Orange-Red Phosphorescent Iridium(III) Complexes Bearing Bisphosphine Ligands: Synthesis, Photophysical and Electrochemical Properties, and DFT Calculations

Abstract

Nine new phosphorus-coordinated iridium­(III) complexes of the form [Ir­(C∧N)2(P∧P)]­PF6, [Ir­(F-piq)2(xantphos)]­PF6 (1), [Ir­(F-piq)2(binap)]­PF6 (2), [Ir­(F-piq)2(dppp)]­PF6 (3), [Ir­(Me-piq)2(xantphos)]­PF6 (4), [Ir­(Me-piq)2(binap)]­PF6 (5), [Ir­(Me-piq)2(dppp)]­PF6 (6), [Ir­(CF3O-piq)2(xantphos)]­PF6 (7), [Ir­(CF3O-piq)2(binap)]­PF6 (8), and [Ir­(CF3O-piq)2(dppp)]­PF6 (9) (F-piq = 1-(4-fluorophenyl)­isoquinoline, Me-piq = 1-(p-tolyl)­isoquinoline, CF3O-piq = 1-(4-(trifluoromethoxy)­phenyl)­isoquinoline, xantphos = 9,9-dimethyl-4,5-bis­(diphenylphosphino)­xanthene, binap = 2,2′-bis­(diphenylphosphino)-1,1′-binaphthyl, dppp = 1,3-bis­(diphenylphosphanyl)­propane), have been synthesized and fully characterized. The crystal structures of 1, 7, and 9 have been determined by X-ray analysis. The most representative molecular orbital energy-level diagrams and the lowest energy electronic transitions of 1–9 have been calculated with density functional theory (DFT) and time-dependent DFT (TD-DFT). All of the complexes are orange-red emissive with quantum efficiencies of 3.2–24.4% and lifetimes of 1.77–3.19 μs in degassed CH2Cl2 solution at room temperature. These research results reveal that the Me-piq C∧N ligand and xantphos P∧P ligand are beneficial for a red shift of absorption and emission wavelength. Complex 4 has better charge transfer ability, which probably promises its use as a red-phosphorescent material.

Cyclometalated Iridium(III) Complexes Containing 2-Phenylbenzo[d]oxazole Ligand: Synthesis, X-ray Crystal Structures, Properties and DFT Calculations

“…Thus, their oxidation processes are assigned to Ir (III) to Ir (IV) and some contributions of the C^N ligands. 26 Based on the oxidation potential, the HOMO energy is derived from the equation E HOMO = -(E ox + 4.8 eV), and the trend is consistent with the theoretical calculations ( Table 2). From these results, it can be seen that because of the different number of nitrogen atoms in the ancillary ligands, the HOMO level of 2b is more stable than that of the analogue 2a, and the oxidation process of 2b is more difficult than that of 2a.…”

Highly efficient yellow‐emitting iridium(III) complexes based on fluorinated 2‐(biphenyl‐4‐yl)‐2H‐indazole ligands: Syntheses, structures, properties, and density functional theory calculations

“…Phosphorescence relative quantum yields (Φ em ) of Ir1 and Ir2 in dichloromethane solution at room temperature were determined to be 72.5 and 49.7% with reference to fac ‐Ir(ppy) 3 (Φ = 40%) . As expected, the quantum yields of two complexes are remarkably improved, resulting from the existence of the C‐F bond of lower vibration frequency .…”

“…The luminescence quantum efficiencies were calculated by comparison of the fluorescence intensities (integrated areas) of a standard sample fac ‐Ir(ppy) 3 and the unknown sample according to the equation where Φ unk and Φ std are the luminescence quantum yield values of the unknown sample and fac ‐Ir(ppy) 3 solutions (Φ std = 0.4), respectively. I unk and I std are the integrated fluorescence intensities of the unknown sample and fac ‐Ir(ppy) 3 solutions, respectively.…”

Synthesis and Characterization of High-Efficiency Red Phosphorescent Iridium(III) Complexes with 1-(4-(Trifluoromethyl)phenyl)isoquinoline Ligand

“…When the temperature is decreased to 77 K, the emission maxima of 2a-2b are a slightly bathochromic shift compared to the 298 K spectra, as reported in our earlier literature. 13 Clearly, these complexes exhibit vibronic bands at 77 K, which again demonstrate that their emission states are hybrid states with 3 MLCT and 3 LC characters.…”

“…A large number of piq-based Ir(III) complexes have been reported during the past decade. [9][10][11][12][13] Among these examples, iridium complexes of fluorinated phenylisoquinoline show strong electroluminescence brightness and efficiency. This is because the fluorine groups could not only modify the electronic properties but also decrease the rate of nonradioactive deactivation and improve phosphorescence quantum yields.…”