Preparation method and application of blue-light iridium (III) complex containing triazole carbene auxiliary ligand

Abstract

The invention provides a triazole carbene ligand, a blue-light triazole carbene iridium (III) compound prepared from the ligand, and a preparation method and application of the blue-light triazole carbene iridium (III) compound, and belongs to the technical field of preparation of organic light-emitting materials. The invention designs and synthesizes a series of cyclometalated iridium complexes which take 2-(2, 4-difluorophenyl) pyridine (DFPPy) as a main ligand and a triazole carbene ligand as an auxiliary ligand. Wherein the triazole ligand synthesis does not need column chromatography separation, and silver oxide promotion is not needed in the metal coordination process, so that large-scale low-cost synthesis can be realized. The formed iridium complex is high in luminous efficiency and stable in structure, the luminescence (including luminous position, optical rotation and the like) of the whole complex can be conveniently adjusted by adjusting the structure of the carbene ligand, and the iridium complex has good application prospect and practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of organic luminescent materials, and specifically relates to a preparation method and application of a blue light iridium (III) complex containing a triazole carbene auxiliary ligand. Background Art

[0002] Organic electroluminescence is the phenomenon that organic materials emit light under the stimulation of electrical energy. It is considered to be the new favorite of the next generation of lighting and display due to its advantages such as response speed, high resolution, thinness and flexible display. Devices made of multi-layer organic thin film structures are called OLED (Organic Light Emitting Diode). OLED devices have the following characteristics: organic polymer materials are used, with a wide range of choices, a wide color gamut, low operating voltage (3~10V), high brightness and high luminous efficiency; wide viewing angle (up to 175° or more), fast response time (~1μs), and good low temperature characteristics; ultra-thin (thickness <1mm) and light, can be made into large sizes while being flexible; the preparation process is relatively simple, low cost, and easy to integrate with other products, with excellent performance-price ratio.

[0003] Studies have shown that when the energy of the singlet electron orbital and the triplet electron orbital in an organic molecular crystal is close and their spatial positions are adjacent, the spin states of the two orbitals can be coupled, causing the triplet electrons to lose their inherent characteristics and exhibit some singlet characteristics, leading to intersystem crossing and phosphorescence emission processes, namely the spin-orbit coupling effect, also known as the spin coupling effect. The spin coupling effect is particularly prominent in metal complexes containing heavy atoms. This is because in metal complexes, due to the combination of metal and ligand, a charge transfer state between the metal and the ligand is generated.

[0004] The most widely used in OLEDs at present are triplet transition metal iridium coordination complexes. The main principles for regulating the luminescent color of such compounds are: first, reducing the number of electrons in the ligand (conjugation length or size) shortens the wavelength of luminescence; increasing the number of electrons in the ligand can lengthen the wavelength of luminescence. Second, connecting electron-withdrawing groups or electron-donating groups at appropriate positions in the molecular structure. According to the characteristics of various chromophores and the electron-withdrawing and electron-donating properties of various chemical groups, suitable ligands are designed and coordinated with metals to obtain iridium complexes with the desired luminescent color, which are further used for preparation and detection to obtain ideal phosphorescent materials. However, the development of blue phosphorescent materials was relatively late and not ideal. Currently, there are relatively few blue phosphorescent materials developed.

[0005] The triazole structure is an aromatic heterocycle with extremely high stability, which can remain stable in both acidic and alkaline conditions. 1,2,4-Triazole compounds are one of the important heterocyclic compounds, existing in many biologically active molecules and showing a variety of biological activities. Triazole has a wide range of application value and has been widely used in many fields of chemistry, especially in medicinal chemistry and metal organic chemistry.

[0006] 1,2,4-Triazole is a medium acceptor group with good thermal stability and suitable triplet energy level. 1,2,4-Triazole has shown wide application in coordination with transition metals. With 1,2,4-triazole as the acceptor, a series of bipolar host materials with special excited state properties can be synthesized by changing the donor structure, the number of donors and the connection mode. By changing the transition pathway of triplet excitons in the host material, the triplet exciton density on the phosphorescent host material is reduced, the utilization rate of triplet excitons is increased, and finally the stability and luminous efficiency of PhOLEDs are improved.

[0007] In doped phosphorescent devices, when the triplet energy of the guest is higher than that of the host material, reverse transfer from the guest material to the host material will occur; if the triplet energy level of the host material is too high, diffusion of excitons from the host material to the electron / hole transport layer will occur, so the host material is required to have a suitable triplet energy level.

[0008] Metal carbene refers to a type of organic molecular species formed by carbon atoms connected to metal atoms by double bonds. Carbene can combine with metals to form complexes and be stabilized. Therefore, metal carbene is a very useful intermediate in organic synthesis.

[0009] In the past research, cyclometallated iridium complexes have made great progress in the pursuit of high-efficiency electrophosphorescent organic light-emitting diodes (OLEDs). However, how to prepare a blue-light cyclometallated iridium complex with triazole carbene as auxiliary ligand, and how to achieve large-scale low-cost production of ligands and complexes, and how to ensure that the formed complex has high luminescence efficiency and stable structure, has become a technical problem that needs to be solved urgently. Summary of the invention

[0010] The present invention is to solve the above technical problems, thereby providing a preparation method of a blue light iridium (III) complex containing a triazole carbene auxiliary ligand and its application. The technical purpose of the present invention is to provide a triazole carbene auxiliary ligand and a blue light triazole carbene iridium (III) compound, as well as a preparation method and application of the above compound.

[0011] The present invention first provides a triazole carbene auxiliary ligand, the structural formula of the triazole carbene auxiliary ligand is shown in the following formula <Ⅰ>:

[0012]

[0013] Wherein, n is an integer greater than or equal to 1; R 1 ~R 4 Any group selected from hydrogen, deuterium, alkyl, aryl, halogen, cyano, acyl, amino and substituted amino, hydroxyl, mercapto, alkoxy, alkylthio, silane, fluorine-containing hydrocarbon, ester or amide; if the above groups contain hydrogen, the corresponding deuterium-substituted groups are also included.

[0014] Furthermore, the substituted amino group includes monosubstituted and disubstituted amino groups.

[0015] Furthermore, the fluorine-containing hydrocarbon group includes a trifluoromethyl group or a difluoromethyl group.

[0016] Furthermore, R 1 ~R 4 Can be the same or different.

[0017] The second object of the present invention is to provide an iridium complex synthesized from the triazole carbene ligand as described above, wherein the structural formula of the iridium complex is shown in the following formula <Ⅱ>:

[0018]

[0019] Wherein, n is an integer greater than or equal to 1; R 1 ~R 4 Any group selected from hydrogen, deuterium, alkyl, aryl, halogen, cyano, acyl, amino and substituted amino, hydroxyl, mercapto, alkoxy, alkylthio, silane, fluorine-containing hydrocarbon, ester or amide; if the above groups contain hydrogen, the corresponding deuterium-substituted groups are also included.

[0020] Furthermore, the synthesis method of the iridium complex is to use 2-(2,4-difluorophenyl)pyridine as the main ligand and the triazole carbene ligand as the auxiliary ligand to prepare the cyclometalated iridium complex.

[0021] Specifically, the reaction formula involved in the synthesis is as follows:

[0022]

[0023] Furthermore, the synthesis method of the iridium complex comprises the following steps:

[0024] Step 1: from compound 1 to 2, the reaction temperature is controlled to be -20 to 80°C, the reaction time is 1 to 72 hours, the molar ratio of compound 1 to trimethyloxonium tetrafluoroboric acid is 1:0.8 to 3, and the solvent is an aprotic dipolar solvent; preferably, the solvent includes dichloromethane, tetrahydrofuran, 1,4-dioxane, 2-methyl-tetrahydrofuran, ether, 1,2-dichloroethane, ethyl acetate, butyl acetate, DMF, DMAc or DMSO;

[0025] Step 2: from compound 2 to 3, the reaction temperature is controlled to be -20 to 80°C, the reaction time is 1 to 72 hours, the molar ratio of compound 1 to phenylhydrazine or phenylhydrazine derivative is 1:0.8 to 3, and the solvent is an aprotic dipolar solvent; preferably, the solvent includes dichloromethane, tetrahydrofuran, 1,4-dioxane, 2-methyl-tetrahydrofuran, ether, 1,2-dichloroethane, ethyl acetate, butyl acetate, DMF, DMAc or DMSO;

[0026] Step 3: from compound 3 to 4, the reaction temperature is controlled to be 80-140°C, the reaction time is 1-72 hours, the molar ratio of compound 1 to triethyl orthoformate is 1:5-100, and the volume ratio of methanol to triethyl orthoformate is 0.1-10:1;

[0027] Step 4: From compound 4 to the target complex, the reaction temperature is controlled at 100-180°C and the reaction time is 1-72 hours. [(DFPPy)Ir(Cl)] 2 The molar ratio of compound 4 to the base is 1:2-5:2-5; the base includes potassium carbonate, sodium carbonate, lithium carbonate, cesium carbonate, potassium acetate, sodium acetate, lithium acetate, cesium acetate, potassium tert-butoxide, sodium tert-butoxide, lithium tert-butoxide or cesium tert-butoxide, and various organic bases such as triethylamine, trimethylamine, DBU, TBD, MTBD or diisopropylethylenediamine; the solvent includes 1,4-dioxane, chlorobenzene, dichlorobenzene or alkyl-substituted benzene.

[0028] A fourth object of the present invention is to provide the use of the iridium complex as described above or the iridium complex synthesized by the method as described above in the preparation of blue light iridium (III) organic light-emitting materials.

[0029] A fifth object of the present invention is to provide the use of the iridium complex as described above in the preparation of OLED devices.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention designs and synthesizes a series of cyclometalated iridium complexes with 2-(2,4-difluorophenyl)pyridine (DFPPy) as a main ligand and triazole carbene ligand as an auxiliary ligand. The synthesis of the triazole ligand does not require column chromatography separation, and does not require silver oxide promotion in the process of coordination with the metal, so it can be synthesized on a large scale at low cost. The formed iridium complex has high luminous efficiency and stable structure, and the luminescence of the entire complex (including luminous position and optical rotation properties, etc.) can be conveniently adjusted by adjusting the structure of the carbene ligand, and has strong innovation and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 UV-visible absorption and emission spectra of three iridium complexes prepared in the examples.

[0033] Figure 2 Schematic diagram of the structure of the electroluminescent device used.

[0034] Figure 3-Figure 5 The luminescence test results of the corresponding device are obtained by taking DF-5R as an example. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described in detail below in conjunction with the embodiments. It is necessary to point out that the following embodiments are only used to explain and illustrate the present invention and are not used to limit the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content still belong to the protection scope of the present invention.

[0036] Example 1

[0037] This embodiment provides a triazole carbene ligand and an iridium complex synthesized from the ligand. The structural formula of the triazole carbene ligand is shown in the following formula <Ⅰ>:

[0038]

[0039] The structural formula of the iridium complex is shown in the following formula <Ⅱ>:

[0040]

[0041] Wherein, n is an integer greater than or equal to 1; R 1 ~R 4 Any group selected from hydrogen, deuterium, alkyl, aryl, halogen, cyano, acyl, amino and substituted amino, hydroxyl, mercapto, alkoxy, alkylthio, silane, fluorine-containing hydrocarbon, ester or amide; if the above groups contain hydrogen, the corresponding deuterium-substituted groups are also included.

[0042] Wherein, the substituted amino group includes monosubstituted and disubstituted amino groups; the fluorine-containing hydrocarbon group includes trifluoromethyl or difluoromethyl; the R 1 ~R 4 Can be the same or different.

[0043] Example 2

[0044] The following provides a method for preparing the iridium complex of Example 1, which is as follows:

[0045] Taking DF-5R (target iridium complex in the following formula) as an example, the synthetic route adopted is as follows:

[0046]

[0047] The specific method in the above-mentioned synthetic route is as follows:

[0048] The first step: from compound 1 to 2, the reaction temperature is controlled to be -20 to 80°C, the reaction time is 1 to 72 hours, the molar ratio of compound 1 to trimethyloxonium tetrafluoroboric acid is 1:0.8 to 3, and the solvent is an aprotic dipolar solvent; the solvent includes dichloromethane, tetrahydrofuran, 1,4-dioxane, 2-methyl-tetrahydrofuran, ether, 1,2-dichloroethane, ethyl acetate, butyl acetate, DMF, DMAc or DMSO;

[0049] Step 2: from compound 2 to 3, the reaction temperature is controlled to be -20 to 80°C, the reaction time is 1 to 72 hours, the molar ratio of compound 1 to phenylhydrazine or phenylhydrazine derivative is 1:0.8 to 3, and the solvent is an aprotic dipolar solvent; the solvent includes dichloromethane, tetrahydrofuran, 1,4-dioxane, 2-methyl-tetrahydrofuran, ether, 1,2-dichloroethane, ethyl acetate, butyl acetate, DMF, DMAc or DMSO;

[0050] Step 3: from compound 3 to 4, the reaction temperature is controlled to be 80-140°C, the reaction time is 1-72 hours, the molar ratio of compound 1 to triethyl orthoformate is 1:5-100, and the volume ratio of methanol to triethyl orthoformate is 0.1-10:1;

[0051] Step 4: From compound 4 to the target iridium complex, the reaction temperature is controlled at 100-180°C and the reaction time is 1-72 hours, [(DFPPy)Ir(Cl)] 2The molar ratio of compound 4 to the base is 1:2-5:2-5; the base includes potassium carbonate, sodium carbonate, lithium carbonate, cesium carbonate, potassium acetate, sodium acetate, lithium acetate, cesium acetate, potassium tert-butoxide, sodium tert-butoxide, lithium tert-butoxide or cesium tert-butoxide, and various organic bases such as triethylamine, trimethylamine, DBU, TBD, MTBD or diisopropylethylenediamine; the solvent includes 1,4-dioxane, chlorobenzene, dichlorobenzene or alkyl-substituted benzene.

[0052] Example 3

[0053] Referring to the synthesis method of Example 2, three iridium complexes DF-5R, DF-6R and DF-6RO were synthesized respectively, and their corresponding structural formulas are as follows:

[0054]

[0055] (1) The photophysical properties of the three iridium complexes prepared above were measured, and the results are shown in Table 1:

[0056] Table 1 Summary of photophysical data of three iridium (III) complexes

[0057]

[0058] Note: a At a concentration of 1×10 -5 M was measured in deoxygenated DCM in a greenhouse; b Determined by relative method, fac-Ir(ppy) 3 As a reference.

[0059] (2) The results of the electrochemical and thermal stability tests on the three iridium complexes are shown in Table 2.

[0060] Table 2 Electrochemical and thermal stability data of triazole carbene iridium (III) complexes

[0061]

[0062] Note: a The energy levels of the frontier molecular orbitals are calculated using the following equation: in is measured in dichloromethane with Ag / AgCl as reference electrode, and the energy gap Eg is estimated using the absorption onset:

[0063] (3) Electroluminescent properties

[0064] A. Device structure used

[0065] The electroluminescent device uses indium tin oxide (ITO) as anode, (PEDDOT:PSS) as hole injection layer, iridium (III) complex dopant in the host as light-emitting layer, (DPEPO) as hole blocking layer, (TmPyPB) as electron transport layer, LiF as electron injection layer, Al as cathode. (TCTA) as host material.

[0066] The device structure is as follows: PEDOT: PSS: 1000r-3s / 4000r-30s (spin coating) / luminescent layer (Ir / TCTA 10%): 1500r-30s (spin coating) / TmPyPB: 50nm / LiF: 1nm / Al: 120nm / DPEPO: 10nm (see Figure 2 ).

[0067] B. The luminous performance of the tested device is shown in Figure 3-Figure 5 , the specific data are shown in Table 3 below:

[0068] Table 3 Summary of EL characteristics of representative phosphorescent, white light and super phosphorescent OLED devices

[0069]

Claims

1. A triazole carbene ligand, characterized in that The structural formula of the triazole carbene ligand is shown in the following formula <Ⅰ>: Wherein, n is an integer greater than or equal to 1; R 1 ~R 4 Any group selected from hydrogen, deuterium, alkyl, aryl, halogen, cyano, acyl, amino and substituted amino, hydroxyl, mercapto, alkoxy, alkylthio, silane, fluorine-containing hydrocarbon, ester or amide; if the above groups contain hydrogen, the corresponding deuterium-substituted groups are also included.

2. The triazole carbene ligand according to claim 1, characterized in that The substituted amino group includes mono-substituted and di-substituted amino groups.

3. The triazole carbene ligand according to claim 1, characterized in that The fluorine-containing hydrocarbon group includes a trifluoromethyl group or a difluoromethyl group.

4. The triazole carbene ligand according to claim 1, characterized in that R 1 ~R 4 Can be the same or different.

5. An iridium complex synthesized from a triazole carbene ligand according to any one of claims 1 to 4, characterized in that: The structural formula of the iridium complex is shown in the following formula <Ⅱ>: Wherein, n is an integer greater than or equal to 1; R 1 ~R 4 Any group selected from hydrogen, deuterium, alkyl, aryl, halogen, cyano, acyl, amino and substituted amino, hydroxyl, mercapto, alkoxy, alkylthio, silane, fluorine-containing hydrocarbon, ester or amide; if the above groups contain hydrogen, the corresponding deuterium-substituted groups are also included.

6. The method for synthesizing the iridium complex according to claim 5, characterized in that: The invention relates to a cyclometalated iridium complex prepared by using 2-(2,4-difluorophenyl)pyridine as a main ligand and the triazole carbene ligand described in any one of claims 1 to 4 as an auxiliary ligand.

7. The method for synthesizing the iridium complex according to claim 6, characterized in that: The reaction formula involved in the synthesis is as follows:

8. The method for synthesizing the iridium complex according to claim 7, characterized in that: The following steps are involved: Step 1: from compound 1 to 2, the reaction temperature is controlled to be -20 to 80°C, the reaction time is 1 to 72 hours, the molar ratio of compound 1 to trimethyloxonium tetrafluoroboric acid is 1:0.8 to 3, and the solvent is an aprotic dipolar solvent; preferably, the solvent includes dichloromethane, tetrahydrofuran, 1,4-dioxane, 2-methyl-tetrahydrofuran, ether, 1,2-dichloroethane, ethyl acetate, butyl acetate, DMF, DMAc or DMSO; Step 2: from compound 2 to 3, the reaction temperature is controlled to be -20 to 80°C, the reaction time is 1 to 72 hours, the molar ratio of compound 1 to phenylhydrazine or phenylhydrazine derivative is 1:0.8 to 3, and the solvent is an aprotic dipolar solvent; preferably, the solvent includes dichloromethane, tetrahydrofuran, 1,4-dioxane, 2-methyl-tetrahydrofuran, ether, 1,2-dichloroethane, ethyl acetate, butyl acetate, DMF, DMAc or DMSO; Step 3: from compound 3 to 4, the reaction temperature is controlled to be 80-140°C, the reaction time is 1-72 hours, the molar ratio of compound 1 to triethyl orthoformate is 1:5-100, and the volume ratio of methanol to triethyl orthoformate is 0.1-10:1; Step 4: from compound 4 to the target complex, the reaction temperature is controlled to be 100-180°C, the reaction time is 1-72 hours, and the molar ratio of [(DFPPy)Ir(Cl)]2 to compound 4 and the base is 1:2-5:2-5; the base includes potassium carbonate, sodium carbonate, lithium carbonate, cesium carbonate, potassium acetate, sodium acetate, lithium acetate, cesium acetate, potassium tert-butoxide, sodium tert-butoxide, lithium tert-butoxide or cesium tert-butoxide, and various organic bases such as triethylamine, trimethylamine, DBU, TBD, MTBD or diisopropylethylenediamine; the solvent includes 1,4-dioxane, chlorobenzene, dichlorobenzene or alkyl-substituted benzene.

9. Use of the iridium complex according to claim 5 or the iridium complex synthesized by the method according to any one of claims 6 to 8 in the preparation of blue light iridium (III) organic light-emitting materials.

10. Use of the iridium complex according to claim 5 or the iridium complex synthesized by the method according to any one of claims 6 to 8 in the preparation of OLED devices.

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