influences the emission peak as well as the metal to ligand charge transfer (MLCT) transition efficiency. The calculated energies of triplets are 3.09 and 3.16 eV, respectively, which are all higher than that of Ir(dfppy)(2)(acac) and FIrpic known as blue phosphorescence materials with 2.69 and 2.73 eV.