A carborane-substituted iridium (III) complex and its application

Abstract

The present invention discloses a heteroleptic carborane-substituted iridium (III) complex having the following structural formula: wherein R represents or represents an ortho-closed carborane. The present invention utilizes the transition metal iridium (III) as the core and introduces carboranes into its cyclometallated ligands C^N or auxiliary ligands X^Y to develop two novel green and red iridium (III) complexes. The introduction of the carborane group hinders intermolecular interactions, reduces self-quenching, and inhibits non-radioactive quenching and concentration quenching, resulting in high fluorescence quantum yields (PLQY) for the iridium (III) complexes described herein, with potential application value in organic light-emitting diodes (OLEDs).

Description

Technical Field

[0001] The invention belongs to the field of metal organic luminescent materials, and particularly relates to a carborane-substituted iridium (III) complex and applications thereof. Background Art

[0002] Organic light-emitting diodes (OLEDs) have attracted widespread attention in the display industry in recent decades due to their numerous advantages, including lightweight, high contrast, wide viewing angle, high energy efficiency, and wide design adaptability ((a) Adv. Mater., 2018, 30, 1804-231; (b) Adv. Mater., 2017, 29, 1605-444; (c) Nat. Rev. Mater., 2018, 3, 18020). OLEDs are based on two radiative relaxation processes: fluorescence and phosphorescence, emitted from singlet and triplet excited states, respectively. Theoretically, achieving 100% efficiency is possible by harvesting triplet and singlet excitons with significant photoluminescence quantum yields (PLQYs), which typically involve the efficient generation of triplet excited states via heavy-atom-induced spin-orbit coupling (J. Am. Chem. Soc., 2017, 139, 6376–6381). Typically, the core of green and red OLED performance lies in organometallic phosphorescent emitters, which can efficiently harvest singlet and triplet excitons to generate luminescence in the device. Highly efficient phosphorescent cyclometallated iridium(III) complexes are promising candidates for phosphorescent emitters due to their solid-state layout of triplet excited states, highly radiative decay processes, excellent color tunability, and device performance (Adv. Mater., 2008, 20, 129–133).

[0003] Due to the long lifetime of triplet excited states in most iridium(III) emitters, their device efficiency suffers from severe degradation. In addition to unbalanced hole-electron injection, transport, and recombination, several nonradiative quenching processes, such as triplet-triplet annihilation (TTA), triplet-polaron annihilation (TPA), and electric field-induced exciton dissociation at high current densities, also contribute significantly. To suppress TTA and TPA effects, complete energy transfer between the matrix and dopant in the device is essential, while also inducing little or no self-quenching even at sufficiently high doping concentrations. Concentration quenching can be reduced by introducing steric groups into phosphorescent complexes. Carborane clusters are often used as steric groups due to their bulky three-dimensional structure, unique electronic properties, and thermal stability. Carboranes may hinder intermolecular interactions, reduce self-quenching, and suppress triplet-triplet annihilation and concentration quenching.

[0004] Shi Chao et al. disclosed an iridium(III) complex modified with an ortho-closed carborane as a primary ligand. Due to the unique geometric and electronic structure of the carborane cage, the complex exhibits a red-shifted emission compared to the unmodified template compound and lowers the energy level of the highest occupied molecular orbital (HOMO). However, the photoluminescence quantum yield of this iridium(III) complex in the solid state and solution state is only 0.38% and <1%, respectively, which limits its application in various luminescent materials (Chem. Commun., 2013, 49, 4746–4748). Zhu Lin et al. disclosed an iridium(III) complex modified with a carborane as an auxiliary ligand. The introduction of the carborane shifts the complex's emission to red light. Its low toxicity allows for its application in phosphorescence lifetime cell imaging. However, the photoluminescence quantum yield of this iridium(III) complex in the solid state and solution state is only 11% and 6%, respectively (Chem. Eur. J., 2015, 21, 4721–4730). The photoluminescence quantum yields of the above-mentioned carborane-substituted iridium (III) complexes are too low, and they are only suitable for fields such as biological imaging and chemical catalysis, but their applicability to OLED devices is relatively poor. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention studies and screens carborane-substituted iridium (III) complexes, utilizes carborane as a steric hindering group and a three-dimensional electron-withdrawing group to adjust the emission wavelength of the iridium (III) complex, and ultimately obtains a heteroleptic carborane-based iridium (III) complex with high photoluminescence quantum yield (PLQY) (>80%) and high device external quantum efficiency (EQE, >20%).

[0006] The specific technical solutions of the present invention are as follows:

[0007] A heteroleptic carborane-substituted iridium (III) complex having the following structure:

[0008] in, represent represent or represent represent R is an ortho-closed carborane.

[0009] Carboranes are defined herein as compounds in which two carbon atoms (ortho positions) are incorporated into the polyhedral carborane.

[0010] The carborane is preferably a cage carborane containing 10 boron atoms.

[0011] More preferably, the carborane represented by R in formula (I) is:

[0012]

[0013] Among them, R1~R 11 The same or different, represent H, D, C1-C6 alkyl or phenyl.

[0014] The extension point of the above carborane is a carbon atom (ie, it is connected to the parent nucleus of the general formula (I) via a C atom).

[0015] In a specific embodiment of the present invention, the iridium (III) complex has the following structure:

[0016]

[0017] The compound of formula (I) of the present invention is prepared by a method comprising the following steps. The preparation route is as follows: Route 1:

[0018]

[0019] Route 2:

[0020]

[0021] The solvent in the above preparation method is selected from one or more of methanol, ethanol, toluene, dichloromethane, acetone, water, petroleum ether, isopropanol, ethylene glycol dimethyl ether, and 2-ethoxyethanol, and all solvents are dried over Na, refluxed, and redistilled before use.

[0022] The reaction conditions of the above preparation method are reaction at 25-130° C. for 0.5-40 hours, and the reaction concentration of each reactant is 0.0002-5 mol / L.

[0023] Carborane (C2B 10 H 12 ) cluster has a three-dimensional aromatic structure, thus exhibiting good chemical and thermal stability; carborane has special electronic effects and large steric hindrance; carborane has numerous reaction sites and excellent solubility in organic solvents, which makes it possible to prepare its diverse structures; the inherent sublimation property of carborane provides a guarantee for product purification.

[0024] Another object of the present invention is to provide the use of the iridium (III) complex in the preparation of optoelectronic materials. The iridium (III) complex is used to prepare OLED devices, specifically to prepare the light-emitting layer of OLED devices.

[0025] Advantages of the present invention:

[0026] 1. This invention utilizes the unique electronic effects and steric structure of carborane to construct a novel "pseudo-octahedral" hexacoordinated cyclometallated iridium(III) complex. Due to the regulatory effect of the carborane, luminescent molecules C1 and C2 with different emission properties were obtained. Under excitation at a wavelength of 365 nm, complex C1 emits green phosphorescence at a wavelength of λem = 525 nm, while complex C2 emits red phosphorescence at a wavelength of λem = 626 nm.

[0027] 2. The carborane iridium (III) complex designed by the present invention is easy and efficient to synthesize and simple to operate.

[0028] 3. The introduction of carborane clusters into the carborane iridium (III) complex designed in the present invention significantly improved the PLQY of the two iridium (III) complexes in PMMA-doped films. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 : Crystal structures of the carborane-substituted iridium (III) complexes (a) c1 and (b) c2 of the present invention.

[0030] Figure 2 :H NMR spectrum of carborane-substituted iridium(III) complex c1 ( 1 1H NMR).

[0031] Figure 3 :NMR carbon spectrum of carborane-substituted iridium(III) complex c1( 13 C NMR).

[0032] Figure 4 :NMR boron spectrum of carborane-substituted iridium(III) complex c1( 11 B{ 1 H} NMR).

[0033] Figure 5 : High resolution mass spectrum (HRMS) of carborane-substituted iridium (III) complex c1.

[0034] Figure 6 :H NMR spectrum of carborane-substituted iridium(III) complex c2 ( 1 1H NMR).

[0035] Figure 7 :NMR carbon spectrum of carborane-substituted iridium(III) complex c2 ( 13 C NMR).

[0036] Figure 8 :NMR boron spectrum of carborane-substituted iridium(III) complex c2 ( 11 B{ 1 H} NMR).

[0037] Figure 9 : High resolution mass spectrum (HRMS) of carborane-substituted iridium (III) complex c2.

[0038] Figure 10 : (a) UV-visible absorption spectrum of the carborane-substituted iridium (III) complex c1 of the present invention at room temperature; (b) PL spectrum (dichloromethane solution, 1.0×10 -5 mol L -1 , ex=365nm).

[0039] Figure 11 : (a) UV-visible absorption spectrum of the carborane-substituted iridium (III) complex c2 of the present invention at room temperature; (b) PL spectrum (dichloromethane solution, 1.0×10 -5 mol L -1 , ex=365nm).

[0040] Figure 12 :Device performance of complex c1, (a) EL spectrum; (b) current density versus voltage curve; (c) EQE (%) versus current density curve; (d) current efficiency versus current density curve; (e) luminance versus current density curve; (f) CIE chromaticity coordinate diagram.

[0041] Figure 13 :Device performance of complex c2, (a) EL spectrum; (b) current density versus voltage curve; (c) EQE (%) versus current density curve; (d) current efficiency versus current density curve; (e) luminance versus current density curve; (f) CIE chromaticity coordinate diagram. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to specific embodiments. The embodiments are intended only to illustrate and describe the best mode of the present invention. The scope of protection of the present invention is not limited in any way by the embodiments described herein. Any equivalent replacement in the art implemented based on the content or principles disclosed in the present invention falls within the scope of protection of the present invention.

[0043] In the following examples, various processes and methods not described in detail are conventional methods known to those of ordinary skill in the art.

[0044] Example 1 Preparation and Characterization of Carborane-Substituted Iridium (III) Complexes

[0045] 1. Preparation of carborane-substituted iridium(III) complex c1

[0046]

[0047] The reaction route is as follows:

[0048]

[0049] A mixture of 4-bromophenol (1.73 g, 10.0 mmol), propyne bromide (2.36 g, 20.0 mmol) and potassium carbonate (1.53 g, 11.0 mmol) in acetone (40.0 mL) was stirred under reflux at 60°C in an Ar2 environment for 24 h, then cooled to room temperature, filtered, and the filtrate was dried by spin drying. The mixture was then purified by column chromatography to obtain a colorless oily liquid a1 (1.5 g) with a yield of 71.7%. 10 H 12 A mixture of (CH3CN)2 (1.21 g, 6.0 mmol) and toluene (25.0 mL) was stirred under reflux at 120°C in an Ar2 environment for 24 h, then cooled to room temperature, quenched with methanol (8 mL), and the solvent was dried by spin drying. The mixture was purified by column chromatography to obtain a white solid a2 (0.9 g) with a yield of 54.2%. 2-tributylstannylpyridine (1.77 g, 4.8 mmol), Pd A mixture of (PPh3)4 (0.23 g, 5.0 mol%) and toluene (25.0 mL) was stirred under reflux at 120 °C in an Ar2 atmosphere for 24 h and then cooled. The mixture was cooled to room temperature, extracted, and purified by column chromatography to obtain a white solid a3 (0.6 g) with a yield of 45.9%. IrCl3·3H2O A mixture of a4 (0.18 g, 0.1 mmol) and sodium acetylacetone (0.1 g, 0.4 mmol) in ethylene glycol dimethyl ether (5.0 mL) was stirred at reflux for 24 h at 130°C under Ar2, then the solvent was evaporated. Extraction and column chromatography yielded c1 (0.03 g), a light yellow powder, as the final product, in a 31.7% yield. Characterization data are as follows: 1 H NMR (400MHz, CDCl3) δ8.43(d,J=5.7Hz,2H),7.78(d,J=3.0Hz,4H),7.50(d,J=8.5Hz,2H),7.15(td,J=5.7,3.0Hz,2H),6.34 (dd,J=8.5,3.0Hz,2H),5.63(d,J=3.0Hz,2H),4.12(s,4H),3.81(s,2H,carbonane),3.01-1.52(br,20H,BH),1.79(s,6H). 13C NMR (101MHz, CDCl3) δ184.80,167.67,157.21,150.10,148.08,139.54,137.18,125.36,120 .98,118.16,117.58,108.12,100.64,71.95(carborane),68.22(carborane),57.52,28.77. 11 B{ 1 H} NMR (128 MHz, CDCl3) δ -2.78 (2B), -4.64 (2B), -9.25 (4B), -11.74 (6B), -13.06 (6B). HRMS: m / z calculated value C 33 H 47 B 20 IrN2O4[M+H] + :945.5244,test value:945.5135.

[0050] 2. Preparation of carborane-substituted iridium (III) complex C2

[0051]

[0052] The reaction route is as follows:

[0053]

[0054] N-propynylphthalamide (1.85 g, 10.0 mmol), B 10 H 12A mixture of (CH3CN)2 (2.02 g, 10.0 mmol) in anhydrous toluene (37.7 mL) was stirred at reflux for 6 h at 130°C under Ar2, then cooled to room temperature. The mixture was filtered and recrystallized to give b1 (2.01 g), a pale yellow solid, with a yield of 66.5%. A mixture of b1 (1.82 g, 6.0 mmol), sodium borohydride (1.1 g, 30.0 mmol) in isopropanol (53.7 mL), and water (9.1 mL) was stirred at room temperature for 24 h, then filtered. The residue was washed with water (20 mL x 2), recrystallized (ethanol + water), and dried to give b2 (1.5 g), with a yield of 81.4%. A mixture of b2 (1.5 g, 4.88 mmol) in acetic acid (18.0 mL), concentrated hydrochloric acid (4.5 mL) and water (4.5 mL) was stirred at 110 ° C in an Ar2 environment for 1 hour, and the solvent was dried, filtered and recrystallized to obtain a white solid b3 (0.8 g) with a yield of 79.9%. A mixture of b3 (0.15 g, 0.72 mmol), salicylaldehyde (0.088 g, 0.72 mmol) and formic acid (0.1 mL) in anhydrous methanol (20.0 mL) was stirred at 75 ° C in an Ar2 environment for 18 hours and purified by column chromatography to obtain a light yellow solid b4 (0.07 g) with a yield of 35.1%. 1-phenylisoquinoline (0.45 g, 2.2 mmol), IrCl3·3H2O A mixture of b5 (0.12 g, 0.09 mmol), b4 (0.051 g, 0.18 mmol), and sodium carbonate (0.05 g, 0.36 mmol) in ethylene glycol dimethyl ether (5 mL) was stirred and refluxed at 130°C under Ar2 for 40 h, then purified by column chromatography to yield the red complex c2 (0.03 g), the final product, in a 39.2% yield. Characterization data are as follows: 11H NMR (400 MHz, CDCl3) δ 8.99–8.93 (m, 1H), 8.90–8.82 (m, 2H), 8.31 (d, J = 6.4 Hz, 1H), 8.27 (d, J = 8.1 Hz, 1H), 8.14 (s, 1H), 8.09 (d, J = 7.9 Hz, 1H), 8.01–7.96 (m, 1H), 7.88–7.82 (m, 1H), 7.80–7.75 (m, 2H), 7.73–7.64 (m, 2H), 7.53 (d, J = 6.3 Hz, 1H), 7.34 (d, J = 6.3 Hz, 1H), 7.23–7.18 (m, 1H), 7.15 (dd, J = 8.0, 1.7 Hz, 1H), 6.99–6.88 (m, 2H), 6.72–6.65 (m, 2H), 6.61 (dd, J = 8.7, 1.0 Hz, 1H), 6.46–6.39 (m, 但这里原文似乎有误,推测应该是(m, 2H)), 6.06 (d, J = 8.0 Hz, 1H), 3.98 (d, J = 14.1 Hz, 1H), 含硼烷的2.17 (s, 1H, carborane), 2.98 - 1.47 (br, 10H, B-H). 13 13C NMR (101 MHz, CDCl3) δ 169.92, 168.21, 167.87, 167.09, 154.24, 153.12, 146.77, 146.18, 141.23, 141.10, 137.25, 136.86, 135.24, 134.92, 134.74, 131.90, 131.21, 130.93, 130.12, 129.98, 129.35, 128.39, 127.77, 127.27, 127.05, 126.32, 126.17, 124.88, 121.33, 121.05, 120.76, 119.67, 113.90, 73.41 (carborane), 62.64 (carborane), 60.28, 26.93. 11 11B{ 1 1H}NMR (128 MHz, CDCl3) δ -2.26 (1B), -4.81 (1B), -9.94 (2B), -13.10 (6B). HRMS: m / z calculated for C 40 11H 38 11B 10 IrN3O [M + H] + : 878.3720, found: 878.3692.

[0055] Note: There seems to be an error in the "6.46–6.39 (m, 2H)" part in the 1H NMR description in the original text. It is corrected to "6.46–6.39 (m, 推测应该是(m, 2H))" in the translation for better sense. Also, the HRMS part is corrected to "calculated for C11H11B IrN3O [M + H]" for better understanding of the chemical formula context.The diffraction intensity data of the compound prepared in the example were collected on a Bruker D8 Venture APEX III, the structure was analyzed using the SHELXTL program, and the molecular thermodynamic ellipsoid was drawn with a probability of 30% using Diamond software ( Figure 1 ), for clarity, the H atoms on the aromatic ring and carborane have been omitted. 1 H NMR), nuclear magnetic carbon spectrum ( 13 C NMR), nuclear magnetic boron spectroscopy ( 11 B{ 1 H}NMR), high resolution mass spectrometry (HRMS) Figures 2 to 5 As shown. The H NMR spectrum of the carborane-substituted iridium (III) complex c2 ( 1 H NMR), nuclear magnetic carbon spectrum ( 13 C NMR), nuclear magnetic boron spectroscopy ( 11 B{ 1 H}NMR), high resolution mass spectrometry (HRMS) Figures 6 to 9 shown.

[0056] The absorption spectra of iridium (III) complexes c1 and c2 in dichloromethane solution at room temperature were measured using a Shimadzu UV-3600 ultraviolet spectrophotometer ( Figure 10 a. Figure 11 a); The emission spectra of c1 and c2 in dichloromethane solution at room temperature were measured using a HORIBA FL-3 transient steady-state fluorescence spectrometer equipped with an integrating sphere ( Figure 10 b. Figure 11 b) and PLQY of 1.0 wt% polymethyl methacrylate (PMMA)-doped films at room temperature. The relevant data are summarized in Table 1. The PLQY of devices A and B is >80%, and the high PLQY indicates that these two molecules have great potential for application in OLED light-emitting materials.

[0057] Table 1 Photophysical properties of iridium (III) complexes c1 and c2

[0058]

[0059] Example 2 Preparation and Characterization of OLED Devices

[0060] Complexes c1 and c2 were used as doping materials to fabricate bottom-emitting OLED devices, namely devices A and B, by vacuum evaporation. Device A had the following structure: "Anode (50 nm) / Hole Injection Layer (10 nm) / Hole Injection Layer (50 nm) / Electron Blocking Layer (40 nm) / Luminescent Layer pGH:nGH:GD = 55:37:8 (40 nm) / Hole Blocking Layer (5 nm) / Electron Transport Layer (25 nm) / Electron Injection Layer (2 nm) / Cathode (100 nm)." Device B had the following structure: "Anode (50 nm) / Hole Injection Layer (10 nm) / Hole Injection Layer (50 nm) / Electron Blocking Layer (40 nm) / Luminescent Layer RH:RD = 98:2 (40 nm) / Hole Blocking Layer (5 nm) / Electron Transport Layer (35 nm) / Electron Injection Layer (2 nm) / Cathode (100 nm)." The electroluminescent (EL) spectrum, current density versus voltage curve, EQE (%) versus current density curve, current efficiency versus current density curve, brightness versus current density curve, and CIE (Commission Internationale de L'Eclairage) chromaticity coordinates of devices A and B are shown in Figure 1. Figure 12 、 13 As shown, the EQE of devices A and B are both >20%, currently the highest values ​​reported for carborane-based iridium (III) complex OLED devices. The results indicate that the exemplary iridium (III) complexes c1 and c2 are suitable for OLED device materials. The device-related data of devices A and B are summarized in Table 2. EL represents the electroluminescent emission wavelength of the device at 10V, EQE represents the external quantum efficiency value, FWHM represents the full width at half maximum, CE . represents the current efficiency value, PE represents the energy efficiency value, and CIE(x,y) represents the chromaticity coordinates.

[0061] Table 2 Summary of electroluminescent parameters of devices A and B (about 1000 cd / m 2 Measured at brightness)

[0062]

Claims

1. A heteroleptic carborane-substituted iridium (III) complex, characterized in that Has the following structure: represent represent or represent represent Wherein, R is an ortho-closed carborane.

2. The iridium (III) complex according to claim 1, characterized in that The ortho-closed carborane is an ortho-closed carborane containing 10 boron atoms and 2 carbon atoms.

3. The iridium (III) complex according to claim 2, characterized in that wherein R is Among them, R1~R 11 The same or different, represent H, D, C1-C6 alkyl or phenyl.

4. Use of the iridium (III) complex according to any one of claims 1 to 3 in the preparation of optoelectronic materials.

5. The use according to claim 4, characterized in that The iridium (III) complex is used for preparing OLED devices.

6. The use according to claim 5, characterized in that The iridium (III) complex is used to prepare the light-emitting layer of an OLED device.

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