Spin–orbit coupling analyses of phosphorescent processes in Ir(Zppy)₃ (Z = NH₂, NO₂ and CN)

Abstract

Appropriate combinations of substituents provide brighter blue-color emission in OLEDs. The present MCSCF + SOCI + SOC calculations suggest that the best material for blue-color emission is fac-Ir(5-NO2ppy)3 or fac-Ir(5-NO2-4,6-dfppy)3, or practically fac-Ir(5-CN-3,4,6-tfppy)3.

Early-Time Excited-State Relaxation Dynamics of Iridium Compounds: Distinct Roles of Electron and Hole Transfer

“…Bokarev et al explored the electronic excitation spectrum of Ir­(ppy) 2 bpy with a series of electronic structure methods . Wu and co-workers have elucidated the unusual photophysical properties of a series of cyclometalated Ir complexes with the DFT and TD-DFT methods. − Escudero and his co-workers have explored photodeactivation pathways, quantitative prediction of photoluminescence quantum yield, and photostability of several Ir complexes using the DFT and TD-DFT methods. − Koseki et al have investigated the geometric effects on the phosphorescence of Ir­(ppy) 3 and its derivatives. − Younker et al. explored the photophysical properties of nine Ir complexes using the spin-coupled TD-DFT method .…”

Theoretical Design of Blue-Color Phosphorescent Complexes for Organic Light-Emitting Diodes: Emission Intensities and Nonradiative Transition Rate Constants in Ir(ppy)2(acac) Derivatives

“…The next modification is the additional introduction of a CN group to the 5′-th site of ppy ligands in 3 (df). This complex, referred to as 3 (456), provides a larger blue shift of the spectral peak, ,, but the relative intensity is still weak compared with that for 2 (df). Then, based on the stronger peak for 3 (6f), the introduction of a CN group to the 5′-th site of ppy ligands in 3 (6f) was considered to be useful for obtaining a stronger intensity.…”

“…Some of the DFT­(B3LYP)/SBKJC+p optimized geometries for the S 0 and T 1 states in the present complexes have been reported in our previous papers. , In the present investigation, the geometries for the S 1 states were also optimized by using the TDDFT­(B3LYP)/SBKJC+p method. − In order to calculate the geometrical displacement vector Δ⃗ caused by electronic transitions, the centers-of-mass of the geometries optimized for the initial and final states of electronic transition were moved to the coordinate origin and their geometries were aligned under the condition that no angular momentum is generated by electronic transition. By using these coordinates, the geometrical displacement vector Δ⃗ was calculated and expanded by the normal modes { Q⃗ j }­( j = 1, 2, ..., 3 N – 6) of the final state: Δ⃗ = ∑ j =1 3 N –6 Δ j Q⃗ j .…”

“…For Ir complexes, effective substituents were successfully selected for specific sites of ligands in order to obtain a pure blue emission. 30,31 Those investigations were useful for obtaining information on spectral peak wavelengths for phosphorescence. However, the reasons why and how spectral broadening occurs were not clarified in those investigations because the vibrational degrees of freedom were not taken into account.…”

“…Our research group has already reported theoretical results for emission spectra in Ir and Pt complexes. − In those investigations performed from a spectroscopic point of view, the spin–orbit coupling matrix elements (SOCs) were calculated by using multireference configuration interaction (MRCI) wave functions constructed by means of multiconfiguration self-consistent field (MCSCF) orbitals, and the peak wavelengths of phosphorescence were estimated on the basis of the electronic transitions among the spin-mixed states. For Ir complexes, effective substituents were successfully selected for specific sites of ligands in order to obtain a pure blue emission. , Those investigations were useful for obtaining information on spectral peak wavelengths for phosphorescence. However, the reasons why and how spectral broadening occurs were not clarified in those investigations because the vibrational degrees of freedom were not taken into account.…”