A class of eight-coordinate europium(III) complexes with deuterated phenanthroline derivatives as ligands and their preparation methods

Abstract

This invention discloses a class of eight-coordinate europium(III) complexes using deuterated phenanthroline derivatives as ligands and their preparation method, belonging to the field of organic semiconductor luminescence technology. The complexes have the structural formula shown in formula (I). This type of material uses D₂O for deuteration to synthesize [D₈]-1,10-phenanthroline ligands and [D₁₀]-dibenzoylmethane ligands, which are then complexed with europium trichloride hexahydrate. When X is H, an eight-coordinate europium(III) complex [D₈]-Eu(DBM)₃Phen is synthesized; when X is D, [D₈]-Eu([D₁₀]-DBM)₃Phen is synthesized. This type of complex uses phenanthroline with a deuterium azide conjugated structure as a ligand, allowing these europium(III) complexes to exhibit better thermodynamic stability and organometallic luminescence performance through stepwise deuteration.

Description

Technical Field

[0001] This invention belongs to the field of organic semiconductor light-emitting technology, specifically relating to the synthesis and preparation method of an octagonal europium(III) complex material with deuterated phenanthroline derivatives as ligands. Background Technology

[0002] Unlike inorganic semiconductors (ISCs), organic semiconductors (OSCs) are optoelectronic materials with unique carbon-based structures. Their unique properties in the solid state, due to their aggregated state, are attributed to van der Waals bonds formed between organic semiconductor molecules by electrostatic interactions. In a single molecule composed of covalent bonds, the presence of a conjugated system leads to the stable delocalization of electronic states resulting from π-conjugation. The shape of this delocalization largely depends on the molecular geometry, making the ability of the electron wavefunction to delocalize within a single molecule highly sensitive to the intermolecular packing. Furthermore, for larger organic molecules, which may contain hundreds of atoms, the excitation of such a large number of atoms under certain external energy can produce different motion modes, known as vibrational modes. This results in highly complex structural dynamics in organic molecules, meaning that the coupling between their electronic and molecular structures produces unique and fascinating phenomena in the solid films of these organic semiconductor molecules.

[0003] The ability to easily alter molecular structure, thereby changing the aggregated state and energy level structure, is one of the advantages of organic semiconductors compared to inorganic semiconductors. Therefore, exploring molecular structures through organic chemical synthesis, gaining a deeper understanding of the properties influenced by molecular structure, optimizing device structures, eliminating external constraints, and addressing the limitations imposed by internal impurities on charge transport have always been the focus of researchers. More importantly, as research into the microscopic charge transport properties at the molecular scale deepens, the requirements for studying the molecular structure of organic semiconductors become increasingly stringent. While the influence of different molecular structures on charge transport performance has been systematically studied, the specific impact of changes in microscopic molecular structure on the carrier transport process has not yet been thoroughly investigated. When organic semiconductor materials are fabricated into semiconductor devices, they are usually in the form of solid thin films. Therefore, different methods and operations in fabricating these films significantly affect the aggregation state of molecules within them. Different aggregation morphologies result in different intermolecular interactions caused by van der Waals forces. Therefore, to study the relationship between molecular structure, structural dynamics, and charge transport properties, it is necessary to fix the intermolecular influences to obtain their internal connections.

[0004] Europium (Eu), one of the seventeen lanthanides, possesses the same outermost valence electron configuration as the other lanthanides. Its half-filled 4f orbitals give Eu a relatively large atomic radius, and the coordination number of the commonly used Eu ion is as high as eight. In early studies of Eu, Weissman discovered that europium(III) complexes can absorb light through ligands other than the central atom and transfer the energy to Eu. 3+ On the ion, the europium(III) complex is photoexcited. The Eu in the europium(III) complex... 3+ The interaction between ions and other ligands has a dual beneficial effect: it protects the central metal ion from vibrational coupling and also facilitates the interaction of Eu ions with other ligands. 3+ The antenna effect of ions enhances the light absorption of europium(III) complexes. As a result, europium(III) complexes have wide applications in luminescent materials, electroluminescence, fluorescent probes, lasers, and other fields. 3+ The introduction of ions gives Eu(III) complexes a stronger electron-withdrawing ability than organic ligands, and the increase in molecular size gives them special charge transport properties in the amorphous state.

[0005] Although europium complexes exhibit high-purity red light emission due to the electronic transitions of the 4f orbitals within europium(III), the overall chemical stability of the molecule needs improvement, and its luminescence lifetime is also affected after it is fabricated into a device.

[0006] This invention replaces the hydrogen atom (H) in the neutral ligand of phenanthroline with a deuterium atom (D), and synthesizes a deuterated europium(III) complex together with the β-diketone derivative dibenzoylmethane as an auxiliary ligand. Since deuterium is an isotope of hydrogen, and the CD bond is more stable than the CH bond, the deuteration of the europium(III) complex enhances the thermal stability of the material without affecting other properties. Furthermore, because deuteration can inhibit the formation of quenchers to a certain extent, it extends the overall device lifespan and improves the luminescent performance of OLEDs, making it a promising candidate for applications in the organic semiconductor field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a class of eight-coordinate europium(III) complexes with deuterated phenanthroline as ligands and their preparation method, which can be used as luminescent materials for high-efficiency, high-purity red OLED devices. This invention is achieved through the following technical solutions:

[0008] A class of eight-coordinate europium(III) complexes using deuterated phenanthroline derivatives as ligands, wherein the material is a neutral phenanthroline ligand containing deuterium atoms and Eu 3+ Europium(III) complex materials of ions,

[0009] It has the structural formula shown in equation (Ⅰ):

[0010]

[0011] A method for preparing an octagonal europium(III) complex material with a deuterated phenanthroline derivative as a ligand, characterized by the reaction formula as shown in formula (II), comprising the following steps:

[0012]

[0013] Step (i) Preparation of the europium(III) complex [D8]-Eu(DBM)3Phen: Benzoylmethane (1.344 g, 6 mmol) and [D8]-1,10-phenanthroline (0.376 g, 2 mmol) were added to a reaction flask, followed by the addition of degassed ethanol (25 mL). The system was stirred at room temperature on a magnetic stirrer, and potassium carbonate aqueous solution (2.07 g / 10 mL) was slowly added via syringe. The pH of the system was titrated to 7-8, and degassed. Europium trichloride hexahydrate (EuCl3·6H2O) was dissolved in 2 mL of water and slowly added dropwise to the reaction system. A yellowish-white solid was observed to rapidly appear in the solution upon the addition of EuCl3·6H2O. To ensure experimental yield, the reaction was carried out at room temperature for 5 h under a nitrogen atmosphere. The resulting reaction mixture was filtered using a vacuum funnel and washed with water. The crude product was dried in a vacuum drying oven at room temperature. The dried crude product was dissolved in 250 mL of hot ethanol and filtered while hot. 125 mL of water was added to the filtrate after it had cooled to room temperature, precipitating a yellow solid. This solid was then placed in a refrigerator at -25 °C for further recrystallization. The filtered product was dried under vacuum at room temperature, and cyclohexane (20 mL of cyclohexane per gram of crude product) was added and stirred to remove excess dibenzoylmethane. The product was then filtered and dried in a vacuum drying oven at room temperature to obtain a bright yellow solid, which is compound [D8]-Eu(DBM)3Phen.

[0014] Step (ii) Preparation of europium(III) complex [D8]-Eu([D10]-DBM)3Phen: [D10]-dibenzoylmethane (1.406 g, 6 mmol) and [D8]-1,10-phenanthroline (0.376 g, 2 mmol) were added to a reaction flask, and degassed ethanol (25 mL) was added to the mixture. The system was stirred at room temperature on a magnetic stirrer, and potassium carbonate aqueous solution (2.07 g / 10 mL) was slowly added using a syringe. The pH of the system was titrated to 7-8, and degassed. Europium trichloride hexahydrate (EuCl3·6H2O) was dissolved in 2 mL of water and slowly added dropwise to the reaction system. A yellowish-white solid was observed to appear rapidly in the solution with the addition of EuCl3·6H2O. To ensure the experimental yield, the reaction was carried out at room temperature for 5 h under a nitrogen atmosphere. The resulting reaction mixture was filtered using a vacuum funnel and washed with water. The crude product was dried in a vacuum oven at room temperature. The dried crude product was dissolved in 250 mL of hot ethanol and filtered while hot. 125 mL of water was added to the filtrate after it had cooled to room temperature, precipitating a yellow solid. This solid was then placed in a refrigerator at -25 °C for further recrystallization. The product was filtered and dried under vacuum at room temperature. Cyclohexane was added (20 mL of cyclohexane per gram of crude product), and the mixture was stirred to remove excess dibenzoylmethane. The product was then filtered and dried in a vacuum oven at room temperature to obtain a bright yellow solid, which was compound [D8]-Eu([D10]-DBM)3Phen.

[0015] Preferably, the molar ratio of europium chloride hexahydrate to [D8]-1,10-phenanthroline in step (i) is 1:1.2.

[0016] Preferably, the molar ratio of europium chloride hexahydrate to [D10]-dibenzoylmethane in step (ii) is 1:3.3.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) This invention introduces Eu 3+ The introduction of ions alters the vibrational energy levels of europium(III) complexes, resulting in luminescence properties that differ from those of the ligands. It also enhances the electron-accepting ability of europium(III) complexes and changes the energy level structure of the molecules.

[0019] (2) Europium (III) complexes, as complexes with highly symmetrical structures, are more stable than the corresponding hydrogen complexes by the introduction of deuterium. This may be related to the stability of CD bonds and lower reactivity.

[0020] (3) Deuterated europium(III) complexes can inhibit the formation of quenchers to a certain extent, thereby extending the overall device lifespan and improving the luminous performance of OLEDs, as well as having more applications in the field of organic semiconductor devices. Attached Figure Description

[0021] Figure 1 The Maldi-Tof spectrum of [D8]-Eu(DBM)3Phen;

[0022] Figure 2 The Maldi-Tof spectrum of [D8]-Eu([D10]-DBM)3Phen;

[0023] Figure 3 TGA images of Eu(DBM)3Phen, [D8]-Eu(DBM)3Phen, and [D8]-Eu([D10]-DBM)3Phen;

[0024] Figure 4 UV-PL images of [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen;

[0025] Figure 5 Images of the lifetime of OLED devices [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen. Detailed Implementation

[0026] To better understand the content of this invention patent, the technical solution and approach of this invention will be further illustrated below with reference to the accompanying drawings and specific experimental steps. However, the following embodiments are not intended to limit this invention.

[0027] Example 1

[0028] A class of eight-coordinate europium(III) complexes using deuterated phenanthroline as a ligand, wherein the material is a deuterated neutral phenanthroline ligand and Eu 3+ Europium(III) complexes of ions have the structural formula shown in formula (I):

[0029]

[0030] An octagonal europium(III) complex material with deuterated phenanthroline as the ligand, the reaction formula is shown in formula (II), and the specific steps are as follows:

[0031]

[0032] (i) Synthesis of europium(III) complex [D8]-Eu(DBM)3Phen

[0033] Benzoylmethane (1.344 g, 6 mmol) and [D8]-1,10-phenanthroline (0.376 g, 2 mmol) were added to a reaction flask, followed by 25 mL of degassed ethanol. The mixture was stirred at room temperature on a magnetic stirrer, and potassium carbonate aqueous solution (2.07 g / 10 mL) was slowly added via syringe. The pH of the mixture was titrated to 7-8, and degassed. Europium trichloride hexahydrate (EuCl3·6H2O) was dissolved in 2 mL of water and slowly added dropwise to the reaction mixture. A yellowish-white solid was observed to rapidly appear in the solution upon the addition of EuCl3·6H2O. To ensure the experimental yield, the reaction was carried out at room temperature for 5 h under a nitrogen atmosphere. The resulting reaction mixture was filtered using a vacuum funnel and washed with water. The crude product was dried in a vacuum drying oven at room temperature. The dried crude product was dissolved in 250 mL of hot ethanol and filtered while hot. 125 mL of water was added to the filtrate after it cooled to room temperature, precipitating a yellow solid. This solid was then placed in a refrigerator at -25°C for further recrystallization. The filtered product was dried under vacuum at room temperature, and then cyclohexane (20 mL of cyclohexane per gram of crude product) was added and stirred to remove excess dibenzoylmethane. The product was then filtered and dried in a vacuum oven at room temperature to obtain a bright yellow solid, which is compound [D8]-Eu(DBM)3Phen.

[0034] (ii) Synthesis of europium(III) complex [D8]-Eu([D10]-DBM)3Phen

[0035] [D10]-dibenzoylmethane (1.406 g, 6 mmol) and [D8]-1,10-phenanthroline (0.376 g, 2 mmol) were added to a reaction flask, and degassed ethanol (25 mL) was added to the mixture. The system was stirred at room temperature on a magnetic stirrer, and potassium carbonate aqueous solution (2.07 g / 10 mL) was slowly added using a syringe. The pH of the system was titrated to 7-8, and degassed. Europium trichloride hexahydrate (EuCl3·6H2O) was dissolved in 2 mL of water and slowly added dropwise to the reaction system. A yellowish-white solid was observed to rapidly appear in the solution upon the addition of EuCl3·6H2O. To ensure the experimental yield, the reaction was carried out at room temperature for 5 h under a nitrogen atmosphere. The resulting reaction mixture was filtered using a vacuum funnel and washed with water. The crude product was dried in a vacuum drying oven at room temperature. The dried crude product was dissolved in 250 mL of hot ethanol and filtered while hot. 125 mL of water was added to the filtrate after it cooled to room temperature, precipitating a yellow solid. This solid was then placed in a refrigerator at -25 °C for further recrystallization. The filtered product was dried under vacuum at room temperature, and then cyclohexane (20 mL of cyclohexane per gram of crude product) was added and stirred to remove excess dibenzoylmethane. The product was then filtered and dried in a vacuum oven at room temperature to obtain a bright yellow solid, which is compound [D8]-Eu([D10]-DBM)3Phen.

[0036] Example 2

[0037] Overview of the physical properties of europium(III) complex materials [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen.

[0038] In this embodiment, the mass-to-nucleus ratio of the deuterated europium(III) complex was characterized by Maldi-Tof mass spectrometry. The thermodynamic properties of [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen were studied by thermogravimetric analysis (TGA). The spectral properties of the europium(III) complex were analyzed and determined using a UV-Vis spectrophotometer (LAMBDA-35) and a fluorescence spectrophotometer (RF-6000). Finally, the cyclic voltammetry curves of the europium(III) complex were determined by electrochemical methods. The specific steps are as follows:

[0039] (1) Weigh 5 mg of [D8]-Eu(DBM)3Phen and dissolve it in 3 mL of dichloromethane. Spot 5 μL of the solution onto a selected matrix on a spotting plate and perform analysis using a Maldi-Tof mass spectrometer. Select the positive ion reflection mode to obtain the MS mass spectrum of [D8]-Eu(DBM)3Phen. The test results are as follows: Figure 1 As shown.

[0040] Depend on Figure 1 It can be seen that the molecular formula C 57 H 33 The peak at molecular weight 1009.98 of D8EuN2O6 corresponds to an m / z of 1010.741 ([M+H]+) at high resolution.

[0041] (2) Weigh 5 mg of [D8]-Eu([D10]-DBM)3Phen and dissolve it in 3 mL of dichloromethane. Spot 5 μL of the sample onto a selected matrix using a Maldi-Tof mass spectrometer for analysis. Select the positive ion reflection mode to obtain the MS mass spectrum of [D8]-Eu([D10]-DBM)3Phen. The test results are as follows: Figure 2 As shown.

[0042] Depend on Figure 2 It can be seen that the molecular formula C 57 H3D 38 The peak at molecular weight 1040.16 of EuN2O6 corresponds to an m / z of 1041.052 ([M+H]+) under high resolution MS.

[0043] (3) Thermogravimetric analysis (TGA) was performed on [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen using STA2500 & DSC214 instruments to measure their thermodynamic stability. The test conditions were heating from room temperature to 600 degrees Celsius (10℃ / min) in a N2 atmosphere. The test results for the two materials were summarized as follows: Figure 3 As shown.

[0044] Depend on Figure 3 It can be seen that, compared with the thermal decomposition temperature of 372.26℃ of the deuterated europium(III) complex (measured with 5% weight loss, the same below), the introduction of deuterium atoms makes the thermal decomposition temperatures of [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen reach 407.13℃ and 452.08℃ respectively, indicating that it has better thermal stability, and also confirming that the CD bond is stronger than the CH bond.

[0045] (4) Weigh out [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen (1 mg) and dissolve them in dichloromethane to prepare a solution with a concentration of 1×10⁻⁶. -5The solutions of [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen were analyzed using a UV-Vis spectrophotometer (LAMBDA-35) and a fluorescence spectrophotometer (RF-6000), respectively. The UV-Vis absorption and fluorescence emission spectra of [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen were obtained. The test results are as follows: Figure 4 As shown.

[0046] Depend on Figure 4 It can be seen that both [D8]-Eu(DBM)3Phen and [D8]-Eu([D10]-DBM)3Phen have two ultraviolet absorption peaks at 265 nm and 351 nm, which almost overlap. The maximum emission peak of the fluorescence spectrum is also at 618 nm, which indicates that the increase of deuteration degree has almost no effect on the photophysical (fluorescence quantum yield) characteristics of europium(III) complexes.

[0047] (5) To explore the relationship between the degree of deuteration and the lifetime of light-emitting devices, we compared the EL performance of OLED devices by adding NPB to HTL and adding deuterated europium(III) complex materials to ETL, respectively, using the parameter of achieving 90% of L0 lifetime. Figure 5 As shown.

[0048] Depend on Figure 5 It can be seen that the lifetime of [D8]-Eu(DBM)3Phen with a deuteration rate of 19.51% is 20.38h, while the lifetime of [D8]-Eu([D10]-DBM)3Phen with a deuteration rate of 92.68% is 44.26h. This proves that as the deuteration rate increases, the lifetime of OLED devices prepared from europium(III) complexes is effectively improved. 90 The relationship between the value and the degree of deuteration shows an almost linear correlation.

[0049] In summary, the introduction of deuterium enhances the chemical stability of these europium(III) complexes. Furthermore, the increasing deuteration process can inhibit quencher formation to some extent, thereby extending the device's luminescent lifetime and improving the luminescent performance of OLEDs, making them promising for applications in the organic semiconductor field.

[0050] While the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.

Claims

1. A class of octagonal deuterated europium(III) complex materials with phenanthroline derivatives as ligands, characterized in that, The complex materials have the structural formula shown in formula (I), including [D8]-Eu(DBM)3Phen, where X is H, and [D8]-Eu([D10]-DBM)3Phen, where X is D.

2. A method for preparing an octagonal deuterated europium(III) complex material with a class of phenanthroline derivatives as ligands, characterized in that, The steps include the following, as shown in equation (II):

3. The method for preparing the octagonal deuterated europium(III) complex material with phenanthroline derivatives as ligands according to claim 2, characterized in that, Step (i) Preparation of europium(III) complex [D8]-Eu(DBM)3Phen: 3 equivalents of dibenzoylmethane and 1 equivalent of [D8]-1,10-phenanthroline were added to a reaction flask, and 214 equivalents of degassed ethanol were added to the mixture; the system was stirred at room temperature, and potassium carbonate aqueous solution was added to adjust the pH of the system to weakly alkaline, and degassed; 1 part of europium trichloride hexahydrate was dissolved in 56 equivalents of water and added dropwise to the reaction system, and the reaction was carried out at room temperature for 5 h under a nitrogen atmosphere; the resulting reaction mixture was filtered and washed with water, and the crude product was dried under vacuum at room temperature; the crude product of compound [D8]-Eu(DBM)3Phen was obtained.

4. The method for preparing an octagonal deuterated europium(III) complex material with a phenanthroline derivative as a ligand according to claim 2, characterized in that, Step (ii) involves the preparation of the europium (III) complex [D8]-Eu([D10]-DBM)3Phen: 3 equivalents of [D10]-dibenzoylmethane and 1 equivalent of [D8]-1,10-phenanthroline are added to a reaction flask, and 214 equivalents of degassed ethanol are added to the mixture; the system is stirred at room temperature, and potassium carbonate aqueous solution is added to adjust the pH of the system to weak alkalinity, followed by degassing; europium trichloride hexahydrate is dissolved in 56 equivalents of water and added dropwise to the reaction system; the reaction is carried out at room temperature for 5 hours under a nitrogen atmosphere.

5. A method for preparing an octagonal deuterated europium(III) complex material with a phenanthroline derivative as a ligand according to claim 3 or 4, characterized in that, The equivalent ratio of potassium carbonate to water is 1:

37.

6. The method for preparing an octagonal deuterated europium(III) complex material with a phenanthroline derivative as a ligand according to claim 2, characterized in that, Step (i) further includes purification, specifically: the dried crude product is dissolved in 2140 parts equivalent of hot ethanol, filtered while hot, and 3500 parts equivalent of water is added to the filtrate after cooling to room temperature, precipitating a yellow solid, which is then recrystallized at -25°C; the product is filtered and dried under vacuum at room temperature, then cyclohexane is added and stirred to remove excess dibenzoylmethane; the product is obtained by suction filtration and then dried under vacuum at room temperature to obtain a bright yellow solid, which is the pure compound [D8]-Eu(DBM)3Phen.

7. The method for preparing an octagonal deuterated europium(III) complex material with a phenanthroline derivative as the ligand according to claim 2, characterized in that, Step (ii) further includes purification and refining, filtering the obtained reaction mixture and washing with water, and drying the crude product under vacuum at room temperature; dissolving the dried crude product in 2150 parts equivalent of hot ethanol, filtering while hot, adding 3525 parts equivalent of water to the filtrate after cooling to room temperature, precipitating a yellow solid, and recrystallizing at -25°C; filtering the product and drying it under vacuum at room temperature, adding cyclohexane and stirring to remove excess [D10]-dibenzoylmethane; filtering the product and drying it under vacuum at room temperature to obtain a bright yellow solid, which is compound [D8]-Eu([D10]-DBM)3Phen.

8. A method for preparing an octagonal deuterated europium(III) complex material with a phenanthroline derivative as a ligand according to claim 6 or 7, characterized in that, The amount of cyclohexane added is 96 equivalents of cyclohexane per gram of crude product.

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