Cationic, luminescent cyclometalated iridium(<scp>iii</scp>) complexes based on substituted 2-phenylthiazole ligands

Stokes, Emily C.; Langdon-Jones, Emily E.; Groves, Lara M.; Platts, James Alexis; Fallis, Ian A.; Coles, Simon J.; Pope, Simon J. A.

doi:10.1039/c4dt03054k

Cited by 12 publications

(3 citation statements)

References 57 publications

(48 reference statements)

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“…In consequence, the use of F and/or F‐containing groups as electron withdrawing substituents has been dropped as a design concept for green emitting LECs and the design and synthesis of fluorine‐free Ir‐iTMCs for LEC application has been pursued. Other electron withdrawing (EW) groups such as sulfur containing groups (e.g., sulfanyl and sulfone) as well as other EW C ^ N ligands like methoxy/methyl substituted 2,3′‐bipyridines have been explored in the attempt to get fluorine‐free green emitting Ir‐iTMCs. Unfortunately, these fluorine‐free Ir‐iTMCs did not lead to an improvement in LEC device lifetime, thereby raising the question whether fluorine indeed is the primary cause of the short lifetime of green LEC devices based on fluorinated iTMCs.…”

Section: Introductioncontrasting

confidence: 96%

Scrutinizing Design Principles toward Efficient, Long‐Term Stable Green Light‐Emitting Electrochemical Cells

Namanga

Gerlitzki

Mudring

2017

Adv Funct Materials

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1 of 8) 1605588be based on non-air sensitive materials allowing for cheap ambient device processing techniques such as spin coating, roll-to-roll, and slot die coating, (iii) even the electrodes can be made out of stable (even noble) metals as the ionic nature of emissive layer omits the need for electrodes made out of metals with low work functions, and (iv) that it is fairly easy to produce large emitting areas. [1][2][3][4][5][6][7][8][9][10] Altogether this makes LECs a very promising low-cost, large area solid state lighting technology solution.LECs based on ionic transition metal complexes (iTMCs) have attracted much research interest, with iridium(III) cationic complexes being the most investigated. [2,11,12] This observation is not surprising considering the overall high photoluminescence quantum yields (PLQY), the relatively short phosphorescent lifetimes for these complexes and the ease with which this class of complexes can be synthesized. [2,11] Equally easily, the emission color of these complexes can be tuned over a wide range through ligand modification. [13][14][15][16] Ir-iTMCs with the generic composition of [Ir(C^N) 2 (N^N)] + [A] − where C^N is a cyclometallated ligand such as 2-phenylpyridine (ppy), N^N a diimine ligand such as 2,2′-bipyridine (bpy) and A − an anion such as hexafluorophosphate [PF 6 ] have been widely studied for LEC device application. Typically, complexes with nonsubstituted C^N ligands like the parent complex [Ir(ppy) 2 (bpy)][PF 6 ] emit in the orange region of the visible spectrum. [11,17,18] In order to obtain emission with shorter wavelengths or higher energy, the phenyl ring of the C^N ligand can be decorated with electron withdrawing groups which results in an energetic stabilization Enhancing the efficiency and lifetime of light emitting electrochemical cells (LEC) is the most important challenge on the way to energy efficient lighting devices of the future. To avail this, emissive Ir(III) complexes with fluoro-substituted cyclometallated ligands and electron donating groups (methyl and tert-butyl)-substituted diimine ancillary (N^N) ligands and their associated LEC devices are studied. Four different complexes of general composition [Ir(4ppy) 2 (N^N)][PF 6 ] (4Fppy = 2-(4-fluorophenyl)pyridine) with the N^N ligand being either 2,2′-bipyridine (1), 4.4′-dimethyl-2,2′-bipyridine (2), 5.5′-dimethyl-2,2′-bipyridine (3), or 4.4′-di-tert-butyl-2,2′-bipyridine (4) are synthesized and characterized. All complexes emit in the green region of light with emission maxima of 529-547 nm and photoluminescence quantum yields in the range of 50.6%-59.9%. LECs for electroluminescence studies are fabricated based on these complexes. The LEC based on (1) driven under pulsed current mode demonstrated the best performance, reaching a maximum luminance of 1605 cd m −2 resulting in 16 cd A −1 and 8.6 lm W −1 for current and power efficiency, respectively, and device lifetime of 668 h. Compared to this, LECs based on (3) and (4) perform lower, with luminance and lifetime of 1314 cd m −2 ,...

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Section: Introductioncontrasting

confidence: 96%

Scrutinizing Design Principles toward Efficient, Long‐Term Stable Green Light‐Emitting Electrochemical Cells

Namanga

Gerlitzki

Mudring

2017

Adv Funct Materials

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“…In addition to the above identified intrinsic σ-antibonding structural instability of Ir-iTMCs, it has been observed that fluorine substitution adds to the shortening of device lifetime for Ir-iTMC-LECs. , Support for this hypothesis is, that in OLEDs (organic light emitting diodes) cleavage of the C-F bond in a blue neutral complex (FIrpic) has been held responsible for a significant shortening of its OLED device lifetime . For that reason fluorine-containing Ir-iTMCs have then been abandoned for green emitting LECs and the focus of research has shifted toward finding fluorine free Ir-iTMCs that emit green light. − However, it turned out that these fluorine free complexes did not meet the expectations and did not yield LECs with improved lifetime, indicating that per se fluorine substitution of the C^N ligand may not be the main reason for the short device lifetime of green LECs based on fluorinated Ir-iTMCs (F-Ir-iTMCs). Recently, we studied a series of green emitting Ir-iTMCs [Ir(4ppy) 2 (N^N)][PF 6 ] with 4Fppy = 2-(4-fluorophenyl)pyridine) and N^N ligand being either 2,2′-bipyridine, 4.4′-dimethyl-2,2′-bipyridine, 5.5′-dimethyl-2,2′-bipyridine or 4.4′-di- tert -butyl-2,2′-bipyridine where we achieved, aside from excellent emission properties, a LEC based on the 2,2′-bipyridine containg complex that showed a lifetime of 668 h, which is appreciably high .…”

Section: Introductionmentioning

confidence: 99%

Supramolecularly Caged Green-Emitting Ionic Ir(III)-Based Complex with Fluorinated C^N Ligands and Its Application in Light-Emitting Electrochemical Cells

Namanga

Gerlitzki

Smetana

et al. 2017

ACS Appl. Mater. Interfaces

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Ionic Ir(III) complexes are the most promising emitters in light emitting electrochemical cells (LECs), especially in the high energy emission range for which it is difficult to find emitters with sufficient efficiencies and lifetimes. To overcome this challenge, we introduced the concept of intramolecular π-π stacking of an ancillary ligand (6-phenyl-2,2'-bipyridine, pbpy) in the design of a new green-emitting iridium ionic transition metal complex with a fluoro-substituted cyclometallated ligand, 2-(4-fluorophenyl)pyridinato (4Fppy). [Ir(4Fppy)(pbpy)][PF] has been synthesized and characterized and its photophysical and electrochemical properties have been studied. The complex emits green light with maxima at 561 and 556 nm under UV excitation from powder and thin film, respectively, and displays a high photoluminescence quantum yield (PLQY) of 78.5%. [Ir(4Fppy)(pbpy)][PF] based LECs driven under pulsed current conditions showed under an average current density of 100 A m (at 50% duty cycle) a maximum luminance of 1443 cd m, resulting in 14.4 cd A and 7.4 lm W current and power efficiencies, respectively. A remarkable long device lifetime of 214 h was observed. Reducing the average current density to 18.5 A m (at 75% duty cycle) led to an exceptional device performance of 19.3 cd A and 14.4 lm W for current and power efficiencies, an initial maximum luminance of 352 cd m and a lifetime of 617 h.

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“…The proligands HL 1 and HL 2 were synthesized via typical condensation of 1,10-phenanthroline-5,6-dione with 4-pyridinecarboxaldehyde and 4-(4-pyridinyl)-benzaldehyde, respectively. , Compounds HL 1 and HL 2 were obtained in moderate to high yields of 52% and 70%, respectively.…”

Section: Resultsmentioning

confidence: 99%

Rational Design and Self-Assembly of Molecular Squares Featuring Cp*M (M = Rh, Ir) Vertices Bridged by Phenanthroline-Derived Ligands

Liu

Lin

Aznárez

et al. 2018

Crystal Growth & Design

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Herein, we describe the design and synthesis of three tetranuclear complexes, [(Cp*Rh)(L 1 )]4(OTf)4 (1a, HL 1 = 2-(pyridin-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline), [(Cp*Ir)(L 1 )]4(OTf)4 (1b), and [(Cp*Rh)(L 2 )]4(OTf)4 (2, HL 2 = 2-(4-(pyridin-4-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline). Owing to the precise design of the phenanthroline-derived ligands, these complexes exhibit perfect square-shaped structures with side lengths of 13.53, 13.57, and 17.95 Å, respectively. These molecules orderly align and assemble into square-shaped, one-dimensional nanotubes. The molecular structures and arrangement of the nanotubes were evidenced by single-crystal X-ray diffraction. Solution behavior was studied by NMR spectroscopy. Fourier transform infrared spectroscopy and elemental analysis were also employed to characterize these complexes.

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Cationic, luminescent cyclometalated iridium(iii) complexes based on substituted 2-phenylthiazole ligands

Cited by 12 publications

References 57 publications

Scrutinizing Design Principles toward Efficient, Long‐Term Stable Green Light‐Emitting Electrochemical Cells

Scrutinizing Design Principles toward Efficient, Long‐Term Stable Green Light‐Emitting Electrochemical Cells

Supramolecularly Caged Green-Emitting Ionic Ir(III)-Based Complex with Fluorinated C^N Ligands and Its Application in Light-Emitting Electrochemical Cells

Rational Design and Self-Assembly of Molecular Squares Featuring Cp*M (M = Rh, Ir) Vertices Bridged by Phenanthroline-Derived Ligands

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