Spin–Orbit Coupling Analyses of the Geometrical Effects on Phosphorescence in Ir(ppy)3 and Its Derivatives

Abstract

Theoretical investigations were performed for typical iridium complexes, Ir(C∧N)3, Ir(C∧N)2(C’∧N’), Ir(C∧N)2(N ∧O) and Ir(C∧N)2(O∧O), at the MCSCF+SOCI+SOC//B3LYP/SBKJC+p level of theory. For Ir(dfppy)2(pic) (so-called FIrpic) and its related complexes, the introduction of a fluoride into ppy ligands provides a blue shift of about 20 nm for emission spectra, while the replacement of a pic ligand by an acac ligand does not seriously affect the emission spectra of these complexes. It is proposed that the homo-cis,hetero-O-cis isomer (HC-5f, see text) of FIrpic should be used as a brighter blue-color material instead of the homo-N-trans isomer (HNT-5f). The energy difference between these isomers is less than 1 kcal/mol, and the energy barrier of the isomerization between these isomers is calculated to be larger than 30 kcal/mol. It was also found that the use of two ancillary ligands, such as Ir(C∧N)(N ∧O)2 and Ir(C∧N)(O∧O)2, is unfortunately inappropriate to energetically lift the π* orbital.