Synthesis method and application of four-membered ring near-infrared iridium complex based on SS coordination

Abstract

The invention relates to the technical field of organic electroluminescent devices, in particular to a synthetic method and application of a four-membered ring near-infrared iridium complex based on SS coordination, the synthetic method of the four-membered ring near-infrared iridium complex based on SS coordination comprises the following steps: S1, synthesizing a near-infrared main ligand and a corresponding iridium chloride bridging product; s2, designing and synthesizing a four-membered ring auxiliary ligand; s3, enabling the iridium chloride bridging products corresponding to the near-infrared main ligands to react with four-membered ring auxiliary ligands to obtain four-membered ring near-infrared iridium complexes; the preparation method comprises the following steps: firstly, carrying out suzuki coupling reaction to obtain three novel main ligands, and then reacting with iridium trichloride to obtain a corresponding iridium chloride bridging product; simultaneously synthesizing auxiliary ligands of four four-membered rings; then, an auxiliary ligand and the iridium chloride bridging product react, and the high-efficiency near-infrared iridium complex luminescent material is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of organic electroluminescent devices, and in particular to a synthesis method and application of a four-membered ring near-infrared iridium complex based on SS coordination. Background Art

[0002] Organic near-infrared luminescent materials (wavelength range 700-2500nm) play an increasingly important role in the fields of optical fiber communication, sensing, biological detection and medical imaging. For example, due to the advantages that biological tissue absorbs less in the near-infrared region and does not emit fluorescence, it is widely used in biological detection. Since oxygenated hemoglobin and reduced hemoglobin in the blood have unique absorption spectra in the near-infrared region, it has become a simple and reliable method for detecting blood components in the medical field.

[0003] Organic near-infrared electroluminescent devices (NIR-OLEDs) have the advantages of light weight, low heat generation, low energy consumption, easy production, and large-scale manufacturing, and are widely used as night vision equipment. In addition, in the field of energy, making full use of sunlight in the near-infrared region can effectively improve the efficiency of solar cells. Due to its low cost, simple preparation process, good flexibility and film-forming properties, good compatibility with existing microelectronics, large-area preparation and multifunctional optoelectronic properties, organic near-infrared luminescent materials have become one of the most promising research fields today.

[0004] In the study of organic electroluminescent materials, small molecule doped transition metal complexes have become the focus of research, such as complexes of iridium, ruthenium, molybdenum, etc. The advantage of this type of complex is that they can obtain very high emission energy from their own triplet states, and among them, metal iridium (III) compounds have always dominated the subsequent research process due to their good stability, mild reaction conditions during the synthesis process, and high electroluminescent properties.

[0005] The application of near-infrared iridium complexes in organic electroluminescent devices needs to consider luminous efficiency, stability, cost, preparation process and the like. Based on the existing technical problems, in the prior art, CN114751941B discloses a binuclear iridium complex and an organic electronic device comprising the same, wherein a single auxiliary ligand simultaneously coordinates two metal heavy atoms Ir, and the bridging ligand group can effectively shorten the Ir-Ir atomic distance, so that the luminescence peak of the molecule is red-shifted, and the emission wavelength reaches 640-650nm, reaching the deep red light region; CN 105820190 B discloses a red to near-infrared phosphorescent iridium complex luminescent material and its application in electroluminescent devices, wherein the first ligand is a 1-phenylisoquinoline derivative and the auxiliary ligand is an amidinoguanidine derivative; CN 110818740 B has a nitrogen-containing aromatic fused ring structure, and the material introduces an electron-withdrawing cyano group on the aromatic fused ring. The iridium complex as a near-infrared luminescent material is doped into a main material and used as a light-emitting layer; the above-mentioned prior arts have promoted the application of near-infrared iridium complexes in organic electroluminescent devices to a certain extent, but there are still deficiencies in the synthesis rate, stability and performance of the main ligands and iridium-chloride bridged products of the near-infrared iridium complexes in organic electroluminescent devices. In this regard, the present application proposes a synthesis method and application of a four-membered ring near-infrared iridium complex based on SS coordination. Summary of the invention

[0006] The purpose of the present invention is to provide a synthesis method and application of a four-membered ring near-infrared iridium complex based on SS coordination. Through the design of a near-infrared main ligand and the design and synthesis of a four-membered ring auxiliary ligand, the two work synergistically to form a new near-infrared iridium complex to achieve emission in the near-infrared region.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] Based on the SS-coordinated four-membered ring near-infrared iridium complex, the main ligand of the near-infrared iridium complex adopts an iridium-chloride bridged product, which reacts with a four-membered ring auxiliary ligand to obtain a four-membered ring near-infrared iridium complex, wherein the four-membered ring auxiliary ligand includes but is not limited to the following structure:

[0009]

[0010] Where X=N is represented by cf3cnn, and X=S is represented by cf3css;

[0011]

[0012] Where X=S, Y=HNEt3 is represented as cf3pss, and X=O, Y=K is represented as cf3poo.

[0013] Furthermore, the four-membered ring near-infrared iridium complex includes but is not limited to the following structure:

[0014]

[0015] Where X=N is represented by (tfmnqz)2Ir(cf3cnn), and X=S is represented by (tfmnqz)2Ir(cf3css);

[0016]

[0017] Where X=N is represented by (tfmnbqz)2Ir(cf3cnn), and X=S is represented by (tfmnbqz)2Ir(cf3css);

[0018]

[0019] Wherein X=N is represented by (tfmabqz)2Ir(cf3cnn), and X=S is represented by (tfmabqz)2Ir(cf3css);

[0020]

[0021] Wherein X=S is represented by (tfmnqz)2Ir(cf3pss), and X=O is represented by (tfmnqz)2Ir(cf3poo);

[0022]

[0023] Wherein X=S is represented by (tfmnbqz)2Ir(cf3pss), and X=O is represented by (tfmnbqz)2Ir(cf3poo);

[0024]

[0025] Among them, X=S is represented by (tfmabqz)2Ir(cf3pss), and X=O is represented by (tfmabqz)2Ir(cf3poo).

[0026] On the other hand, the present invention provides a method for synthesizing the above-mentioned four-membered ring near-infrared iridium complex based on SS coordination, comprising:

[0027] S1: Synthesis of near-infrared primary ligands and corresponding iridium-chloride bridged products;

[0028] S2: Design and synthesis of four-membered ring auxiliary ligands;

[0029] S3: The iridium-chloride bridged product corresponding to the near-infrared main ligand is reacted with the four-membered ring auxiliary ligand to obtain a four-membered ring near-infrared iridium complex.

[0030] Furthermore, the general synthesis formula of the near-infrared main ligand and the corresponding iridium-chlorine bridged product is as follows:

[0031]

[0032] The synthesis method of the main ligand and the chloro-linked product is as follows: Boric acid raw materials (1eq) and chlorinated raw materials (1eq) are reacted at 110°C for 12h under the conditions of Pd(PPh3)4 (0.05eq) as a catalyst, K2CO3 (5eq) as a base, toluene (10eq) as a reaction solvent, and a small amount of ethanol (0.1eq) for 12h to obtain the main ligand product. The yield of this type of suzuki reaction is very high, about 75%-90%. The main ligand (1eq) obtained and iridium trichloride monohydrate (1.5eq) are then reacted at 110°C for 12h in ethylene glycol ethyl ether (15eq) and water (3eq). After the reaction is completed, it is cooled to room temperature, and then (10eq) of distilled water is added to the reaction system. It is found that a large amount of precipitates are generated, which are filtered and dried to obtain the chloro-linked product. The yield of this type of reaction is very high and can be directly used for the next step of the synthesis reaction without further purification.

[0033] Further, the synthesis of the near-infrared main ligand and the corresponding iridium-chloride bridged product is as follows:

[0034] The three main ligands are obtained by reacting the corresponding boric acid and chlorinated product by Suzuki reaction; and then reacting with iridium trichloride to obtain iridium-chloride bridged products corresponding to the three main ligands.

[0035] The synthesis method of the CNN-type auxiliary ligand is as follows: the imine raw material (1 eq) and the CNN skeleton raw material (1 eq) are dissolved in THF (10 eq) solvent, reacted at 0°C for 30 min, then n-BuLi (1 eq) is added, and the reaction is continued for 3 h. After the reaction is completed, the salt of the CNN-based auxiliary ligand is directly obtained by vacuum distillation, which can be directly used for the next step of synthesis without purification.

[0036] Synthesis of CSS auxiliary ligand: The imine raw material (1 eq), n-BuLi (1 eq) and CS2 (10 eq) were stirred at room temperature for 5 h. After the reaction, the auxiliary ligand salt based on CSS was obtained by vacuum distillation, which can be directly used in the next step of synthesis without further purification.

[0037] Synthesis of PSS auxiliary ligand: Phosphorus monochloride raw material (1 eq), sulfur powder (1 eq) and triethylamine (10 eq) were stirred at room temperature for 5 h. After the reaction, the salt based on PSS auxiliary ligand was obtained by vacuum distillation, which can be used for the next reaction without purification.

[0038] Synthesis of POO auxiliary ligand: Phosphorus monochloride raw material (1 eq) and H2O2 (10 eq) and KOH (1 eq) were stirred at room temperature for 5 h. After the reaction, the salt based on POO auxiliary ligand was directly obtained by decompression and spin drying, which can be directly used in the next reaction without purification.

[0039] Furthermore, the design and synthesis formula of the four-membered ring auxiliary ligand is as follows:

[0040]

[0041] The lithium salts of two auxiliary ligands, cf3cnn and cf3css, are obtained by reacting n-BuLi and bis(4-(trifluoromethyl)phenyl)amine with N,N′-diisopropylcarbodimethylamine or carbon disulfide respectively; the amine salts or potassium salts of two auxiliary ligands, cf3pss and cf3poo, are obtained by reacting bis(4-(trifluoromethyl)phenyl)phosphine with sulfur powder or hydrogen peroxide respectively.

[0042] Furthermore, the iridium-chloride bridged product corresponding to the near-infrared main ligand is reacted with the four-membered ring auxiliary ligand to obtain the four-membered ring near-infrared iridium complex, including but not limited to:

[0043] The three iridium-chloride bridged products corresponding to the main ligands were used to react with the lithium salts cf3cnn and cf3css of the four-membered ring auxiliary ligands to obtain six four-membered ring near-infrared iridium complexes based on Ir-NCN and Ir-SCS coordination configurations.

[0044] The general reaction formulas are as follows:

[0045]

[0046] The synthesis is as follows: the chloro-linked product (1 eq), the auxiliary ligand salt (2 eq) and potassium carbonate (5 eq) are reacted at 110°C for 12 h with ethylene glycol ethyl ether as the reaction solvent (10 eq). After the reaction is completed, the mixture is extracted and washed with DCM and water three times, and the crude product is obtained under reduced pressure, and then separated by column chromatography to obtain a pure iridium complex.

[0047]

[0048]

[0049] The three iridium-chloride bridging products corresponding to the main ligands were reacted with the four-membered ring auxiliary ligands amine salt or potassium salt cf3pss and cf3poo respectively to obtain six four-membered ring near-infrared iridium complexes based on Ir-SPS and Ir-OPO coordination configurations.

[0050] Another object of the present invention is to provide the use of the synthesized four-membered ring near-infrared iridium complex in an organic electroluminescent device.

[0051] Another object of the present invention is to provide an organic electroluminescent device of a four-membered ring near-infrared iridium complex; the organic electroluminescent device of the four-membered ring near-infrared iridium complex is prepared by vacuum coating.

[0052] Beneficial effects of the present invention:

[0053] The present invention greatly improves the luminescence efficiency of near-infrared iridium complexes by designing a four-membered ring structure with SS coordination. This structure increases the π-π conjugation effect by adjusting the charge distribution and electron transition path within the molecule, making the energy transfer of the excited state more efficient. Due to its unique triplet luminescence characteristics, the iridium complex can directly transition from the triplet excited state to the ground state, emitting efficient near-infrared light, thereby greatly improving the fluorescence quantum yield of the luminescent material. This emission characteristic is very suitable for application in optical fiber communication and biomedical imaging, because its wavelength coincides with the transparent window of biological tissue, thereby improving the signal-to-noise ratio of detection and imaging.

[0054] The present invention realizes the synthesis of the main ligand with high yield by adopting the simple and effective organic synthesis method of Suzuki coupling reaction. A new main ligand can be obtained through one reaction, and then reacted with iridium trichloride to form an iridium-chlorine bridged product; the main ligand is synthesized by a one-step method, and has a very high synthesis yield (greater than 85%); the corresponding iridium-chlorine bridged product also has a very high yield (greater than 90%). The design of the four-membered ring auxiliary ligand introduces lithium salt and potassium salt forms with strong air stability, which not only saves the complicated purification steps, but also improves the overall efficiency of the reaction and the practicality of the product. The method avoids the use of harsh conditions during the synthesis process, reduces the cost and the impact on the environment, and is a green synthesis route. The four auxiliary ligands lithium salts CF3CNN, CF3CSS and amine salts or potassium salts CF3PSS, CF3POO obtained by the reaction at the same time are of high purity and very stable in the air, and can be directly used to react with the iridium-chlorine bridged product without further purification, which greatly improves the synthesis efficiency.

[0055] In the present invention, the synthesized four-membered ring near-infrared iridium complexes exhibit excellent thermal stability and photoelectrochemical performance. The three iridium-chloride bridged products corresponding to the main ligands are used to react with the four-membered ring auxiliary ligands respectively, and 6 four-membered ring near-infrared iridium complexes based on Ir-NCN and Ir-SCS coordination configurations are obtained; 6 four-membered ring near-infrared iridium complexes based on Ir-SPS and Ir-OPO coordination configurations are obtained; the main ligand has a large π conjugated system, which is conducive to achieving an effective red shift of the emission spectrum; through thermogravimetric analysis (TGA), ultraviolet-visible absorption spectroscopy and electrochemical tests, it is confirmed that these materials can still maintain chemical stability and electroluminescent properties under high temperature conditions. Its highly stable structure makes it difficult to degrade or fail in practical applications, and is suitable for use in optoelectronic devices that work for a long time, especially for those industrial applications that require high reliability, such as night vision equipment and sensors.

[0056] The iridium complex obtained by the present invention has a three-dimensional octahedral configuration, which can effectively suppress the quenching effect caused by concentration, thereby realizing the vacuum evaporation method used in the present invention to prepare organic electroluminescent devices (OLEDs). Compared with the traditional spin coating method, the evaporation method can form a more uniform and tightly packed organic film. This technology is conducive to improving the migration rate and recombination efficiency of holes and electrons in the device, and improving the photoelectric performance of the overall device. In addition, by selecting 26DCzppy with good bipolar transmission as the main material, guest doping with near-infrared iridium complexes, accurately controlling the electronic energy level and device structure of the light-emitting layer, further optimizing the thickness of the hole transport layer TAPC and the electron transport layer TmPypb, the luminous efficiency and stability of the device are improved. These innovations and adjustments not only improve the performance of OLED devices, but also lay the foundation for large-area manufacturing and other optoelectronic applications in the future.

[0057] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0059] Figure 1 It is a schematic diagram of the technical route of the present invention;

[0060] Figure 2 is the H NMR spectrum of (tfmnqz)2Ir(cf3css) described in the embodiments of the present invention;

[0061] Figure 3This is a schematic diagram of an OLED device of the near-infrared iridium complex described in an embodiment of the present invention;

[0062] Figure 4 This is a spectrum diagram of the electroluminescent device described in an embodiment of the present invention. DETAILED DESCRIPTION

[0063] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] The invention discloses a method for synthesizing a four-membered ring near-infrared iridium complex based on SS coordination, which comprises the following steps: synthesizing a near-infrared main ligand and a corresponding iridium-chloride bridging product; designing and synthesizing a four-membered ring auxiliary ligand; and then reacting the iridium-chloride bridging product corresponding to the near-infrared main ligand with the four-membered ring auxiliary ligand to obtain a four-membered ring near-infrared iridium complex. The two act synergistically to form a novel near-infrared iridium complex to achieve emission in the near-infrared region. The synthesized four-membered ring near-infrared iridium complex is applied to organic electroluminescent devices.

[0065] The present invention will be described below in conjunction with specific embodiments:

[0066] Example 1

[0067] The four-membered ring near-infrared iridium complex based on SS coordination described in this embodiment, the main ligand of the near-infrared iridium complex adopts an iridium-chloride bridged product, and reacts with a four-membered ring auxiliary ligand to obtain a four-membered ring near-infrared iridium complex, wherein the four-membered ring auxiliary ligand includes but is not limited to the following structure:

[0068]

[0069] Where X=N is represented by cf3cnn, and X=S is represented by cf3css;

[0070]

[0071] Where X=S, Y=HNEt3 is represented as cf3pss, and X=O, Y=K is represented as cf3poo.

[0072] In this embodiment, the four-membered ring near-infrared iridium complex includes but is not limited to the following structure:

[0073]

[0074] Where X=N is represented by (tfmnqz)2Ir(cf3cnn), and X=S is represented by (tfmnqz)2Ir(cf3css);

[0075]

[0076] Where X=N is represented by (tfmnbqz)2Ir(cf3cnn), and X=S is represented by (tfmnbqz)2Ir(cf3css);

[0077]

[0078] Wherein X=N is represented by (tfmabqz)2Ir(cf3cnn), and X=S is represented by (tfmabqz)2Ir(cf3css);

[0079]

[0080] Wherein X=S is represented by (tfmnqz)2Ir(cf3pss), and X=O is represented by (tfmnqz)2Ir(cf3poo);

[0081]

[0082] Wherein X=S is represented by (tfmnbqz)2Ir(cf3pss), and X=O is represented by (tfmnbqz)2Ir(cf3poo);

[0083]

[0084] Among them, X=S is represented by (tfmabqz)2Ir(cf3pss), and X=O is represented by (tfmabqz)2Ir(cf3poo).

[0085] Example 2

[0086] The method for synthesizing a four-membered ring near-infrared iridium complex based on SS coordination described in this embodiment comprises:

[0087] S1: Synthesis of near-infrared primary ligands and corresponding iridium-chloride bridged products;

[0088] S2: Design and synthesis of four-membered ring auxiliary ligands;

[0089] S3: The iridium-chloride bridged product corresponding to the near-infrared main ligand is reacted with the four-membered ring auxiliary ligand to obtain a four-membered ring near-infrared iridium complex.

[0090] In this embodiment, the general synthesis formula of the near-infrared main ligand and the corresponding iridium-chloride bridged product is as follows:

[0091]

[0092] Utilize suzuki coupling reaction to obtain three novel primary ligands by corresponding boric acid and chloro-substituent reaction, and then respectively react with iridium trichloride to obtain the iridium chlorine bridged products corresponding to these three primary ligands. Their synthetic route is as shown above. The primary ligand in the present embodiment can be synthesized by a one-step method, and has a very high synthesis yield, in addition, the iridium chlorine bridged products corresponding to them also have a very high productive rate.

[0093] Example 3

[0094] The design and synthesis formula of the four-membered ring auxiliary ligand described in this embodiment are as follows:

[0095]

[0096] In this embodiment, the design and synthesis of the four-membered ring auxiliary ligand are as follows:

[0097] The lithium salts of two auxiliary ligands cf3cnn and cf3css are obtained by reacting n-BuLi and bis(4-(trifluoromethyl)phenyl)amine with N,N′-diisopropylcarbodimethylamine or carbon disulfide respectively; the amine salts or potassium salts of two auxiliary ligands cf3pss and cf3poo are obtained by reacting bis(4-(trifluoromethyl)phenyl)phosphine with sulfur powder or hydrogen peroxide respectively. As shown above. The four auxiliary ligands obtained by the reaction are of high purity and very stable in the air, and can be directly used to react with the iridium-chlorine bridged product without further purification, which greatly improves the synthesis efficiency.

[0098] Example 4

[0099] The four-membered ring near-infrared iridium complex obtained by reacting the iridium-chloride bridging products corresponding to the near-infrared main ligand with the four-membered ring auxiliary ligand described in this embodiment includes but is not limited to: using the three iridium-chloride bridging products corresponding to the main ligand (D1, D2, D3) to react with the four-membered ring auxiliary ligand lithium salt (cf3cnn and cf3css) to obtain 6 four-membered ring near-infrared iridium complexes based on Ir-NCN and Ir-SCS coordination configurations; similarly, using the three iridium-chloride bridging products corresponding to the main ligand (D1, D2, D3) to react with the four-membered ring auxiliary ligand triethylamine salt or potassium salt (cf3pss and cf3poo) to obtain 6 four-membered ring near-infrared iridium complexes based on Ir-SPS and Ir-OPO coordination configurations.

[0100] The general reaction formulas are as follows:

[0101]

[0102]

[0103] The structure of the new near-infrared iridium complex was characterized by nuclear magnetic hydrogen spectrum, fluorine spectrum, high-resolution mass spectrometry and XRD single crystal analysis. Then, the photophysical properties, thermal stability, electrochemical properties and electron cloud density distribution of the new near-infrared iridium complex were studied by UV-visible absorption spectroscopy, fluorescence spectrometer, TGA, electrochemistry and theoretical calculations. The relationship between the molecular structure of the iridium complex and these properties was explored, and near-infrared iridium complex luminescent materials with excellent performance were screened out.

[0104] Example 5

[0105] The application of the synthesized four-membered ring near-infrared iridium complex in organic electroluminescent devices described in this embodiment.

[0106] In this embodiment, the organic electroluminescent device of the four-membered ring near-infrared iridium complex is prepared by vacuum coating.

[0107] In this embodiment, a vacuum evaporation method is used to prepare an organic electroluminescent device (OLEDs) of a near-infrared iridium complex. Compared with the solution spin coating method used to prepare devices for existing near-infrared iridium complexes, this embodiment has more obvious advantages, such as the evaporated organic film is more uniform, the molecular arrangement is more regular, and it is more conducive to the transmission and recombination of holes and electrons in the light-emitting layer, which can improve the device performance to a certain extent. Secondly, according to the energy level of the near-infrared iridium complex, 26DCzppy with bipolar transmission performance can be selected as the main material, and the near-infrared iridium complex is guest doped to prepare its OLEDs device, such as Figure 3 At the same time, the device structure can also be optimized to a certain extent, such as changing the doping concentration and thickness of the near-infrared iridium complex, and changing the thickness of the hole transport layer TAPC and the electron transport layer TmPypb, so that holes and electrons can be transported and recombine more efficiently, thereby improving device performance.

[0108] In summary, the present invention first obtains three new main ligands through Suzuki coupling reaction, and then reacts with iridium trichloride to obtain corresponding iridium-chloride bridged products; simultaneously synthesizes four four-membered ring auxiliary ligands; then utilizes the auxiliary ligands to react with the iridium-chloride bridged products to obtain corresponding near-infrared iridium complex luminescent materials; further prepares OLEDs devices, studies their device performance, further optimizes the devices, and improves the device performance. Through the analysis of device data, the molecular design of near-infrared iridium complexes is further guided, and finally a high-efficiency near-infrared iridium complex luminescent material is obtained.

[0109] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A four-membered ring near-infrared iridium complex based on SS coordination, wherein the main ligand of the near-infrared iridium complex adopts an iridium-chloride bridged product, which reacts with a four-membered ring auxiliary ligand to obtain a four-membered ring near-infrared iridium complex, characterized in that: The four-membered ring auxiliary ligand includes but is not limited to the following structures: Where X=N is represented by cf3cnn, and X=S is represented by cf3css; Where X=S, Y=HNEt3 is represented as cf3pss, and X=O, Y=K is represented as cf3poo.

2. The four-membered ring near-infrared iridium complex based on SS coordination as claimed in claim 1, characterized in that: The four-membered ring near-infrared iridium complex includes but is not limited to the following structures: Where X=N is represented by (tfmnqz)2Ir(cf3cnn), and X=S is represented by (tfmnqz)2Ir(cf3css); Where X=N is represented by (tfmnbqz)2Ir(cf3cnn), and X=S is represented by (tfmnbqz)2Ir(cf3css); Wherein X=N is represented by (tfmabqz)2Ir(cf3cnn), and X=S is represented by (tfmabqz)2Ir(cf3css); Wherein X=S is represented by (tfmnqz)2Ir(cf3pss), and X=O is represented by (tfmnqz)2Ir(cf3poo); Wherein X=S is represented by (tfmnbqz)2Ir(cf3pss), and X=O is represented by (tfmnbqz)2Ir(cf3poo); Among them, X=S is represented by (tfmabqz)2Ir(cf3pss), and X=O is represented by (tfmabqz)2Ir(cf3poo).

3. The method for synthesizing the complex according to claim 1 or 2, characterized in that: include: S1: Synthesis of near-infrared primary ligands and corresponding iridium-chloride bridged products; S2: Design and synthesis of four-membered ring auxiliary ligands; S3: The iridium-chloride bridged product corresponding to the near-infrared main ligand is reacted with the four-membered ring auxiliary ligand to obtain a four-membered ring near-infrared iridium complex.

4. The synthesis method according to claim 3, characterized in that: The general synthesis formula of the near-infrared main ligand and the corresponding iridium-chlorine bridged product is as follows: a.Pd(Pph3)4,toluene,EtOH,H2O b.IrCl3,2-ethoyxethanol,H2O Boric acid raw materials and chlorinated raw materials are reacted at 110°C for 12 hours in the presence of Pd(PPh3)4 as a catalyst, K2CO3 as a base, toluene as a reaction solvent, and a small amount of ethanol to obtain a main ligand product. The main ligand obtained and iridium trichloride monohydrate are then reacted in ethylene glycol ether and water at 110°C for 12 hours. After the reaction is completed, the reaction is cooled to room temperature. Distilled water is then added to the reaction system, and a large amount of precipitate is found to be generated. The precipitate is filtered and dried to obtain an iridium-chloro-co-alkyne product.

5. The synthesis method according to claim 3, characterized in that: The synthesis of the near-infrared main ligand and the corresponding iridium-chloride bridged product is as follows: three main ligands are obtained by reacting the corresponding boric acid and chlorine through the Suzuki coupling reaction; and then they are reacted with iridium trichloride respectively to obtain the iridium-chloride bridged products corresponding to the three main ligands.

6. The synthesis method according to claim 3, characterized in that: The design and synthesis formula of the four-membered ring auxiliary ligand are as follows: The design and synthesis formula of the four-membered ring auxiliary ligand are as follows: The lithium salts of two auxiliary ligands, cf3cnn and cf3css, are obtained by reacting n-BuLi and bis(4-(trifluoromethyl)phenyl)amine with N,N′-diisopropylcarbodimethylamine or carbon disulfide respectively; the amine salts or potassium salts of two auxiliary ligands, cf3pss and cf3poo, are obtained by reacting bis(4-(trifluoromethyl)phenyl)phosphine with sulfur powder or hydrogen peroxide respectively.

7. The synthesis method according to claim 3, characterized in that: The iridium-chloride bridged product corresponding to the near-infrared main ligand is reacted with the four-membered ring auxiliary ligand to obtain the four-membered ring near-infrared iridium complex, including but not limited to: The three iridium-chloride bridged products corresponding to the main ligands were used to react with the lithium salts cf3cnn and cf3css of the four-membered ring auxiliary ligands to obtain six four-membered ring near-infrared iridium complexes based on Ir-NCN and Ir-SCS coordination configurations. The general reaction formulas are as follows: The three iridium-chloride bridging products corresponding to the main ligands were reacted with the four-membered ring auxiliary ligands amine salt or potassium salt cf3pss and cf3poo respectively to obtain six four-membered ring near-infrared iridium complexes based on Ir-SPS and Ir-OPO coordination configurations.

8. Use of the four-membered ring near-infrared iridium complex as claimed in claim 1 or 2 in an organic electroluminescent device.

9. The use according to claim 8, characterized in that The organic electroluminescent device of the four-membered ring near-infrared iridium complex is prepared by vacuum coating.

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