A mono- / binuclear iridium complex with anti-saturation absorption capability and its preparation method and application

Abstract

The present invention discloses a mono- / binuclear iridium complex with reverse saturation absorption capability and a preparation method and application thereof, belonging to the field of optical limiting materials. The primary purpose of the present invention is to provide a novel optical limiting material with reverse saturation absorption capability, and another purpose is to provide a preparation method of the mono- / binuclear iridium complex. The mono- / binuclear iridium complex prepared by the present invention is compared with a standard sample fullerene C 60 The comparison shows that they all have excellent anti-saturation absorption performance, and their optical limiting properties are significantly better than those of the standard sample. 2 When fullerene C 60 The energy density of the emitted light is 0.75 J / cm 2 (transmittance is 37.5%), while the output light energy density of the mononuclear iridium complex and the binuclear iridium complex is reduced to 0.45 J / cm 2 and 0.62 J / cm 2 (The transmittances are 22.5% and 31% respectively).

Description

Technical Field

[0001] The invention belongs to the field of optical limiting materials, and in particular relates to a mono- / binuclear iridium complex with anti-saturation absorption capability, and a preparation method and application thereof. Background Art

[0002] With the rapid development of laser technology, optoelectronic devices are increasingly exposed to strong laser environments and are extremely vulnerable to laser attacks. On the basis of ensuring the normal operation of these devices, it is an urgent problem to make them resistant to laser attacks. The development of high-performance strong laser protection materials is one of the main ways to achieve effective laser protection. Optical limiting materials can have both high transmittance for weak light and low transmittance for strong light at the same wavelength. They have obvious advantages in ultrafast response protection against high-energy, continuous wide-band lasers. They are currently recognized as the most practical laser protection materials. Among many material systems, metal organic complexes are considered to be one of the most effective optical limiting materials. They show good optical limiting performance in the visible light region and even the near-infrared region, with high damage threshold and short response time.

[0003] Cyclometallic iridium (Ir) complexes have been widely used as anti-saturable absorbers in the field of light-limiting materials in the past decade due to their advantages such as high intersystem crossing efficiency, long luminescence lifetime, good photostability and easy structural modification. Ir complexes have long-lived triplet excited states, whose excited state absorption is stronger than ground state absorption and have anti-saturable absorption ability, which makes iridium complexes widely studied as anti-saturable absorbers in the field of light-limiting materials. Although there have been many studies on iridium complexes, most reports focus on mononuclear iridium complexes. Dinuclear iridium complexes have not been fully explored due to (1) synthetic challenges and separation difficulties caused by isomerization reactions; (2) unpredictable properties related to complex intramolecular and intermolecular processes; (3) low emission quantum yields induced by non-radiative processes promoted by bridging ligands, and related research is still relatively limited. However, the feasible intramolecular π-π and metal-metal interactions in dinuclear iridium complexes are expected to change the properties and energies of singlet and triplet excited states, and have special photophysical properties. Based on this, the present invention explores the effect of increasing the number of metal centers on the excited state properties. By systematically studying the excited state properties and optical limiting performance of mono / binuclear iridium complexes, the difference between the structure and optical properties of mono / binuclear iridium complexes is revealed, and a new optical limiting material with excellent anti-saturation absorption performance is developed. Summary of the invention

[0004] The invention provides a mono- / binuclear iridium complex with reverse saturation absorption capability and a preparation method and application thereof. The prepared mono- / binuclear iridium complex has excellent reverse saturation absorption performance, and its optical limiting property is significantly better than that of a standard sample.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A mono- / binuclear iridium complex with anti-saturation absorption ability, named Mono-Ir and Di-Ir, respectively, has the following chemical structure:

[0007]

[0008] The method for preparing the above-mentioned mono- / binuclear iridium complex comprises the following steps:

[0009] (1) placing isatin, acetophenone and potassium hydroxide in a reaction bottle, keeping the reaction system oxygen-free, and carrying out a cycloaddition reaction at 75-85° C. in an alkaline environment for 46-50 hours to obtain 2-phenyl-4-quinolinecarboxylic acid;

[0010] (2) placing 2-phenyl-4-quinolinecarboxylic acid and anhydrous ethanol in a reaction bottle, keeping the reaction system oxygen-free, and carrying out an esterification reaction at 75 to 85° C. for 15 to 18 hours to obtain ethyl 2-phenyl-4-quinolinecarboxylate;

[0011] (3) dissolving the ethyl 2-phenyl-4-quinolinecarboxylate and iridium trichloride trihydrate in a solvent, keeping the reaction system oxygen-free, and performing a coordination reaction at 115 to 125° C. for 21 to 25 hours to obtain an iridium chloride dimer;

[0012] (4) dissolving the iridium chloride dimer and 2,2'-bipyrimidine in a solvent, keeping the reaction system oxygen-free, reacting at 55-65° C. for 22-25 hours to obtain the target mononuclear iridium complex Mono-Ir;

[0013] (5) dissolving the iridium chloride dimer and 2,2'-bipyrimidine in a solvent, increasing the amount of the iridium chloride dimer, keeping the reaction system oxygen-free, reacting at 55-65° C. for 22-28 hours to obtain the target binuclear iridium complex Di-Ir;

[0014] In the above steps, the reaction system is oxygen-free and preferably carried out under an argon atmosphere;

[0015] The molar ratio of indigo carmine to acetophenone in step (1) is 1:(1.1-1.3); the base used in the alkaline environment is preferably potassium hydroxide, potassium carbonate, potassium acetate; the molar ratio of indigo carmine to base is 1:(2.3-3.2)

[0016] In step (2), the ratio of 2-phenyl-4-quinolinecarboxylic acid to anhydrous ethanol is 1 g: (3-5) mL, the reaction solvent of the esterification reaction is toluene, and the volume ratio of anhydrous ethanol to toluene is 1: (1.3-1.7);

[0017] The molar ratio of ethyl 2-phenyl-4-quinolinecarboxylate to iridium trichloride trihydrate in step (3) is 1:(0.3-0.6); the solvent is a mixed solvent of water and 2-ethoxyethanol in a volume ratio of 1:(2.7-3.3), and the amount ratio of ethyl 2-phenyl-4-quinolinecarboxylate to water is 1 g:(8-15) mL;

[0018] The molar ratio of the iridium chloride dimer to 2,2'-bipyrimidine in step (4) is 1:(0.3-0.6); the solvent is a mixed solvent of methanol and dichloromethane in a volume ratio of 1:(1.7-2.4), and the amount ratio of the iridium chloride dimer to methanol is 1 g:(16-23) mL;

[0019] In step (5), the molar ratio of the iridium chloride dimer to 2,2'-bipyrimidine is 1:(0.9-1.2); the solvent is a mixed solvent of methanol and dichloromethane in a volume ratio of 1:(2.7-3.4), and the amount ratio of the iridium chloride dimer to methanol is 1g:(16-23)mL;

[0020] The above-mentioned mono- / binuclear iridium complex is applied in optical limiting materials.

[0021] Beneficial effects: The present invention provides a mono- / binuclear iridium complex with anti-saturation absorption capability and a preparation method and application thereof. Compared with the prior art, the present invention has the following advantages:

[0022] 1. The preparation method of the mono / bi-iridium complex of the present invention is simple, the raw materials are readily available, and the purification is convenient and easy to operate;

[0023] 2. The maximum emission wavelength of the mononuclear iridium complex Mono-Ir of the present invention in dichloromethane solution is located at 615nm, and it shows the characteristics of being sensitive to oxygen, indicating that the emission comes from the phosphorescence emission of its triplet excited state, and the emission of Mono-Ir in the solid state also comes from the phosphorescence emission of the triplet excited state; the binuclear iridium complex Di-Ir does not show obvious emission either in the deoxygenated dichloromethane solution or in the solid state;

[0024] 3. The molar absorption coefficient of the binuclear iridium complex Di-Ir of the present invention is significantly improved, which is almost twice that of the mononuclear iridium complex Mono-Ir. This is mainly attributed to the fact that the structures of Mono-Ir and Di-Ir are basically the same, and Di-Ir has a left-right symmetrical structure, and both parts have the same transition absorption as Mono-Ir;

[0025] 4. The iridium complex of the present invention has excellent triplet excited state performance. The triplet excited state lifetime of the mononuclear complex Mono-Ir at 530nm is about 385ns, while the lifetime of the binuclear complex Di-Ir is significantly extended, and its triplet excited state lifetime at 530nm reaches 3.8μs;

[0026] 5. The iridium complex of the present invention has excellent reverse saturation absorption performance, and exhibits a wide absorption peak in the entire visible light region and near infrared region, indicating that the excited state absorption of the complex is greater than the ground state absorption within this wavelength range. It also shows that within this spectral range, the two iridium complexes can undergo reverse saturation absorption, and the performance is much higher than that of the standard reference substance C 60 , excellent core performance;

[0027] 6. The iridium complex of the present invention is subjected to laser (535nm, 2.0J / cm 2 ) irradiation, it has a strong absorption capacity for laser, compared with the standard sample fullerene C 60 Under this condition, the transmittance is 37.5%. The transmittance of the mononuclear iridium complex can be reduced to 22.5%, and the transmittance of the binuclear iridium complex can be reduced to 31%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The synthetic route of the mono- / binuclear iridium complexes Mono-Ir and Di-Ir in the embodiments of the present invention;

[0029] Figure 2 The UV-visible absorption spectra of mono- and binuclear iridium complexes Mono-Ir and Di-Ir in dichloromethane solution (c = 1.0 × 10 -5 mol / L);

[0030] Figure 3 (a) Normalized emission spectra of the mononuclear iridium complex Mono-Ir in dichloromethane solution and solid state; (b) Phosphorescence emission spectra of the mononuclear iridium complex Mono-Ir in dichloromethane solution in nitrogen and air atmospheres;

[0031] Figure 4 The time-dependent transient absorption spectra of the mononuclear iridium complex Mono-Ir and the binuclear iridium complex Di-Ir in degassed toluene solution (c = 1×10 -5 mol / L,λex=355nm);

[0032] Figure 5 Under 532nm laser irradiation, the mononuclear iridium complex Mono-Ir, the binuclear complex Di-Ir and C 60 Incident light-outgoing light energy curve in dichloromethane solution. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0034] Example 1

[0035] like Figure 1 As shown, the preparation method of the mono- / binuclear iridium complex comprises the following steps:

[0036] Preparation of 2-phenyl-4-quinolinecarboxylic acid:

[0037] Indigo carmine (2.94 g), acetophenone (2.88 g) and potassium hydroxide (3.36 g) were placed in a 100 mL single-mouth bottle, and then 50 mL of anhydrous ethanol was added to dissolve the reactants. The mixture was stirred in an argon atmosphere, and the reaction system was refluxed at 80°C for 48 h. The reaction slowly turned into dark brown. After the reaction was completed, dilute hydrochloric acid (2 M) was slowly added dropwise under ice bath conditions to adjust the pH value to 5, and a brown solid was obtained by vacuum filtration;

[0038] Preparation of ethyl 2-phenyl-4-quinolinecarboxylate:

[0039] 2-Phenyl-4-quinolinecarboxylic acid (10 g) was added to a 250 mL two-necked flask, and 40 mL of anhydrous ethanol and 60 mL of toluene were added. The oxygen in the reaction system was removed under argon protection, and the reaction liquid temperature was raised to 80° C. and the reaction was carried out for 16 hours. After the reaction was completed, the reaction liquid was cooled to room temperature, and the mixed system was washed and extracted to obtain an organic phase, which was dried over anhydrous sodium sulfate, filtered, and the solvent was removed by distillation under reduced pressure to obtain a residue, which was purified by column chromatography (200-300 silica gel, eluent: petroleum ether / ethyl acetate=10 / 1, v / v) to obtain yellow oily liquid 2-phenyl-4-quinolinecarboxylic acid ethyl ester;

[0040] Preparation of iridium chloride dimer:

[0041] In a 100 mL round-bottomed double-necked flask, iridium trichloride trihydrate (1.27 g), ethyl 2-phenyl-4-quinolinecarboxylate (2 g), 2-ethoxyethanol (60 mL) and water (20 mL) were added. The oxygen in the reaction system was removed under an argon atmosphere. The reaction liquid temperature was raised to 120° C. and the reaction was continued for 24 h. The mixed system gradually turned into a deep red color. After the reaction was completed, the reaction mixture was completely cooled to room temperature and the solvent was removed by suction filtration to obtain a precipitate. The precipitate was then washed with water and ethanol to remove unreacted raw materials. The obtained solid was dried in a vacuum drying oven. Finally, a deep red solid powder was collected as the corresponding iridium chloride dimer.

[0042] Preparation of mononuclear iridium complex Mono-Ir:

[0043] The corresponding iridium chloride dimer (120 mg), 2,2'-bipyrimidine (26 mg), dichloromethane (20 mL), and methanol (10 mL) were added to a 100 mL two-necked flask, and the mixed system was refluxed at 60°C for 24 h under an argon atmosphere. After cooling, potassium hexafluorophosphate (0.5 g) was added and continued to stir for 1 h. After the reaction was completed, the mixed system was washed with saturated brine and extracted with dichloromethane to obtain an organic phase, and then the solvent was removed by distillation under reduced pressure to obtain a residue, which was purified by column chromatography (200-300 silica gel, eluent: dichloromethane / methanol=200 / 1, v / v) to obtain a red solid. The product was further purified by recrystallization from dichloromethane and n-hexane to obtain an orange-red crystalline solid powder; the nuclear magnetic resonance data are as follows:

[0044] 1 H NMR (400MHz, DMSO): δ = 9.16 (dd, J 1 =4.72Hz,J 2 =1.96Hz,2H),8.83(s,2H),8.45-8.40(m,4H),8.34(d,J=8.4Hz,2H),7.90(t,J=5.2Hz,2H),7.57-7.53(m,2H) ,7.28-7.22(m,6H),6.91(t,J=7.36Hz,2H),6.52(d,J=7.64Hz,2H),4.58-4.52(m,4H),1.47(t,J=7.16Hz,6H).

[0045] Preparation of binuclear iridium complex Di-Ir:

[0046] The corresponding dimer (240 mg), 2,2'-bipyrimidine (26 mg), dichloromethane (20 mL), and methanol (10 mL) were added to a 100 mL two-necked flask, and the mixed system was refluxed at 60 ° C for 24 h under an argon atmosphere. After cooling, potassium hexafluorophosphate (0.5 g) was added and stirred for 1 h. After the reaction, the mixed system was washed with saturated brine and extracted with dichloromethane to obtain an organic phase, and then the solvent was removed by vacuum distillation to obtain a residue, which was purified by column chromatography (200-300 silica gel, eluent: dichloromethane / methanol = 200 / 1, v / v) to obtain a brown solid. The product was further purified by recrystallization from dichloromethane and n-hexane to obtain a brown flaky solid; the nuclear magnetic resonance data are:

[0047] 1 H NMR (400MHz, CD 2 Cl 2): δ=8.70(d,J=5.52Hz,4H),8.66(s,4H),8.43(d,J=8.4Hz,4H),8.26(t,J=5.6Hz,2H),8.14(d,J=7.88Hz,4H),7.35-7.27( m,8H),6.86(t,J=7.36Hz,4H),6.55(d,J=3.64Hz,8H),6.37(d,J=7.68Hz,4H),4.69-4.52(m,8H),1.61(t,J=7.12Hz,12H).

[0048] Test 1:

[0049] The concentration is 1.0×10 -5 mol / L dichloromethane solution of mono- / binuclear iridium complexes Mono-Ir and Di-Ir; at room temperature, a baseline scan (range: 200-800nm) was performed on the blank solution of dichloromethane using a 1cm quartz cuvette. After background subtraction, the sample was configured with a concentration of 1×10 -5 mol / L dichloromethane solution was scanned, and then the data within a specific range were selected and plotted using Origin 2018 to obtain the UV-visible absorption spectra of the mono / binuclear iridium complexes Mono-Ir and Di-Ir in dichloromethane solution. Figure 2 As shown, the two iridium complexes exhibit highly similar ground-state absorption properties in dichloromethane solution.

[0050] The strong absorption peak between 280 nm and 410 nm can be attributed to the spin-allowed 1 π,π* transition; the complexes Mono-Ir and Di-Ir both have two strong absorptions at about 290nm and 365nm, which come from the cyclometal ligand and the bipyrimidine ligand respectively. 1 In addition, Di-Ir also exhibits a weak absorption peak at 324nm. Considering that Mono-Ir and Di-Ir have the same cyclometallated ligand and N^N ligand, the weak absorption peak at 324nm comes from the central π conjugated structure formed by the coordination of the pyrimidine ligand and the two iridium atoms. 1 π,π* absorption, these two complexes also show a wide weak absorption peak after 410nm, which mainly comes from the metal to ligand charge transfer (MLCT) transition absorption peak and the ligand to ligand charge transfer (LLCT) transition absorption peak. By comparing the peak shape and intensity of the absorption peak and comparing it with the previous iridium complex with similar structure, it can be seen that the strong absorption peak between 410nm-500nm mainly comes from the spin-allowed singlet charge transfer absorption peak ( 1 MLCT and 1LLCT), while the weaker absorption peak after 500nm mainly comes from the spin-forbidden triplet charge transfer absorption peak ( 3 MLCT and 3 LLCT). Compared with the complex Mono-Ir, the molar absorption coefficient of Di-Ir has been significantly improved, almost twice that of Mono-Ir. This is mainly attributed to the fact that the structures of Mono-Ir and Di-Ir are basically the same, while Di-Ir has a left-right symmetrical structure and both parts have the same transition absorption as Mono-Ir.

[0051] Test 2:

[0052] The concentration is 1.0×10 -5 mol / L dichloromethane solution of mono- and binuclear iridium complexes Mono-Ir and Di-Ir. At room temperature, a 1 cm quartz cuvette was used with a scanning range of 300-850 nm. The solution was then scanned for emission spectra, and data within a specific range was selected and plotted using Origin 2018 to obtain emission spectra of mono- and binuclear iridium complexes Mono-Ir and Di-Ir in dichloromethane solution.

[0053] like Figure 3As shown, the mononuclear iridium complex Mono-Ir exhibits obvious emission in the excited state, and its maximum emission wavelength in dichloromethane solution is located at 615nm, and it shows oxygen sensitivity. Compared with its luminescence intensity in air, the emission intensity of Mono-Ir in deoxygenated dichloromethane solution is enhanced by about four times, which indicates that the emission of Mono-Ir here comes from the phosphorescence emission of its triplet excited state. In addition, Mono-Ir still exhibits strong emission in the solid state, and compared with the luminescence properties in solution, the maximum emission wavelength and waveform under solid conditions have no obvious changes, which indicates that the emission of Mono-Ir in the solid state also comes from the phosphorescence emission of the triplet excited state. However, the binuclear iridium complex Di-Ir does not show obvious emission either in deoxygenated dichloromethane solution or in solid conditions. Considering the efficient spin-orbit coupling of iridium atoms, in Mono-Ir with only a single iridium atom, the molecule in the triplet excited state can easily return to the ground state through radiative transition, thereby generating phosphorescent emission; and for the complex Di-Ir, the further introduction of iridium atoms may increase the charge transfer (MMLCT) between metal to metal to ligand within the complex. In addition, after the two iridium atoms and the bipyrimidine ligands are coordinated, the π-conjugated system of the N^N ligand is increased, and the charge transfer between molecules is further increased under solid-state stacking conditions, which may cause the attenuation of the radiative transition path, resulting in the binuclear iridium complex Di-Ir having no obvious emission either in the deoxygenated dichloromethane solution or in the solid state.

[0054] Test 3:

[0055] The transient difference absorption spectrum and triplet excited state lifetime with nanosecond time resolution were measured using an Edinburgh Instruments LP980 laser flash photolysis spectrometer. -5 mol / L toluene solution of mono- and binuclear iridium complexes Mono-Ir and Di-Ir. All test solutions were degassed with argon bubbling for 20 minutes before each measurement. The Nd:YAG laser (Quantel Brilliant, pulse width ~4.1ns, 1Hz) equipped in the LP980 spectrometer was used as the excitation light source (λex = 355nm). The transient difference absorption spectra of the mono- and binuclear iridium complexes Mono-Ir and Di-Ir were scanned, and then the data within a specific range were selected for plotting, and the transient absorption spectra of the mono- and binuclear iridium complexes Y-1-Mono and Y-1-Di were obtained as shown in the figure. Figure 4 As shown, the triplet excited state lifetime is obtained by fitting calculation.

[0056] The introduction of iridium atoms can increase the intersystem crossing effect, so the molecule is more likely to transition from the singlet excited state to the triplet excited state, thereby changing the triplet excited state properties of the complex. Although the two iridium complexes exhibit similar ground state absorption spectra, their transient absorption spectra are different.

[0057] The two iridium complexes exhibit broad absorption peaks throughout the visible light region and near-infrared region, indicating that within this wavelength range, the excited state absorption of the complexes is greater than the ground state absorption. It also indicates that within this spectral range, the two iridium complexes can undergo reverse saturation absorption. It is worth noting that although the binuclear iridium complex Di-Ir exhibits stronger ground state absorption than the mononuclear iridium complex Mono-Ir, before 500nm, the transient absorption spectrum intensity of the binuclear iridium complex is much higher than that of the mononuclear iridium complex, indicating that the excited state absorption of Di-Ir in this band is much stronger than that of Mono-Ir. The broad excited state absorption of the two iridium complexes mainly comes from their triplet charge transfer absorption ( 3 MLCT / 3 LLCT). However, their triplet lifetimes are different. The triplet excited state lifetime of Mono-Ir at 530nm is about 385ns, which is similar to its phosphorescence emission lifetime; while the lifetime of Di-Ir is greatly extended, reaching 3.8μs at 530nm, which is much longer than that of the single-core Mono-Ir. The results show that increasing the number of iridium atoms can effectively enhance the triplet excited state absorption of the complex and extend the triplet excited state lifetime, which is more conducive to the improvement of the anti-saturation absorption performance.

[0058] Test 4:

[0059] In order to evaluate the optical limiting performance of the samples under the same conditions, fullerene C was selected 60 As a reference sample. At room temperature, the transmittance of all samples under 532nm laser is 80%. Mono-Ir and Di-Ir are dissolved in dichloromethane solution, and fullerene C 60 The samples were dispersed in a dry N,N-dimethylformamide solution by ultrasonic. The Nd:YAG laser was used as the excitation source, and a pulse laser with a wavelength of 532nm, a pulse width of 5ns, and a frequency of 10Hz was selected. The samples were placed in a sample cell with a width of 2mm. 60 The laser incident energy-transmitted energy test was performed. The spot diameter of the laser irradiated on the sample was 110 μm.

[0060] The experimental results of nonlinear transmittance are shown in Figure 5As shown in the figure, both iridium complexes exhibit good nonlinear characteristics under 532nm laser radiation. As the incident laser energy gradually increases, the transmittance gradually decreases, successfully achieving laser defense. 60 In comparison, the light limiting properties of the iridium complex are significantly better than those of the standard sample. When the incident light energy density reaches 2.0 J / cm 2 When fullerene C 60 The energy density of the emitted light is 0.75 J / cm 2 (transmittance is 37.5%), while the energy density of the emitted light of the mononuclear iridium complex Mono-Ir and the binuclear iridium complex Di-Ir is reduced to 0.45 J / cm 2 and 0.62 J / cm 2 (The transmittances are 22.5% and 31%, respectively). In addition, comparing the transmittances of Mono-Ir and Di-Ir under 532nm laser, the optical limiting performance of Di-Ir is not as good as that of the mononuclear complex Mono-Ir, but it is still better than that of fullerene C 60 Considering that the mononuclear iridium complex Mono-Ir has a high phosphorescence quantum efficiency, a part of the laser is absorbed and used as an excitation light source to produce obvious phosphorescence emission. This phosphorescence emission can consume part of the incident laser radiation, but on the other hand, it will also produce new pollution light sources, affecting the recognition and detection of the human eye during the laser defense process. In contrast, the binuclear iridium complex Di-Ir, although its optical limiting ability is slightly inferior to that of the mononuclear iridium complex Mono-Ir, is still better than the standard fullerene C 60 In addition, Di-Ir does not have obvious phosphorescence emission, which to a certain extent avoids the influence of additional light pollution and is also expected to play an application value in the field of new light limiting materials.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A mono- / binuclear iridium complex having anti-saturation absorption capability, characterized in that: The chemical structure of the mononuclear iridium complex is: ； The chemical structure of the binuclear iridium complex is: 。 2. The method for preparing the mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 1, characterized in that: The following steps are involved: (1) Place isotonic acid, acetophenone and potassium hydroxide in an anaerobic reaction system, and undergo a cycloaddition reaction at 75-85°C in an alkaline environment for 46-50 h to obtain 2-phenyl-4-quinolinecarboxylic acid; (2) placing 2-phenyl-4-quinolinecarboxylic acid and anhydrous ethanol in an anaerobic reaction system, and causing an esterification reaction at 75-85°C for 15-18 hours to obtain ethyl 2-phenyl-4-quinolinecarboxylate; (3) dissolving ethyl 2-phenyl-4-quinolinecarboxylate and iridium trichloride trihydrate in a solvent, keeping the reaction system oxygen-free, and carrying out coordination reaction at 115-125° C. for 21-25 h to obtain an iridium chloride dimer; (4) dissolving an iridium chloride dimer and 2,2'-bipyrimidine in a solvent, wherein the molar ratio of the iridium chloride dimer to 2,2'-bipyrimidine is 1:(0.3-0.6); keeping the reaction system oxygen-free, reacting at 55-65° C. for 22-25 hours to obtain a mononuclear iridium complex; (5) Dissolving the iridium chloride dimer and 2,2'-bipyrimidine in a solvent, wherein the molar ratio of the iridium chloride dimer to 2,2'-bipyrimidine is 1:(0.9-1.2); keeping the reaction system oxygen-free, reacting at 55-65° C. for 22-28 hours to obtain a binuclear iridium complex.

3. The method for preparing a mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 2, characterized in that: The oxygen-free state was carried out under an argon atmosphere.

4. The method for preparing the mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 2 or 3, characterized in that: The molar ratio of indigo carmine to acetophenone in step (1) is 1:(1.1-1.3); the molar ratio of indigo carmine to the base used in the alkaline environment is 1:(2.3-3.2).

5. The method for preparing the mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 4, characterized in that: The alkali used in the alkaline environment is potassium hydroxide, potassium carbonate or potassium acetate.

6. The method for preparing the mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 2 or 3, characterized in that: In step (2), the ratio of 2-phenyl-4-quinolinecarboxylic acid to anhydrous ethanol is 1 g: (3-5) mL, the reaction solvent of the esterification reaction is toluene, and the volume ratio of anhydrous ethanol to toluene is 1: (1.3-1.7).

7. The method for preparing the mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 2 or 3, characterized in that: The molar ratio of ethyl 2-phenyl-4-quinolinecarboxylate to iridium trichloride trihydrate in step (3) is 1:(0.3-0.6); the solvent is a mixed solvent of water and 2-ethoxyethanol in a volume ratio of 1:(2.7-3.3), and the amount ratio of ethyl 2-phenyl-4-quinolinecarboxylate to water is 1 g:(8-15) mL.

8. The method for preparing the mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 2 or 3, characterized in that: The solvent in step (4) is a mixed solvent of methanol and dichloromethane in a volume ratio of 1:(1.7-2.4), and the amount ratio of the iridium chloride dimer to methanol is 1 g:(16-23) mL.

9. The method for preparing the mono- / binuclear iridium complex having reverse saturation absorption capacity according to claim 2 or 3, characterized in that: The solvent in step (5) is a mixed solvent of methanol and dichloromethane in a volume ratio of 1:(2.7-3.4), and the dosage ratio of the iridium chloride dimer to methanol is 1 g:(16-23) mL.

10. The mono- / binuclear iridium complex with reverse saturation absorption capability as claimed in claim 1 is used in optical limiting materials.

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