A cyclic palladium dimer, its preparation method and application

Abstract

This invention provides a cyclic palladium dimer, its preparation method, and its applications, belonging to the field of optoelectronic materials technology. The cyclic palladium dimer provided by this invention can be used as a novel phosphorescent material in organic light-emitting diodes (OLEDs), addressing the shortcomings of existing phosphorescent materials and offering new insights into the design of phosphorescent material structures using Pd metal.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials technology, and in particular to a cyclic palladium dimer, its preparation method, and its application. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are light-emitting diodes that use organic compounds as the light-emitting layer material. They have attracted widespread attention due to their advantages such as fast response speed, thinness, flexibility, and excellent light quality. To improve the electroluminescence efficiency of OLEDs, various emitting materials based on fluorescence and phosphorescence have been developed. Phosphorescent materials can utilize both singlet and triplet excitons simultaneously, enabling a quantum efficiency upper limit of 100%, while traditional fluorescent materials can only achieve an upper limit of 25%. Furthermore, the color of phosphorescent materials can be adjusted across the entire visible light range through molecular design. Therefore, phosphorescent organic light-emitting diodes (PHOLEDs) have the advantage of simultaneously achieving high luminous efficiency and color purity. However, the development of phosphorescent materials is currently insufficient, and the variety is limited. Summary of the Invention

[0003] The purpose of this invention is to provide a cyclic palladium dimer, its preparation method, and its application. The cyclic palladium dimer provided by this invention can be used as a novel phosphorescent material in organic light-emitting diodes, solving the problem of insufficient existing phosphorescent materials, and providing a new approach for the application of Pd metal in the design of phosphorescent material structures.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a cyclic palladium dimer having the structure shown in any one of (I) to (VI):

[0006]

[0007] Among them, the for or

[0008] R1 is H, F, methyl, tert-butyl, or phenyl;

[0009] R2 is H, alkyl, or phenyl.

[0010] Preferably, it has the structure shown in any one of (Ⅰ-1), (Ⅰ-2), (Ⅰ-3), (Ⅱ-1), (Ⅱ-2), (Ⅱ-3), (Ⅲ-1), (Ⅲ-2), and (Ⅲ-3):

[0011]

[0012] Preferably, it has C1 to C13 The structure shown in any of the items:

[0013]

[0014] This invention provides a method for preparing the cyclic palladium dimer described above, comprising the following steps: mixing the cyclic palladium carboxylic acid dimer with... A first polar solvent and a basic reagent are mixed to carry out a displacement reaction to obtain the cyclic palladium dimer;

[0015] The cyclic palladium carboxylic acid dimer has the structure shown in any one of (XIV) to (XIX):

[0016]

[0017] Preferably, the cyclic palladium carboxylic acid dimer and The molar ratio is 1:(2.1~5).

[0018] Preferably, the molar ratio of the cyclic palladium carboxylic acid dimer to the alkaline reagent is 1:(2-4).

[0019] Preferably, the alkaline reagent is an alkali metal alkoxide.

[0020] Preferably, when for In this case, the first polar solvent is acetone;

[0021] when for or In this case, the first polar solvent is acetone or methanol;

[0022] when for or In this case, the first polar solvent is acetone, methanol, or tetrahydrofuran.

[0023] Preferably, when for The displacement reaction is carried out under light-protected conditions for 5–10 hours. for or The displacement reaction is carried out at a temperature of 45–70°C for 3–6 hours. for or The displacement reaction is carried out at a temperature of 45–80°C for 5–10 hours.

[0024] This invention provides the application of the cyclic palladium dimer described in the above-described scheme or the cyclic palladium dimer prepared by the above-described preparation method in the emitting layer of an organic light-emitting diode.

[0025] This invention provides a cyclic palladium dimer with excellent luminous efficiency and long luminous lifetime, which can be used as the emitting layer of an organic light-emitting diode (OLED). Attached Figure Description

[0026] Figures 1-10 It is a cyclic palladium dimer with C1, C3, C4, C6, C7, C8, C9, and C6 ions. 10 C 12 C 13 Molecular structure diagram;

[0027] Figure 11 The UV-Vis absorption spectra of cyclic palladium dimers C1–C6 in solution at 25 °C are shown.

[0028] Figure 12 It is a cyclic palladium dimer C7~C 11 UV-Vis absorption spectrum in solution at 25°C;

[0029] Figure 13 Normalized emission spectra of cyclic palladium dimers C1–C6 in PMMA films at 2% mass fraction on a quartz plate at 25 °C;

[0030] Figure 14 It is a cyclic palladium dimer C7~C 11 Normalized emission spectrum at 25°C in a 2% mass fraction PMMA film on a quartz plate;

[0031] Figure 15 The normalized emission spectra of cyclic palladium dimers C1–C6 in solid powder form at 25 °C are shown.

[0032] Figure 16 The palladium complexes of this invention are C7-C6. 11 Normalized emission spectrum at 25°C in solid powder state. Detailed Implementation

[0033] This invention provides a cyclic palladium dimer having the structure shown in any one of (I) to (VI):

[0034]

[0035] Among them, the for or

[0036] R1 is H, F, methyl, tert-butyl, or phenyl;

[0037] R2 is H, alkyl, or phenyl.

[0038] In this invention, the alkyl group is preferably tert-butyl, methyl, ethyl, or isopropyl.

[0039] The cyclic palladium dimer of the present invention is a palladium complex, in which N and Pd are linked by coordinate bonds.

[0040] In this invention, the cyclic palladium dimer preferably has the structure shown in any one of (Ⅰ-1), (Ⅰ-2), (Ⅰ-3), (Ⅱ-1), (Ⅱ-2), (Ⅱ-3), (Ⅲ-1), (Ⅲ-2), and (Ⅲ-3); more preferably, it has C1 to C1. 13 The structure shown in any of the items (as listed above, will not be repeated here).

[0041] This invention provides a method for preparing the cyclic palladium dimer described above, comprising the following steps: mixing the cyclic palladium carboxylic acid dimer with... A first polar solvent and a basic reagent are mixed to carry out a displacement reaction to obtain the cyclic palladium dimer;

[0042] The cyclic palladium carboxylic acid dimer has the structure shown in any one of formulas (XIV) to (XIX):

[0043]

[0044] In this invention, unless otherwise specified, all raw materials used are commercially available products well known in the art or prepared using methods well known in the art.

[0045] In this invention, the cyclic palladium carboxylic acid dimer is preferably prepared by self-preparation, and the preparation method of the cyclic palladium carboxylic acid dimer preferably includes the following steps:

[0046] The ligand was dissolved in a second polar solvent, and palladium acetate was added to the resulting solution to carry out an addition reaction, yielding a cyclic palladium carboxylic acid dimer; the ligand has the structure shown in any one of (VIII) to (XIII):

[0047]

[0048] In this invention, the molar ratio of the ligand to palladium acetate is preferably 1:(1 to 1.1).

[0049] In this invention, the second polar solvent is preferably dichloromethane or glacial acetic acid. There are no special requirements for the amount of the second polar solvent used, as long as it is sufficient to completely dissolve the ligand.

[0050] In this invention, the addition reaction time is preferably 8–12 h, more preferably 9–11 h; the addition reaction is preferably carried out under stirring conditions. In this invention, when the second polar solvent is dichloromethane, the addition reaction temperature is preferably room temperature; when the second polar solvent is glacial acetic acid, the addition reaction temperature is preferably 80–100 °C, and carried out under reflux conditions.

[0051] In this invention, the equation for the addition reaction is as follows:

[0052]

[0053] After the addition reaction is completed, the present invention preferably evaporates the resulting reaction mixture to dryness, washes it with diethyl ether, and then purifies it by recrystallization to obtain the cyclic palladium carboxylic acid dimer.

[0054] After obtaining the cyclic palladium carboxylic acid dimer, the present invention further describes the cyclic palladium carboxylic acid dimer, A first polar solvent and a basic reagent are mixed to carry out a displacement reaction to obtain the cyclic palladium dimer.

[0055] In this invention, the cyclic palladium carboxylic acid dimer and The molar ratio is preferably 1:(2.1 to 5), more preferably 1:(2.5 to 4.5), and even more preferably 1:(3 to 4).

[0056] In this invention, the alkaline reagent is preferably an alkali metal alkoxide; the alkali metal alkoxide preferably includes sodium methoxide or potassium tert-butoxide. In this invention, the molar ratio of the cyclic palladium carboxylic acid dimer to the alkaline reagent is preferably 1:(2-4), more preferably 1:3.

[0057] In this invention, the type of the first polar solvent and the conditions of the displacement reaction are preferably determined according to... The type is determined, when for In this process, the first polar solvent is preferably acetone; the displacement reaction is preferably carried out under light-protected conditions, and the displacement reaction time is preferably 5-10 hours, more preferably 6-9 hours, and even more preferably 7-8 hours.

[0058] when for or In this process, the first polar solvent is preferably acetone or methanol; the temperature of the displacement reaction is preferably 45-70°C, more preferably 50-65 h, and the time is preferably 3-6 h, more preferably 4-5 h.

[0059] when for or In this process, the first polar solvent is preferably acetone, methanol, or tetrahydrofuran; the temperature of the displacement reaction is preferably 45–80°C, more preferably 50–75°C, and the time is preferably 5–10 h, more preferably 6–8 h.

[0060] After the displacement reaction is completed, the solvent is preferably removed by rotary evaporation of the displacement reaction mixture, followed by washing with methanol until the washings are clear, and purification to obtain the cyclic palladium dimer.

[0061] In this invention, the purification method is preferably based on... The type is determined, when for or In this case, the preferred purification method is recrystallization. When the substance is otherwise specified, the preferred purification method is column chromatography. This invention does not impose special requirements on the recrystallization and column chromatography processes, as long as the target product can be purified.

[0062] This invention provides the application of the cyclic palladium dimer described in the above-described scheme or the cyclic palladium dimer prepared by the above-described preparation method in the emitting layer of an organic light-emitting diode.

[0063] The following detailed description of the cyclic palladium dimer and its preparation method provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0064] Example 1

[0065] The synthetic route for cyclic palladium dimer C1 is as follows:

[0066]

[0067] The specific preparation steps are as follows:

[0068] (i) Ligand VIII-2 (426 mg, 2.23 mmol) was placed in a round-bottom flask, and 40 mL of dichloromethane was added to dissolve it. Then, palladium acetate (500 mg, 2.23 mmol) was weighed and added to the reaction flask, and the mixture was stirred for 10 h. After the reaction was completed, a mixture was obtained. The reaction mixture was evaporated to dryness, washed three times with diethyl ether, and purified by recrystallization to obtain the cyclic palladium carboxylic acid dimer XIV-2.

[0069] (ii) Cyclic palladium carboxylic acid dimer XIV-2 (200 mg, 0.28 mmol), XX-1 (138 mg, 0.70 mmol), and sodium methoxide (46 mg, 0.84 mmol) were added to a round-bottom flask, followed by 20 mL of acetone. The mixture was reacted at room temperature in the dark for 8 h. After the reaction was complete, the solvent was removed by rotary evaporation of the reaction mixture. The mixture was washed three times with methanol until the washings were clear. The mixture was then purified by column chromatography to obtain cyclic palladium dimer C1.

[0070] Example 2

[0071] The synthetic route for palladium complex C2 is as follows:

[0072]

[0073] The specific preparation steps are the same as in Example 1, except that compound VIII-2 is replaced with compound VIII-1.

[0074] Example 3

[0075] The synthetic route for cyclic palladium dimer C3 is as follows:

[0076]

[0077] The specific preparation steps are the same as in Example 1, except that compound VIII-2 is replaced with compound VIII-3.

[0078] Example 4

[0079] The synthetic route for cyclic palladium dimer C4 is as follows:

[0080]

[0081] The specific preparation steps are the same as in Example 1, except that compound VIII-2 is replaced with compound IX-1.

[0082] Example 5

[0083] The synthetic route for cyclic palladium dimer C5 is as follows:

[0084]

[0085] The specific preparation steps are the same as in Example 1, except that compound VIII-2 is replaced with compound X-1.

[0086] Example 6

[0087] The synthetic route for cyclic palladium dimer C6 is as follows:

[0088]

[0089] The specific preparation steps are the same as in Example 1, except that compound VIII-2 is replaced with compound VIII-4.

[0090] Example 7

[0091] The synthetic route for cyclic palladium dimer C7 is as follows:

[0092]

[0093] The specific preparation steps are as follows:

[0094] (i) The specific preparation steps are described in Example 1(i).

[0095] (ii) A mixture of 2,2,6,6-tetramethyl-3,5-heptadecane (220 mg, 1.00 mmol) and hydrazine hydrate (50 mg, 1.00 mmol) was placed in a round-bottom flask and heated at 70 °C for 2 h to give compound XXI-1. After the reaction time was complete, the product was a white solid and no further purification was required.

[0096] (iii) Cyclic palladium carboxylic acid dimer XIV-2 (200 mg, 0.28 mmol), XXI-1 (127 mg, 0.70 mmol), and sodium methoxide (46 mg, 0.84 mmol) were added to a pressure-resistant flask, followed by the addition of 6 mL of acetone. The mixture was heated at 65 °C for 5 h. After the reaction was complete, the reaction mixture was cooled to room temperature, and the solvent was removed by rotary evaporation. The mixture was washed three times with methanol until the washings were clear. The mixture was then purified by column chromatography to obtain cyclic palladium dimer C7.

[0097] Example 8

[0098] The synthetic route for cyclic palladium dimer C8 is as follows:

[0099]

[0100] The specific preparation steps are as described in Example 7, except that compound VIII-2 is replaced with compound VIII-1.

[0101] Example 9

[0102] The synthetic route for cyclic palladium dimer C9 is as follows:

[0103]

[0104] The specific preparation steps are as described in Example 7, except that compound VIII-1 is replaced with compound VIII-3.

[0105] Example 10

[0106] Cyclic palladium dimer C 10The synthetic route is as follows:

[0107]

[0108] The specific preparation steps are as described in Example 7, except that compound VIII-2 is replaced with compound IX-1.

[0109] Example 11

[0110] Cyclic palladium dimer C 11 The synthetic route is as follows:

[0111] The specific preparation steps are as described in Example 7, except that compound VIII-2 is replaced with compound X-1.

[0112] Example 12

[0113] Cyclic palladium dimer C 12 The synthetic route is as follows:

[0114]

[0115] The specific preparation steps are as described in Example 7, except that compound VIII-2 is replaced with compound VIII-4.

[0116] Example 13

[0117] Cyclic palladium dimer C 13 The synthetic route is as follows:

[0118]

[0119] The specific preparation steps are as described in Example 7, except that compound VIII-2 is replaced with compound VIII-3 and compound XXI-1 is replaced with compound XXII-1.

[0120] Structural and performance characterization:

[0121] For C1, C3, C4, C6, C7, C8, C9, C 10 C 12 C 13 The molecular structure was analyzed by single-crystal X-ray diffraction, and the results are shown in the table below. Figures 1-10 . Figures 1-10 In the figure, the thermal ellipsoid is drawn at a probability level of 30%. Hydrogen atoms are omitted for clarity. Figures 1-10 It can be seen that a cyclic palladium dimer with the target structure was obtained.

[0122] The cyclic palladium dimer C1~C 11 The samples were dissolved separately in dichloromethane, and their UV-Vis absorption spectra were measured at 25℃. The results are shown below. Figure 11and Figure 12 .

[0123] The cyclic palladium dimer C1~C 11 The normalized emission spectrum of a PMMA film with a 2% mass fraction was measured on a quartz plate at 25°C (2% refers to the ratio of the cyclic palladium dimer to the total mass of the cyclic palladium dimer and PMMA). The results are shown in [Figure number missing]. Figure 13 and Figure 14 .

[0124] The cyclic palladium dimer C1~C 11 The normalized emission spectrum of the powder was measured at 25℃ in its solid powder state, and the results are shown in the figure. Figure 15 and Figure 16 .

[0125] The luminescence properties of the cyclic palladium dimer prepared by this invention under the above-mentioned different states are summarized below, as shown in Table 1.

[0126] Table 1 Cyclic palladium dimers C1~C 11 Photophysical properties

[0127]

[0128]

[0129] Note: In Table 1, "a" represents the measurement of the compound in dichloromethane at room temperature, "Em" represents the "emission wavelength", "Φ" represents the "phosphorescence quantum yield", "τ" represents the "phosphorescence lifetime", "Solid" represents the "solid state", and "PMMA" represents the "PMMA thin film state". The phosphorescence quantum yield was measured using an integrating sphere. The radiative rate constant (Kr) and the non-radiative rate constant (Knr) were estimated using the following equations: Kr = Φ / τ, Knr = (1–Φ) / τ.

[0130] As shown in Table 1, the cyclic palladium dimer provided by the present invention has excellent quantum yield and phosphorescence lifetime in the micrometer range, indicating that it has a long luminescence lifetime, which meets the requirements for the fabrication of OLED devices.

Claims

1. A cyclic palladium dimer, characterized in that, It has the structure shown in any one of (Ⅰ-1), (Ⅰ-2), (Ⅰ-3), (Ⅱ-1), (Ⅱ-2), (Ⅱ-3), (Ⅲ-1), (Ⅲ-2), and (Ⅲ-3): ； In (Ⅰ-1), (Ⅰ-3), (Ⅱ-1), (Ⅱ-2), (Ⅱ-3), (Ⅲ-1), (Ⅲ-2), and (Ⅲ-3): R1 is H, F, methyl, tert-butyl, or phenyl; R2 is H, alkyl, or phenyl; and the alkyl group is tert-butyl, methyl, ethyl, or isopropyl. In (Ⅰ-2), R1 is H, F, methyl, tert-butyl or phenyl; R2 is alkyl or phenyl; and the alkyl group is tert-butyl, methyl, ethyl or isopropyl.

2. A cyclic palladium dimer, characterized in that, Having C1~C 13 The structure shown in any of the items: 、 、 、 、 、 、 、 、 、 、 、 、 。 3. The method for preparing the cyclic palladium dimer according to claim 1, comprising the following steps: Dimer of cyclic palladium carboxylic acid, A first polar solvent and a basic reagent are mixed to carry out a displacement reaction to obtain the cyclic palladium dimer; The cyclic palladium carboxylic acid dimer has the structure shown in any one of (XIV) to (XVI): ； The for , or .

4. The preparation method according to claim 3, characterized in that, The cyclic palladium carboxylic acid dimer and The molar ratio is 1:(2.1~5).

5. The preparation method according to claim 3, characterized in that, The molar ratio of the cyclic palladium carboxylic acid dimer to the alkaline reagent is 1:(2~4).

6. The preparation method according to claim 3 or 5, characterized in that, The alkaline reagent is an alkali metal alkoxide.

7. The preparation method according to claim 3, characterized in that, when for In this case, the first polar solvent is acetone; when for In this case, the first polar solvent is acetone or methanol; when for In this case, the first polar solvent is acetone, methanol, or tetrahydrofuran.

8. The preparation method according to claim 3, characterized in that, when for The displacement reaction is carried out under light-protected conditions for 5-10 hours. for or The temperature of the displacement reaction is 45~70℃, and the time is 3~6 h.

9. The application of the cyclic palladium dimer according to any one of claims 1 to 2 or the cyclic palladium dimer prepared by the preparation method according to any one of claims 3 to 8 in the emitting layer of an organic light-emitting diode.

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