B3LYP, RHF and PM5 theoretical studies on phosphorescent cyclometalated Ir(III) complexes

PM5, RHF/3-21G and B3LYP/cc-pVDZ ground sate geometries are reported for two Ir(III) complexes with cyclometalated and β-diketonate ligands. Subsequently, electronic spectra were predicted using time-dependent density functional (TD-DFT) at PM5 and B3LYP/cc-pVDZ geometries. Despite the fact that PM5 predicts reasonable interatomic distances in the coordination polyhedron, this method presents large deviations in the N1-C2-C3-C4 dihedral angle, in cyclometalated ligands, when compared to X-ray geometries. B3LYP and RHF methods thus seem to be more suitable to predict ground state geometries for both complexes, whereas TD-DFT calculations, using B3LYP/cc-pVDZ geometries, yield excited states in good agreement to experimental ones.