Tris-cyclometalated iridium (iii) complexes containing viologen units, and methods of making and using the same

Abstract

The application belongs to the technical field of organic photoelectric material, and discloses a kind of tricyclic metal iridium (III) complex containing viologen unit and a preparation method and application thereof, and the iridium (III) complex is composed of two ring metal C^N ligands with strong electron-withdrawing effect modification and a C^N ligand with electroactive viologen substituent group;Two ring metal C^N ligands are modified by electron-withdrawing group to regulate the orbital energy level of iridium (III) complex, reduce the emission energy, promote the near-infrared luminescence of the complex before electric stimulation, utilize the strong electron-withdrawing ability and reversible redox characteristics of viologen substituent group, combine the rich excited state properties of iridium (III) complex, under electric stimulation, the reversible redox reaction of iridium (III) complex occurs, and the electric stimulation phosphorescence response of the material is realized;With the electron-donating property of viologen unit after electric reduction, the transition mode of iridium complex is changed, and the C^N ligand containing viologen substituent group is forced to participate in the excited state transition, realizing the luminescence conversion from near-infrared light to visible light.

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronic materials technology, specifically relating to the preparation and application of a class of near-infrared-visible photo-stimulated phosphorescent tricyclic metallic iridium(III) complexes containing viologen units. Background Technology

[0002] Electrostimulated phosphorescent responsive materials can undergo a transformation in their luminescence properties under electrical stimulation, exhibiting advantages such as low energy consumption, low manufacturing cost, ease of processing and molding, and easy integration into electronic devices. This has led to their widespread application in sensors, smart displays, information storage, and information security. Electrostimulated phosphorescent responsive materials generally consist of an electroresponsive unit and a luminescent host. The electro-oxidation and reduction of the electroresponsive unit further influences the luminescence properties of the luminescent host, achieving an electrostimulation-induced luminescence response. Among numerous organic electroresponsive units, viologen and its derivatives are widely used in various electrostimulation-responsive materials due to their abundant redox states and good redox reversibility. Furthermore, viologen can undergo both single-electron and two-electron reduction under an applied electric field, exhibiting significant differences in electron-donating and electron-withdrawing properties before and after reduction, which can greatly influence the molecules to which it is attached. Therefore, viologen can be used in the preparation of electrostimulation-induced luminescence-responsive materials.

[0003] Phosphorescent iridium(III) complexes possess large Stokes shifts, high luminescence quantum yields, and broad visible light absorption bands, and their emission properties are easily tunable. They have attracted widespread attention over the past 30 years as a class of luminescent hosts with excellent properties, high tunability, and a wide wavelength range. Therefore, by introducing viologen units with strong electron-trapping capabilities into iridium(III) complexes, and relying on the redox reaction of the viologen units under an electric field, the electrostimulated phosphorescence response of the iridium(III) complexes can be achieved.

[0004] For example, our research group previously disclosed a type of electrostimulation-responsive iridium(III) complex in patent document CN113278035 B. This complex is constructed by modifying ethylpyridinium salt units at different sites on the benzene or pyridine rings of the C^N ligands of the complex to form viologen ligands, and then introducing electron-withdrawing amide groups or electron-donating methyl groups onto the N^N ligands. It mainly utilizes the reversible redox properties of the viologen structure, combined with the influence of electron-donating or electron-withdrawing groups on the electron transfer state of the complex. Under external stimulation, the electron transfer state of the iridium(III) complex is changed, thereby changing the photophysical properties of the complex. This can achieve a visible change in light color, which can be applied to the fields of information storage and encryption. However, the visible light color change of the electrostimulation-responsive device prepared using this method is not very significant, and the wavelength change range is limited. It is difficult to significantly distinguish the changes in luminous information before and after energization, which is not conducive to information storage and encryption identification.

[0005] For example, another patent document previously published by our research group, CN105237578B, describes an ionic transition metal complex containing viologen derivatives. Although it can achieve a visible light-emitting process under electrical stimulation, the applied voltage is as high as 10V, and it is in a light-emitting off state before electrical stimulation. The instrument cannot detect the relevant photophysical data, which is not conducive to the application of low-energy information display, storage, and security devices. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a class of tricyclic metallic iridium(III) complexes containing viologen units, their preparation methods, and applications. The tricyclic metallic iridium(III) complexes containing viologen units can achieve phosphorescence response with a large wavelength change from near-infrared to visible light under photoelectric stimulation under low-energy conditions.

[0007] Common phosphorescent metal iridium(III) complexes include two types: tricyclic metal ligand iridium(III) complexes and bicyclic metal ligand iridium(III) complexes. The former is formed by the coordination of three phenylquinoline and its derivative ligands with the iridium metal center. Under this coordination mode, the excited state has a relatively clear metal ligand charge transfer mode (MLCT). The emission state can be precisely controlled by regulating the electron-donating and electron-withdrawing properties of the phenylquinoline ligand. Therefore, this application introduces electron-withdrawing groups on two of the phenylpyridine ligands to form cyclic metal C^N ligands with strong electron-withdrawing effects, thereby reducing the emission band gap and tuning the emission wavelength of the complex to the near-infrared region. At the same time, another phenylpyridine ligand is introduced into the viologen unit as a C^N ligand with an electroactive viologen substituent to achieve electrostimulation. By utilizing the strong electron-withdrawing ability and reversible redox properties of the viologen substituent combined with the rich excited-state properties of the iridium(III) complex, the iridium(III) complex undergoes a reversible redox reaction under electrostimulation, realizing the electrostimulation phosphorescence response of the material. In addition, by taking advantage of the electron-donating properties after the electroreduction of the viologen unit, the transition mode of the iridium complex is changed, forcing the C^N ligand containing the viologen substituent to participate in the excited-state transition, realizing the emission conversion from near-infrared light to visible light after electrostimulation of the complex. This application uses a tricyclic metal ligand iridium(III) complex as the luminescent host. Under electric field stimulation, the material can achieve wavelength switching from invisible near-infrared to visible light. This wavelength change is as high as 150nm or more, which has excellent resolution. Moreover, the near-infrared emission before power-on cannot be detected by the naked eye. The information encryption and decryption process can be realized by instruments, which can be used for information confidentiality and anti-counterfeiting.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A class of tricyclic metallic iridium(III) complexes containing viologen units exhibit electrostimulation phosphorescence response properties. The structural formula of the tricyclic metallic iridium(III) complex is as follows:

[0010]

[0011] The C^N ligand can be any one of the following, where * indicates the linkage site:

[0012]

[0013] This invention also provides a method for preparing the above-mentioned tricyclic metallic iridium(III) complex, the synthetic route of which is as follows:

[0014]

[0015]

[0016] The specific preparation steps include: coordinating the C^N ligand compound with iridium trichloride trihydrate in a molar ratio of 2:1 to 2.5:1 to obtain a cyclometalated iridium(III) chloride-bridged dimer [(C^N)2Ir(m-Cl)2Ir(C^-N)2]; using 4-bromophenylboronic acid and 2,5-dibromopyridine in a molar ratio of 2:1 to 3:1 to obtain intermediate compound 1 via a Suzuki coupling reaction; coordinating intermediate compound 1 with the cyclometalated iridium(III) chloride-bridged dimer in a molar ratio of 2:1 to 2.5:1 to obtain intermediate compound 2; using intermediate compound 2 with 4-pyridineboronic acid in a molar ratio of 1:2 to 1:2.5 via a Suzuki coupling reaction to obtain intermediate compound 3; and nucleophilically substituting intermediate compound 2 with iodomethane in a molar ratio of 2:1 to 3:1 followed by ion exchange with KPF6 to obtain iridium(III) complex 4.

[0017] The C^N ligand compound is Any one of them.

[0018] Thirdly, the present invention also provides the application of the above-mentioned tricyclic iridium(III) complex in the fabrication of an electrostimulated luminescent device. The application involves using the tricyclic iridium(III) complex as the active layer material of the electrostimulated luminescent device. As a preferred embodiment, the application specifically includes the following steps: a simple sandwich-shaped device is prepared by stacking two indium tin oxide (ITO) glasses and the complex material active layer; the tricyclic iridium(III) complex is dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate, using tetrabutylammonium hexafluorophosphate as the electrolyte; the above-mentioned tricyclic iridium(III) complex, 1-butyl-3-methylimidazolium hexafluorophosphate, and the electrolyte are mixed to form the active layer, which is then drop-coated onto indium tin oxide (ITO) glass and covered with another ITO glass. This process yields a sandwich-shaped electrostimulated luminescent device. An electrostimulated luminescent response of the complex active layer is achieved by applying a voltage through electrodes clamped on the ITO glass, and the process is reversible by applying a reverse voltage.

[0019] Preferably, the ITO glass is a substrate that has undergone ultrasonic washing pretreatment and has a surface resistivity of 6 Ω / mm².

[0020] Preferably, the mass-to-volume ratio of the tricyclic iridium(III) complex to the 1-butyl-3-methylimidazolium-hexafluorophosphate is 1 mg: 1 mL;

[0021] Preferably, the volume-to-mass ratio of the iridium complex solution to the tetrabutylammonium hexafluorophosphate is 1 mL: 15 mg.

[0022] Preferably, the thickness of the film formed after the active layer is drop-coated is 0.5 mm.

[0023] Fourthly, this invention also provides the application of the aforementioned tricyclic iridium(III) complex in information encryption and anti-counterfeiting. Referring to the fabrication of a sandwich electrostimulation luminescent response device, one of the ITO glass pieces is replaced with an ITO glass cover etched with a specific shape, allowing the etched area to conduct electricity as encrypted information. Before voltage is applied, the entire information recording device is colorless and transparent to the naked eye, and the encrypted information is not visible to the naked eye under ultraviolet excitation. After voltage is applied, no change is observed under sunlight, but the encrypted information is gradually observed to appear within seconds under ultraviolet irradiation. This process can be reversible by applying a reverse voltage to erase the encrypted information. Furthermore, by using a near-infrared camera, the near-infrared encrypted information can be decrypted before power is applied.

[0024] Preferably, the applied voltage is specifically a 3V voltage applied for 10s, and the applied reverse voltage is specifically a -3V voltage applied for 10s.

[0025] The beneficial effects of this invention are as follows: By introducing viologen units into a class of tricyclic iridium(III) complexes containing viologen units, this invention utilizes the reversible redox properties to construct an electrically controlled phosphorescent switch. Furthermore, the emission wavelength is modulated by electron-withdrawing substituents with a specific structure provided by this invention. This allows the tricyclic iridium(III) complexes provided by this invention to achieve a significant switching of emission wavelengths from near-infrared to visible light under a relatively low electric field (3V), thereby achieving information security and anti-counterfeiting. It can be used to prepare electrically stimulated phosphorescent response devices and information security and anti-counterfeiting devices. Moreover, the synthesis steps of the tricyclic iridium(III) complexes containing viologen units provided by this invention are simple, and can be completed through mature dichlorobridge reactions, coordination reactions, and substitution reactions. Attached Figure Description

[0026] Figure 1a The emission spectra of the iridium(III) complex prepared in Example 1 in acetonitrile solution before and after the addition of sodium borohydride are shown.

[0027] Figure 1bThe emission spectra of the iridium(III) complex prepared in Example 2 in acetonitrile solution before and after the addition of sodium borohydride are shown.

[0028] Figure 2a The images show the device effects of the iridium(III) complex prepared in Example 1 before and after energizing in the thin film state;

[0029] Figure 2b The images show the device effects of the iridium(III) complex prepared in Example 2 before and after energizing in the thin film state;

[0030] Figure 3a The emission spectra of the iridium(III) complex prepared in Example 1 before and after electrolysis in the thin film state are shown.

[0031] Figure 3b The emission spectra of the iridium(III) complex prepared in Example 2 before and after electrolysis in the thin film state are shown.

[0032] Figure 4 This is a diagram showing the effect of information recording and encryption / decryption devices using the iridium(III) complex prepared in Example 1 in thin film form. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention are further described below through specific embodiments and accompanying drawings, but should not be construed as limiting the present invention. Modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the essence of the present invention are all within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0034] The sources of raw materials involved in the following embodiments are as follows:

[0035]

[0036] Example 1

[0037] The molecular structure of the iridium(III) complex prepared in Example 1 is as follows:

[0038]

[0039] The synthetic route for this iridium(III) complex is as follows:

[0040]

[0041] The preparation method of this iridium(III) complex is as follows:

[0042] Step 1. Preparation of Compound 1-1: 3.00 mmol of 2,5-dibromopyridine, 7.60 mmol of 4-bromophenylboronic acid, 10.50 mmol of potassium carbonate, and 0.23 mmol of tetra(triphenylphosphine)palladium Pd(PPh3)4 were added to a reaction flask. The flask was protected from light, evacuated, and purged with nitrogen. This evacuation and purging process was repeated three times. Under a nitrogen atmosphere, 10 ml of deoxygenated tetrahydrofuran (THF) and 5 ml of deoxygenated water were sequentially added to the reaction flask, and the mixture was stirred until the solid was completely dissolved. The mixture was heated to 50°C and refluxed with stirring for 15 h. After the reaction was complete, the mixture was cooled to room temperature, the solvent was removed by vacuum distillation, and the organic phase was extracted with dichloromethane. The organic phase was concentrated and purified by silica gel column chromatography using dichloromethane / methanol (v / v = 80:1) as the eluent to obtain intermediate molecule 1-1 in 65% yield.

[0043] Step 2. Synthesis of cyclometalated iridium(III) chloride-bridged dimer 1-2: 3.12 mmol of 2-(2,4-difluorophenyl)pyridine and 1.42 mmol of IrCl3·3H2O were added to a two-necked flask. The mixture was deoxygenated three times under nitrogen. 9.0 mL of 2-ethoxyethanol (after deoxygenation under nitrogen for 20 minutes) and 3.0 mL of deionized water were then added. The apparatus was placed in an oil bath and heated to 110 °C for 24 h. After the reaction was complete, the apparatus was removed, and the flask was allowed to cool to room temperature. 20 mL of deionized water was added to the flask. The precipitate was filtered and washed with a small amount of ethanol. The precipitate was then placed in a vacuum drying oven and dried for 4 h. The final product was a yellow solid cyclometalated iridium(III) chloride-bridged dimer 1-2, with a yield of 76.0%.

[0044] Step 3. Synthesis of Complexes 1-3: Weigh 0.60 mmol of compound 2, 1.6 mmol of molecule 1-1, and 0.01 mmol of silver trifluoromethanesulfonate (AgOTf) into a round-bottom flask. Deoxygenate three times under nitrogen purging. Add 7 mL of 2-ethoxyethanol (deoxygenated for 20 minutes). Protect the apparatus from light, place it in an oil bath, and heat to 120 °C under a nitrogen atmosphere. Stir and reflux for 18 h. After the reaction, allow to cool naturally to room temperature. Add 20 mL of deionized water to the flask, filter the precipitate, wash with a small amount of ethanol, and place in a vacuum drying oven to dry for 4 h. Purify the precipitate using rapid silica gel column chromatography with dichloromethane as the eluent. Dry the pure product in a vacuum drying oven for 4 h to obtain a yellow powder, complex 1-3, with a yield of 75%. MALDI-TOF MS: calcd. for [M] + :884.5; found:885.5.

[0045] Step 4. Synthesis of complexes 1-4: 0.32 mmol of complex 3, 0.66 mmol of 4-pyridineboronic acid, 1.60 mmol of potassium carbonate, and 0.06 mmol of tetra(triphenylphosphine)palladium were added to a reaction flask. The mixture was protected from light, evacuated, and purged with nitrogen for three cycles. Under a nitrogen atmosphere, 45.0 mL of toluene, 15.0 mL of ethanol, and 15.0 mL of deionized water were added sequentially to the reaction flask until the solid was completely dissolved. The mixture was heated to 80 °C and refluxed with stirring for 24 h. After the reaction was complete, the mixture was cooled to room temperature, and the solvent was removed by vacuum distillation. The mixture was extracted with dichloromethane and water, retaining the organic phase. A suitable amount of magnesium sulfate was added for drying, and the resulting anhydrous organic solution was obtained by filtration and evaporated to dryness. The solution was purified by silica gel column chromatography using dichloromethane / methanol (v / v = 50:1) as the eluent to obtain orange complexes 1-4 in 80% yield. 1 H NMR (400MHz, DMSO-d6, 25℃, TMS): δ (ppm): 8.61 (d, J = 6.3Hz, 2H), 8.54 (d, J = 6.1Hz, 2H), 8.45 (d, J = 8.6Hz, 1H), 8.35 (d ,J=8.5Hz,1H),8.29(dd,J=16.2,8.6Hz,2H),8.08(d,J=8.2Hz,1H),8.00(t,J=8.3Hz,1H),7.91(t,J=7.9Hz,1H),7.7 7(d,J=4.0Hz,1H),7.73(d,J=3.9Hz,1H),7.69(d,J=2.1Hz,1H),7.40(d,J=6.1Hz,2H),7.35(d,J=8.4Hz,1H),7.31(d ,J=6.0Hz,3H),7.23(t,J=6.6Hz,1H),6.94(d,J=1.9Hz,1H),6.80-6.72(m,1H),6.72-6.64(m,1H),6.21-6.12(m,2H). 13C NMR (100MHz, DMSO-d6, 25℃, TMS): δ (ppm): 165.8-164.8 (m), 162.1-161.5 (m), 160.2 (s), 150.9 ( s), 150.6 (s), 148.5 (d, J = 29.4Hz), 145.1 (d, J = 11.5Hz), 143.1 (s), 138.8 (d, J = 27.9Hz), 136.8 (s),133.5(s),132.7(s),128.2(d,J=8.5Hz),126.3(s),124.1(d,J=12.3Hz),123.3(t,J=21.4 Hz), 121.3 (s), 121.0 (s), 120.8 (s), 120.4 (s), 117.6 (dd, J = 25.7, 15.7Hz), 97.0 (q, J = 27.4Hz). 19 F NMR (376.5MHz, DMSO-d6, 25℃, TMS): δ (ppm): -109.22 (d, J = 9.6Hz), -109.37 (d, J = 9.6Hz), -109.95 (d, J = 9.3Hz), -110.18 (d, J = 9.6Hz).MALDI-TOF MS:calcd.for[M-PF6 - ] + :880.9; found:881.7.

[0046] Step 5. Synthesis of Complexes 1-5: 0.10 mmol of Complex 4 was added to a two-necked reaction flask, evacuated, and purged with nitrogen. 6 mL of acetonitrile was injected to completely dissolve the complex, followed by the addition of 0.25 mmol of iodomethane. The mixture was heated to 40 °C and reacted for 12 h. After reflux, the solution was cooled to room temperature and then evaporated to dryness. The resulting solid was dissolved in 50 mL of a saturated potassium hexafluorophosphate methanol solution and stirred at room temperature for 2 h. After filtration, the solid was recrystallized from acetonitrile and diethyl ether. The precipitate was filtered and dried to obtain the final product, Complexes 1-5, with a yield of 82%. 1H NMR(400MHz,CD3CN,25℃,TMS):δ(ppm):8.56(d,J=6.3Hz,2H),8.47(d,J=6.4Hz,2H),8.40(d,J=8.5Hz,1H),8.33(dd,J=8.5,2.0Hz,3H),8.10(d,J=8.3Hz,1H),7.96(d,J=2.0Hz,1H),7.94-7.90(m,4H),7.89-7.81(m,2H),7.80(d,J=4.9Hz,1H),7.72(d,J=5.2Hz,1H),7.51(dd,J=8.3,2.1Hz,1H),7.20(d,J=2.1Hz,1H),7.17-7.13(m,1H),7.11-7.06(m,1H),6.60-6.40(m,2H),6.23(dd,J=9.4,2.5Hz,1H),6.14(dd,J=8.7,2.5Hz,1H),4.25(s,3H),4.21(s,3H). 13 C NMR(100MHz,CD3CN,25℃,TMS):δ(ppm):167.60(s),163.91-163.40(m),163.00-162.46(m),157.05(s),152.27(s),149.17(s),148.76(s),147.99(s),147.71(s),146.04(s),145.48(s),138.77(d,J=12.1Hz),137.89(s),135.93(s),135.54(s),130.60(s),128.92(d,J=38Hz),127.28(s),125.35(s),125.25(s),124.16-123.66(m),121.73(s),121.54(s),97.29(t,J=27.2Hz),48.42(s),47.93(s). 19 F NMR(376.5MHz,CD3CN,25℃,TMS):δ(ppm):-72.87(d,J=704.1Hz),-110.61(d,J=9.7Hz),-111.01(q,J=9.8Hz),-111.11(d,J=9.8Hz).MALDI-TOF MS:calcd.for[M-PF6 - ] + :1056.0;found:1056.8.calcd.for[M-2PF6 - ] +:911.0; .found:911.7.

[0047] Example 2

[0048] The molecular structure of the iridium(III) complex prepared in Example 2 is as follows:

[0049]

[0050] The synthetic route for this iridium(III) complex is as follows:

[0051]

[0052] The preparation method of this iridium(III) complex is as follows:

[0053] Step 1. In this step, the amounts of 2,5-dibromopyridine, 4-bromophenylboronic acid, potassium carbonate, and tetra(triphenylphosphine)palladium are 3.00 mmol, 7.50 mmol, 10.00 mmol, and 0.25 mmol, respectively. The remaining specific operations are the same as in Step 1 of Example 1.

[0054] Step 2. Synthesis of cyclometalated iridium(III) chloride-bridged dimer 2-2: 3.12 mmol of 2-[4-(trifluoromethyl)phenyl]pyridine and 1.42 mmol of IrCl3·3H2O were added to a two-necked flask. The mixture was deoxygenated three times under nitrogen. 9.0 mL of 2-ethoxyethanol and 3.0 mL of deionized water (after deoxygenation under nitrogen for 20 minutes) were then added. The apparatus was placed in an oil bath and heated to 110 °C for 24 h. After the reaction was complete, the apparatus was removed, and the flask was allowed to cool to room temperature. 20 mL of deionized water was added to the flask. The precipitate was filtered and washed with a small amount of ethanol. The precipitate was then placed in a vacuum drying oven and dried for 4 h. The final product was yellow cyclometalated iridium(III) chloride-bridged dimer 2, with a yield of 74.0%.

[0055] Step 3. In this step, the molar amounts of cyclometalated iridium(III) chloride bridged dimer 2-2 and molecule 2-1 are 0.60 mmol and 1.6 mmol, respectively, and the remaining specific operations are the same as in step 3 of Example 1; the yield of intermediate 2-3 is 65.0%;

[0056] Step 4. In this step, the molar amounts of complex 2-3,4-pyridineboronic acid, potassium carbonate, and tetra(triphenylphosphine)palladium are 0.32 mmol, 0.66 mmol, 1.6 mmol, and 0.06 mmol, respectively. The remaining specific operations are the same as in step 4 of Example 1; the yield of the intermediate product 2-4 is 77.0%. 1HNMR(400MHz, DMSO-d6)δ8.60(d,J=5.2Hz,2H),8.50(d,J=5.2Hz,2H),8.44-8.25(m,4H),8.08-7.96(m,4H),7.93(t,1H),7 .81(d,J=5.5Hz,1H),7.74(s,2H),7.41-7.23(m,7H),7.19(t,J=9.3Hz,2H),7.01(s,1H),6.92(d,J=13.0Hz,2H).MALDI-TOF MS:calcd.for[M] + :945.2; found:945.0.

[0057] Step 5. In this step, the molar amounts of iodomethane in complexes 2-4 were 0.10 mmol and 0.25 mmol, respectively. The remaining specific operations were the same as in Step 5 of Example 1. The yield of product 2-5 was 92.5%. ¹H NMR (400 MHz, CD3CN, 25C, TMS): δ=8.76(dt, J=4.9, 1.3 Hz, 1H), 8.23(dd, J=4.4, 2.6 Hz, 2H), 8.02(d, J=1.8 Hz, 1H), 7.88(s, 1H), 7.86(s, 1H), 7.65(s, 1H), 7.63(s, 1H), 7.57(dd, J=2.8, 1.1 Hz, 1H), 7.55(d, J=1.1 Hz, 0H), 3.40(s, 2H) ppm. MALDI-TOF MS: calcd. for [M] + :975.2; found:974.8.

[0058] Test example: Chemical reduction simulating electrostimulation luminescence response

[0059] The final products prepared in Examples 1 and 2 were used as iridium complexes, and a concentration of 10 was prepared. -4 An acetonitrile solution of the M-iridium complex was pipetted into a cuvette. Two times the equivalent amount of sodium borohydride was added to the cuvette, and the reaction was allowed to proceed fully. The phosphorescence emission spectra were then measured with and without sodium borohydride, at an excitation wavelength of 405 nm. The test results for the iridium complex in Example 1 are as follows: Figure 1a As shown: In the absence of NaBH4, the complex exhibits near-infrared luminescence on the spectrometer. With the addition of two equivalents of NaBH4, the complex shows a significant change in photoluminescence wavelength, with the maximum emission wavelength shifting to 574 nm. It can be seen that the difference in the maximum emission wavelength between the presence and absence of NaBH4 is 169 nm. The test results of the iridium complex in Example 2 are as follows... Figure 1bAs shown, with the addition of twice the equivalent of NaBH4 in the complex, the complex exhibits a significant change in photoluminescence wavelength, shifting from the initial near-infrared emission wavelength of 719 nm to the visible wavelength of 569 nm, with a maximum wavelength difference of 150 nm.

[0060] Test Example: Electrical Stimulation Response Experiment of Iridium Complex Thin Films

[0061] An ITO glass substrate with dimensions of 20 mm × 50 mm × 1.1 mm and a surface resistivity of 6 Ω / mm² was ultrasonically cleaned using water, ethanol, and acetone sequentially for 15 min. An iridium complex solution was prepared by dissolving 3 mg of complex 5 in 3 mL of 1-butyl-3-methylimidazolium-hexafluorophosphate BMIM-PF6. 15 mg of tetrabutylammonium hexafluorophosphate electrolyte was added to 1 mL of the iridium complex 1-5 and iridium complex 2-5 solutions from Examples 1 and 2, and the mixture was ultrasonicated for 30 min. 50 μL of the mixture was then dropped onto the glass substrate using a drop-coating method, resulting in a film thickness of approximately 0.5 mm. The film was allowed to stand at room temperature for 10 min. The conductive side of another ITO glass piece was then bonded together to fabricate an electrostimulation-responsive device, which was subsequently sealed for protection and used in electrostimulation-responsive experiments.

[0062] The test results of complexes 1-5 are as follows: Figure 2a As shown: Under sunlight irradiation, no significant change was observed in the electrostimulated luminescent device after applying a 3V voltage for 10 seconds. However, under continuous ultraviolet irradiation, applying a 3V voltage resulted in a gradual change from unobservable emission to noticeable yellow-green emission. During this process, the emission spectrum of the complex was simultaneously measured. The data showed that before applying the 3V voltage, the emission wavelength of the complex was at 674nm, with most of the wavelength in the near-infrared band, making emission almost unobservable. After applying the 3V voltage, the emission wavelength shifted to 509nm. Figure 3a As shown.

[0063] The test results of complex 2-5 are as follows Figure 2b As shown: The luminescence changes at 0V and 3V under sunlight and continuous ultraviolet irradiation are similar to those of complexes 1-5. Reading the thin film spectral data reveals that before applying 3V, the emission wavelength of the complex is at 693nm, with most wavelengths in the near-infrared band, making luminescence almost unobservable. However, after applying 3V, the emission wavelength shifts to 535nm. Figure 3b As shown.

[0064] Test Example: Experiment on recording, encrypting, and decrypting information in iridium complex thin films

[0065] Complexes 1-5 and 2-5 from Examples 1 and 2 were dissolved in 1-butyl-3-methylimidazolium-hexafluorophosphate. Tetrabutylammonium hexafluorophosphate was selected as the electrolyte. The mixture was used as the active layer and drop-coated onto indium tin oxide (ITO) glass with a width and thickness of 20 mm × 50 mm × 1.1 mm and a surface resistance of 6 Ω / mm². Another piece of ITO glass with the letter M etched on it was used to cover the surface, thus fabricating information recording and encryption / decryption devices in thin film state.

[0066] Test results are as follows Figure 4 As shown: For devices fabricated using complexes 1-5, when no voltage is applied, they exhibit near-infrared emission under 375nm UV lamp illumination, which is not visible to the naked eye. After applying a 3V voltage for 10 seconds, green luminescent letters appear under the same 375nm UV lamp illumination. No emission is observed around the letters, but by taking a picture with a near-infrared camera, the hidden near-infrared emission information around the letters can be captured, enabling information decryption. After further applying a reverse -3V voltage for 10 seconds, the green luminescent letters disappear. For devices fabricated using complexes 2-5, the thin film effect observed by the naked eye during the testing process is consistent with that of devices fabricated using complexes 1-5.

Claims

1. A class of tricyclic metallic iridium(III) complexes containing viologen units, characterized in that: The structural formula of the iridium(III) complex is: , The C^N ligand can be any one of the following, where * indicates the linkage site: 。 2. The method for preparing the tricyclic metallic iridium(III) complex according to claim 1, characterized in that, The synthetic route of the preparation method is as follows: ； ； The specific preparation steps include: coordinating the C^N ligand compound with iridium trichloride trihydrate in a molar ratio of 2:1 to 2.5:1 to obtain a cyclometalated iridium(III) chloride-bridged dimer [(C^N)2Ir(m-Cl)2Ir(C^N)2]; using 4-bromophenylboronic acid and 2,5-dibromopyridine in a molar ratio of 2:1 to 3:1 to obtain intermediate compound 1 via a Suzuki coupling reaction; coordinating intermediate compound 1 with the cyclometalated iridium(III) chloride-bridged dimer in a molar ratio of 2:1 to 2.5:1 to obtain intermediate compound 2; using intermediate compound 2 with 4-pyridineboronic acid in a molar ratio of 1:2 to 1:2.5 via a Suzuki coupling reaction to obtain intermediate compound 3; and then performing nucleophilic substitution of intermediate compound 3 with iodomethane in a molar ratio of 2:1 to 3:1 followed by ion exchange with KPF6 to obtain iridium(III) complex 4. The C^N ligand compound is Any one of them.

3. The application of the tricyclic metallic iridium(III) complex of claim 1 in the fabrication of electrostimulated luminescent devices, characterized in that, The application method is to use the tricyclic metallic iridium (III) complex of claim 1 as the active layer material of an electrostimulated luminescent device.

4. The application as described in claim 3, characterized in that, The specific application includes the following steps: dissolving the tricyclic iridium (III) complex in 1-butyl-3-methylimidazolium-hexafluorophosphate, using tetrabutylammonium hexafluorophosphate as the electrolyte, mixing the above tricyclic iridium (III) complex, 1-butyl-3-methylimidazolium-hexafluorophosphate and the above electrolyte as the active layer, drop-coating it onto indium tin oxide (ITO) glass, and covering it with another piece of ITO glass to prepare a sandwich electrostimulation luminescent response device.

5. The application as described in claim 4, characterized in that, The ITO glass is a substrate that has undergone ultrasonic washing pretreatment and has a surface resistivity of 6 Ω / mm².

6. The application as described in claim 4, characterized in that, The mass-to-volume ratio of the tricyclic iridium(III) complex to the 1-butyl-3-methylimidazolium-hexafluorophosphate is 1 mg:1 mL, and the volume-to-mass ratio of the iridium complex solution to the tetrabutylammonium hexafluorophosphate is 1 mL:15 mg.

7. The application as described in claim 4, characterized in that, The film thickness formed after the active layer is drop-coated is 0.5 mm.

8. The application of the tricyclic metallic iridium (III) complex of claim 1 in information encryption or anti-counterfeiting.

9. The application as described in claim 8, characterized in that, The specific application includes the following steps: dissolving the tricyclic iridium (III) complex in 1-butyl-3-methylimidazolium-hexafluorophosphate, using tetrabutylammonium hexafluorophosphate as the electrolyte, mixing the tricyclic iridium (III) complex, 1-butyl-3-methylimidazolium-hexafluorophosphate, and the electrolyte as the active layer, and drop-coating it onto indium tin oxide (ITO) glass. Then, an ITO glass cover with a specific etched shape is used, allowing the etched area to conduct electricity as encrypted information. Before applying voltage, the entire information recording device is colorless and transparent to the naked eye, and the encrypted information cannot be identified by the naked eye under ultraviolet excitation. After applying voltage, no change is observed under sunlight, but the encrypted information is gradually observed to appear within a few seconds under ultraviolet irradiation. The encrypted information can be erased by applying a reverse voltage to achieve reversibility. At the same time, a near-infrared camera is used to decrypt the near-infrared encrypted information before power-on.

10. The application as described in claim 9, characterized in that, The applied voltage is specifically a 3 V voltage applied for 10 s, and the applied reverse voltage is specifically a -3 V voltage applied for 10 s.

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