Theoretical studies of cyclometalated phenylpyrazol Ir(III) complex using density functional theory

The ground state and low-lying excited electronic states in the Ir(III) complex fac-Ir(ppz)3 are studied using density functional theory where ppz=phenylprazol and fac=facial. We reported before that this complex was pure blue phosphorescent material with about 450 nm of electroluminescent peak. Herein, the electronic properties of the molecule are studied using the B3LYP functional and the structure analysis of the optimized geometries are processed in comparison with structures of ppz ligand and fac-Ir(ppy)3. Excited triplet and singlet states are examined using time-dependent density functional theory (TD-DFT). The calculated energies of the lowest triplet and singlet states are 3.14 and 3.56 eV. All of the low-lying transitions calculated in this study are categorized as metal-to-ligand charge-transfer (MLCT) transitions because the metal orbitals involved in the transitions have significant admixture of ligand π orbitals with amount of metal 5d character of three highest occupied molecular orbitals which are 50.2%, 47.8% and 47.8%, respectively. From the analysis of absorption spectrum of this complex, it was found that the singlets and triplets calculated in this study are distributed in the range of 270-350 and 340-410 nm in absorption spectrum.