Heteroleptic Ir(<scp>iii</scp>) phosphors with bis-tridentate chelating architecture for high efficiency OLEDs

Tong, Bihai; Ku, Hsiao-Yun; Chen, I.-Jen; Chi, Yun; Kao, Hao-Che; Yeh, Chih-Ting; Chang, Chih-Hao; Liu, Shih-Hung; Lee, Gene‐Hsiang; Chou, Pi‐Tai

doi:10.1039/c5tc00163c

Cited by 56 publications

(41 citation statements)

References 62 publications

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“…Despite the obvious advantages, these associated studies were greatly hampered by the lack of systematic syntheses and poor performances on OLEDs. These difficulties were recently solved by proper selection of chelates to give the charge‐neutral architecture and the installment of a higher field strength coordination unit …”

Section: Methodsmentioning

confidence: 99%

Bis‐Tridentate Ir(III) Metal Phosphors for Efficient Deep‐Blue Organic Light‐Emitting Diodes

et al. 2017

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which the developments still lag behind the green and red counterparts due to the intrinsically wider energy gaps. [2] Efficient blue-emitters are expected to reduce power consumption and improve color gamut; therefore, they have emerged as one paradigm of the full-color OLED displays and solid-state lighting. [3] Among the various known blue phosphors, the sky-blue emitter FIrpic is considered to be the archetypal design; hence, its modulation is at the forefront of modern research in OLEDs. [4] OLEDs made with FIrpic typically have Commission Internationale de l'Eclairage (CIE (x,y) ) coordinates of (0.17, 0.34) which is far from the National Television Standards Committee pure blue values of (0.14, 0.08). Progress with blue phosphors is further complicated by other issues, such as chemical and physical stabilities, emission quantum yield, and relative radiative lifetime. Moreover, almost all reports of decent blue phosphors were focused on the so-called tris-bidentate architectures, i.e., with either three bidentate cyclometalates of higher ligand-centered ππ* energy gap or two of these cyclometalate plus a third bidentate ancillary. [5] However, these complexes suffer from possible chelate dissociation upon excitation, giving inferior device performances and longevity. [6] Recently, Whittle and Williams, [7] Haga and co-workers, [8] De Cola and co-workers, [9] and Esteruelas and co-workers [10] have independently conducted studies on emitters bearing two tridentate chelates; namely bis-tridentate metal complexes. This class of molecular designs is expected to be more robust and should be of higher efficiency attributed to the concomitant higher rigidity versus the traditional design bearing three bidentate chelates. [11] Despite the obvious advantages, these associated studies were greatly hampered by the lack of systematic syntheses and poor performances on OLEDs. These difficulties were recently solved by proper selection of chelates to give the charge-neutral architecture [12] and the installment of a higher field strength coordination unit. [13] One known bis-tridentate metal complex is the sky-blue Ir(III) phosphor [Ir(mimf)(pzpyph F )] (SB = "sky-blue"), [14] where the tridentate 6-pyrazolyl-2-phenylpyridine (pzpyph F ) and pincer dicarbene chelate (mimf) act as the chromophoric and ancillary chelates, respectively (Scheme 1). These ligands control the emission color and give the greater ligand field strength needed for the efficient phosphors. [15] Hence, the OLED derived from SB gave maximum external quantum efficiency (max. EQE) of 27% and EQE of 24% at the practical Emissive Ir(III) metal complexes possessing two tridentate chelates (bis-tridentate) are known to be more robust compared to those with three bidentate chelates (tris-bidentate). Here, the deep-blue-emitting, bis-tridentate Ir(III) metal phosphors bearing both the dicarbene pincer ancillary such as 2,6-diimidazolylidene benzene and the 6-pyrazolyl-2-phenoxylpyridine chromophoric chelate are synthesized. A deep-blue organic light-em...

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Section: Methodsmentioning

confidence: 99%

Bis‐Tridentate Ir(III) Metal Phosphors for Efficient Deep‐Blue Organic Light‐Emitting Diodes

et al. 2017

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“…The last example of Pt II complexes bearingt he dianionic tridentate chelate were assembled using the class of 2-phenyl-6-(1,2,4-triazol-5-yl) pyridine, that is, tz Bu pyPh 2F H 2 ,t ogether with four distinctive ancillaries, namely:P Ph 3 (60), 4-amylpyridine (61), 2,6-dimethylphenylisocyanide (62), and tert-butylisocyanide (63). [61] It revealed that the steric interference between the cyclometalated phenylg roup adjacent to the ancillary (L) has forced the out-of-plane tilting and twisting of this monodentate ligand.D epending on their bulkiness, variable tilt anglesa re obtained that also block the intermolecular interactions to differente xtents, affordingv ariable emission color in the regime from green, orange to red in the solid state.…”

Section: Dianionic Tridentate Pz R Pyph Chelates and Analoguesmentioning

confidence: 99%

“…Although there have been many precedents focused on Ir III metal phosphors with three bidentate chelates, very few studies have focusedo nI r III complexes bearing either as ingle tridentatec helate or those containing ab is-tridentate architecture. [64] Accordingly,t reatment of IrCl 3 with one equivalent of functionalized 1,3-dipyrid-2-yl benzene in refluxing2 -methoxyethanol, followed by coordinationo ft he functional pz CF3 pyph chelates to the Ir III cation in decalin and in the presence of NaOAc, [63] afforded six bis-tridentateI r III complexes 64-69 [the abbreviations dpyb F2 H, dpy Bu b F2 H, dpyb Bu H, diqb Bu Hp z CF3 pyph CF3 H 2 ,a nd pz CF3 pyph Bu H 2 represent 1,3-difluoro-4,6-di(pyridin-2-yl)b enzene, 1,3-difluoro-4,6-di(4-tert-butylpyridin-2-yl) benzene, 1,3di(pyridin-2-yl)-5-tert-butylbenzene, 1,3-di(isoquinolinyl)-5-tertbutylbenzene, 2-(5-trifluoromethyl-1H-pyrazol-3-yl)-6-(4-trifluoromethylphenyl) pyridine, and 2-(5-trifluoromethyl-1H-pyrazol-3-yl)-6-(4-tert-butylphenyl) pyridine, respectively]. [63] Moreover,f or constructingt he needed charge-neutral bis-tridentate Ir III metal complexes, another tridentate chelate is required that would turn monoanionic upon reactingw ith the Ir III metal ion.…”

Section: Dianionic Tridentate Pz R Pyph Chelates and Analoguesmentioning

confidence: 99%

“…[62] Consequently,C hi and co-workersa ttempted the preparation of bis-tridentate Ir III metal complexes bearing these dianionic chelates exemplified by pz CF3 pyph, and documented their applications in the fabrication of phosphorescent OLEDs. [63] Moreover,f or constructingt he needed charge-neutral bis-tridentate Ir III metal complexes, another tridentate chelate is required that would turn monoanionic upon reactingw ith the Ir III metal ion. One possible design is the functional 1,3-dipyridin-2-ylb enzene, for which the chelate is associated with the metal through central phenyl group and two terminal pyridyl fragments.…”

Section: Dianionic Tridentate Pz R Pyph Chelates and Analoguesmentioning

confidence: 99%

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Metal Complexes with Azolate‐Functionalized Multidentate Ligands: Tactical Designs and Optoelectronic Applications

Wang

Chi

2016

Chemistry A European J

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This review is aimed at updating the recent development on the metal complexes bearing azolate-containing chelates that have received a growing attention from both the industrial and academic sectors. Particular emphasis is given to the luminescent metal complexes, for which tridentate and multidentate bonding interactions give rise to both higher ligand field strength and better rigidity versus their bidentate counterparts-consequently, this is beneficial to the chemical stability and emission efficiency needed for applications such as organic light-emitting diodes and bio-imaging. Their basic designs involve chelates, such as monoanionic 6-azolyl 2,2'-bipyridine, dianionic 2,6-diazolylpyridine, and 2-azolyl-6-phenylpyridine, and the core metal ion spanning from main group elements, such as Ga and In , to the late transition metal ions such as Ru , Os , Ir , and Pt and even the lanthanides. Furthermore, the great versatility of these azolate chelates for assembling the robust and emissive metal complexes, provides bright prospect in future optoelectronic investigations.

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“…In general, the CRI and CCT should exceed 80 and be within 4000-6500 K, respectively,f or domesticl ighting applications. [21] Consequently,t he bis-tridentate Ir III complex 10 with deep-red CIE coordinate (0.63, 0.37) and high quantum yield (F = 0.63), [22] for which its structural drawing is depicted in Figure 11 a, and commercially available[Ir(ppy) 2 (acac)] wereselected as the redand green-emitting phosphors. [23] These emitters are next sandwiched between the dual EML (i.e.,E ML1 and EML2)o fB 2 to achieve stabilized white emission.…”

Section: Calculated Absorption State and Mo Transitions [A]mentioning

confidence: 99%

Role of the Diphosphine Chelate in Emissive, Charge‐Neutral Iridium(III) Complexes

Liao

Devereux

Fox

et al. 2017

Chemistry A European J

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A class of neutral tris-bidentate Ir metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppBz)(tht)Cl ] (1, dppBz=1,2-bis(diphenylphosphino)benzene, tht=tetrahydrothiophene) with fppzH (3-trifluoromethyl-5-(2'-pyridyl)-1H-pyrazole) afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppBz)(fppz)Cl ] (2) and cis-(Cl,Cl)[Ir(dppBz)(fppz)Cl ] (3). The reaction of 3 with the dianionic chelate precursor, 5,5'-di(trifluoromethyl)-3,3'-bipyrazole (bipzH ) or 5,5'-(1-methylethylidene)-bis(3-trifluoromethyl-1H-pyrazole) (mepzH ), in DMF gave the tris-bidentate complex [Ir(dppBz)(fppz)(bipz)] (4) or [Ir(dppBz)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppBz)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: diethylene glycol monomethyl ether (DGME). All complexes 2-6 are luminescent in powder form and thin films where the dichlorides (2, 3) emit with maxima at 590-627 nm (orange) and quantum yields (QYs) up to 90 % whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458 nm (blue) with QYs up to 70 %. Hybrid (time-dependent) DFT calculations showed considerable metal-to-ligand charge transfer contribution to the orange-emitting 2 and 3 but substantial ligand-centered π-π* transition character in the blue-emitting 4-6. The dppBz does not participate in the radiative transitions in 4-6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an organic light-emitting diode (OLED) with dopant 5 gave a deep-blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir complexes containing phosphine chelates.

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Heteroleptic Ir(iii) phosphors with bis-tridentate chelating architecture for high efficiency OLEDs

Abstract: Emissive Ir(iii) complexes bearing two tridentate chelates were synthesized. The multiple coordination mode of the chelate warrants a new class of metal-based phosphors for OLED applications.

Cited by 56 publications

References 62 publications

Bis‐Tridentate Ir(III) Metal Phosphors for Efficient Deep‐Blue Organic Light‐Emitting Diodes

Bis‐Tridentate Ir(III) Metal Phosphors for Efficient Deep‐Blue Organic Light‐Emitting Diodes

Metal Complexes with Azolate‐Functionalized Multidentate Ligands: Tactical Designs and Optoelectronic Applications

Role of the Diphosphine Chelate in Emissive, Charge‐Neutral Iridium(III) Complexes

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