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.

FIrpic: archetypal blue phosphorescent emitter for electroluminescence

“…Koseki et al proposed an intensive discussion on FIrpiclike molecules using density-and wavefunction-based methods and including the effect of spin-orbit coupling, 64 rationalising the different stability and properties of [Ir(diFppy) 2 ( pic)] isomers.…”

Unraveling the Degradation Mechanism of FIrpic-Based Blue OLEDs: I. A Theoretical Investigation

“…22 The isomerization barriers of a small model Ir complex where calculated in Ref. 23 However, the isomerization of larger, emissive Ir-complexes, will require to overcome quite large energy barriers, because of the steric hindrance of the ligands. 24 Therefore, a complete understanding of the degradation pathways, based on atomistic modeling, is still missing to date.…”

Ab Initio Many-Body Perturbation Theory Calculations of the Electronic and Optical Properties of Cyclometalated Ir(III) Complexes

“…Examples are the application of the DFT+Hubbard U method, 14 the explicit inclusion of SOC [15][16][17][18] and the use of multireference approaches. 19,20 Many Body Perturbation Theory (MBPT), particularly the GW and Bethe Salpeter Equation (BSE) 21 methods provide an alternative theoretical framework to access both ground and excited state properties of condensed matter [22][23][24][25][26][27] and molecular systems. [28][29][30][31][32] Most importantly, the BSE method appears to describe on an equal foot local and chargetransfer excitations, [33][34][35] without fine tuning of the Hartee-Fock fraction or Coulomb range separation.…”

“…Figure 1: Set of molecules used to analyze the basis set convergence of G 0 W 0 and BSE calculations.For the acac molecule we choose the enolic form, which is more stable than the keto form in gas phase. The Ir-small complex is taken from Ref 19. …”