An organoiridium metal complex with photo-switching properties, its preparation method and application

Abstract

This invention discloses a photo-switching organoiridium metal complex, its preparation method, and its applications, belonging to the field of photoisomerization materials technology. This invention involves forming an N^N ligand through a Sonogashira coupling reaction between alkynyl spiropyran and phenanthroline, and finally coordinating with a bridging ligand to form a photo-switching organoiridium metal complex. This photo-switching iridium metal material combines nonlinear optical materials with photoisomerizing spiropyran molecules, exhibiting excellent optical limiting performance, good photothermal stability, photoisomerization characteristics, fatigue resistance, bleaching resistance, and excellent laser protection performance. Furthermore, after ultraviolet irradiation, the expansion of the complex's conjugation degree due to the ring-opening of the spiropyran molecule further enhances its laser protection performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoisomerization materials, and particularly relates to an organic iridium metal complex with photo-switching characteristics and a preparation method and application thereof. BACKGROUND

[0002] With the gradual maturity of laser weapons, it is particularly important to protect the human eye, lenses and light-sensitive sensor equipment from laser damage. At present, pure organic small molecules, metal-organic complexes, fullerene carbon C60, graphene, carbon nanotubes and other new materials are commonly used in the research of laser protection materials. Among many material systems, metal-organic complexes are one of the most effective optical limiting materials.

[0003] As one of the important materials for laser protection, the research of optical limiting materials has extremely important significance. Intelligent response materials with both optical limiting performance and controllable switching performance can better meet the needs of preparing new optical limiting devices. By introducing some functional groups, light control molecular switches with NLO switchable characteristics can be constructed. NLO switching means that the NLO response of the molecule can be reversibly changed, especially the hyperpolarizability of the molecule can be changed due to external stimulation. Due to the different optical physical properties before and after light irradiation, photoisomerization molecules have attracted widespread attention, and based on different isomerization mechanisms and isomerization forms, photoisomerization materials have been applied to many different fields. So far, there have been few reports on using photoisomerization strategy to construct optical switches to improve the optical limiting performance of materials in the field of laser protection. For a long time, most of the optical limiting materials are based on a single state, while intelligent optical limiting materials with switching characteristics have greater application potential in the future. SUMMARY

[0004] The application provides an organic iridium metal complex with photo-switching characteristics and a preparation method and application thereof. The prepared material exhibits good optical limiting performance, and has good photo-thermal stability, photoisomerization characteristics and laser protection performance.

[0005] To achieve the above object, the application adopts the following technical solutions:

[0006] An organic iridium metal complex with photo-switching characteristics has the following structure:

[0007]

[0008] The preparation method of the above-mentioned organic iridium metal complex material with photo-switching characteristics comprises the following steps:

[0009] (1) 2-phenyl-4-quinolinecarboxylic acid (1.0 g) and anhydrous ethanol (40 mL) were added to a reaction bottle, and concentrated sulfuric acid (10 mL) was slowly added dropwise, the reaction system was kept oxygen-free, and esterification was carried out at room temperature for 10-14 hours to obtain compound A2;

[0010] (2) Trimethylsilyl acetylene (7.5 mL-8.0 mL), compound A3 (6.23 g) and a catalyst (0.58 g-1.16 g) were added to a solvent, the reaction system was kept oxygen-free, and Suzuki coupling reaction was carried out at 50-55°C for 10-14 hours to obtain compound A4;

[0011] (3) Compound A4 (4.84 g) and iodomethane (2.5 g-5 g) were added to a solvent, the reaction system was kept oxygen-free, and reaction was carried out at 80°C under reflux for 10-14 hours to obtain compound A5;

[0012] (4) 5-nitrosalicylaldehyde (0.81 g-0.85 g) and compound A5 (1.78 g) were added to a solvent, the reaction system was kept oxygen-free, and cyclization reaction was carried out at 80-85°C for 10-14 hours to obtain compound A6;

[0013] (5) Compound A6 (1.47 g) and anhydrous potassium carbonate (0.69 g-0.75 g) were added to a solvent, and deprotection was carried out in dark conditions for 1-2 hours to obtain compound A7;

[0014] (6) Compound A7 (1.40 g-1.45 g), 5-bromo-1,10 phenanthroline (0.72 g), tetrakis triphenylphosphine palladium (0.156 g-0.16 g) and anhydrous potassium carbonate (2.20 g-2.25 g) were added to a solvent, and reaction was carried out under oxygen-free conditions for 12-24 hours to obtain compound NN-SP;

[0015] (7) Compound A2 (0.72 g-0.75 g) and iridium trichloride (0.50 g) were added to a solvent, the reaction system was kept oxygen-free, and reaction was carried out at 120°C for 24-48 hours to obtain bridged ligand A8;

[0016] (8) Bridged ligand A8 (0.4 g) and NN-SP (0.46 g-0.50 g) were added to a solvent, the reaction system was kept oxygen-free, and reaction was carried out at 120°C for 24-48 hours, and then potassium hexafluorophosphate was added, and stirring was carried out at room temperature for three hours to obtain Ir-NN-SP.

[0017] In the above steps, the reaction system being kept oxygen-free is preferably carried out under an argon atmosphere.

[0018] The above iridium metal complex material with photoisomerization properties is applied to the field of nonlinear optical materials.

[0019] Beneficial effects: the application provides an organic iridium metal complex with photo-switching characteristics and a preparation method and application thereof, a nonlinear optical material is combined with a photo-isomerization molecule, a spiropyran, to prepare a light-switching metal iridium complex light limiting material, and the reversible light-switching characteristics are used to study the nonlinear optical performance thereof; the heavy atom effect of iridium is easy to produce strong spin-orbit coupling, effectively improves the intersystem crossing between the singlet and the triplet, the triplet excited state absorption, prolongs the triplet excited state lifetime, and ensures that the material has good light limiting performance, the iridium metal complex material with photo-isomerization characteristics prepared by the application has good photo-thermal stability, photo-isomerization characteristics, fatigue resistance, anti-bleaching performance and OPL performance, and after ultraviolet light irradiation, due to the ring opening of the spiropyran molecule, the expansion of the conjugation degree of the complex further improves the laser protection performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A preparation flowchart of the organic iridium metal complex material with photo-switching characteristics in the embodiments of the application is shown in the figure.

[0021] Figure 2 The UV-Vis absorption spectra and photoluminescence (the excitation wavelength of emission is 440 nm) of Ir-Ref (a) and Ir-NN-SP (b) in dichloromethane solution with a concentration of 1×10 -5 M are shown in the figure. The UV-Vis absorption spectra of Ir-Ref (c) and Ir-NN-SP (d) in different polar solvents (concentration: 1×10 -5 M) are shown in the figure.

[0022] Figure 3 The UV-Vis absorption spectrum changes (200-800 nm) of Ir-NN-SP in CH2Cl2 solution (c=1×10 -5 M) under irradiation of 365 nm at ambient temperature are shown in the figure (a). The UV-Vis absorption spectrum changes (560-660 nm wavelength) of Ir-NN-SP in CH2Cl2 solution (c=1×10 -5 M) under irradiation of 365 nm at ambient temperature are shown in the figure (b). The UV-Vis absorption spectrum of Ir-NN-SP under ultraviolet light and the recovery in the dark (ultraviolet light: 365 nm, 20 W, 60 s; dark: 60 s) are shown in the figure (c). The monitoring of the light switching cycle is shown in the figure (d), in which the absorbance at 610 nm under the alternating irradiation of 365 nm light (60 s) and darkness (60 s) (365 nm: 20 W, 60 s; dark: all light sources are turned off).

[0023] Figure 4 The cyclic voltammogram and energy level diagram of the iridium metal complex with photo-switching characteristics in the embodiments of the application are shown in the figure.

[0024] Figure 5 Fig. 9 is a transient absorption spectrum of the degassed toluene solution of Ir-Ref (a) and Ir-NN-SP (b) at room temperature before and after irradiation, (c) transient absorption spectrum of the Ir-NN-SP complex after UV irradiation for 150 seconds, (d) Jacobinsky plot of the reverse saturable absorption process of the complex Ir-NN-SP before and after UV irradiation in an embodiment of the present application;

[0025] Figure 6 Fig. 10 is a graph of the relationship between the incident laser energy and the outgoing laser energy of the iridium complex with optical switching characteristics in an embodiment of the present application;

[0026] Figure 7 Fig. 11 is a diagram of the double modulation strategy involved in the optical limiting mechanism in an embodiment of the present application. DETAILED DESCRIPTION

[0027] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0028] As shown in Fig. 1, a method for preparing an iridium complex material with photoisomerization characteristics includes the following steps: Figure 1

[0029] Synthesis of compound A2:

[0030] 2-phenyl-4-quinoline carboxylic acid (1.0 g, 4.01 mmol) was added to ethanol (40 mL), and sulfuric acid (10 mL) was added dropwise. The mixture was stirred at room temperature under argon protection for 12 hours. After evaporation of the solvent, the crude mixture was purified by silica gel column chromatography to obtain the desired yellow-brown solid compound A2 (0.86 g, 85%) 1 H NMR (400 MHz, Chloroform-d) δ 8.78 (dd, J = 8.6, 1.4 Hz, 1H), 8.42 (s, 1H), 8.31-8.20 (m, 3H), 7.79 (ddd, J = 8.4, 6.9, 1.4 Hz, 1H), 7.65 (ddd, J = 8.4, 6.9, 1.3 Hz, 1H), 7.58 (t, J = 7.8 Hz, 2H), 7.54-7.48 (m, 1H), 4.58 (q, J = 7.1 Hz, 2H), 1.53 (t, J = 7.1 Hz, 3H).

[0031] Synthesis of compound A4:

[0032] ​Compound A3 (5-bromo-2,3,3-trimethyl-3H-indole) (6.23 g, 27.6 mmol), Pd(PPh3)2Cl2(0.58 mg, 0.829 mmol, 3 mol%), CuI (0.16 mg, 0.831 mmol, 3 mol%) and trimethylsilyl acetylene (7.90 mL) were subjected to Suzuki coupling reaction at 50 °C for 10 h, after cooling to room temperature, the reaction mixture was diluted with diethyl ether (100 mL) and washed with water (2 x 100 mL) and brine (100 mL), the organic phase was dried and evaporated, leaving a red-brown oily residue, which was flash filtered over silica gel, affording yellow oil A4 (4.86 g, 72%). 1 H NMR (400 MHz, CDC13): δ 7.43 (d, J = 7.8 Hz, 1H), 7.41 (dd, J = 7.8, 1.2 Hz, 1H) 7.38 (d, J = 1.2 Hz, 1H), 2.27 (s, 3H), 1.28 (s, 6H), 0.25 (s, 9H).

[0033] Synthesis of compound A5:

[0034] Compound A4 (4.84 g, 19.9 mmol) and Mel (2.5 g, 40 mmol) were added to MeCN (30 mL) and heated at 80 °C under reflux for 10 h, the residue was suspended in EtOAc (30 mL) and the solid was collected by vacuum filtration, washed with EtOAc and Et20 and air dried, affording dark grey solid A5 (5.35 g, 70%). 1 H NMR (400 MHz, CDC13): δ 7.65 (dd, J = 8.4, 1.2 Hz, 1H), 7.61 (d, J = 8.4 Hz, 1H), 7.59 (m, 1H), 4.26 (s, 3H), 3.12 (s, 3H), 1.66 (s, 6H), 0.27 (s, 9H)

[0035] Synthesis of compound A6:

[0036] 5-nitroso salicylaldehyde (0.81 g, 4.88 mmol), A5 (1.78 g, 4.83 mmol) and triethylamine (0.91 g, 10.74 mmol) were added to ethanol (100 mL) and stirred at 80 °C under argon for 10 h; after evaporation of the solvent, the crude mixture was purified by column chromatography over silica gel, affording the desired yellow-brown solid A6 (1.56 g, 77%). 1H NMR (400 MHz, Chloroform-d): δ 8.04-7.99 (2H, m), 7.35 (1H, dd, J = 8.0, 1.5 Hz), 7.19 (1H, d, J = 1.5 Hz), 6.93 (1H, d, J = 10.5 Hz), 6.74 (1H, d, J = 9.0 Hz), 6.46 (1H, d, J = 8.0 Hz), 5.83 (1H, d, J = 10.5 Hz), 2.74 (3H, s), 1.27 (3H, s), 1.16 (3H, s), 0.24 (9H, s).

[0037] Synthesis of compound A7:

[0038] Compound A6 (1.47 g, 3.51 mmol), CH2Cl2(20 mL), K2CO3(0.69 g, 5.05 mmol) were added to methanol (20 mL), then stirred for 1 hour in the dark under N2protection, after the reaction was completed, it was cooled to room temperature, filtered, extracted with ethyl acetate and saturated sodium chloride solution, the organic phase was collected three times, silica gel (100-200 mesh) was added, rotary evaporation was prepared into a sand sample, purified by silica gel column chromatography (200-300 mesh, petroleum ether / ethyl acetate = 5:1 (V / V)) to obtain yellow-brown solid compound A7, with a yield of 87%. 1 H NMR (400 MHz, Chloroform-d): δ 8.04-7.99 (2H, m), 7.35 (1H, dd, J = 8.0, 1.5 Hz), 7.19 (1H, d, J = 1.5 Hz), 6.93 (1H, d, J = 10.5 Hz), 6.74 (1H, d, J = 9.0 Hz), 6.46 (1H, d, J = 8.0 Hz), 5.83 (1H, d, J = 10.5 Hz), 2.74 (3H, s), 1.27 (3H, s), 1.16 (3H, s), 0.24 (9H, s).

[0039] Synthesis of compound NN-SP:

[0040] In a two-necked round bottom flask was added 5-bromo-1,10-phenanthroline (0.70 g, 2.7 mmol), compound A7 (1.40 g, 4.04 mmol), Pd(ph3p)4(0.156 g, 0.13 mmol), K2CO3(2.25 g, 16.28 mmol) and toluene / water (30 mL / 10 mL), then the reaction mixture was stirred smoothly, heated to reflux under argon for 24 hours, after the reaction was completed, it was cooled to room temperature, filtered, extracted with ethyl acetate and saturated sodium chloride solution, the organic phase was collected three times, silica gel (100-200 mesh) was added, rotary evaporation was prepared into a sand sample, column chromatography was carried out on silica gel (200-300 mesh, dichloromethane / methanol = 50:1 (V / V)), 2 mL of triethanolamine was added per 100 mL of dichloromethane to purify the crude product, and orange yellow powder compound NN-SP was obtained with a yield of 35% to 40%. 1 H NMR (400 MHz, DMSO-d6) δ 9.19 (s, 2H), 8.90 (d, J = 8.2 Hz, 2H), 8.52 (d, J = 9.7 Hz, 2H), 8.33-8.27 (m, 2H), 8.05 (dd, J = 9.1, 2.7 Hz, 1H), 7.93 (dd, J = 8.2, 4.1 Hz, 2H), 7.82 (dd, J = 8.1, 4.2 Hz, 2H), 7.29 (d, J = 10.4 Hz, 1H), 6.96 (d, J = 9.0 Hz, 1H), 6.78 (d, J = 8.0 Hz, 1H), 6.06 (d, J = 10.4 Hz, 1H).

[0041] Synthesis of compound A8:

[0042] In a two-necked round bottom flask was added IrCl3.3H2O (0.50 g, 1.67 mmol), compound A2 (0.70 g, 2.52 mmol) and 2-methoxyethanol (20 mL), then the reaction mixture was stirred smoothly at 120°C and heated to reflux under argon for 48 hours, after the reaction was completed, the reaction solution was cooled to room temperature, the reaction solution was slowly dropped into distilled water, and the solid was filtered;

[0043] Synthesis of complex Ir-NN-SP:

[0044] In a two-necked round bottom flask was added compound A8 (0.40 g, 0.26 mmol), NN-SP (0.46 g, 0.87 mmol) and 2-methoxyethanol (30 mL), then the reaction mixture was stirred smoothly and heated to 120 °C under argon atmosphere for 24 h. After the reaction was completed, the KPF6 (3 mmol) aqueous solution was mixed at room temperature (R.T.) for 3 h. The solvent was removed and the crude product was purified by silica gel column chromatography with dichloromethane / methanol = 40 / 1 (V / V) to obtain an orange powder with a yield of 35%~38%. 1 H NMR (400 MHz, DMSO-d6) δ 9.06 (d, J = 8.3 Hz, 1H), 8.89-8.81 (m, 2H), 8.72 (d, J = 8.3 Hz, 1H), 8.58 (d, J = 4.5 Hz, 1H), 8.51-8.37 (m, 4H), 8.34 (d, J = 2.3 Hz, 1H), 8.26 (d, J = 3.3 Hz, 1H), 8.21 (d, J = 8.3 Hz, 3H), 8.12-8.01 (m, 2H), 7.60-7.51 (m, 2H), 7.28 (d, J = 9.8 Hz, 6H), 6.98-6.92 (m, 5H), 6.78-6.73 (m, 1H), 6.64-6.57 (m, 2H), 6.03 (dd, J = 10.2, 2.4 Hz, 1H), 3.54 (d, J = 7.3 Hz, 4H), 2.77 (d, J = 2.6 Hz, 3H), 1.25 (d, J = 10.1 Hz, 6H), 1.16 (d, J = 4.9 Hz, 6H). HRMS (m / z): calcd for [C 70 H 55 IrN6O7] + ,1383.3761; found, 1283.3692.

[0045] Reference Ir-Ref was synthesized without introducing photoisomerization molecules in the synthesis, the specific process is as follows:

[0046] In a two-necked round bottom flask was added compound A8 (0.40 g, 0.26 mmol), 1,10-phenanthroline (0.12 g, 0.676 mmol) and 2-methoxyethanol (30 mL), then the reaction mixture was stirred smoothly and heated to reflux under argon atmosphere for 24 h. After the reaction was completed, the KPF6 (3 mmol) aqueous solution was mixed at room temperature (R.T.) for 3 h. The solvent was removed and the crude product was purified by silica gel column chromatography with dichloromethane / methanol = 50 / 1 (V / V) to obtain an orange powder with a yield of 50%~52%. 1H NMR (400MHz, DMSO-d6) δ8.84(s,2H),8.77(d,J=8.2Hz,2H),8.19(d,J=8.4Hz,2H),8.13-8.05(m,4H),7.31(ds,J=2 2.5,7.6Hz,7H),6.92(dt,J=14.1,7.6Hz,4H),6.60(d,J=7.7Hz,2H),4.52(q,J=7.1Hz,4H),1.45(t,J=7.1Hz,6H).

[0047] Performance testing

[0048] The photophysical properties of organic materials are important parameters that provide crucial information about their conformation and electronic structure. Figure 2 The UV-Vis absorption spectra of the Ir-Ref and Ir-NN-SP complexes are shown. The absorption peak types and wavelength ranges of the two complexes are similar, mainly due to their similar ligand structures. Furthermore, the complexes exhibit a strong absorption band between 280 nm and 425 nm. Considering the large molar extinction coefficient and weak solubility effect, this strong absorption peak (before 425 nm) originates from the N^N ligand. 1 The π,π* transition, accompanied by a certain charge transfer within the ligand, results in a weak absorption band beyond 425 nm, which may originate from singlet metal-to-ligand charge transfer. 1 MLCT) and ligand-to-ligand charge transfer (MLCT) 1 LLCT, and triplet metal-to-ligand charge transfer and ligand-to-ligand charge transfer ( 3 MLCT and 3 Experimental results show that the absorbance of the entire complex increases with a slight red shift after the addition of spiropyran to the phenanthroline ligand. This is due to the extension of the conjugation length of the molecular skeleton. By introducing a strong electron-withdrawing substituent nitro group to enhance electron affinity, the N^N ligand becomes a more powerful and complex ICT system.

[0049] At a concentration of 1×10 -5 Emission spectra were tested in a mol / L dichloromethane solution, and Table 1 summarizes the relevant emission parameters.

[0050] Table 1. Relevant parameters of the emission spectra of the complexes in dichloromethane solution.

[0051]

[0052] a. The maximum absorption band and molar extinction coefficient of ultraviolet-visible absorption in CH2Cl2 at room temperature.

[0053] b is the decay lifetime in CH2Cl2 at room temperature, c = 1 × 10 -5 M. The reference used is a degassed aqueous solution of [Ru(bpy)3]Cl2 (Φ em =0.042, λ ex =436nm).

[0054] c. Triple excited state lifetime measured in toluene at a wavelength of 532 nm.

[0055] d Ir-NN-MC is the form of Ir-NN-SP after irradiation with 365nm ultraviolet light.

[0056] Considering the significant Stokes shift and oxygen-sensitive quenching exhibited by these two complexes in the deoxygenated state, their emission is attributed to phosphorescence. Furthermore, after 365 nm UV irradiation, a redshift of approximately 10 nm occurs compared to before irradiation. This is primarily because the two orthogonal heterocycles in the spiropyran intermolecular state are connected by spirocarbon atoms, at which point there is no conjugated system in the molecule (the orthogonal structure prevents π electrons from leaving the structural domain). Before and after UV irradiation, the CO bonds in the spirocycles break, and the two heterocycles transform into a coplanar configuration, forming an extended π-conjugated system, thereby increasing π electron delocalization and leading to a decrease in the band gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The emission of the Ir-Ref and Ir-NN-SP complexes is mainly due to… 3 Emissions of π, π*, and 3MLCT were observed. Furthermore, the solution emission spectra of the Ir-NN-SP complex in different solvents (toluene, THF, DCM, DMSO, MeOH) were tested; this complex exhibited a relatively weak solvent response. With increasing solvent polarity, 3 The energy of the MLCT state decreases, thereby altering the relaxation path and causing a slight redshift in the emission spectrum. This phenomenon further verifies the emission of the cation iridium complex. 3 MLCT characteristics.

[0057] At a concentration of 1×10 -5 The photoisomerization behavior of the complex Ir-NN-SP was tested by UV-Vis absorption spectroscopy in a mol / L dichloromethane solution. Since a new absorption peak for the spiropyran molecule appeared near 600 nm after irradiation with 365 nm UV light, the test range was specifically controlled within the range of 550–650 nm to monitor the appearance of this new absorption peak. Figure 3As shown in Figure c, compared to the unirradiated sample, a distinct absorption peak appeared in the 580–650 nm wavelength range after 60 seconds of UV irradiation. Furthermore, after storing the sample in darkness for 1 minute, the UV-Vis absorption spectrum was re-measured; the new peak had disappeared, consistent with the spectrum before irradiation, indicating that it had returned to its initial closed-loop state. The color also shows that the sample was pale yellow without irradiation, but turned pale blue after 60 seconds of 365 nm UV irradiation; after 60 seconds in darkness, it returned to pale yellow, confirming that the composite optical switch underwent photoisomerization under 365 nm UV irradiation. In addition, the UV-Vis absorption spectra in the 280–700 nm and 550–650 nm spectral ranges were measured under continuous 365 nm UV irradiation. Within the short wavelength range, the absorbance increases with increasing irradiation time, mainly due to the breakage of the CO bond after spiropyran photoisomerization, where the spiromorph (SP) changes to the cyanine morph (MC), thereby increasing the spatial conjugation of the complex. The content of the cyanine morph gradually increases with increasing irradiation time, reaching a photostatic state after 150s of irradiation with 365nm ultraviolet light.

[0058] Furthermore, Ir-NN-SP exhibits both forward and reverse photochromic reactions under 365 nm UV irradiation and in darkness. After five complete cycles, the changes in the open and closed absorption spectra are negligible, indicating that Ir-NN-SP possesses good fatigue resistance. To investigate its photobleaching behavior, Ir-NN-SP in dichloromethane was irradiated with 365 nm UV light (20 W) for an extended period at room temperature. Under prolonged irradiation, the absorbance at 610 nm gradually decreased, but the decrease was less than 4% within 5 minutes. These results demonstrate that Ir-NN-SP possesses good photoreversibility and stability, opening up broader application prospects for its practical applications.

[0059] Cyclic voltammetry was performed at room temperature in dichloromethane containing 0.1 M tetrabutylammonium hexafluorophosphate as the supporting electrolyte (using the standard ferrocene / ferrocene (Fc / Fc+) redox system as an internal standard).

[0060] The HOMO and LUMO energy levels of a molecule can be calculated using the following formula.

[0061]

[0062] Where E Fc This is the measured value of Fc (relative to Ag / AgCl), with a redox potential of 0.18V.

[0063] The relevant calculated values ​​are shown in Table 2, and the energy level diagram is shown in [reference needed]. Figure 4The redox curves show that the introduction of spiropyran into the iridium complex leads to a decrease in the initial oxidation potential, HOMO level, and band gap of the Ir-NN-SP complex due to the enhanced electron-withdrawing ability and conjugation of the ligands. Furthermore, comparing the redox sites and band gap before and after ring-opening, the initial oxidation potential of the ring-opened Ir-NN-MC complex is lower, consistent with the previous absorption and emission spectra.

[0064] Table 2 Electrochemical properties of Ir-Ref and Ir-NN-SP in the ring-opening state

[0065]

[0066] a. The initial oxidation potential and reduction potential determined based on the cyclic voltammogram of CH2Cl2 / Bu4NPF6.

[0067] The b-band gap is estimated based on the initiation potential.

[0068] In Table c, Ir-NN-MC is the open-ring form of Ir-NN-SP after one minute of 365nm ultraviolet irradiation.

[0069] The transient absorption spectra of Ir-Ref and Ir-NN-SP complexes before and after irradiation with degassed toluene solution were measured at room temperature, and their attenuation characteristics were investigated. Figure 5As can be seen, both complexes exhibit significant positive absorption in the wavelength ranges of 400–600 nm and greater than 750 nm, indicating that these two iridium complexes exhibit good transient absorption characteristics in most of the visible light region due to their stronger excited-state absorption than ground-state absorption. This broad absorption band and enhanced excited-state absorption suggest that reverse saturable absorption behavior may occur in this wavelength range. In the wavelength range of 600–750 nm, the Ir-Ref and Ir-NN-SP complexes show negative bleaching absorption peaks. This is because when the pump light excites the ground-state molecules to the excited state, the number of ground-state molecules decreases, resulting in a reduction in the absorption of the probe light at the ground-state absorption peak, forming a negative peak. Compared with the TA spectra recorded before UV irradiation, Ir-NN-SP exhibits stronger excited-state absorption in the 450–550 nm range, with a larger change in ΔOD than Ir-Ref. Notably, after UV irradiation, the excited-state absorption in this range further increased (ΔOD increased from 0.02 to 0.04). This enhancement is attributed to UV-induced isomerization of spiropyran molecules. The isomerization of spiropyran improves the spatial conjugation of the complex, resulting in a more significant enhancement of the excited-state absorption compared to the ground-state absorption. Furthermore, the negative peak showed a significant enhancement in the 600–750 nm range. This enhancement is attributed to the increase in ground-state absorption after spiropyran ring opening, leading to a new absorption peak in this specific wavelength range. This observation further confirms that the Ir-NN-SP complex possesses the ability to undergo photoisomerization. It is noteworthy that this complex exhibits a sharp and strong absorption peak at approximately 450 nm. Comparing its emission-state characteristics with previously reported metal complexes with similar conjugated structures reveals that the triplet excited state of this complex is mainly attributed to… 3 π, π*. To explain the excited-state characteristics of the Ir-NN-SP complex and the different transient absorption behaviors before and after 365nm ultraviolet irradiation, Jacobsky plots were drawn ( Figure 5 After absorbing energy, the photon reaches a single excited state and then enters a triplet excited state through effective intersystemic crossover (ISC). Reverse saturable absorption (RSA) occurs when the absorption cross-section of the triplet excited state exceeds that of the ground state. The ring-opening isomerization of spiropyran significantly enhances the π-conjugation, which improves the energy distribution of the triplet excited state, thereby enhancing RSA performance by strengthening excited-state absorption.

[0070] To further explore the optical limiting properties of the complex, a nonlinear transmission experiment was conducted on the complex by irradiating it with a 532 nm (ns) laser in an acetonitrile solution. Figure 6The curves of incident and output energy densities show that the complex exhibits linear absorption at low incident energy densities. However, as the incident laser energy density increases, the output energy density of the complex increases non-linearly, and the rate of increase gradually decreases. Firstly, from... Figure 6 It can be seen from this that when the incident energy density is 3.0 J / cm² 2 At that time, the emission energy density of the Ir-Ref complex was only 1.0 J / cm³. 2 It exhibits good optical limiting characteristics. Introducing spiropyran as a functional group into the complex enhances the π-conjugation effect, resulting in a longer lifetime for the T1 state. 3 π, π* state, long lifetime 3 The π,π* states enhance the reverse saturable absorption of the Ir-NN-SP complex, thereby further improving the reverse saturable absorption effect. This leads to a decrease in the emission energy density of the Ir-NN-SP complex to 0.51 J / cm². 2 After 150 seconds of irradiation with a 365nm UV lamp, spiropyran underwent ring-opening. This structural change made the excited-state absorption more significant, further reducing its laser output energy density to 0.47 J / cm². 2 This further improves the optical limiting performance. Considering the relatively low excited-state energy level and long lifetime of Ir-NN-MC at 532 nm, compared with Ir-NN-SP, Ir-NN-MC absorbs more energy and is excited to a higher triplet state after isomerization, thus exhibiting stronger anti-saturation absorption characteristics. Therefore, the optical limiting performance after isomerization is further improved. In addition, the Ir-NN-SP complex was irradiated with 365 nm ultraviolet light for 150 seconds and then placed in darkness for 60 seconds. Figure 6 As can be seen, the recovered Ir-NN-SP(R) has similar light confinement properties to the original Ir-NN-SP, which further confirms the stability of the optical switching complex.

[0071] Figure 7 The optical limiting mechanism involves a dual adjustment strategy: (1) Under irradiation with a 532nm high-energy pulsed laser, the complex consumes the incident energy through anti-saturation absorption; (2) Subsequently, irradiation with 365nm ultraviolet light (150s exposure) induces spiropyran ring-opening isomerization, triggering an overall conformational change in the complex that further reduces the emitted laser energy.

[0072] The embodiments described above are merely preferred embodiments of the present invention, used to explain the invention and not to limit its scope. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. An organoiridium metal complex with photo-switching properties, characterized in that, The structure is: 。 2. A method for preparing an organoiridium metal complex with photo-switching properties, characterized in that, The method comprises the following steps: (1) 2-phenyl-4-quinoline carboxylic acid and anhydrous ethanol are added to a reaction bottle, concentrated sulfuric acid is slowly added dropwise, the reaction system is kept oxygen-free, compound A2 is obtained through esterification, and the reaction formula is as follows: ； (2) Trimethylsilyl acetylene, compound A3 and a catalyst are added to a solvent, the reaction system is kept oxygen-free, compound A4 is obtained through Suzuki coupling reaction, and the reaction formula is as follows: ； (3) Compound A4 and iodomethane are added to a solvent, the reaction system is kept oxygen-free, compound A5 is obtained through reflux reaction, and the reaction formula is as follows: ； (4) 5-nitrosalicylaldehyde and compound A5 are added to a solvent, the reaction system is kept oxygen-free, compound A6 is obtained through cyclization reaction, and the reaction formula is as follows: ； (5) Compound A6 and anhydrous potassium carbonate are added to a solvent, and compound A7 is obtained through reaction and deprotection in the dark, and the reaction formula is as follows: ； (6) Compound A7, 5-bromo-1,10-phenanthroline, tetrakis(triphenylphosphine)palladium and anhydrous potassium carbonate are added to a solvent, and compound NN-SP is obtained through reaction under oxygen-free conditions, and the reaction formula is as follows: ； (7) Compound A2 and iridium trichloride are added to a solvent, the reaction system is kept oxygen-free, and bridged ligand A8 is obtained through reaction, and the reaction formula is as follows: ； (8) Bridged ligand A8 and NN-SP are added to a solvent, the reaction system is kept oxygen-free, and then potassium hexafluorophosphate is added to obtain an organic iridium metal complex with photo-switching characteristics, and the reaction formula is as follows: 。 3. The method for preparing the photo-switching organoiridium metal complex according to claim 2, characterized in that, In step (1), the amount ratio of 2-phenyl-4-quinoline carboxylic acid to anhydrous ethanol is 1 g:40 mL; the volume ratio of the anhydrous ethanol to concentrated sulfuric acid is 4:1, the reaction time is 10-14 hours, and the reaction temperature is room temperature.

4. The method for preparing photo-switchable organic iridium complex according to claim 2, characterized in that, In step (2), the amount ratio of compound A3 to trimethylsilyl acetylene is 1 g:(1.2-1.3) mL; the mass ratio of the compound A3 to the catalyst is 1:(0.09-0.2); the reaction temperature is 50-55 DEG C, and the reaction time is 10-14 hours.

5. The method for preparing the photo-switching organoiridium metal complex according to claim 2, characterized in that, In step (3), the mass ratio of the compound A4 to iodomethane is 1:(0.5-1.1).

6. The method for preparing the photo-switching organoiridium metal complex according to claim 2, characterized in that, In step (4), the mass ratio of the compound A5 to 5-nitrosalicylaldehyde is 1:(0.4-0.5); the reaction temperature is 80-85 DEG C, and the reaction time is 10-14 hours.

7. The method for preparing the photo-switching organoiridium metal complex according to claim 2, characterized in that, In step (5), the mass ratio of the compound A6 to anhydrous potassium carbonate is 1:(0.45-0.55); and the reaction time is 1-2 hours.

8. The method for preparing the photo-switching organoiridium metal complex according to claim 2, characterized in that, In step (6), the mass ratio of the compound A7 to 5-bromo-1,10-phenanthroline is (1.9-2.1):1; the mass ratio of the 5-bromo-1,10-phenanthroline to tetrakis(triphenylphosphine)palladium is 1:(0.2-0.3); the mass ratio of the 5-bromo-1,10-phenanthroline to anhydrous potassium carbonate is 1:(3-3.2); and the reaction time is 12-24 hours.

9. The method for preparing the photo-switching organoiridium metal complex according to claim 2, characterized in that, In step (7), the mass ratio of compound A2 to iridium trichloride is (1.4-1.5):1; the reaction time is 24-48 hours, and the reaction temperature is 120 DEG C.

10. The method for preparing the photo-switching organoiridium metal complex according to claim 2, characterized in that, The mass ratio of bridged ligand A8 and NN-SP in step (8) is 1:(1.15-1.25); the reaction time is 24-48 hours, and the reaction temperature is 120℃; after adding potassium hexafluorophosphate, stirring for three hours at room temperature.

11. The application of the organic iridium metal complex with photo-switching characteristics in claim 1 to laser protection.

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