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Theoretical Approach for the Luminescent Properties of Ir(III) Complexes to Produce Red-Green-Blue LEC Devices.

ABSTRACT: With an appropriate mixture of cyclometalating and ancillary ligands, based on simple structures (commercial or easily synthesized), it has been possible to design a family of eight new Ir(III) complexes (1A, 1B, 2B, 2C, 3B, 3C, 3D and 3E) useful as luminescent materials in LEC devices. These complexes involved the use of phenylpyridines or fluorophenylpyridines as cyclometalating ligands and bipyridine or phenanthroline-type structures as ancillary ligands. The emitting properties have been evaluated from a theoretical approach through Density Functional Theory and Time-Dependent Density Functional Theory calculations, determining geometric parameters, frontier orbital energies, absorption and emission energies, injection and transport parameters of holes and electrons, and parameters associated with the radiative and non-radiative decays. With these complexes it was possible to obtain a wide range of emission colours, from deep red to blue (701-440 nm). Considering all the calculated parameters between all the complexes, it was identified that 1B was the best red, 2B was the best green, and 3D was the best blue emitter. Thus, with the mixture of these complexes, a dual host-guest system with 3D-1B and an RGB (red-green-blue) system with 3D-2B-1B are proposed, to produce white LECs.

SUBMITTER: Santander-Nelli M

PROVIDER: S-EPMC9104581 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature

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Theoretical Approach for the Luminescent Properties of Ir(III) Complexes to Produce Red-Green-Blue LEC Devices.

Santander-Nelli Mireya M Boza Bastián B Salas Felipe F Zambrano David D Rosales Luis L Dreyse Paulina P

Molecules (Basel, Switzerland) 20220419 9

With an appropriate mixture of cyclometalating and ancillary ligands, based on simple structures (commercial or easily synthesized), it has been possible to design a family of eight new Ir(III) complexes (1A, 1B, 2B, 2C, 3B, 3C, 3D and 3E) useful as luminescent materials in LEC devices. These complexes involved the use of phenylpyridines or fluorophenylpyridines as cyclometalating ligands and bipyridine or phenanthroline-type structures as ancilla ...[more]

PMID: 35565982

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Project description:A structure-property relationship study of neutral heteroleptic (1 and 2, [Ir(C∧N)2(L∧X)]) and homoleptic (3 and 4, fac-[Ir(C∧N)3]) Ir(III) complexes (where L∧X = anionic 2,2,6,6-tetramethylheptane-3,5-dionato-κO3,κO6 (thd) and C∧N = a cyclometalating ligand bearing a pentafluorosulfanyl (-SF5) electron-withdrawing group (EWG) at the C4 (HL1) and C3 (HL2) positions of the phenyl moiety) is presented. These complexes have been fully structurally characterized, including by single-crystal X-ray diffraction, and their electrochemical and optical properties have also been extensively studied. While complexes 1 ([Ir(L1)2(thd)]), 3 (Ir(L1)3), and 4 (Ir(L2)3) exhibit irreversible first reduction waves based on the pentafluorosulfanyl substituent in the range of -1.71 to -1.88 V (vs SCE), complex 2 ([Ir(L2)2(thd)]) exhibits a quasi-reversible pyridineC∧N-based first reduction wave that is anodically shifted at -1.38 V. The metal + C∧N ligand oxidation waves are all quasi-reversible in the range of 1.08-1.54 V (vs SCE). The optical gap, determined from the lowest energy absorption maxima, decreases from 4 to 2 to 3 to 1, and this trend is consistent with the Hammett behavior (σm/σp with respect to the metal-carbon bond) of the -SF5 EWG. In degassed acetonitrile, for complexes 2-4, introduction of the -SF5 group produced a blue-shifted emission (λem 484-506 nm) in comparison to reference complexes [Ir(ppy)2(acac)] (R1, where acac = acetylacetonato) (λem 528 nm in MeCN), [Ir(CF3-ppy) (acac)] (R3, where CF3-ppyH = 2-(4-(trifluoromethyl)phenyl)pyridine) (λem 522 nm in DCM), and [Ir(CF3-ppy)3] (R8) (λem 507 nm in MeCN). The emission of complex 1, in contrast, was modestly red shifted (λem 534 nm). Complexes 2 and 4, where the -SF5 EWG is substituted para to the Ir-CC∧N bond, are efficient phosphorescent emitters, with high photoluminescence quantum yields (ΦPL = 58-79% in degassed MeCN solution) and microsecond emission lifetimes (τε = 1.35-3.02 μs). Theoretical and experimental observations point toward excited states that are principally ligand centered (3LC) in nature, but with a minor metal-to-ligand charge-transfer (3MLCT) transition component, as a function of the regiochemistry of the pentafluorosulfanyl group. The 3LC character is predominant over the mixed 3CT character for complexes 1, 2, and 4, while in complex 3, there is exclusive 3LC character as demonstrated by unrestricted density functional theory (DFT) calculations. The short emission lifetimes and reasonable ΦPL values in doped thin film (5 wt % in PMMA), particularly for 4, suggest that these neutral complexes would be attractive candidate emitters in organic light-emitting diodes.

Dataset Information

Theoretical Approach for the Luminescent Properties of Ir(III) Complexes to Produce Red-Green-Blue LEC Devices.

Publications

Theoretical Approach for the Luminescent Properties of Ir(III) Complexes to Produce Red-Green-Blue LEC Devices.

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