Towards deep‐blue phosphorescence: molecular design and property prediction of iridium complexes with pyridinylphosphinate ancillary ligand

Abstract

A series of iridium complexes (1-5), which consist of two 2-(2,4difluorophenyl)pyridine (dfppy)-based primary ligands and one pyridinylphosphinate ancillary ligand, have been investigated theoretically for screening highly efficient deep-blue light-emitting materials. Compared with the reported dfppy-based emitter 1, the designed iridium complexes 3-5 with the introduction of a stronger electron-withdrawing (-CN, -CF 3 , or o-carborane) group and a bulky electron-donating (tert-butyl) group in dfppy ligands can be achieved to display the emission peaks at 443, 442, and 447 nm, respectively. The electronic structures, absorption and emission properties, radiative and nonradiative processes of their excited states, and charge injection and transport properties of the iridium complexes are analyzed in detail. The calculated results show that designed iridium complexes have comparable radiative and nonradiative rate constants with 1, and are expected to have similar quantum efficiency with 1. Meanwhile, these designed complexes keep the advantages of the charge transport properties of 1, indicating that they are potential iridium complexes for efficient deep-blue phosphorescence. This work provides more in-depth understanding the structure-property relationship of dfppy-based iridium complexes, and shed lights on molecular design for deep-blue phosphorescent metal complexes.

Saturated-blue-emitting [3+2+1] coordinated iridium(iii) complexes for vacuum-deposited organic light-emitting devices

“…Meanwhile, extensive effort has been made towards developing phosphorescent cyclometalated iridium( iii ), platinum( ii ), palladium( ii ) and gold( iii ) complexes with saturated blue emission, as well as thermally activated delayed fluorescence (TADF) materials. 3,6–9 In particular, iridium( iii ) complexes bearing cyclometallated ligands such as 2-phenylpyridine-, 3,10–22 phenyltriazoly- 23 and N-heterocyclic carbene (NHC) 24–34 are commonly used materials for achieving deep-blue emission, as the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of these ligands could be easily manipulated and thus widen the energy gap. 35,36 For instance, our group has recently reported a new series of [3+2+1] coordinated blue phosphorescent iridium( iii ) complexes, which exhibit emission colors spanning from ultraviolet to blue, i.e.…”

Unraveling the Marked Differences of the Excited-State Properties of Arylgold(III) Complexes with C∧N∧C Tridentate Ligands

“…We tested various hybrid functionals including B3LYP (20% HF exc ), , PBE0 (25% HF exc ), , M062X (54% HF exc ), and Cam-B3LYP (19% HF exc at short-range and 65% HF exc at long-range) to optimize the structure of complex 3 and compared the results with parameters obtained from the crystal structure . The computational results demonstrate that the PBE0 functional provides relatively accurate results (Table S1 in Supporting Information) and has been successfully applied in our previous investigations on the calculation of iridium­(III) and platinum­(II) complexes. ,, Therefore, we chose to use the PBE0 functional for our calculations and employed mixed “double-ζ” quality basis sets with LANL2DZ , for the Au atom and 6-31G­(d,p) for the ligand.…”

“…21 The computational results demonstrate that the PBE0 functional provides relatively accurate results (Table S1 in Supporting Information) and has been successfully applied in our previous investigations on the calculation of iridium(III) and platinum(II) complexes. 29,32,44 Therefore, we chose to use the PBE0 functional for our calculations and employed mixed "double-ζ" quality basis sets with LANL2DZ 45,46 for the Au atom and 6-31G(d,p) for the ligand.…”

Advancing the a Posteriori Quest for Deep-Blue Phosphorescence: Quantifying Excitation-Induced Metal-to-Ligand Charge Transfer as a Guiding Indicator

“…Using host materials that have a higher triplet-state energy has improved the efficiency of blue emission from FIrpic. , Developing novel host materials and optimizing device structures has enabled further increasing the efficiency of emission from FIrpic. , However, those devices exhibit 1931 Commission Internationale de L’Eclairage coordinates, CIE x , y , of (0.16, 0.29), which remain far from the coordinates of pure deep blue (0.14, 0.08). Besides FIrpic, other iridium­(III) complexes have been synthesized with other ancillaries or substituents instead of the picolinate ancillary of FIrpic, including pyrazolyl-borate (FIr6), pyridyl triazolate (FIrtaz), tetrazolate (FIrN 4 ), , and others. − As another class of deep-blue-phosphorescent emitters, carbene-based iridium­(III) complexes have been reported. − Owing to the strong ligand field of carbene, blue emission can be achieved without introducing fluorine-based substituents, which are suspected to reduce the device operational lifetime. However, these complexes are recognized to emit only sky blue, and their efficiency is not high.…”