Iridium(III) Complexes with Sulfonyl and Fluorine Substituents: Synthesis, Stereochemistry and Effect of Functionalisation on their Photophysical Properties

Ragni, Roberta; Orselli, Enrico; Kottas, Gregg S.; Omar, Omar Hassan; Babudri, Francesco; Pedone, Adriana; Naso, Francesco; Farinola, Gianluca M.; Cola, Luisa De

doi:10.1002/chem.200801270

Cited by 60 publications

(34 citation statements)

References 72 publications

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“…1) were prepared according to the literature by a double-step synthetic procedure involving the preliminary synthesis of dichloro-bridged dimer iridium View Article Online complexes from the functionalized ppy ligands and iridium(III) chloride hydrate, and their subsequent reaction with 2,4-decanedione in the presence of sodium carbonate as the base. 9 Substitution effects on the photophysical properties of iridium complexes…”

Section: Resultsmentioning

confidence: 99%

Influence of electronic and steric effects of substituted ligands coordinated to Ir(iii) complexes on the solution processed OLED properties

et al. 2015

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Orange and green phosphorescent heteroleptic iridium complexes 1 and 2 [(1): iridium(iii)bis[2-(5′-benzylsulfonyl)phenylpyridinato-N,C2′](2,4-decanedionate) and (2): iridium(iii)bis[2-(5′-benzylsulfonyl-3′,6′-difluoro)phenylpyridinato-N,C2′](2,4-decanedionate)] are used as dopant emitters in solution processed organic light-emitting diodes. These emitters bear one sterically hindered 2,4-decanedionate and two phenylpyridine (ppy) ligands functionalized with electron withdrawing benzylsulfonyl groups and fluorine atoms. The steric and electronic effects of such substituents on the photophysical properties and performance of devices of 1 and 2 are investigated by making comparison with the green emitting reference phosphor Ir(ppy)2(acac) [iridium(iii)bis(2-phenylpyridinato-N,C2′)-acetylacetonate]. In particular, the functionalization of ppy ligands with the benzylsulfonyl group enhances the photoluminescence quantum yield (Φ) and red shifts the emission of complex 1 with respect to Ir(ppy)2(acac). Further substitution of the same ligands with two fluorine atoms in 2 restores the green emission of the reference complex, increasing its Φ. Hence, the combination of the two kinds of substituents represents a suitable functionalization pattern to increase the photoluminescence efficiency of 2vs. the unfunctionalized Ir(ppy)2(acac). Interestingly, a fully solution processed phosphorescent light-emitting device (PHOLED) made using complex 2 as an emitter and with properly tailored architecture, which includes an electron transporting layer of a PEG substituted polyfluorene (PEG: poly(ethylene glycol)), exhibits high external emission quantum efficiency (EQE up to 12%) and a high luminous efficiency (LE up to 24.2 cd A-1). We attribute such a high performance to the bulky effect of both benzylsulfonyl groups in ppy and of the alkyl chain in the β-diketonate ligand, as well as to the enhanced electron mobility induced by fluorine atoms. This device outperforms the control diode based on Ir(ppy)2(acac) (EQE 5.5% and LE 17 cd A-1) and approaches the best efficiencies achieved so far for green Ir(iii) complex based PHOLEDs

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Section: Resultsmentioning

confidence: 99%

Influence of electronic and steric effects of substituted ligands coordinated to Ir(iii) complexes on the solution processed OLED properties

et al. 2015

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“…30 Although impressive performances have been achieved in solution, translating these performances into devices with good stability and efficiency metrics is still a challenge. 17 Thus, the design and syntheses of new blue-emitting phosphors for OLEDs and LEECs are essential.…”

Section: Introductionmentioning

confidence: 99%

Blue-to-Green Emitting Neutral Ir(III) Complexes Bearing Pentafluorosulfanyl Groups: A Combined Experimental and Theoretical Study

et al. 2017

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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.

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“…Dupont's catalyst proved to be very efficient in the synthesis of non‐symmetric BTD derivatives 2a , 2b , 2c , which could be obtained in good yields (71–75%). The beneficial effect of fluorine for the photophysical properties of fluorescent π‐extended compounds is known . Considering there is a very electron deficient substituent in the phenyl group in derivative 2a (fluorine atom) on one side of the BTD ring, which results in a high polarization of the structure (high dipole moment, as calculated herein), we decided to incorporate on the other side a group with a long alkyl chain (C8) and try to observe a possible liquid crystalline behavior (Scheme ) in a similar strategy already used for symmetrical BTDs .…”

Section: Resultsmentioning

confidence: 99%

Designed non‐symmetrical 4,7‐pi‐extended‐2,1,3‐benzothiadiazole derivatives: Synthesis guided by DFT predictions

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et al. 2013

J of Physical Organic Chem

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A series of rationally designed, non‐symmetrical, 4,7‐π‐extended‐2,1,3‐benzothidiazole derivatives had their electronic and geometrical properties evaluated by means of DFT calculations. The data obtained from the calculated 2,1,3‐benzothiadiazole (BTD) intermediates allowed the design and synthesis of a final structure bearing a fluorine‐containing aromatic group on one side of the BTD ring and a C≡C spacer linking a long chain‐containing (C8) aromatic group on the other side. This specific molecular architecture is expected to display liquid crystalline behavior. The new designed structure was therefore synthesized in good overall yield using cross‐coupling reactions (Suzuki and Sonogashira reactions). Copyright © 2013 John Wiley & Sons, Ltd.

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Iridium(III) Complexes with Sulfonyl and Fluorine Substituents: Synthesis, Stereochemistry and Effect of Functionalisation on their Photophysical Properties

Cited by 60 publications

References 72 publications

Influence of electronic and steric effects of substituted ligands coordinated to Ir(iii) complexes on the solution processed OLED properties

Influence of electronic and steric effects of substituted ligands coordinated to Ir(iii) complexes on the solution processed OLED properties

Blue-to-Green Emitting Neutral Ir(III) Complexes Bearing Pentafluorosulfanyl Groups: A Combined Experimental and Theoretical Study

Designed non‐symmetrical 4,7‐pi‐extended‐2,1,3‐benzothiadiazole derivatives: Synthesis guided by DFT predictions

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