Preparation method and application of aggregation-induced emission iridium complex

Abstract

The invention discloses a preparation method and application of an iridium complex with aggregation-induced emission property, and belongs to the field of phosphorescent materials. Three iridium complexes are prepared by taking 2-phenylpyridine and derivatives thereof as cyclometalated ligands and 5-phenyl-2, 2 '-dipyridyl as auxiliary ligands, and research on photophysical properties of the iridium complexes shows that the iridium complexes prepared by the invention have excellent aggregation-induced emission properties and have important application value in the field of phosphorescent materials.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of three cyclometalated iridium complexes with aggregation-induced emission properties, and belongs to the field of phosphorescent materials. Background Art

[0002] Traditional fluorescent molecules usually have strong fluorescence in dilute solutions, but the fluorescence will weaken or even quench at high concentrations. In 2001, Tang Benzhong et al. found that a class of organic small molecules had basically no fluorescence in dilute solutions, but showed bright fluorescence emission in the aggregated state (Chem. Commun., 2001, 1740 - 1741). They named this new phenomenon aggregation-induced emission (abbreviated as AIE). The discovery of the aggregation-induced emission phenomenon provides an effective idea for solving the major scientific problem of aggregation-caused luminescence quenching, and greatly promotes the application and development of highly efficient solid-state luminescent materials. So far, most of the AIE molecules reported in the literature are pure organic small molecules, and there are relatively few new aggregation-induced phosphorescent emission (abbreviated as AIPE) materials based on transition metal complexes. As a kind of phosphorescent material, cyclometalated iridium complexes have been widely used in OLED (Small, 2017, 13, 1603780; J. Mater. Chem. C, 2018, 6, 3298 - 3309), photodynamic therapy (Dalton Trans., 2022, 51, 111 - 128), cell imaging (Chem. Commun., 2013, 49, 11095 - 11097; J. Mater. Chem. C, 2014, 2, 5615 - 5628), sensors (Sens. Actuators B Chem., 2022, 350, 130894), etc. Therefore, it is of great application value to create iridium complexes with excellent aggregation-induced emission properties. Summary of the Invention

[0003] The object of the present invention is to provide a preparation method of iridium complexes Ir1 - Ir3 with aggregation-induced emission properties and their aggregation-induced emission properties.

[0004] The technical solution adopted by the present invention is that the preparation method of iridium complexes Ir1 - Ir3 is to synthesize a cyclometalated ligand from 2-bromopyridine and an arylboronic acid derivative as reactants, and then simultaneously coordinate the cyclometalated ligand and the auxiliary ligand 5-phenyl-2,2'-bipyridine with iridium metal ions, and finally synthesize by replacing anions. The structure is as follows:

[0005]

[0006] The preparation methods of the cyclometalated ligand, auxiliary ligand and iridium complexes Ir1 - Ir3 are as follows. The specific synthesis steps are as follows:

[0007] (1) Synthesis of the cyclometalated ligand: In air, add 1.0 mmol of 2 - bromopyridine, arylboronic acid derivative (1.5 equiv.), potassium carbonate (2.0 equiv.), palladium acetate (1.5% equiv.) into a round - bottom flask in sequence. Then add 12 mL of ethanol / water mixed solution with a volume ratio of 3:1. Carry out the Suzuki cross - coupling reaction under magnetic stirring at 80 °C. Track the reaction progress by thin - layer chromatography. After the reaction is complete, extract three times with dichloromethane, combine the organic phases, concentrate under reduced pressure, and separate by column chromatography to obtain the cyclometalated ligand;

[0008] (2) Synthesis of the auxiliary ligand: Add 1.0 mmol of 5 - bromo - 2,2'-bipyridine, phenylboronic acid (1.5 equiv.), potassium carbonate (2.0 equiv.), tetrakis(triphenylphosphine)palladium (3.0% equiv.) into a round - bottom flask in sequence. Evacuate and protect with N 2 protection. Under N 2 protection, add 12 mL of pre - deoxygenated ethanol / water mixed solution with a volume ratio of 3:1. Stir the reaction magnetically at 80 °C for 12 h. After the reaction is completed, extract three times with dichloromethane, combine the organic phases, concentrate under reduced pressure, and separate by column chromatography to obtain the auxiliary ligand 5 - phenyl - 2,2'-bipyridine;

[0009] (3) Synthesis of the iridium complex: Add IrCl 3 ·3H 2 O and 2.5 equivalents of the cyclometalated ligand into a round - bottom flask. In a pre - deoxygenated ethylene glycol monoethyl ether / water mixed solution with a volume ratio of 3:1, under N 2 protection, stir the reaction magnetically at 120 °C for 24 h. After the reaction is completed, concentrate the reaction solution under reduced pressure to obtain a dichloro - bridged intermediate product. Add the dichloro - bridged intermediate product and 3.0 equivalents of 5 - phenyl - 2,2'-bipyridine into a round - bottom flask. Using pre - deoxygenated ethylene glycol monoethyl ether as the solvent, heat and reflux at 120 °C for 24 h under nitrogen protection. After the reaction is completed, cool to room temperature, then add 20 mL of saturated aqueous KPF 6 solution and stir at room temperature for 12 h. Extract the reaction solution with dichloromethane, concentrate under reduced pressure to obtain a crude product. Use dichloromethane / petroleum ether as the eluent and separate and purify by column chromatography to obtain the target product. The product structure is confirmed by 1 1H NMR, 13 13C NMR and high - resolution mass spectrometry.

[0010] The above-mentioned iridium complexes include the following derivatives:

[0011] Compound Ir1: The cyclometalating ligand is selected from 2-phenylpyridine;

[0012] Compound Ir2: The cyclometalating ligand is selected from 2-(4-biphenylyl)pyridine;

[0013] Compound Ir2: The cyclometalating ligand is selected from 2-(4-N,N-diphenylphenyl)pyridine.

[0014] Advantages of the present invention:

[0015] 1. The method for synthesizing the cyclometalating ligand by Suzuki cross-coupling reaction is environmentally friendly, simple and efficient.

[0016] 2. Cyclometalated iridium complexes modified with different substituents can be obtained by modular design and using 5-phenyl-2,2'-bipyridine as the auxiliary ligand, and iridium complexes with excellent aggregation-induced emission properties can be obtained. Description of the drawings

[0017] Figure 1 is the emission spectrum of Compound Ir1 at different water contents (the solvent is acetonitrile / water, 5 × 10 -5 mol / L).

[0018] Figure 2 is the emission spectrum of Compound Ir2 at different water contents (the solvent is acetonitrile / water, 5 × 10 -5 mol / L).

[0019] Figure 3 is the emission spectrum of Compound Ir3 at different water contents (the solvent is acetonitrile / water, 5 × 10 -5 mol / L). Detailed implementation manners

[0020] Example 1 Synthesis of Compound Ir1

[0021] (1) Synthesis of the cyclometalating ligand:

[0022] In air, 1.0 mmol of 2-bromopyridine, phenylboronic acid (1.5 equiv.), potassium carbonate (2.0 equiv.), palladium acetate (1.5% equiv.) were successively added to a round-bottom flask, and then 12 mL of an ethanol / water mixed solution with a volume ratio of 3:1 was added. The Suzuki cross-coupling reaction was carried out under magnetic stirring at 80 °C. The reaction progress was monitored by thin-layer chromatography. After the reaction was complete, 20 mL of saturated brine was added, and the mixture was extracted three times with dichloromethane. The organic phases were combined and concentrated under reduced pressure, and then separated by column chromatography to obtain the cyclometalating ligand with a yield of 90%;

[0023] (2) Synthesis of the auxiliary ligand:

[0024] Add 1.0 mmol of 5-bromo-2,2'-bipyridine, phenylboronic acid (1.5 equiv.), potassium carbonate (2.0 equiv.), and tetrakis(triphenylphosphine)palladium (3.0% equiv.) to a round-bottom flask in sequence. Evacuate and fill with N 2 Protect, and add 12 mL of a pre-deoxygenated ethanol / water mixed solution with a volume ratio of 3:1 under N 2 protection. Stir the reaction magnetically at 80 °C for 12 h. After the reaction is completed, add 20 mL of saturated brine, extract three times with dichloromethane, combine the organic phases, concentrate under reduced pressure, and separate by column chromatography to obtain the auxiliary ligand 5-phenyl-2,2'-bipyridine with a yield of 70%;

[0025] (3) Synthesis of the iridium complex:

[0026] Add IrCl 3 ·3H 2 O and 2.5 equivalents of the cyclometalated ligand to a round-bottom flask. In a pre-deoxygenated ethylene glycol monoethyl ether / water mixed solution with a volume ratio of 3:1, stir magnetically at 120 °C under N 2 protection for 24 h. After the reaction is completed, concentrate the reaction solution under reduced pressure to obtain a dichloro-bridged intermediate. Add the dichloro-bridged intermediate and 3.0 equivalents of 5-phenyl-2,2'-bipyridine to a round-bottom flask, use pre-deoxygenated ethylene glycol monoethyl ether as the solvent, and react at 120 °C for 24 h under nitrogen protection. After the reaction is completed, cool to room temperature, then add 20 mL of a saturated aqueous solution of KPF 6 and stir at room temperature for 12 h. Extract the reaction solution with dichloromethane, concentrate under reduced pressure to obtain a crude product, and purify by column chromatography using dichloromethane / petroleum ether as the eluent to obtain the target product with a yield of 64%. The structural characterization data are as follows: 1 H NMR (400 MHz, DMSO-d 6) δ 8.94 (dd, J = 8.4, 4.3Hz, 2H), 8.59 (dd, J = 8.5, 2.2 Hz, 1H), 8.32 - 8.24 (m, 3H), 8.04 (d, J =2.2 Hz, 1H), 7.97 - 7.88 (m, 5H), 7.81 (d, J = 4.6 Hz, 1H), 7.73 - 7.69 (m,1H), 7.66 (d, J = 5.1 Hz, 1H), 7.50 - 7.43 (m, 3H), 7.42 - 7.37 (m, 2H), 7.21- 7.12 (m, 2H), 7.09 - 7.01 (m, 2H), 6.98 - 6.90 (m, 2H), 6.26 (dd, J = 11.9,7.0 Hz, 2H). 13 C NMR (151 MHz, DMSO-d 6 ) δ 166.74, 166.70, 155.12, 154.11,150.63, 150.26, 149.88, 149.37, 148.96, 147.16, 143.94, 143.87, 139.69,139.33, 138.86, 138.75, 137.09, 134.29, 131.18, 130.31, 130.22, 129.71,129.49, 128.61, 126.62, 125.10, 125.06, 124.07, 124.00, 122.39, 122.29,120.12, 119.98. HRMS(Synapt G2-Si HDMS, m / z) Theoretical value: C 38 H 28 N 4 Ir [M-PF 6 + 733.1943, found: 733.1940. HRMS(Synapt G2-Si HDMS, m / z) Theoretical value: PF 6 - 144.9642, found: 144.9650.

[0027] Example 2 Synthesis of Compound Ir2

[0028] Example 2 was prepared in the same manner as Example 1, except that: in the synthesis of the cyclometalated ligand in Example 2, the arylboronic acid derivative used was 4-biphenylboronic acid.​

[0029] The yield of Ir2 was 67%, and the structural characterization data are as follows: 1 H NMR (400 MHz, DMSO-d 6 ) δ 8.95 (dd, J =6.4, 2.9 Hz, 2H), 8.61 (dd, J = 6.4, 1.7 Hz, 1H), 8.36 - 8.27 (m, 3H), 8.15(d, J = 1.7 Hz, 1H), 8.07 - 7.95 (m, 5H), 7.89 (d, J = 3.3 Hz, 1H), 7.79 -7.71 (m, 2H), 7.43 (s, 5H), 7.39 - 7.32 (m, 10H), 7.29 (t, J = 4.5 Hz, 2H),7.25 - 7.16 (m, 2H), 6.51 (dd, J = 9.7, 1.4 Hz, 2H). 13 C NMR (151 MHz, DMSO-d 6 ) δ 166.40, 155.13, 154.13, 151.21, 150.74, 150.14, 149.61, 149.21, 147.34,143.44, 143.39, 141.86, 141.42, 140.33, 140.16, 139.70, 139.24, 138.93,138.83, 137.01, 134.26, 129.74, 129.43, 129.01, 128.88, 128.85, 128.73,127.58, 126.59, 126.45, 126.42, 125.58, 125.11, 125.08, 124.08, 124.00,121.39, 121.24, 120.34, 120.18. HRMS(Synapt G2-Si HDMS, m / z) Theoretical value: C 50 H 36 N 4 Ir[M-PF 6 + 885.2569, measured value: 885.2568.

[0030] Synthesis of Compound Ir3 in Example 3

[0031] ​Example 3 was prepared in the same manner as Example 1, except that: in the synthesis of the cyclometalated ligand in Example 3, the arylboronic acid derivative used was triphenylamine-4-boronic acid.

[0032] The yield of Ir3 was 70%, and the structural characterization data was as follows: 1 H NMR (400 MHz, DMSO-d 6 ) δ 8.90 (dd, J =8.5, 5.9 Hz, 2H), 8.60 (dd, J = 6.4, 1.7 Hz, 1H), 8.29 (td, J = 5.9, 1.2 Hz,1H), 8.21 (d, J = 1.6 Hz, 1H), 8.07 (d, J = 2.9 Hz, 1H), 7.86 - 7.77 (m, 3H),7.72 (dd, J = 10.8, 6.5 Hz, 2H), 7.61 - 7.50 (m, 7H), 7.34 (d, J = 4.4 Hz,1H), 7.26 (t, J = 5.9 Hz, 5H), 7.20 (t, J = 5.9 Hz, 4H), 7.09 - 7.01 (m, 4H),6.97 (d, J = 5.5 Hz, 4H), 6.88 (d, J = 5.3 Hz, 4H), 6.69 (dt, J = 14.3, 5.0Hz, 2H), 6.61 (dd, J = 6.4, 1.8 Hz, 1H), 6.53 (dd, J = 6.4, 1.8 Hz, 1H), 5.82(dd, J = 7.5, 1.8 Hz, 2H). 13 C NMR (151 MHz, DMSO-d 6) δ 166.28, 166.10, 155.06, 154.15, 152.04, 151.39, 150.17, 148.68, 148.48, 148.10, 147.89, 147.23, 146.31, 146.21, 139.55, 139.29, 137.81, 137.77, 137.03, 136.90, 136.42, 134.40, 129.91, 129.54, 129.41, 129.35, 128.71, 126.67, 125.77, 125.71, 125.43, 125.00, 124.84, 123.85, 123.68, 122.84, 122.34, 122.03, 121.81, 119.17, 118.79, 114.80, 113.75. HRMS(Synapt G2-Si HDMS, m / z) Theoretical value: C 62 H 46 N 6 Ir [M-PF 6 + 1067.3413, Measured value: 1067.3407.

[0033] Example 4: AIE property test of compound Ir1

[0034] Dissolve Ir1 in acetonitrile to prepare a solution with a concentration of 5 × 10 -4 mol / L, and then mix the above solution, acetonitrile and water in different volume ratios to prepare mixed solutions with different water contents (concentration of 5 × 10 -5 mol / L), and then measure their emission spectra. Figure 1 The results show that in the acetonitrile / water mixed solution, as the water content of the poor solvent increases, the luminescence of the compound remains basically unchanged first. When the water content increases to 90%, the emission intensity increases significantly and the emission wavelength blue-shifts. At this time, the emission intensity reaches the maximum, and I / I 0 is 3.65 (I represents the emission intensity of Ir1 in the acetonitrile / water system, and I 0 represents the emission intensity of Ir1 in pure acetonitrile). This result indicates that compound Ir1 has excellent aggregation-induced emission properties.

[0035] Example 5: AIE property test of compound Ir2

[0036] Dissolve Ir2 in acetonitrile to prepare a solution with a concentration of 5 × 10 -4 ​A solution of [mol / L], and then mix the above solution, acetonitrile and water in different volume ratios to prepare mixed solutions with different water contents (concentration: 5 × 10 -5 mol / L), and then measure their emission spectra. Figure 2 The results show that in the acetonitrile / water mixed solution, as the water content of the poor solvent increases, the luminescence of the compound gradually increases. When the water content increases to 80%, the emission intensity increases significantly and the emission wavelength blueshifts. When the water content is 90%, the emission intensity reaches the maximum, and I / I 0 is 7.94. This result indicates that compound Ir2 has excellent aggregation-induced emission properties.

[0037] Example 6: AIE property test of compound Ir3

[0038] Dissolve Ir3 in acetonitrile to prepare a solution with a concentration of 5 × 10 -4 mol / L, and then mix the above solution, acetonitrile and water in different volume ratios to prepare mixed solutions with different water contents (concentration: 5 × 10 -5 mol / L), and then measure their emission spectra. Figure 3 The results show that in the acetonitrile / water mixed solution, as the water content of the poor solvent increases, the luminescence of the compound is very weak at the beginning. When the water content increases to 70%, the luminescence begins to increase significantly and the emission wavelength blueshifts. When the water content is 90%, the emission intensity reaches the maximum, and I / I 0 is 58.53. This result indicates that compound Ir3 has excellent aggregation-induced emission properties.

Claims

1. An aggregation-induced emission iridium complex, characterized in that: The iridium complex is formed by using 2-phenylpyridine and its derivatives as cyclometallic ligands and 5-phenyl-2,2'-bipyridine as auxiliary ligands to coordinate with iridium metal ions, and its structure is as follows: ； The 2-phenylpyridine and its derivatives are selected from 2-phenylpyridine, 2-(4-biphenylyl)pyridine or 2-(4-N,N-diphenylphenyl)pyridine.

2. The method for preparing the aggregation-induced emission iridium complex according to claim 1, characterized in that: The synthesis steps of the iridium complex are as follows: (1) Synthesis of cyclometallated ligands: Using 2-bromopyridine and arylboronic acid derivatives as reactants, potassium carbonate as a base, palladium acetate as a catalyst, and an ethanol / water mixed solution as a solvent, a Suzuki cross-coupling reaction is carried out in air at 80°C without the addition of an external ligand. After the reaction is completed, the target product is isolated; (2) Synthesis of auxiliary ligand: 5-bromo-2,2'-bipyridine and phenylboronic acid are used as reactants, potassium carbonate is used as a base, tetrakis(triphenylphosphine)palladium is used as a catalyst, and an ethanol / water mixed solution is used as a solvent. A Suzuki cross-coupling reaction is carried out at 80°C under N2 protection. After the reaction is completed, the target product 5-phenyl-2,2'-bipyridine is isolated and obtained; (3) Synthesis of iridium complex: IrCl3·3H2O and 2.5 equivalents of cyclometallated ligand were added to a round-bottom flask, and the mixture was stirred magnetically at 120°C under N2 protection in a mixed solution of ethylene glycol monoethyl ether / water with a volume ratio of 3:1 for 24 h. After the reaction, the reaction solution was concentrated under reduced pressure to obtain a dichloro bridge intermediate. The dichloro bridge intermediate and 3.0 equivalents of 5-phenyl-2,2'-bipyridine were added to a round-bottom flask, and ethylene glycol monoethyl ether was used as solvent. The mixture was heated to reflux under nitrogen protection. After the reaction, the mixture was cooled to room temperature, and a saturated aqueous solution of KPF6 was added and stirred at room temperature. The reaction solution was extracted, and the collected organic phase was concentrated under reduced pressure to obtain a crude product, which was then purified to obtain the target product.

3. The use of the aggregation-induced emission iridium complex according to claim 1, characterized in that: The cyclometalated iridium complex is applied in the field of phosphorescent materials.

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