Iridium (iii) complex with low-voltage phosphorescent switching response and preparation and application thereof

Abstract

The application discloses an iridium (III) complex with low-voltage phosphorescent switch response and a preparation and application thereof, and belongs to the technical field of organic photoelectric materials. The iridium (III) complex is composed of two ring metal C^N ligands and one N^N ligand with an electrically active viologen derivative unit. The electrically active unit in the N^N ligand of the complex is composed of a methyl viologen bridged benzene ring. By virtue of the reversible redox characteristics of the methyl viologen substituent and the rich excited state properties of the iridium (III) complex, under voltage stimulation, the iridium (III) complex undergoes reversible redox reaction, and the response of the material photoluminescence intensity is realized. The luminescence "switch" of the complex has reversibility, and since the viologen unit is only bridged by a single benzene ring, the oxidation is high, and the electrochemical reduction can be realized at a low voltage (1.5 V). By virtue of the characteristics, a switch type electrically stimulated phosphorescent response device can be prepared, and the electrically stimulated phosphorescent response device can be used for information recording.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic photoelectric materials, and particularly relates to an iridium (III) complex with low-voltage phosphorescent switch response and a preparation and application thereof. BACKGROUND

[0002] Generally, the electro-stimulated luminescence response material is composed of an electro-active unit and a luminophore. It is crucial to select a suitable electro-active unit and luminophore for constructing the electro-stimulated luminescence material. Among numerous organic electro-responsive units, viologen and its derivatives are applied to various electro-stimulated luminescence materials due to their rich redox properties and good redox reversibility. The electro-responsive properties of viologen can be realized by bridging other groups, introducing heteroatoms, and changing N substituents.

[0003] The phosphorescent iridium (III) complex has a large Stokes shift, a high luminescence quantum yield, and a rich emission state, and is a luminescent host with excellent properties, strong adjustability, and stable electrochemical properties. Therefore, the viologen unit with strong electron capture ability is introduced into the iridium (III) complex, and the electro-stimulated phosphorescent response of the iridium (III) complex can be realized by relying on the redox properties of the viologen unit under an electric field. At the same time, by regulating the bridging unit of the viologen unit, the electro-responsive properties of the viologen unit are fully regulated, and under the condition of an external electric field, the viologen realizes the change from a dication to a neutral state through electrochemical reduction, which influences the energy level of the iridium complex by changing the push-pull electron properties, and then realizes the luminescence conversion of the iridium complex, thereby realizing different electro-stimulated luminescence responses.

[0004] Chinese patent CN113278035B discloses an electro-stimulated iridium (III) complex, which is constructed by bridging a methyl viologen salt on a phenylpyridine molecule and using the molecule as an iridium complex ligand to construct an electro-stimulated luminescence response molecule with luminescence color change. However, the obtained complex has a luminescence response device that depends on a non-significant visible light color change, and the wavelength change range is limited, which is difficult to significantly distinguish the luminescence information change before and after power-on, and is not conducive to information recording and encryption identification.

[0005] Chinese patent CN105237578B discloses an ionic transition metal complex containing a viologen derivative, which is constructed by bridging a methyl viologen salt on a bipyridine molecule and using the molecule as an iridium complex ligand to construct an electro-stimulated luminescence response molecule with luminescence intensity response. Although it can realize the luminescence opening process visible to the naked eye under electro-stimulation, the applied voltage is as high as 10V, which is not conducive to the application of low-energy consumption information display, storage and security devices. SUMMARY

[0006] The present application aims to provide an iridium (III) complex with low-voltage phosphorescent switching response and its preparation and application, which conjugates a single benzene ring bridged viologen unit to an iridium complex bipyridine N^N ligand, realizes large switching of luminous intensity under low-voltage stimulation by using its reversible redox characteristics and lower reduction potential, and thus realizes information recording and erasing process; and the material synthesis steps are relatively simple and the yield is good.

[0007] The technical solution of the present application is an iridium (III) complex with low-voltage phosphorescent switching response, which is composed of a single benzene ring bridged methyl viologen unit to form an electric response unit N^N ligand, and then coordinates the N^N ligand to an iridium complex with different C^N ligands, and the structural general formula of the complex is as follows:

[0008]

[0009] Among them, the C^N ligand is any one of the following:

[0010]

[0011] The preparation route of the above-mentioned iridium (III) complex with low-voltage phosphorescent switching response is as follows:

[0012]

[0013] The specific preparation steps are as follows:

[0014] The C^N ligand compound and the iridium trichloride trihydrate are mixed in a molar ratio of 2:1 to 2.5:1, and then injected into a solvent in an inert environment, and an oil bath reaction is carried out to obtain a cyclometalated iridium (III) chloride bridged dimer;

[0015] Compound 1 is obtained by Suzuki coupling reaction of 2,5-dibromophenylboronic acid and 4-bromo-2,2'-bipyridine in a molar ratio of 1:1 to 1.5:1;

[0016] Compound 2 is obtained by Suzuki coupling reaction of compound 1 and 4-pyridine boronic acid in a molar ratio of 1:2 to 1:2.5;

[0017] Compound 2 and different cyclometalated iridium (III) chloride bridged dimers are coordinated in a molar ratio of 2:1 to 2.5:1 to obtain complex 3;

[0018] After nucleophilic substitution of iodomethane and complex 3 in a molar ratio of 2:1 to 3:1, ion exchange is carried out with potassium hexafluorophosphate to obtain the final product iridium (III) complex;

[0019] The C^N ligand compound is any one of the following structures:

[0020]

[0021] The low-voltage phosphorescent switch-responsive iridium (III) complex containing the methyl viologen derivative unit can be applied to the preparation of an electrically stimulated luminescence responsive device. The switch-responsive iridium (III) complex containing the methyl viologen derivative unit is used as an active layer material of the electrically stimulated luminescence responsive device. Under the condition of continuous ultraviolet irradiation, the device changes from weak luminescence to obvious yellow-green luminescence with enhanced intensity when a voltage of 1.5 V is applied. The luminescence intensity is weakened again when a reverse voltage of -1.5 V is applied.

[0022] The low-voltage phosphorescent switch-responsive iridium (III) complex containing the methyl viologen derivative unit can be applied in an information recording device. The iridium (III) complex is prepared into an iridium (III) complex film. A conductive area with a specific shape is etched on one side of the substrate of the film. Under the condition of ultraviolet excitation, weak luminescence signals can be observed by naked eyes when no voltage is applied. When a forward voltage is applied, recording information with enhanced luminescence intensity can be observed by naked eyes under the condition of ultraviolet excitation. The recording information is erased when a reverse voltage is applied, realizing reversibility.

[0023] Further, the specific information of the applied voltage is as follows: a forward voltage of 1.5 V for 10 s. Recording information can be observed under the condition of ultraviolet excitation. The recording information is erased when a reverse voltage of -1.5 V for 10 s is applied, realizing reversibility.

[0024] Further, the preparation process of the iridium (III) complex film is as follows: the iridium (III) complex is dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate. Tetrabutylammonium hexafluorophosphate is selected as an electrolyte. The above-mentioned part is mixed as an active layer, and is dropped and coated on a substrate. Another substrate with a specific shape etched is used for covering, allowing the etched part to conduct electricity, so as to prepare the film.

[0025] The iridium (III) complex of the type [Ir(N^C)2(N^N)](PF6)3 containing a methyl viologen unit disclosed in the application is bridged by a single benzene ring to the methyl viologen unit and is conjugated to the bipyridine N^N ligand of the iridium complex, the molecule causes a photoinduced electron transfer process between the iridium luminophore and the viologen unit due to the presence of the strong electron-withdrawing viologen unit before electrical stimulation, but the electron-withdrawing ability of the methyl viologen derivative bridged by the benzene ring is reduced compared with the methyl viologen structure, which affects the PET effect between the viologen unit and the iridium metal luminophore, so the complex has a certain weak luminescence intensity before being electrified, and the luminescence of the complex is not completely quenched. After the voltage is applied, the methyl viologen unit is electrochemically reduced to form a quinone structure, which cuts off the photoinduced electron transfer process between the iridium luminophore, and the luminescence opening process is observed. The luminescence "switch" of the complex is reversible, and since the viologen unit is bridged by only a single benzene ring and has high oxidizability, the complex can be electrochemically reduced at a low voltage (1.5 V). We use the low-voltage phosphorescent switch response viologen complex to prepare a switch-type electrical stimulation luminescence response device, which can be applied to an information recording device, and the recording process can be realized reversibly by erasing the recorded information by reversing the voltage. The electrical stimulation response type iridium (III) complex containing the methyl viologen derivative unit has the advantages of low response energy consumption, easy synthesis and low cost.

[0026] The application has the following beneficial effects:

[0027] 1. The electrical stimulation response type iridium (III) complex disclosed in the application combines the long luminescence lifetime and large Stokes shift of the transition metal iridium (III) complex with the reversible redox property of the viologen unit to construct a new type of electrical stimulation response material; the complex is mainly composed of two ring metal C^N ligands and one N^N ligand with an electroactive viologen derivative unit, the electroactive viologen derivative unit in the N^N ligand is formed by bridging a methyl viologen with a benzene ring, and the reversible redox characteristics of the viologen substituent group are combined with the rich excited state properties of the iridium (III) complex to realize the response of the material photoinduced luminescence intensity under voltage stimulation; the luminescence "switch" of the complex is reversible, and since the viologen unit is bridged by only a single benzene ring and has high oxidizability, the complex can be electrochemically reduced at a low voltage (1.5 V);

[0028] 2. The low-voltage response iridium (III) complex disclosed in the application is made into a switch-type electrical stimulation luminescence response device, which can realize the electrical stimulation luminescence switch response of the active layer of the complex by applying a small voltage, and can realize a reversible process by further applying a reverse voltage, the luminescence intensity changes obviously, which is beneficial to observation;

[0029] 3. The low-voltage-responsive iridium (III) complex disclosed in the application can be applied to an information recording device, which cannot be recognized by naked eyes before or after applying a voltage, and the entire information recording device is colorless and transparent under naked eyes. Before applying a voltage, the device can only observe a very weak luminescent signal under UV excitation, and cannot recognize information. When a voltage of 1.5 V is applied, strong luminescent information display is gradually observed within a few seconds, realizing information recording. The recording process can also be reversed by applying a reverse voltage to erase the recorded information.

[0030] 4. The synthesis steps of the switch-type electrically-stimulated iridium (III) complex containing a methyl viologen derivative unit provided in the application are simple, which can be completed through mature dichloro bridge reaction, coordination reaction and substitution reaction, and is beneficial to popularization. The application also provides a new idea and method for further developing new electrically-stimulated phosphorescent response materials and devices. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The emission spectrum diagrams of the iridium (III) complexes prepared in Examples 1 and 2 in acetonitrile solution before and after adding sodium borohydride, wherein the subgraph a is the emission spectrum diagram of the complex 1-5, and the subgraph b is the emission spectrum diagram of the complex 2-5;

[0032] Figure 2 The device effect diagrams of the iridium (III) complexes prepared in Examples 1 and 2 in a thin film state before and after applying electricity, wherein the subgraph a is the device effect diagram of the complex 1-5, and the subgraph b is the device effect diagram of the complex 2-5;

[0033] Figure 3 The emission spectrum diagrams of the iridium (III) complexes prepared in Examples 1 and 2 in a thin film state before and after applying electricity, wherein the subgraph a is the emission spectrum diagram of the complex 1-5, and the subgraph b is the emission spectrum diagram of the complex 2-5;

[0034] Figure 4 The information recording and erasing device effect diagrams of the iridium (III) complexes prepared in Examples 1 and 2 in a thin film state, wherein the subgraph a is the information recording and erasing device effect diagram of the complex 1-5, and the subgraph b is the information recording and erasing device effect diagram of the complex 2-5;

[0035] Figure 5 The cyclic voltammetry test results of the iridium (III) complexes prepared in Examples 1 and 2, wherein the subgraph a is the cyclic voltammetry test result of the complex 1-5, and the subgraph b is the cyclic voltammetry test result of the complex 2-5. DETAILED DESCRIPTION

[0036] In order to better understand the content of the present application, the technical solutions of the present application are further illustrated below through specific examples and drawings, specifically including synthesis, material structure characterization and light response process test. However, these examples do not limit the present application. Modifications and replacements made to the methods, steps or conditions of the present application without departing from the essence of the present application shall fall within the scope of the present application. If not specifically indicated, the technical means used in the examples are conventional means familiar to those skilled in the art.

[0037] The raw materials involved in the following examples are as follows:

[0038]

[0039]

[0040] Example 1: Preparation of an iridium (III) complex (phenylquinoline ligand)

[0041] The structural formula of the iridium (III) complex is as follows:

[0042]

[0043] The specific synthesis route is as follows:

[0044]

[0045] (1) Preparation of compound 1-1: 2.34 mmol of 2,5-dibromophenylboronic acid, 2.13 mmol of 4-bromo-2,2'-bipyridine, 5.32 mmol of potassium carbonate, and 0.21 mmol of tetrakis(triphenylphosphine)palladium were taken into a reaction bottle, protected from light, vacuumed, filled with nitrogen, and circulated three times; 30.0 mL of oxygen-free toluene, 10.0 mL of oxygen-free ethanol, and 10.0 mL of oxygen-free deionized water were sequentially injected into the reaction bottle under a nitrogen atmosphere, and the solids were stirred to completely dissolve. The temperature was raised to 85°C, and the solution was stirred and refluxed for 24 h. After the reaction was completed, the temperature was lowered to room temperature, the solvent was removed under reduced pressure, the organic phase was extracted with dichloromethane, concentrated, and purified by silica gel column chromatography using dichloromethane / methanol (v / v = 80:1) as the eluent to obtain 580 mg of compound 1-1 with a yield of 65%;

[0046] 1H NMR (400 MHz, CD3Cl-d) δ 8.74-8.70 (m, 1H), 7.78 (td, J = 7.7, 1.8 Hz, 1H), 7.69 (d, J = 2.5 Hz, 1H), 7.60 (dt, J = 7.9, 1.1 Hz, 1H), 7.53 (d, J = 8.5 Hz, 1H), 7.38 (dd, J = 8.5, 2.5 Hz, 1H), 7.32 (ddd, J = 7.6, 4.9, 1.2 Hz, 1H).

[0047] (2) Preparation of compound 1-2: Take 8.51 mmol of compound 1-1, 20 mmol of 4-pyridine boronic acid, 21.21 mmol of potassium carbonate, 0.85 mmol of tetrakis(triphenylphosphine)palladium into a reaction bottle, avoid light, vacuum, nitrogen, cycle three times; under the atmosphere of nitrogen, inject 30.0 mL of deoxygenated toluene, 10.0 mL of deoxygenated ethanol, 10.0 mL of deoxygenated deionized water into the reaction bottle in turn, stir to dissolve the solid completely. Heat to 85℃, stir reflux for 24h. After the reaction is completed, reduce to room temperature, remove the solvent under reduced pressure, extract with dichloromethane to leave the organic phase, concentrate, use dichloromethane / methanol (v / v = 80:1) as eluent, separate and purify by silica gel column chromatography to obtain compound 1-2, 240 mg, yield 30%;

[0048] 1 H NMR (400 MHz, CD3Cl-d) δ 8.77-8.71 (m, 2H), 8.68 (d, J = 3.9 Hz, 1H), 8.56-8.50 (m, 3H), 8.49 (s, 1H), 8.44 (d, J = 8.1 Hz, 1H), 7.91-7.79 (m, 3H), 7.65-7.59 (m, 3H), 7.35 (ddd, J = 7.5, 4.8, 1.2 Hz, 1H), 7.20-7.14 (m, 2H), 6.97 (dd, J = 5.0, 1.8 Hz, 1H);

[0049] (3) Synthesis of cyclometalated iridium (III) chloride bridge dimer 1-3: Take 3.12 mmol of 2-phenylquinoline and 1.42 mmol of IrCl3·3H2O into a double-mouth flask, blow nitrogen, deoxygenate three times, inject 9.0 mL of 2-ethoxyethanol and 3.0 mL of deionized water. Put the device into an oil bath, reflux the reaction under light for 24h at 110℃. After the reaction is completed, cool the flask to room temperature, add 20 mL of deionized water to the flask, filter, wash the filter residue with a small amount of ethanol, and dry under vacuum for 4h. Finally, 500 mg of purple solid product is obtained, which is compound 1-3, with a yield of 70.0%.

[0050] (4) Synthesis of compound 1-4: 0.31 mmol of compound 1-2 and 0.15 mmol of 2- (quinoline)pyridine dichloro bridge dimer (i.e. compound 1-3 prepared in the previous step) were dissolved in 15 mL of a mixture of methanol / dichloromethane (1:2, v / v) under a nitrogen atmosphere, heated to 40 °C and stirred under reflux for 6 h. After completion of the reaction, the reaction solution was cooled to room temperature, then 0.6 mmol of potassium hexafluorophosphate (KPF6) was added and stirring was continued for 2 h. Then the solvent was removed, deionized water (30 mL) was added and extracted with dichloromethane (20 mL x 3), and the organic phase was collected and dried over anhydrous magnesium sulfate. The crude product after removal of the solvent was separated and purified by silica gel column chromatography, and the eluent was dichloromethane / methanol (40:1, v / v). Finally, 30 mg of yellow solid product was obtained, i.e. compound 1-4, with a yield of 30.0%.

[0051] 1 H NMR (400 MHz, CD3CN-d3) δ 8.75-8.66 (m, 2H), 8.46 (d, J = 8.8 Hz, 1H), 8.42-8.27 (m, 5H), 8.23 (d, J = 6.6 Hz, 1H), 8.15 (dd, J = 11.5, 8.0 Hz, 2H), 8.06 (d, J = 5.8 Hz, 1H), 8.02-7.93 (m, 3H), 7.92-7.83 (m, 4H), 7.72 (d, J = 6.1 Hz, 2H), 7.64 (d, J = 8.0 Hz, 1H), 7.56-7.44 (m, 3H), 7.35 (t, J = 8.3 Hz, 2H), 7.32-7.28 (m, 1H), 7.19 (q, J = 8.2, 7.6 Hz, 3H), 7.10-7.04 (m, 1H), 7.01 (d, J = 4.9 Hz, 2H), 6.86-6.79 (m, 2H), 6.53 (d, J = 7.8 Hz, 2H). MALDI-TOF MS: calcd. for [M-PF6-]+: 987.3; found: 987.7.

[0052] (5) Synthesis of complex 1-5: 0.02 mmol of complex 1-4 and 0.06 mmol of iodomethane were placed in a two-necked flask, sealed, deoxygenated by nitrogen blowing, and 1 mL of dichloromethane was injected as a solvent. The reaction was carried out at 40 °C under a nitrogen atmosphere for 12 h. The solution was cooled to room temperature and evaporated under reduced pressure. The obtained solid was dissolved in 5 mL of saturated potassium hexafluorophosphate methanol solution, and stirred at room temperature for 2 h. A brown precipitate was observed, which was collected and washed with ether. Recrystallization was performed using acetonitrile / ether, the precipitate was filtered and dried, and finally 35 mg of complex 1-5 was obtained as yellow crystals, with a yield of 82%.

[0053] 1H NMR (400 MHz, Acetonitrile-d3) δ 8.72 (d, J = 6.5 Hz, 2H), 8.47-8.39 (m, 3H), 8.38-8.31 (m, 5H), 8.29-8.25 (m, 1H), 8.23-8.16 (m, 3H), 8.13 (d, J = 7.9 Hz, 2H), 8.10 (d, J = 5.8 Hz, 1H), 8.04-7.92 (m, 3H), 7.90 (dd, J = 8.2, 1.5 Hz, 1H), 7.81 (d, J = 8.1 Hz, 1H), 7.72-7.67 (m, 2H), 7.57-7.46 (m, 3H), 7.38 (dd, J = 18.3, 8.9 Hz, 2H), 7.24-7.15 (m, 3H), 7.15-7.08 (m, 2H), 6.84 (tt, J = 7.4, 1.5 Hz, 2H), 6.58-6.54 (m, 1H), 6.52-6.46 (m, 1H), 4.35 (s, 3H), 4.29 (s, 3H). MALDI-TOF MS: calcd. for [M-PF6-]+: 1307.3; found: 1308.0.

[0054] Example Two: Preparation of an Iridium (III) Complex (phenylpyridine ligand)

[0055] The structure of the iridium (III) complex is as follows:

[0056]

[0057] The specific synthesis route is as follows:

[0058]

[0059] (1) Preparation of compound 2-1: In this step, the molar amounts of 2,5-dibromophenylboronic acid, 4-bromo-2,2'-bipyridine, potassium carbonate, and tetrakis(triphenylphosphine)palladium are 2.36 mmol, 2.24 mmol, 5.40 mmol, and 0.25 mmol, respectively, and the remaining specific operations are the same as those in the preparation of compound 1-1 in Example 1.

[0060] 1H NMR (400 MHz, CD3Cl-d) δ 8.74-8.70 (m, 1H), 7.78 (td, J = 7.7, 1.8 Hz, 1H), 7.69 (d, J = 2.5 Hz, 1H), 7.60 (dt, J = 7.9, 1.1 Hz, 1H), 7.53 (d, J = 8.5 Hz, 1H), 7.38 (dd, J = 8.5, 2.5 Hz, 1H), 7.32 (ddd, J = 7.6, 4.9, 1.2 Hz, 1H).

[0061] (2) Preparation of compound 2-2: In this step, the molar amounts of compound 2-1, potassium carbonate, tetrakis(triphenylphosphine)palladium were 8.65 mmol, 200 mmol, 21.25 mmol and 0.90 mmol, respectively, and the remaining specific operations were the same as those in the preparation of compound 1-2 in Example 1.

[0062] 1 H NMR (400 MHz, CD3Cl-d) δ 8.77-8.71 (m, 2H), 8.68 (d, J = 3.9 Hz, 1H), 8.56-8.50 (m, 3H), 8.49 (s, 1H), 8.44 (d, J = 8.1 Hz, 1H), 7.91-7.79 (m, 3H), 7.65-7.59 (m, 3H), 7.35 (ddd, J = 7.5, 4.8, 1.2 Hz, 1H), 7.20-7.14 (m, 2H), 6.97 (dd, J = 5.0, 1.8 Hz, 1H);

[0063] (3) Synthesis of cyclometalated iridium (III) chloride bridge dimer 2-3: 3.15 mmol of 2-phenylpyridine and 1.42 mmol of IrCl3·3H2O were taken into a two-necked flask, and nitrogen was blown in three times to remove oxygen. Then 9.0 mL of 2-ethoxyethanol and 3.0 mL of deionized water were injected. The device was placed in an oil bath, and the reaction was carried out at 110°C under dark for 24 h. After the reaction was completed, the flask was cooled to room temperature, 20 mL of deionized water was added to the flask, and then filtered. The filter residue was washed with a small amount of ethanol and dried in vacuum for 4 h. Finally, 490 mg of yellow solid product was obtained, which was compound 2-3, and the yield was 72.0%.

[0064] (4) Synthesis of compound 2-4: Under a nitrogen atmosphere, 0.32 mmol of compound 2-2 and 0.15 mmol of 2-(phenyl)pyridine dichloride bridge dimer (i.e. compound 2-3 prepared in the previous step) were dissolved in 15 mL of a mixture of methanol / dichloromethane (1:2, v / v), heated to 40°C, and stirred for 6 h. After the reaction was completed, the reaction solution was cooled to room temperature, and then 0.6 mmol of potassium hexafluorophosphate (KPF6) was added and stirred for 2 h. Then the solvent was removed, deionized water (30 mL) was added, and dichloromethane (20 mL x 3) was used for extraction. The organic phase was collected and dried over anhydrous magnesium sulfate. The crude product after removal of the solvent was separated and purified by silica gel column chromatography, and the eluent was dichloromethane / methanol (40:1, v / v). Finally, 32 mg of yellow solid product was obtained, which was compound 2-4, and the yield was 35.0%.

[0065] 1H NMR (400 MHz, CD3CN-d3) δ 8.80-8.76 (m, 2H), 8.69-8.64 (m, 2H), 8.31-8.25 (m, 2H), 8.10 (d, J = 2.2 Hz, 1H), 8.06 (d, J = 2.0 Hz, 1H), 8.01-7.96 (m, 3H), 7.96-7.91 (m, 2H), 7.91-7.85 (m, 1H), 7.85-7.76 (m, 3H), 7.76-7.70 (m, 2H), 7.67-7.62 (m, 2H), 7.61-7.55 (m, 2H), 7.55-7.48 (m, 2H), 7.30 (td, J = 7.6, 1.4 Hz, 1H), 7.24-7.17 (m, 2H), 7.11 (td, J = 7.3, 1.4 Hz, 2H), 7.01-6.94 (m, 2H), 6.56 (d, J = 1.3 Hz, 2H). MALDI-TOF MS: calcd. for [M-PF6-]+: 887.3; found: 887.6.

[0066] (5) Synthesis of complex 2-5: 0.02 mmol of complex 2-4 and 0.06 mmol of iodomethane were weighed into a two-necked flask, the apparatus was sealed, purged with nitrogen, and deoxygenated. 1 mL of dichloromethane was injected as solvent, and the reaction was carried out at 40 °C for 12 h under a nitrogen atmosphere. The solution was cooled to room temperature and evaporated under reduced pressure. The resulting solid was dissolved in 5 mL of saturated potassium hexafluorophosphate methanol solution, and stirred at room temperature for 2 h. A brown precipitate was observed, which was collected and washed with diethyl ether. Recrystallization was performed using acetonitrile / diethyl ether, the precipitate was filtered and dried, and finally 42 mg of complex 2-5 was obtained as yellow crystals in a yield of 86%.

[0067] 1H NMR (400 MHz, Acetonitrile-d3) δ 9.06 - 9.01 (m, 2H), 8.54 - 8.49 (m, 2H), 8.47 - 8.41 (m, 2H), 8.28 (dd, J = 7.8, 1.3 Hz, 2H), 8.10 (d, J = 1.9 Hz, 1H), 8.01 - 7.85 (m, 6H), 7.80 (td, J = 7.7, 1.3 Hz, 2H), 7.76 - 7.70 (m, 2H), 7.64 (dd, J = 7.6, 1.3 Hz, 2H), 7.59 (dd, J = 9.2, 1.9 Hz, 1H), 7.51 (ddd, J = 8.5, 7.7, 1.2 Hz, 1H), 7.30 (td, J = 7.6, 1.4 Hz, 1H), 7.24 - 7.17 (m, 2H), 7.11 (td, J = 7.4, 1.4 Hz, 2H), 7.01 - 6.94 (m, 3H), 6.56 (d, J = 1.2 Hz, 3H), 4.37 (s, 6H). MALDI-TOF MS: calcd. for [M-PF6-]+: 917.3; found: 917.8.

[0068] Test Example 1: Chemically reduced simulated electro-stimulated luminescence response

[0069] Using the complexes 1-5 and 2-5 prepared in two examples, the concentration of the solution was adjusted to 10 -5 The acetonitrile solution of the iridium complex of M, 2 times the equivalent of sodium borohydride acetonitrile solution was added dropwise to the cuvette, and after the reaction was complete, the phosphorescence emission spectrum before and after the addition of sodium borohydride was tested, and the excitation wavelength was 375 nm. The test results of complex 1-5 are shown in Figure 1-5a in the figure: Figure 1 As shown in Figure 1-5a in the figure: when there is no NaBH4, the maximum emission wavelength of the complex on the spectrometer is at 594 nm, the emission peak is low, and the luminescence intensity is weak. With the addition of two equivalents of NaBH4, the maximum emission wavelength does not shift significantly, but the complex exhibits a significant photoluminescence intensity change, and the emission peak of the complex at the maximum emission wavelength rises significantly, and the luminescence intensity increases. The test results of complex 2-5 are shown in Figure 2-5b in the figure: Figure 1 As shown in Figure 2-5b in the figure, the response to NaBH4 is consistent with complex 1-5, that is, with the addition of NaBH4, the emission peak of the complex rises significantly, and the luminescence intensity increases, but due to the different ligands from complex 1-5, the emission peak with increased intensity of this complex has a certain blue shift, and the wavelength is 559 nm.

[0070] Test Example 2: Electro-stimulated luminescence response film

[0071] ITO glass with length, width and thickness of 20 mm x 50 mm x 1.1 mm and surface resistance of 6 Ω / square millimeter was taken as the substrate, and the substrate was sequentially washed with water, ethanol and acetone by ultrasonic washing; 3 mg of complexes 1-5 and 2-5 prepared in the examples were respectively dissolved in 3 mL of 1-butyl-3-methylimidazolium hexafluorophosphate to configure iridium complex ionic liquid, 15 mg of tetrabutylammonium hexafluorophosphate electrolyte was added, and ultrasonic was performed for 30 min; 50 μL of the mixture was dropped on the glass substrate in a drop coating manner, and the mixture was left to stand at room temperature for 10 min; another piece of ITO glass was taken to conduct electrically conductive adhesion to form an electrically stimulated luminescence response sandwich device, and then the device was sealed and protected for electrically stimulated response experiment.

[0072] The device test results of the complex 1-5 synthesized in Example 1 are shown in the a small graph of Figure 2 The device was not observed to have obvious changes before and after applying a voltage of 1.5 V for 10 s by naked eye observation, but the device was observed to have a change from weak orange light to obviously yellow-green light with strong intensity under the condition of applying a voltage of 1.5 V under ultraviolet continuous irradiation, and the light intensity was observed to be weakened again by applying a reverse voltage. The emission spectrum of the complex was measured at the same time in the process, as shown in the a small graph of Figure 3 Before applying a voltage of 1.5 V, the emission wavelength of the complex was at 594 nm, and the light intensity was low; after applying a voltage of 1.5 V, the emission wavelength was almost unchanged, but the emission intensity was obviously increased; and after further applying a reverse voltage, the light intensity of the complex was decreased again.

[0073] The device test results of the complex 2-5 synthesized in Example 2 are shown in the b small graph of Figure 2 The emission spectrum is shown in the b small graph of Figure 3 Compared with the complex 1-5, the complex has the same luminescence response behavior, but due to the difference in the main ligand, the luminescence wavelength has a certain difference from the complex 1-5 in the whole electric stimulation process, and a blue shift occurs. After applying a voltage of 1.5 V, the emission intensity at 559 nm is obviously increased, and the yellow-green light is obviously enhanced, and after further applying a reverse voltage, the light intensity of the complex is decreased again.

[0074] Test Example 3: Information recording and information erasing device test

[0075] The complexes 1-5 and 2-5 prepared in two examples were respectively dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate, and tetrabutylammonium hexafluorophosphate was selected as the electrolyte, and the amount was consistent with that in Test Example 2. The above part was mixed as an active layer, and was dropped onto an indium tin oxide (ITO) glass with a length of 20 mm, a width of 50 mm, a thickness of 1.1 mm, and a surface resistance of 6 Ω / square millimeter, and another ITO glass with an A letter conductive part etched was used to cover, so as to make an information recording and encryption and decryption device in a thin film state.

[0076] The test results of the complex 1-5 are shown in the a small graph in Figure 4 Figure 1. Under the irradiation of a 375 nm ultraviolet flashlight, weak orange light was observed in the whole film without applying a voltage. When a 1.5 V voltage was applied for 10 s, under the irradiation of the 375 nm ultraviolet flashlight, orange light with a high light intensity was observed, and the letter A was realized. Further, after the positive and negative electrodes were replaced and a reverse -1.5 V voltage was applied for 10 s, the intensity of the orange light letter decreased, and the letter disappeared, and information erasure was realized.

[0077] The test results of the complex 2-5 are shown in the b small graph in Figure 4 Figure 2. Similar to the complex 1-5, when a 1.5 V voltage was applied for 10 s, under the irradiation of the ultraviolet flashlight, yellow-green light with a high light intensity was observed, and the letter A gradually disappeared after a reverse -1.5 V voltage was applied for 10 s.

[0078] Test Example 4: Cyclic voltammetry test

[0079] In order to prove that the complex of this type has good reversibility and chemical stability, the complexes 1-5 and 2-5 prepared in two examples were subjected to cyclic voltammetry test. Since the reversibility depends on the reversible oxidation and reduction of the viologen unit, here, the reversible oxidation and reduction peaks of the viologen unit in the compound were subjected to 50 cycles of stability scanning. The electrochemical measurement was performed on an electrochemical workstation CHI660E. A platinum column electrode was used as a counter electrode; a glassy carbon electrode and an Ag / AgNO3 (dissolved in CH3CN at a concentration of 0.1 mol dm -3 -5) electrode were used as a working electrode and a reference electrode, respectively. All the electrochemical test solutions were deoxygenated by using argon. The electrochemical test used ferrocene as an internal standard, and all the potentials were finally corrected with reference to a standard calomel electrode (SCE). The test results are shown in the a small graph (complex 1-5) and the b small graph (complex 2-5) in Figure 5 Figure 3. It can be found that during the 50 cycles of redox cycles, the oxidation and reduction peaks of the methyl viologen do not fluctuate obviously. Considering the complex redox environment of the complex itself, this phenomenon can prove that the methyl viologen unit of the two example complexes has good reversible cycle stability.

[0080] The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which are made by using the content of the present application specification and drawings, are also included in the patent protection scope of the present application.

Claims

1. A class of iridium(III) complexes exhibiting low-voltage phosphorescent switching response, characterized in that, It is formed by bridging a single benzene ring with a methyl viologen unit to form an electroresponsive unit N^N ligand, and then coordinating this N^N ligand to an iridium complex with different C^N ligands. The general structural formula of this type of complex is as follows: The C^N ligand can be any one of the following: 。 2. The method for preparing an iridium(III) complex with low-voltage phosphorescent switching response as described in claim 1, characterized in that, The specific synthesis route is as follows: 。 3. The method for preparing an iridium(III) complex with low-voltage phosphorescent switching response as described in claim 2, characterized in that, The preparation steps are as follows: C^N ligand compounds were mixed with iridium trichloride trihydrate in a molar ratio of 2:1 to 2.5:1 and then injected into a solvent under an inert environment. After the reaction in an oil bath, cyclometalated iridium(III) chloride-bridged dimers were obtained. Compound 1 was obtained by using 2,5-dibromophenylboronic acid and 4-bromo-2,2'-bipyridine in a molar ratio of 1:1 to 1.5:1 via a Suzuki coupling reaction. Compound 2 was obtained by reacting compound 1 with 4-pyridineboronic acid in a molar ratio of 1:2 to 1:2.5 via a Suzuki coupling reaction; Compound 2 and different cyclometalated iridium(III) chloride-bridged dimers were coordinated in a molar ratio of 2:1 to 2.5:1 to obtain complex 3; Iodomethane was nucleophilically substituted with complex 3 in a molar ratio of 2:1 to 3:1, and then ion-exchanged with potassium hexafluorophosphate to obtain the final product, iridium(III) complex. The C^N ligand compound is any one of the following structures: 。 4. The application of an iridium(III) complex with low-voltage phosphorescent switching response as described in claim 1 in information recording devices, characterized in that, An iridium (III) complex is made into an iridium (III) complex film. A conductive region of a specific shape is etched on one side of the substrate of the film. When no voltage is applied, a weak light emission signal can be observed with the naked eye under ultraviolet excitation. When a positive voltage is applied, the recorded information with enhanced light emission intensity can be observed with the naked eye under ultraviolet excitation. When a reverse voltage is applied, the recorded information is erased, achieving reversibility.

5. The application of an iridium(III) complex with low-voltage phosphorescent switching response as described in claim 4 in information recording devices, characterized in that, The specific information regarding the applied voltage is as follows: a forward voltage of 1.5 V for 10 s allows for the observation of recorded information under ultraviolet excitation; a reverse voltage of -1.5 V for 10 s erases the recorded information, thus achieving reversibility.

6. The application of an iridium(III) complex with low-voltage phosphorescent switching response as described in claim 4 in information recording devices, characterized in that, The preparation process of the iridium (III) complex film is as follows: the iridium (III) complex is dissolved in 1-butyl-3-methylimidazolium-hexafluorophosphate, tetrabutylammonium hexafluorophosphate is selected as the electrolyte, the above part is mixed as the active layer, and drop-coated onto the substrate. Another substrate with a specific shape is used to cover it, allowing the etched part to conduct electricity, thus forming a thin film.

Images