Schiff base iridium complex with aggregation-induced emission effect and its preparation and application

Abstract

The present invention discloses a Schiff base iridium complex with aggregation-induced emission effect and its preparation and application, relating to the technical field of metal complex luminescent materials. The present invention designs and synthesizes a Schiff base iridium complex with a novel structure. Testing shows that the luminescence intensity of the Schiff base iridium complex in an aggregated state is significantly stronger than that of a low-concentration solution, and has a significant aggregation-induced emission effect. The complex has broad application prospects in technical fields such as biological cell imaging, organic light-emitting diode devices, chemical probes, and optical films.

Description

Technical field:

[0001] The present invention relates to the technical field of metal complex luminescent materials, and in particular to a Schiff base iridium complex with aggregation-induced luminescence effect, and the preparation and application thereof. Background technology:

[0002] In recent years, electronic devices such as foldable phones, curved televisions, and flexible screens have become a popular part of people's daily lives. Behind this surge in the field of electronic technology is the rapid development of organic light-emitting materials. Organometallic iridium complexes are at the forefront of organic light-emitting materials applications and serve as a key component of organic optoelectronic functional materials. Organometallic iridium complexes offer advantages such as easily adjustable color, stable molecular structure, excellent electron transport properties, and high luminescence efficiency. They are widely used in biological cell imaging, organic light-emitting diodes, solar cells, and chemical and biological sensing. Organometallic iridium complexes are susceptible to changes in their photophysical properties due to the influence of modifying groups in the ligands. By continuously adjusting the type and structure of the ligands, new light-emitting materials with superior properties can be developed.

[0003] However, the photophysical properties of metal organic iridium complexes in the aggregated state (including luminescence color and phosphorescence quantum yield) are often inconsistent with those in the single molecule state. Therefore, it is difficult to regulate the luminescence properties of molecules in the aggregated state through structural modification of iridium complexes. It is worth noting that the introduction of hydrophilic groups into the ligands of metal organic iridium complexes can effectively change the aggregation-induced emission properties of molecules, effectively enhance the radiation transition pathways of molecules in high-concentration solutions, thin films or solid states, improve the quantum efficiency and luminescence properties of materials, and have important significance for broadening the application of metal organic iridium complexes in organic light-emitting diodes, organic thin-film solar cells, chemical sensors and other fields. Summary of the invention:

[0004] In order to overcome the shortcomings of the existing technology, the technical problem to be solved by the present invention is to provide a method for preparing a Schiff base iridium complex, in which amino-polyethylene glycol-carboxylic acid and a metal organic iridium complex are connected through a carbon-nitrogen double bond to obtain a Schiff base iridium complex with aggregation-induced emission effect.

[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0006] The first object of the present invention is to provide a Schiff base iridium complex having aggregation-induced emission effect, the structural formula of which is as follows:

[0007]

[0008] Here, m is an integer ranging from 1 to 12.

[0009] The second object of the present invention is to provide a method for preparing the aforementioned Schiff base iridium complex, comprising the following steps:

[0010] (1) reacting 2-(2-pyridyl)benzimidazole with 1,6-dibromohexane to obtain 6-bromohexyl-2-(2-pyridyl)-benzimidazole;

[0011] (2) reacting 6-bromohexyl-2-(2-pyridyl)benzimidazole with 3,6-di-tert-butylcarbazole to obtain 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole;

[0012] (3) reacting 4-(2-pyridyl)-benzaldehyde with iridium trichloride to obtain a chloro-bridged iridium complex containing a 4-(2-pyridyl)-benzaldehyde ligand;

[0013] (4) reacting 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole, a chloro-bridged iridium complex containing a 4-(2-pyridyl)-benzaldehyde ligand, and KPF6 to obtain an iridium complex having a 4-(2-pyridyl)-benzaldehyde ligand as a main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as a secondary ligand;

[0014] (5) An iridium complex with 4-(2-pyridyl)-benzaldehyde as the main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as the auxiliary ligand is reacted with amino-polyethylene glycol-carboxylic acid to obtain a metal organic iridium complex containing a Schiff base structure.

[0015] The third object of the present invention is to provide the use of the aforementioned Schiff base iridium complex as an aggregation-induced emission material.

[0016] A fourth object of the present invention is to provide applications of the aforementioned aggregation-induced emission materials in biological cell imaging, organic light-emitting diode devices, chemical probes, and optical films.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention designs and synthesizes a novel structure of Schiff base iridium complex. Tests show that the luminescence intensity of the Schiff base iridium complex in the aggregated state is significantly stronger than that of the low-concentration solution, and has a significant aggregation-induced luminescence effect. It has broad application prospects in the fields of biological cell imaging, organic light-emitting diode devices, chemical probes, optical films, etc.

[0019] (2) The preparation method of the Schiff base iridium complex provided by the present invention is simple and easy, has good repeatability and high stability, and is suitable for the batch production of this type of Schiff base iridium complex. Description of the drawings:

[0020] Figure 1 Aggregation-induced emission effect of the Schiff base iridium complex prepared in Example 5 in a mixed solution of n-hexane and dichloromethane;

[0021] Figure 2 This is the aggregation-induced emission effect of the Schiff base iridium complex prepared in Example 5 in a mixed solution of water and methanol. Specific implementation method:

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific embodiments and illustrations.

[0023] The present invention provides a Schiff base iridium complex having an aggregation-induced emission effect. The structural formula of the Schiff base iridium complex is as follows:

[0024]

[0025] Here, m is an integer ranging from 1 to 12.

[0026] The Schiff base iridium complex described in the present invention is a tridentate heteroleptic cationic complex composed of two main ligands (C^N ligand) and one auxiliary ligand (N^N ligand), the C^N ligand is 4-(2-pyridyl)-benzaldehyde, the N^N ligand is 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridine)benzimidazole, the Schiff base group is imino-polyethylene glycol-carboxylic acid, and the alkyl chain is a straight-chain hexyl group.

[0027] The present invention also provides a method for preparing the aforementioned Schiff base iridium complex, comprising the following steps:

[0028] (1) reacting 2-(2-pyridyl)benzimidazole with 1,6-dibromohexane to obtain 6-bromohexyl-2-(2-pyridyl)-benzimidazole;

[0029] (2) reacting 6-bromohexyl-2-(2-pyridyl)benzimidazole with 3,6-di-tert-butylcarbazole to obtain 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole;

[0030] (3) reacting 4-(2-pyridyl)-benzaldehyde with iridium trichloride to obtain a chloro-bridged iridium complex containing a 4-(2-pyridyl)-benzaldehyde ligand;

[0031] (4) reacting 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole, a chloro-bridged iridium complex containing a 4-(2-pyridyl)-benzaldehyde ligand, and KPF6 to obtain an iridium complex having a 4-(2-pyridyl)-benzaldehyde ligand as a main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as a secondary ligand;

[0032] (5) An iridium complex with 4-(2-pyridyl)-benzaldehyde as the main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as the auxiliary ligand is reacted with amino-polyethylene glycol-carboxylic acid to obtain a metal organic iridium complex containing a Schiff base structure.

[0033] Preferably, the molar ratio of 2-(2-pyridyl)benzimidazole to 1,6-dibromohexane in step (1) is 1:(1.0-1.5).

[0034] Preferably, the reaction temperature in step (1) is 0-30°C.

[0035] Preferably, the molar ratio of 6-bromohexyl-2-(2-pyridyl)benzimidazole to 3,6-di-tert-butylcarbazole in step (2) is 1:(1.0-1.5).

[0036] Preferably, the reaction temperature in step (2) is 105-115° C., and potassium hydroxide solution is used as a strong base.

[0037] Preferably, the strong base is at least one of sodium hydroxide, potassium hydroxide, sodium acetate, sodium ethoxide, potassium carbonate, sodium carbonate, and potassium phosphate. Other strong bases known in the art may also be used.

[0038] Preferably, the molar ratio of 4-(2-pyridyl)-benzaldehyde to iridium trichloride in step (3) is (1-2.5):1.

[0039] Preferably, the reaction temperature in step (3) is 120-130°C.

[0040] Preferably, the molar ratio of 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole, the iridium chloride complex containing 4-(2-pyridyl)-benzaldehyde ligand, and KPF6 in step (4) is 1:(2.0-2.5):(2.0-4.0).

[0041] Preferably, the reaction temperature in step (4) is 120-150°C.

[0042] Preferably, in step (5), the molar ratio of the iridium complex with 4-(2-pyridyl)-benzaldehyde as the main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as the auxiliary ligand to amino-polyethylene glycol-carboxylic acid is 1:(2 to 2.5).

[0043] Preferably, the reaction temperature in step (5) is 40-60°C.

[0044] Preferably, the reaction in step (5) is carried out by stirring or ultrasonic reaction in a solvent; the grinding reaction is carried out in the absence of a solvent, and the grinding method can be mechanical grinding.

[0045] More preferably, the solvent is at least one of tetrahydrofuran, triethylamine, dichloromethane and ethanol.

[0046] The reaction time in steps (1) to (5) depends on the amount of feed and the degree of reaction.

[0047] The present invention also provides the use of the aforementioned Schiff base iridium complex as an aggregation-induced emission material.

[0048] The present invention also provides applications of the aforementioned aggregation-induced luminescence material in biological cell imaging, organic light-emitting diode devices, chemical probes, and optical films.

[0049] Example 1

[0050] Dry the 250mL three-necked flask, glass rod, constant pressure dropping funnel, etc. Sodium hydride (0.12g, 4.9mmol) was placed in the reaction flask for nitrogen protection, and the reaction apparatus was placed in an ice bath for cooling. 30mL of a tetrahydrofuran solution of 2-(2-pyridyl)benzimidazole (0.20g, 1.0mmol) was slowly dripped into the above reaction flask under ice bath conditions. As the reaction continued, the reaction system turned into a brick red suspension, and the entire reaction lasted for 2h. After the addition was complete, the reaction system was warmed to room temperature and continued to stir for about 12h. 1,6-dibromohexane (0.35g, 1.0mmol) was then quickly injected at one time. The mixture was then heated to 90°C and refluxed. After the reaction is completed, the solution is cooled to room temperature, and the product is washed and extracted with dichloromethane and distilled water, then dried over anhydrous sodium sulfate, and separated and purified by column chromatography to obtain a yellow gum-like viscous product 6-bromohexyl-2-(2-pyridyl)-benzimidazole. 1H NMR (400MHz, CDCl3) δ (ppm): 8.70–8.69 (m, 1H), 8.42 (d, J = 8.0Hz, 1H), 7.87–7.83 (m, 2H), 7.46–7.44 ( m,1H),7.37–7.31(m,3H),4.85–4.81(m,2H),3.38–3.34(m,2H),1.92–1.78(m,4H),1.49–1.36(m,4H).

[0051]

[0052] Example 2

[0053] 6-Bromohexyl-2-(2-pyridyl)-benzimidazole (0.36 g, 1.0 mmol) was placed in a 100 mL three-necked flask. Tetrabutylammonium bromide (0.16 g, 0.5 mmol), 3,6-di-tert-butylcarbazole (0.28 g, 1.0 mmol), potassium hydroxide (0.04 g, 0.4 mmol), 35 mL of toluene, and 10 mL of water were added sequentially under nitrogen protection. The temperature was raised to 110°C and the reaction was carried out for 12 hours. The reaction mixture was cooled to room temperature, washed with water, extracted with dichloromethane, and then dried over anhydrous sodium sulfate. The mixture was separated and purified by column chromatography to obtain 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)-benzimidazole as a white solid. 1 H NMR (400MHz, CDCl3) δ (ppm): 8.55 (d, J = 4.7Hz, 1H), 8.38 (d, J = 8.0Hz, 1H), 8.09 (d, J = 1.7Hz, 2H), 7.84–7.78 (m, 2H), 7.49–7.46 (m ,2H),7.40–7.36(m,1H),7.32–7.23(m,5H),4.81–4.77(m,2H),4.21–4.18(m,2H),1.89–1.77(m,4H),1.67(s,2H),1.45(s,20H).

[0054]

[0055] Example 3

[0056] To a 100 mL three-necked flask, add 4-(2-pyridyl)-benzaldehyde (0.57 g, 3.15 mmol), iridium trichloride (1.86 g, 1.57 mmol), 30 mL of ethylene glycol monomethyl ether, and 10 mL of water. Under nitrogen, heat to 120°C and reflux for reaction. After the reaction, remove the solvent to obtain the product. 1H NMR(400MHz, DMSO-d6)δ(ppm):9.82–9.72(m,4H),8.50–8.45(m,4H),8.35–8.11(m,4H),8.08–7.89(m,8H),7.62–7.02(m,8H),6.85–6.92(m,4H).

[0057]

[0058] Example 4

[0059] The iridium chloride complex containing 4-(2-pyridyl)-benzaldehyde ligand (4.70 g, 0.40 mmol) was mixed with 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)-benzimidazole (0.45 g, 0.80 mmol), and 20 mL of ethylene glycol monoethyl ether was added. The oil bath temperature was controlled at 120 ° C and nitrogen was introduced. The reaction was carried out for about 12 hours. After the reaction was completed, the mixture was cooled to room temperature and KPF6 (0.20 mmol, 0.37 g) was added. , dichloromethane was added and the phases were separated using a separatory funnel, the organic liquid after separation was evaporated to dryness by rotary evaporation, and the obtained compound was separated by column chromatography after making sand with silica gel (the stationary phase was 300-400 mesh silica gel, and the eluent was a mixed solvent of dichloromethane and petroleum ether in a ratio of 1:1) to obtain a light yellow solid powder of an iridium complex with 4-(2-pyridyl)-benzaldehyde as the main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as the auxiliary ligand. 1 H NMR (400MHz, DMSO-d6) δ (ppm): 9.75 (d, J=8.0Hz, 2H), 8.51–8.47 (m, 1H), 8.22–8.11 (m, 3H), 8.04–7.28 (m, 19H), 7.02–6.97 (m,2H),6.81–6.72(m,2H),6.29–6.23(m,1H),4.26–4.22(m,2H),3.50–3.39(m,2H),1.98–1.83(m,4H),1.46–1.44(m,22H).

[0060]

[0061] Example 5

[0062] An iridium complex (1.26 g, 1 mmol) with 4-(2-pyridyl)-benzaldehyde as the main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as the auxiliary ligand, amino-heptapeglycol-carboxylic acid (0.79 g, 2 mmol), and sodium acetate (0.25 g, 3 mmol) were dissolved in 30 mL of tetrahydrofuran, heated to 55 ° C for 1.5 h, washed with water and extracted with dichloromethane, and freeze-dried to obtain a metal organic iridium complex containing a Schiff base structure. 1 H NMR (400MHz, DMSO-d6) δ (ppm): 11.96 (m, 2H), 8.63–8.56 (m, 2H), 8.61 (d, J = 8.4Hz, 1H), 8.3 2–8.25(m,1H),8.21–8.15(m,2H),7.93–7.57(m,6H),7.42–7.34(m,6H),7.09–7.02(m,8H), 6.72–6.64(m,2H),6.12–6.10(m,2H),5.83(m,4H),4.93–4.81(m,2H),4.25(s,2H),3.75–3 .42(m,56H),2.80–2.52(m,4H),1.85(s,2H),1.66(s,2H),1.38(s,18H),1.28–1.23(m,4H).

[0063]

[0064] Example 6

[0065] The difference between Example 6 and Example 5 is that 0.79 g of amino-heptapeglyethylene glycol-carboxylic acid is replaced by 0.70 g of amino-octaeglyethylene glycol-carboxylic acid. 1 H NMR (400MHz, DMSO-d6) δ (ppm): 11.96 (m, 2H), 8.63–8.56 (m, 2H), 8.61 (d, J = 8.4Hz, 1H), 8.3 2–8.25(m,1H),8.21–8.15(m,2H),7.93–7.57(m,6H),7.42–7.34(m,6H),7.09–7.02(m,8H), 6.72–6.64(m,2H),6.12–6.10(m,2H),5.83(m,4H),4.93–4.81(m,2H),4.25(s,2H),3.75–3 .42(m,64H),2.80–2.52(m,4H),1.85(s,2H),1.66(s,2H),1.38(s,18H),1.28–1.23(m,4H).

[0066]

[0067] Example 7

[0068] The difference between Example 7 and Example 5 is that 0.79 g of amino-heptamethylene glycol-carboxylic acid is replaced by 0.80 g of amino-nonamethylene glycol-carboxylic acid. 1 H NMR (400MHz, DMSO-d6) δ (ppm): 11.96 (m, 2H), 8.63–8.56 (m, 2H), 8.61 (d, J = 8.4Hz, 1H), 8.3 2–8.25(m,1H),8.21–8.15(m,2H),7.93–7.57(m,6H),7.42–7.34(m,6H),7.09–7.02(m,8H), 6.72–6.64(m,2H),6.12–6.10(m,2H),5.83(m,4H),4.93–4.81(m,2H),4.25(s,2H),3.75–3 .42(m,72H),2.80–2.52(m,4H),1.85(s,2H),1.66(s,2H),1.38(s,18H),1.28–1.23(m,4H).

[0069]

[0070] In addition, through multiple experiments, it was found that by changing the amount of reactants, reaction solvent, catalyst, reaction temperature and reaction time in Examples 1-7, the Schiff base iridium complexes prepared in Examples 5-7 can also be obtained.

[0071] Example 8

[0072] The Schiff base iridium complex prepared in Example 5 was dissolved in a mixed solvent of n-hexane / dichloromethane with a volume ratio of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% to prepare a concentration of 10 -5 mol / L mixed solution, the aggregation-induced emission effect was tested using an emission spectrometer, and the results are shown in Figure 1 .

[0073] Example 9

[0074] The Schiff base iridium complex prepared in Example 5 was dissolved in a mixed solvent with a water / methanol content ratio of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% to prepare a solution concentration of 10 -5 mol / L mixed solution, using emission spectrometer to test the aggregation-induced emission effect, the results are shown in Figure 2 .

[0075] from Figure 1and Figure 2 It can be seen that: ① In a mixed solution of n-hexane and dichloromethane, the luminescence intensity of the Schiff base iridium complex increases continuously as the n-hexane content increases from 0% to 90%, and the maximum emission wavelength blue-shifts from 370-380 nm to 360-370 nm, which is a typical aggregation-induced emission effect; ② In a mixed solution of water and methanol, the emission intensity of the Schiff base iridium complex increases continuously as the water content increases from 0% to 70%. When the water content increases to 70-90%, the luminescence intensity decreases, and the maximum emission wavelength blue-shifts from 365-375 nm to 360-370 nm, which also has an aggregation-induced emission effect.

[0076] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A Schiff base iridium complex having aggregation-induced emission effect, characterized in that: The structural formula of the Schiff base iridium complex is as follows: Here, m is an integer ranging from 1 to 12.

2. The method for preparing the Schiff base iridium complex according to claim 1, wherein The following steps are involved: (1) reacting 2-(2-pyridyl)benzimidazole with 1,6-dibromohexane to obtain 6-bromohexyl-2-(2-pyridyl)-benzimidazole; (2) reacting 6-bromohexyl-2-(2-pyridyl)benzimidazole with 3,6-di-tert-butylcarbazole to obtain 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole; (3) reacting 4-(2-pyridyl)-benzaldehyde with iridium trichloride to obtain a chloro-bridged iridium complex containing a 4-(2-pyridyl)-benzaldehyde ligand; (4) reacting 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole, a chloro-bridged iridium complex containing a 4-(2-pyridyl)-benzaldehyde ligand, and KPF6 to obtain an iridium complex having a 4-(2-pyridyl)-benzaldehyde ligand as a main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as a secondary ligand; (5) An iridium complex with 4-(2-pyridyl)-benzaldehyde as the main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as the auxiliary ligand is reacted with amino-polyethylene glycol-carboxylic acid to obtain a metal organic iridium complex containing a Schiff base structure.

3. The preparation method according to claim 2, wherein: The molar ratio of 2-(2-pyridyl)benzimidazole to 1,6-dibromohexane in step (1) is 1:(1.0-1.5); The reaction temperature in step (1) is 0-30°C.

4. The preparation method according to claim 2, wherein: The molar ratio of 6-bromohexyl-2-(2-pyridyl)benzimidazole to 3,6-di-tert-butylcarbazole in step (2) is 1:(1.0-1.5); The reaction temperature in step (2) is 105-115°C; In step (2), a strong base is added to the reaction; the strong base is at least one of sodium hydroxide, potassium hydroxide, and sodium ethoxide.

5. The preparation method according to claim 2, wherein: The molar ratio of 4-(2-pyridyl)-benzaldehyde to iridium trichloride in step (3) is (1-2.5):1; The reaction temperature in step (3) is 120-130°C.

6. The preparation method according to claim 2, wherein: The molar ratio of 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole, the iridium chloride complex containing a 4-(2-pyridyl)-benzaldehyde ligand, and KPF6 in step (4) is 1:(2.0-2.5):(2.0-4.0); The reaction temperature in step (4) is 120-150°C.

7. The preparation method according to claim 2, characterized in that: In step (5), the molar ratio of the iridium complex with 4-(2-pyridyl)-benzaldehyde as the main ligand and 6-(3,6-di-tert-butylcarbazole)hexyl-2-(2-pyridyl)benzimidazole as the auxiliary ligand to amino-polyethylene glycol-carboxylic acid is 1:(2-2.5); The reaction temperature in step (5) is 40-60°C.

8. The preparation method according to claim 2, wherein: The reaction in step (5) is carried out by stirring or ultrasonic reaction in a solvent; or by grinding reaction in the absence of a solvent; The solvent is at least one of tetrahydrofuran, triethylamine, dichloromethane and ethanol.

9. Use of the Schiff base iridium complex according to claim 1 as an aggregation-induced emission material.

10. The use according to claim 9, characterized in that: Application of the aggregation-induced emission material in organic light-emitting diode devices and optical films.

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