Pyrroloquinoxaline organic nitrogen-containing electroactive material as well as synthesis and application thereof

Abstract

The invention relates to a pyrroloquinoxaline organic nitrogen-containing electroactive material as well as synthesis and application thereof, discloses a pyrroloquinoxaline organic nitrogen-containing semiconductor luminescent layer material as well as a synthesis method and application thereof in preparation of an electrochromic device, and belongs to the technical field of organic semiconductor materials. A pyrrolo [1, 2-alpha] quinoxaline skeleton is introduced to be combined with triphenylamine, the optical and electrochemical properties of the material are adjusted by using a molecular engineering technology, the electrochromic material with excellent properties is synthesized, and the material has the characteristics of high thermal stability, reversible electrochromic property, high response speed, good cycle stability, high optical transmittance and the like. An electrochromic device prepared from the material as an electrochromic layer has a remarkable electrochromic effect, faster coloring and fading time, good cycling stability and high optical transmittance, and a new thought and direction are provided for development of an electrochromic technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic semiconductor materials, and particularly relates to a pyrroloquinoxaline organic nitrogen-containing electroactive material, a synthesis method thereof, and an application thereof in preparing electrochromic devices. Background Art

[0002] As a kind of intelligent material, electrochromic materials can reversibly change their colors under external electrical stimuli and adjust their absorption, transmission, and reflection characteristics, thus showing broad application prospects in fields such as electronic paper, rearview mirrors, energy storage systems, smart windows, and displays. Electrochromic materials are classified into three major categories according to their main costs: inorganic, organic, and inorganic-organic hybrid materials. Among them, organic electrochromic materials are considered to have great potential due to their excellent characteristics such as high optical contrast, fast response time, and high coloring efficiency.

[0003] In recent years, significant progress has been made in the research of organic electrochromic materials. Researchers can flexibly adjust their optical and electrochemical properties through various molecular engineering techniques to meet different application requirements. Triarylamine (TPA) is a nitrogen-containing organic small molecule composed of three aromatic groups, with good solubility, thermal stability, and excellent redox activity. It is easily oxidized into a highly stable radical cation, making compounds based on triarylamine (TPA) have important potential applications in photoluminescence and electrochromism. In recent years, researchers have further expanded the performance and application scope of TPA-based electrochromic materials by introducing different functional groups and structural units. Compounds based on TPA have important potential applications in photoluminescence and electrochromism. Researchers have continuously expanded the performance and application scope of TPA-based electrochromic materials by introducing different functional groups and structural units, making them show more excellent comprehensive performance while meeting specific requirements. For example, some TPA-based electrochromic materials exhibit excellent photoluminescence performance in the solid state, and at the same time have good electrochromic response speed and stability. Pyrrolo[1,2-α]quinoxaline and its derivatives are a class of important nitrogen heterocyclic compounds, with highly conjugated, planar configurations, remarkable rigidity, and adjustable frameworks. These characteristics make pyrrolo[1,2-α]quinoxaline and its derivatives have broad application prospects in optoelectronic devices, sensors, organic synthesis, and other fields. In recent years, researchers have conducted in-depth studies on the photophysical properties of pyrrolo[1,2-α]quinoxaline and its derivatives, and adjusted their properties by changing functional groups. For example, some solid-state luminescent materials based on pyrrolo[1,2-α]quinoxaline exhibit unique fluorescence emission characteristics, providing new ideas for the design of electrochromic materials.

[0004] Although significant progress has been made in the research of organic electrochromic materials, there are still some deficiencies in the existing technologies. For example, the color change range of some pyrroloquinoxaline-based electrochromic materials is limited, making it difficult to meet the diverse application requirements; the response speed of some materials is slow, affecting their application effects in fields such as high-speed dynamic display; in addition, the stability and cycle life of the materials are also important factors restricting their wide application; meanwhile, the development of new electrochromic materials also faces challenges. Summary of the Invention

[0005] Aiming at the problems in the prior art such as the lack of variety of organic electrochromic materials and the difficulty in regulating their properties, and the limited color change range, slow response speed, insufficient stability and cycle life of the existing pyrroloquinoxaline-based electrochromic materials, the present invention aims to provide a pyrroloquinoxaline organic nitrogen-containing electroactive material, its synthesis method and the application in preparing electrochromic devices. By introducing the pyrrolo[1,2-α]quinoxaline skeleton combined with triphenylamine (TPA), the optical and electrochemical properties of the material are flexibly adjusted by using molecular engineering technology, improving the performance of the electrochromic material.

[0006] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides a pyrroloquinoxaline organic nitrogen-containing electroactive material, the structural formula of which is shown in Formula 1:

[0007] Wherein, R1 is a tert-butyl group or a hydrogen atom; R2 is any one of a hydrogen atom, a trifluoromethyl group and a methyl group.

[0008] Further, it includes any one of the structural formulas shown in Formulas 2 to 4 below: .

[0009] The present invention provides a synthesis method of the above pyrroloquinoxaline organic nitrogen-containing electroactive material, including: (1) Under an inert atmosphere, dissolve compound 1, compound 3 and an auxiliary agent, add a catalyst and a ligand and stir well, and carry out a coupling reaction to obtain a crude product; The structural formula of the compound 1 is: , wherein, R2 is any one of a hydrogen atom, a trifluoromethyl group and a methyl group; The structural formula of the compound 3 is , wherein, R1 is a tert-butyl group or a hydrogen atom; The auxiliary agent is any one of cesium carbonate, potassium carbonate and sodium carbonate, the catalyst is any one of bis(dibenzylideneacetone)palladium, palladium acetate and bis(tri-tert-butylphosphine)palladium, and the ligand is any one of 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl and triphenylphosphine; (2) Purify the crude product obtained in step (1) to obtain a pyrroloquinoxaline organic nitrogen-containing electroactive material.

[0010] The preparation of the compound 1 is specifically as follows: It is obtained by reacting compound 2 with 4-bromobenzaldehyde. The structural formula of the compound 2 is: , wherein, R2 is any one of a hydrogen atom, a trifluoromethyl group, and a methyl group.

[0011] Furthermore, the molar ratio of the compound 2 to 4-bromobenzaldehyde is 1:1, and the reaction conditions are stirring reaction at 80-90 °C for 10-14 h.

[0012] The molar ratio of the compound 1 to the compound 3 is (1-1.6):1; the molar ratio of the auxiliary agent to the compound 1 is (2.5-1):1, the molar ratio of the catalyst to the compound 1 is (0.05-0.1):1, and the molar ratio of the ligand to the compound 1 is (0.05-0.1):1.

[0013] Furthermore, the molar ratio of the compound 1 to the compound 3 is 1:1; the molar ratio of the catalyst to the compound 1 is 2:1.

[0014] Furthermore, the auxiliary agent is Cs2CO3, the catalyst is Pd2(dba)3, and the ligand is XPhos.

[0015] In step (1), the coupling reaction temperature is: 80-120 °C.

[0016] In step (1), the solvent used for dissolution is any one of toluene, acetonitrile, and dichloromethane.

[0017] Furthermore, the solvent used for dissolution in step (1) is toluene.

[0018] The purification is carried out by silica gel column chromatography, and the mobile phase is petroleum ether and dichloromethane with a volume ratio of (2-5):1.

[0019] Furthermore, the mobile phase is petroleum ether and dichloromethane with a volume ratio of 2:1.

[0020] The present invention provides the application of the above-mentioned pyrroloquinoxaline organic nitrogen-containing electroactive material in the preparation of an electrochromic device.

[0021] The electrochromic device uses the above-mentioned pyrroloquinoxaline organic nitrogen-containing electroactive material as an electrochromic layer, and the electrochromic layer generates electrochromism under the action of an external electric field.

[0022] The concentration of the pyrroloquinoxaline organic nitrogen-containing electroactive material is 2.0×10 -3mol / L to 1×10 -5 mol / L, and the solvent is an acetonitrile solution of tetrabutylammonium hexafluorophosphate with a concentration of 0.1 mol / L to 0.5 mol / L.

[0023] Compared with the prior art, the present invention has the following beneficial effects: A pyrroloquinoxaline organic nitrogen-containing electroactive material provided by the present invention combines a pyrrolo[1,2-α]quinoxaline skeleton with triphenylamine, and adjusts the optical and electrochemical properties of the material by using molecular engineering technology, synthesizing an electrochromic material with excellent performance. This material has high thermal stability, reversible electrochromic performance, fast response speed, good cycle stability, and high optical transmittance. Coated on a conductive substrate as an electrochromic layer, an electrochromic device can be prepared, which produces color changes under the action of an external electric field. Compared with the prior art, the electrochromic device provided by the present invention has faster coloring and fading times, good cycle stability, and high optical transmittance, providing new ideas and directions for the development of electrochromic technology.

[0024] Furthermore, the pyrroloquinoxaline organic nitrogen-containing optoelectronic material has good thermal stability, and the 95% thermal decomposition temperatures are 259 o °C (Formula 2), 358 o °C (Formula 3) and 317 o °C (Formula 4); it has stable absorption characteristics during the electrochromic process; the coloring times of the devices prepared therefrom are 206 s (Formula 2), 300 s (Formula 3) and 136 s (Formula 4) respectively, and the fading times are 132 s (Formula 2), 170 s (Formula 3) and 268 s (Formula 4) respectively, which can meet the requirements of most practical applications, especially in occasions where rapid color switching is required; the cycle stability of the devices is 200 (Formula 2), 70 (Formula 3) and 300 cycles (Formula 4), and this characteristic is crucial for the long-term stable operation of electrochromic devices, ensuring the reliability and durability of the devices in practical applications; the maximum transmittance of the devices at 475 nm is 50% (Formula 2), 60% (Formula 3) and 80% (Formula 4) respectively. The high optical transmittance makes these devices have broad application prospects in fields such as transparent electronic devices and smart windows.

[0025] The synthesis method of the pyrroloquinoxaline organic nitrogen-containing electroactive material provided by the present invention combines a pyrrolo[1,2-α]quinoxaline skeleton with triphenylamine, and flexibly adjusts the molecular structure of the material by using molecular engineering technology, successfully preparing a high-performance electrochromic material. This method is simple to operate, uses environmentally friendly raw materials and solvents, has mild reaction conditions, reduces the generation of harmful waste, and the prepared electrochromic material has good stability and reusability, which helps to reduce production costs and environmental pollution.

[0026] The application provided by the present invention is based on the above-mentioned pyrroloquinoxaline organic nitrogen-containing optoelectronic material to prepare an electrochromic device, and the electrochromic device can maintain stable performance during long-term use; this material has a flexible molecular structure, and various color changes can be achieved by adjusting its chemical composition and molecular configuration to meet the requirements of different application scenarios; the electrochromic layer has a fast color change response speed under the action of an external electric field, which is of great significance for electrochromic devices that require rapid response, such as smart windows, displays, etc.; during the electrochromic process, a high color contrast can be exhibited, making the electrochromic device have a clearer and more prominent effect when displaying information or adjusting light; the present invention provides new ideas and directions for the development of electrochromic technology. Description of the Drawings

[0027] Figure 1 It is the ultraviolet-visible absorption and fluorescence spectra of the pyrroloquinoxaline organic nitrogen-containing electroactive materials of Examples 1 to 3 of the present invention; Figure 2 It is the fluorescence lifetime diagram of the pyrroloquinoxaline organic nitrogen-containing electroactive materials of Examples 1 to 3 of the present invention; Figure 3 It is the thermogravimetric diagram of the pyrroloquinoxaline organic nitrogen-containing electroactive materials of Examples 1 to 3 of the present invention; Figure 4 It is the emission spectrum diagram of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 2) of Example 1 of the present invention in different polar solvents; Figure 5 It is the emission spectrum diagram of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 3) of Example 2 of the present invention in different polar solvents; Figure 6 It is the emission spectrum diagram of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 4) of Example 3 of the present invention in different polar solvents; Figure 7 It is the cyclic voltammogram of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 2) of Example 1 of the present invention.

[0028] Figure 8 It is the cyclic voltammogram of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 3) of Example 2 of the present invention; Figure 9 It is the cyclic voltammogram of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 4) of Example 3 of the present invention; Figure 10 It is the spectroelectrochemical test of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 2) of Example 1 of the present invention; Figure 11Spectroelectrochemical test of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 3) in Example 2 of the present invention; Figure 12 Spectroelectrochemical test of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 4) in Example 3 of the present invention; Figure 13 Graph of the coloring time (Tc) and fading time (Tb) of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 2) in Example 1 of the present invention; Figure 14 Graph of the coloring time (Tc) and fading time (Tb) of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 3) in Example 2 of the present invention; Figure 15 Graph of the coloring time (Tc) and fading time (Tb) of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 4) in Example 3 of the present invention; Figure 16 Spectral graph of the ion radical property test of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 2) in Example 1 of the present invention; Figure 17 Spectral graph of the ion radical property test of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 3) in Example 2 of the present invention; Figure 18 Spectral graph of the ion radical property test of the pyrroloquinoxaline organic nitrogen-containing electroactive material (Formula 4) in Example 3 of the present invention; Figure 19 Cyclic stability test graph of the pyrroloquinoxaline organic nitrogen-containing electroactive materials in Examples 1 to 3 of the present invention; Figure 20 Electron paramagnetic resonance spectral graph of the pyrroloquinoxaline organic nitrogen-containing electroactive materials in Examples 1 to 3 of the present invention; Detailed implementation manners In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings: I. Specific embodiments Embodiment 1 This embodiment provides a pyrroloquinoxaline organic nitrogen-containing electroactive material, and the specific preparation process is as follows: A mixture of 5-methyl-2-(1H-pyrrol-1-yl)aniline (3.0 mmol, 513.7 mg), 4-bromobenzaldehyde (3.0 mmol, 1.0 equiv., 555.0 mg), and ethanol (10 mL) was added to a round-bottom flask (25 mL), and acetic acid (0.6 mmol, 36 mg, 0.2 equiv.) was added. Then the reaction mixture was heated to 85 °C and stirred for 12 hours; after the reaction was completed, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography to obtain 7-methyl-4-(4'-bromophenyl)pyrrolo[1,2-α]quinoxaline.

[0031] Under nitrogen protection, 7-methyl-4-(4'-bromophenyl)pyrrolo[1,2-α]quinoxaline (194.2 mg, 0.5 mmol), bis(4-tert-butylphenyl)amine (0.5 mmol, 1.1 equiv., 123.7 mg), and Cs2CO3 (325.8 mg, 1.0 mmol, 2 equiv.) were dissolved in toluene (10 mL) and magnetically stirred. Subsequently, Pd2(dba)3 (14 mg, 0.015 mmol, 0.03 equiv.) and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (XPhos, 28.6 mg, 0.06 mmol, 0.12 equiv.) were added to the mixture. At 100 oThe reaction was carried out at

[0032] C. Monitored by TLC, after the reaction was completed, the reaction was quenched with ice-saline, extracted with dichloromethane, the organic phases were combined, the organic layer was dried over anhydrous magnesium sulfate, filtered by suction, concentrated, and the crude product was obtained. Purified by silica gel column chromatography (petroleum ether:dichloromethane = 1:2) to obtain a yellow solid (228 mg, yield 85%), which was the pyrroloquinoxaline organic nitrogen-containing electroactive material. 1 H NMR (400 MHz, Chloroform- d ) δ : 7.94 (dd, J J = 2.8, 1.3 Hz, 1H), 7.90 –7.86 (m, 2H), 7.83 (t, J J = 1.5 Hz, 1H), 7.75 (d, J J = 8.3 Hz, 1H), 7.31 (d, J J = 2.3Hz, 2H), 7.30 (q, J J = 2.8, 2.3 Hz, 3H), 7.19 – 7.16 (m, 2H), 7.14 – 7.09 (m,4H), 7.04 (dd, J J = 4.1, 1.3 Hz, 1H), 6.86 (dd, J J = 4.0, 2.7 Hz, 1H), 2.50 (s,3H), 1.34 (s, 18H). 13 C NMR (101 MHz, Chloroform- d ) δ : 153.8, 149.7, 146.3, 144.7, 136.3,134.9, 131.2, 129.8, 129.4, 128.1, 126.1, 125.3, 124.9, 124.6, 121.7, 114.2,113.5, 113.3, 108.3, 34.3, 31.4, 21.1. HRMS-ESI (m / z) Calcd for C 38 H 39 N3[M+H] + : 538.3144; Found: 538.3146. The confirmed structural formula is as follows: .

[0033] Example 2 This example provides a pyrroloquinoxaline organic nitrogen-containing electroactive material, and the specific preparation process is as follows: A mixture of 2-(1H-pyrrol-1-yl)aniline (3.0 mmol, 507.6 mg), 4-bromobenzaldehyde (3.0 mmol, 1.0 equiv., 555.0 mg), and ethanol (10 mL) was added to a round-bottom flask (25 mL). After adding acetic acid (0.6 mmol, 36 mg, 0.2 equiv.), the reaction mixture was then heated to 85 °C and stirred for 12 hours. After the reaction was completed, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography to obtain 4-(4'-bromophenyl)pyrrolo[1,2-α]quinoxaline.

[0034] Under nitrogen protection, 4-(4'-bromophenyl)pyrrolo[1,2-α]quinoxaline (183.1 mg, 0.5 mmol), bis(4-tert-butylphenyl)amine (0.5 mmol, 1.1 equiv., 123.7 mg), and Cs2CO3 (325.8 mg, 1.0 mmol, 2 equiv.) were dissolved in toluene (10 mL) and magnetically stirred. Subsequently, Pd2(dba)3 (14 mg, 0.015 mmol, 0.03 equiv.) and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (XPhos, 28.6 mg, 0.06 mmol, 0.12 equiv.) were added to the mixture. The reaction was carried out at 100 o °C. Monitored by TLC, after the reaction was completed, the reaction was quenched with ice brine, extracted with dichloromethane, the organic phases were combined, the organic layer was dried over anhydrous magnesium sulfate, filtered by suction, concentrated, and a crude product was obtained. Purification by silica gel column chromatography (petroleum ether:dichloromethane = 1:2) gave a yellow solid (209 mg, yield 80%), which was the pyrroloquinoxaline organic nitrogen-containing electroactive material.

[0035] The corresponding physical and chemical identification data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ: 8.03 (d, J J = 7.7 Hz, 1H), 8.00 – 7.97(m, 1H), 7.88 (t, J J = 9.1 Hz, 3H), 7.52 – 7.41 (m, 2H), 7.31 (d, J J = 8.6 Hz, 4H),7.18 (d,J = 8.6 Hz, 2H), 7.11 (d, J = 8.6 Hz, 4H), 7.07 (d, J = 3.7 Hz, 1H), 6.91– 6.87 (m, 1H), 1.34 (s, 18H). 13 C NMR (100 MHz, Chloroform- d ) δ: 154.0, 149.9, 146.4, 144.6, 130.0,129.5, 129.0, 127.1, 126.2, 125.4, 125.3, 124.6, 121.7, 114.5, 113.9, 113.6,108.7, 34.4, 31.5. HRMS-ESI (m / z) Calculated: C 37 H 37 N3[M+H] + : 524.2987; Found: 524.3058. The confirmed structural formula is as follows: 。

[0036] Example 3 This example provides a pyrroloquinoxaline organic nitrogen-containing electroactive material, and the specific preparation process is as follows: A mixture of 5-(trifluoromethyl)-2-(1H-pyrrol-1-yl)aniline (3.0 mmol, 741.5 mg), 4-bromobenzaldehyde (3.0 mmol, 1.0 equiv, 555.0 mg), and ethanol (10 mL) was added to a round-bottom flask (25 mL). After adding acetic acid (0.6 mmol, 36 mg, 0.2 equiv), the reaction mixture was heated to 85 °C and stirred for 12 h. After completion of the reaction, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography to obtain 7-(trifluoromethyl)-4-(4'-bromophenyl)pyrrolo[1,2-α]quinoxaline.

[0037] Under nitrogen protection, 7-trifluoromethyl-4-(4'-bromophenyl)pyrrolo[1,2-α]quinoxaline (246.6 mg, 0.5 mmol), bis(4-tert-butylphenyl)amine (0.5 mmol, 1.1 equiv., 123.7 mg) and Cs2CO3 (325.8 mg, 1.0 mmol, 2 equiv.) were dissolved in toluene (10 mL) and stirred magnetically. Subsequently, Pd2(dba)3 (14 mg, 0.015 mmol, 0.03 equiv.) and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (XPhos, 28.6 mg, 0.06 mmol, 0.12 equiv.) were added to the mixture. The reaction was carried out at 100 o °C and monitored by TLC. After the reaction was completed, the reaction was quenched with ice brine, extracted with dichloromethane, the organic phases were combined, the organic layer was dried over anhydrous magnesium sulfate, filtered by suction, concentrated, and the crude product was obtained. It was purified by silica gel column chromatography (petroleum ether: dichloromethane = 1:2) to obtain a yellow solid (266 mg, yield 90%), which was the pyrroloquinoxaline organic nitrogen-containing electroactive material.

[0038] The corresponding physical and chemical identification data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ : 8.29 (s, 1H), 8.00 (s, 1H), 7.93 (d, J = 8.6 Hz, 1H), 7.90 – 7.87 (m, 2H), 7.69 (d, J = 8.5 Hz, 1H), 7.31 (dd, J = 8.6,2.0 Hz, 5H), 7.16 (dd, J = 8.7, 1.9 Hz, 3H), 7.11 (dd, J = 8.6, 1.9 Hz, 6H), 6.94(dt, J = 4.1, 2.3 Hz, 1H), 1.34 (d, J = 2.0 Hz, 18H). 13 C NMR (100 MHz, Chloroform- d ) δ : 155.2, 150.3, 146.7, 144.5, 136.2, 130.2, 129.5, 129.1, 127.5(d,J = 4.4 Hz), 127.5, 126.2, 125.5, 124.8, 123.2 (d, J = 3.8 Hz), 123.2, 121.3, 117.4, 115.1, 114.7, 114.2, 109.7, 34.4, 31.4. HRMS-ESI (m / z) Theoretical: C 38 H 36 F3N3[M + H] + : 592.2861; Experimental: 592.2940. The structural formula is as follows: .

[0039] Example 4 Based on Examples 1 - 3, the pyrroloquinoxaline organic nitrogen - containing electroactive materials obtained in Examples 1 - 3 were subjected to UV - Vis absorption spectroscopy, fluorescence spectroscopy, and thermogravimetric tests. The specific results are shown in the appendix Figures 1 - 6 .

[0040] See the appendix Figure 1 , which are the UV - Vis absorption and fluorescence spectra of the pyrroloquinoxaline organic nitrogen - containing electroactive materials obtained in Example 1 (Formula 2), Example 2 (Formula 3), and Example 3 (Formula 4) of the present invention. The maximum absorption wavelengths are 377 nm, 376 nm, and 388 nm respectively. These absorption peaks are attributed to the absorption caused by π - π* transitions, that is, the electrons in the molecule transition from the π orbital in the ground state to the π orbital in the excited state; the maximum emission wavelengths of the pyrroloquinoxaline organic nitrogen - containing electroactive materials in Example 1 (Formula 2), Example 2 (Formula 3), and Example 3 (Formula 4) of the present invention are 517 nm, 521 nm, and 532 nm respectively. This is attributed to the emission caused by intramolecular charge transfer (ICT), that is, the electrons in the molecule transfer from the donor part to the acceptor part. Since the acceptor PQ(CH3 < H < CF3) enhances the electron - accepting ability, the intramolecular charge - transfer effect gradually increases. Therefore, Compound Formula 4 exhibits the longest emission wavelength.

[0041] See the appendix Figure 2 , which shows that the fluorescence lifetimes of the three compounds of the pyrroloquinoxaline organic nitrogen - containing electroactive materials obtained in Example 1 (Formula 2), Example 2 (Formula 3), and Example 3 (Formula 4) of the present invention are 4.68 ns, 4.36 ns, and 5.62 ns respectively.

[0042] See the appendix Figure 3, the three compounds of pyrroloquinoxaline organic nitrogen-containing electroactive materials obtained in Example 1 (Formula 2), Example 2 (Formula 3) and Example 3 (Formula 4) of the present invention all exhibit good stability, and their thermal decomposition temperatures are 358 o °C, 259 o °C and 317 o °C.

[0043] See the appendix Figures 4 - 6 , for the three compounds of pyrroloquinoxaline organic nitrogen-containing electroactive materials obtained in Example 1 (Formula 2), Example 2 (Formula 3) and Example 3 (Formula 4) of the present invention, in the emission spectra in different polar solvents, as the solvent polarity increases, the three compounds show an obvious solvatochromic effect, which further indicates that the emission peaks of the three compounds originate from intramolecular charge transfer.

[0044] II. Performance Testing 1. Cyclic Voltammetry Testing Based on Examples 1 to 3, cyclic voltammetry testing was carried out on the pyrroloquinoxaline organic nitrogen-containing electroactive materials obtained in Examples 1 to 3. The cyclic voltammograms of Compounds Formula 2, Formula 3 and Formula 4 are as Figures 7 - 9 shown.

[0045] A three-electrode system was adopted, with a platinum electrode as the counter electrode, a silver / silver chloride electrode as the reference electrode, a platinum-ITO glass plate as the working electrode, ferrocene as the internal standard substance, and tetrabutylammonium hexafluorophosphate (Bu4NPF6) as the electrolyte for testing. The CV curve shows two paired redox peaks at the conversion center of the nitrogen atom in the triphenylamine part in the neutral state or the radical cation state within the potential range of 0 V to 1.8 V. Compared with those with electron-withdrawing substituents such as trifluoromethyl group (Formula 4), the pyrrolo[1,2-α]quinoxaline core with electron-donating substituents such as methyl group (Formula 2) is more easily oxidized. In fact, the oxidation potential value of the electron-donating group is much lower than that of the electron-withdrawing group. We conclude that the obvious reversible redox peaks of Compounds Formula 2, Formula 3 and Formula 4 at 1.11 V, 1.10 V and 1.19 V are attributed to the cation radicals formed by the single-electron oxidation of the triphenylamine nitrogen atom center, while the anodic peak at 0.9 V is attributed to the oxidation of TBAPF6. Among the three compounds, Formula 2 has the lowest first oxidation peak at 1.10 V, indicating the strongest electron-donating ability and IV-CT resonance effect between the TPA center and the methyl group. As the applied potential increases, the second oxidation peak of Formula 2 appears at 1.27 V, indicating that the pyrrolo[1,2-α]quinoxaline structure generates additional redox active sites. Other compounds show CV curves similar to those of Formula 2. The redox capacity and electrochromic reversibility of Compound Formula 4 are in the range of 0 to 1.8 V (Ag / Ag +remains almost unchanged during the repeated scanning process of (). This result confirms that replacing the CF3 group on the receptor endows the cation radical and dication states with comparable stability.

[0046] III. Application Examples 1. Preparation of an electrochromic device based on Example 1 (Formula 2) The electrochromic device has a sandwich structure. A liquid cavity is constructed between two ITO-coated glass plates, and the electrochromic active material is placed in the sandwich cavity to obtain the electrochromic device. The materials used are ITO glass (with a resistance of 10 Ω / square), multimeter, tweezers, scissors, syringe, 3M double-sided tape, UV curable glue, copper sticker, etc. First, the ITO glass (2.0 cm × 4.0 cm) is ultrasonically cleaned in acetone for thirty minutes and then blown dry with nitrogen; next, a liquid groove is constructed on one piece of ITO glass using 3M double-sided tape and combined with the other piece of ITO glass to obtain an ITO sandwich with a liquid cavity structure; finally, an acetonitrile solution containing 2.0×10 -3 mol / L of Formula 2 and 0.1 mol / L of tetrabutylammonium hexafluorophosphate is injected into the liquid cavity to obtain a liquid electrochromic device.

[0047] 2. Preparation of an electrochromic device based on Example 2 (Formula 3) The electrochromic device has a sandwich structure. A liquid cavity is constructed between two ITO-coated glass plates, and the electrochromic active material is placed in the sandwich cavity to obtain the electrochromic device. The materials used are ITO glass (with a resistance of 10 Ω / square), multimeter, tweezers, scissors, syringe, 3M double-sided tape, UV curable glue, copper sticker, etc. First, the ITO glass (2.0 cm × 4.0 cm) is ultrasonically cleaned in acetone for thirty minutes and then blown dry with nitrogen; next, a liquid groove is constructed on one piece of ITO glass using 3M double-sided tape and combined with the other piece of ITO glass to obtain an ITO sandwich with a liquid cavity structure; finally, an acetonitrile solution containing 2.0×10 -3 mol / L of Formula 3 and 0.1 mol / L of tetrabutylammonium hexafluorophosphate is injected into the liquid cavity to obtain a liquid electrochromic device.

[0048] 3. Preparation of an electrochromic device based on Example 3 (Formula 4) The electrochromic device adopts a sandwich structure. A liquid cavity is constructed between two glass plates covered with ITO, and the electrochromic active material is placed in the sandwich cavity to obtain the electrochromic device. They are ITO glass (with a resistance of 10 Ω / square), multimeter, tweezers, scissors, syringe, 3M double-sided tape, ultraviolet curable glue, copper sticker, etc. First, the ITO glass (2.0 cm × 4.0 cm) is ultrasonically cleaned in acetone for thirty minutes and blown clean with nitrogen; next, a liquid groove is constructed on one piece of ITO glass using 3M double-sided tape and combined with another piece of ITO glass to obtain an ITO sandwich with a liquid cavity structure; finally, an acetonitrile solution containing 2.0×10 -3 mol / L of formula 4 and 0.1 mol / L of tetrabutylammonium hexafluorophosphate is injected into the liquid cavity to obtain a liquid electrochromic device.

[0049] 4. Performance Testing (1)Spectroelectrochemical Testing The optical properties of the above-mentioned electrochromic device (ECD) were evaluated by using spectroelectrochemistry, and the results are shown in the appendix Figures 10 - 12 as follows.

[0050] In the neutral state, that is, at 0 V, compound of formula 2 exhibits a strong absorption at a wavelength of about 378 nm, which is the characteristic peak of triphenylamine. The absorption peaks of compounds of formula 3 and formula 4 in the initial neutral state are at 377 nm and 388 nm respectively. As the applied voltage increases from 0 to 2.0 V, the intensity of the absorption peak at 460 nm gradually increases. In addition, compounds of formula 3 and formula 4 exhibit similar electrochromic properties, and their color change wavelengths are 462 nm and 475 nm respectively. This spectral change is attributed to the formation of stable cation radicals within the TPA structure in the compound. When the applied voltage increases to 2.5 V, a new broadband centered at 695 nm is formed. This spectral change can be attributed to the formation of dication. The ultraviolet-visible absorption changes of the ECD observed at different potentials are completely reversible and are accompanied by significant color changes. In the absence of voltage or with negative voltage, the cation radicals turn back into neutral molecules again. The completely reversible electrochromic mechanism provides the feasibility for the fabrication of electrochromic devices. The ECDs of compounds of formula 2, formula 3, and formula 4 change from the transmissive neutral state (light yellow) to the highly absorptive semi-oxidized (yellow) and fully oxidized (brown or orange) states.

[0051] (2)Color Change Performance Testing The coloring time (Tc) and fading time (Tb) of the three devices were studied. The coloring time refers to the time required for the color-changing material to change from a neutral state to a colored state; while the fading time refers to the time required for the color-changing material to return to a neutral state from a colored state. Generally, the coloring / fading time is the time required for the transmittance to reach 90% of the maximum transmittance difference before and after the color change. From the electrochemical spectrum, it can be seen that the maximum absorption produced by the color change of Formula 2, Formula 3 and Formula 4 is at 675-700 nm. Figure 13 , 14 As shown in Figures 1 and 2, the fading times of the devices based on Formula 2, Formula 3, and Formula 4 are 206 s, 300 s, and 136 s, respectively, and are 132 s, 170 s, and 268 s. It can be seen that Formula 4 has a faster coloring time, which indicates that the stability of the cation radical of Formula 4 is more stable than that of Formula 2 and Formula 3. Figure 16 As shown, the cycle stability of the three materials was tested, and the cycle stability refers to the number of cycles between the colored state and the faded state of the device. The cycle stability of the devices of Formulas 2 to 4 is 200, 70 and 300 cycles. Formula 4 has stronger cycle stability than Formulas 2 and 3.

[0052] (3) Cationic free radical characteristics test The cation radicals of triphenylamine derivatives generated in DCM / ACN (1:1, V / V) solvent were characterized by UV absorption spectroscopy. After adding 1.0 equivalent of Cu(ClO4)2, the original absorption peak of compound 2 at 372 nm decreased, and new absorption peaks gradually appeared at 475 nm and 688 nm, compound 3 showed new absorption peaks at 461 nm and 686 nm, and compound 4 showed new absorption peaks at 476 nm and 689 nm. Figures 17 - 19 All the higher wavelength peaks start from the addition of 0.6 equivalents of oxidant. This is because the triphenylamine structure in the compound generates free radical cations under the oxidation of Cu(ClO4)2, and then some of the free radical cations are converted to cationic states through secondary oxidation. Figure 20 Similar three-line EPR spectra of compounds 2, 3, and 4 in the range of 3300-3500 G were shown, and the g values ​​of these cation radicals were 2.0005, 2.0002, and 2.0004, respectively.

[0053] This embodiment comprehensively evaluates the performance of electrochromic devices based on compound formula 2, formula 3 and formula 4 through spectroelectrochemical testing, color change performance testing and cation free radical characteristic testing. The results show that these devices have significant electrochromic effects, good reversibility and cycle stability, and characteristic cation free radical characteristics. In particular, compound formula 4 has a faster coloring time and stronger cycle stability, showing application potential in the field of electrochromic devices.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention. The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A pyrroloquinoxaline organic nitrogen-containing electroactive material, characterized in that: The structural formula is shown in Formula 1: Wherein, R1 is a tert-butyl group or a hydrogen atom; R2 is any one of a hydrogen atom, a trifluoromethyl group and a methyl group.

2. A pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 1, characterized in that: Including any one of the structural formulas shown in Formula 2 to Formula 4: 。 3. A method for synthesizing a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 1 or 2, characterized in that: include: (1) Under an inert atmosphere, compound 1, compound 3 and an auxiliary agent are dissolved, a catalyst and a ligand are added and stirred, and a coupling reaction is performed to obtain a crude product; The structural formula of the compound 1 is: , wherein R2 is any one of a hydrogen atom, a trifluoromethyl group and a methyl group; The structural formula of the compound 3 is , wherein R1 is a tert-butyl group or a hydrogen atom; The auxiliary agent is any one of cesium carbonate, potassium carbonate, and sodium carbonate; the catalyst is any one of tris-dibenzylideneacetone dipalladium, palladium acetate, and bis(tri-tert-butylphosphine)palladium; and the ligand is any one of 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl and triphenylphosphine; (2) Purifying the crude product obtained in step (1) to obtain a pyrroloquinoxaline organic nitrogen-containing electroactive material.

4. The method for synthesizing a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 3, characterized in that: The preparation of the compound 1 is as follows: Compound 2 is reacted with 4-bromobenzaldehyde to obtain the compound 1, wherein the structural formula of the compound 2 is: , wherein R2 is any one of a hydrogen atom, a trifluoromethyl group and a methyl group.

5. The method for synthesizing a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 4, characterized in that: The molar ratio of the compound 2 to 4-bromobenzaldehyde is 1:1, and the reaction conditions are stirring at 80-90° C. for 10-14 hours.

6. The method for synthesizing a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 3, characterized in that: The molar ratio of the compound 1 to the compound 3 is (1-1.6):1; the molar ratio of the auxiliary agent to the compound 1 is (2.5-1):1; the molar ratio of the catalyst to the compound 1 is (0.05-0.1):1; and the molar ratio of the ligand to the compound 1 is (0.05-0.1):

1.

7. The method for synthesizing a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 3, characterized in that: In step (1), the coupling reaction temperature is 80-120°C.

8. The method for synthesizing a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 3, characterized in that: In step (1), the solvent used for dissolving is any one of toluene, acetonitrile and dichloromethane.

9. The method for synthesizing a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 3, characterized in that: The purification was performed by silica gel column chromatography, and the mobile phase was petroleum ether and dichloromethane in a volume ratio of (2-5):

1.

10. Use of a pyrroloquinoxaline organic nitrogen-containing electroactive material according to claim 1 or 2 in the preparation of an electrochromic device, characterized in that: The electrochromic device uses the pyrroloquinoxaline organic nitrogen-containing electroactive material as the electrochromic layer, and the concentration of the pyrroloquinoxaline organic nitrogen-containing electroactive material is 2.0×10 -3 mol / L~1×10 -5 mol / L.

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