CN111875602B - A kind of cyano group-modified pyridoimidazole derivatives and preparation method and application thereof - Google Patents

Abstract

The invention discloses a cyano-modified pyridoimidazole derivative, a preparation method and application thereof, wherein the cyano-modified pyridoimidazole derivative has a molecular structure shown as a formula (I):

wherein R1 is hydrogen or cyano, R2 is hydrogen or cyano, and R1 and R2 are not simultaneously hydrogen. The invention introduces C \8230, H \8230, pi stacking structure and cyano group into the pyridine imidazole derivatives to obtain higher fluorescence quantum yield, enhanced electron-withdrawing capability of acceptor groups and red shift of spectra, and the derivatives also have better AIE effect, high-efficiency Thermally Activated Delayed Fluorescence (TADF) property, good thermal stability and solubility, can be used as red light emitting materials, light emitting devices or light emitting intelligent materials and the like, and can be applied to the fields of full-color display, solid state lighting and the like.

Description

A kind of cyano group-modified pyridoimidazole derivatives and preparation method and application thereof

technical field

The invention relates to the technical field of organic light-emitting materials, and more particularly, to a cyano group-modified pyridoimidazole derivative and a preparation method and application thereof.

Background technique

The technology of organic light-emitting materials used as organic light-emitting diodes (OLEDs) has a wide range of applications in flat panel displays, smart phones, and solid-state light emitting. Significant advantages such as fast response speed and flexibility.

However, due to its inherent narrow band gap, the red light emitting materials in the current organic light emitting materials will greatly enhance the non-radiative transition rate of molecules, resulting in large energy loss, so there are low solid-state fluorescence quantum yield, thermal stability. and poor solubility.

For example, Chinese patent CN102070632B discloses a pyridoimidazole derivative and its application in an organic electroluminescent device. The pyridoimidazole derivative red-shifts its light-emitting position to the visible light region by introducing a substituent group with a rigid structure , improve the luminous efficiency, destroy the coplanarity of the molecules, and improve the thermal stability of the compound, but the compound still has the problems of low fluorescence quantum yield and poor solubility.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the defects and deficiencies of low fluorescence quantum yield and poor solubility of the existing pyridoimidazole derivative light-emitting materials, and provide a cyano group-modified pyridoimidazole derivative, which is It has high fluorescence quantum yield, can produce aggregation-induced emission (AIE) effect, can emit red light, and has good thermal stability and solubility.

Another object of the present invention is to provide a preparation method of cyano group-modified pyridoimidazole derivatives.

Another object of the present invention is to provide an application of cyano group-modified pyridoimidazole derivatives.

The above-mentioned purpose of the present invention is achieved through the following technical solutions:

A cyano group-modified pyridoimidazole derivative has the molecular structure shown in formula (I):

其中R1为氢或氰基，R2为氢或氰基，R1和R2不同时为氢。

wherein R1 is hydrogen or cyano, R2 is hydrogen or cyano, and R1 and R2 are not both hydrogen.

The cyano group-modified pyridoimidazole derivatives provided by the present invention, on the one hand, due to the introduction of a bridged benzene ring between the N-aromatic anthracenyl group (or called hydrogenated phenoxazinyl group) and the carbonyl group in its structure, it forms a larger Conjugated planes; on the other hand, due to the existence of C…H…π stacking (provided by hydrogenated phenoxazine groups and N atoms on pyridoimidazole), the above structures are all conducive to molecular luminescence and obtain higher fluorescence quantum yields . In addition, the cyano group also introduced into the molecule enhances the electron-donating ability of the molecule, resulting in a red shift of the spectrum, red light emission, and a significant reduction in the energy level difference between the singlet state and the triplet state, which makes the thermally activated delayed fluorescence (TADF) properties more excellent. Because the cyano group-modified pyridoimidazole derivatives also contain carbonyl groups, they can cause molecular vibrations, can produce aggregation-induced emission (AIE) effect, can effectively inhibit exciton annihilation, and make molecules in a high-concentration aggregation state than in a low-concentration state. It has stronger fluorescence emission, thus has higher luminescence intensity and better AIE performance. In addition, due to the relatively large relative molecular weight of the cyano-modified pyridoimidazole derivatives, the N-containing heterocyclic structure (pyridimidazole group) and the N-containing aromatic anthracenyl structure are conjugated, so that the prepared cyano group-modified Pyridimidazole derivatives have the advantage of good thermal stability. In addition, the aromatic ring on the structure of the above-mentioned cyano-modified pyridoimidazole derivatives has a smaller volume and better solubility.

β＝95.651(2)°；Preferably, when R1 is a cyano group, and when R2 is a hydrogen group, the cyano group-modified pyridoimidazole derivatives are crystallized in an orthorhombic crystal system, the space group is P21/n, and the unit cell parameter is

β=95.651(2)°;

β＝102.328(2)°。Or when R1 is hydrogen and R2 is cyano, the cyano group-modified pyridoimidazole derivatives are crystallized in an orthorhombic system, and the space group is P21/c,

β=102.328(2)°.

The present invention protects the preparation method of the above-mentioned cyano group-modified pyridoimidazole derivatives, wherein the compound of formula (I) is prepared by Buchwald-Hartwig cross-coupling reaction between the pyridoimidazole derivatives and 10-hydro-phenoxazine; The pyridoimidazole derivatives are 4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)benzonitrile, 4-(2-(4-bromophenyl)imidazo[1] ,a]) One of pyridin-3-yl)pyridinenitrile and 4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)benzyl-pyridinenitrile.

Preferably, the molar ratio of the pyridoimidazole derivatives to 10-hydro-phenoxazine is 1:1-2.

More preferably, the molar ratio of the pyridoimidazole derivatives to 10-hydro-phenoxazine is 1:1-1.2.

Further preferably, the molar ratio of the pyridoimidazole derivatives to 10-hydro-phenoxazine is 1:1.1.

Preferably, the Buchwald-Hartwig cross-coupling reaction is carried out at 120-130° C. for 12-15 hours.

More preferably, the Buchwald-Hartwig cross-coupling reaction is carried out at 128-130° C. for 13-15 hours.

Further preferably, the Buchwald-Hartwig cross-coupling reaction is carried out at 130° C. for 15 hours.

Preferably, the Buchwald-Hartwig cross-coupling reaction is carried out at a pH of 10-14.

Preferably, the catalyst for the Buchwald-Hartwig cross-coupling reaction is a palladium catalyst.

Preferably, the palladium catalyst is palladium acetate.

Preferably, the Buchwald-Hartwig cross-coupling reaction is carried out in an inert atmosphere.

Preferably, the inert atmosphere is one of nitrogen, argon and helium.

Preferably, the (4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)benzonitrile is derived from (E)-4-(3-(4-bromophenylhydrazine) Benzonitrile and 2-aminopyridine are obtained by Michael cyclization reaction in the presence of iodine element.

Preferably, the molar ratio of (E)-4-(3-(4-bromophenylhydrazine))benzonitrile, 2-aminopyridine and iodine is 1-1.1:2-2.2:0.23-0.25.

More preferably, the molar ratio of ((E)-4-(3-(4-bromophenylhydrazine))benzonitrile, 2-aminopyridine and iodine is 1:2:0.23.

Preferably, the (4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)pyridinecarbonitrile is derived from (E)-4-(3-(4-bromophenylhydrazine) ) benzyl and 2-amino 4-cyanopyridine are obtained by Michael cyclization reaction in the presence of iodine element.

Preferably, the molar ratio of ((E)-4-(3-(4-bromophenylhydrazine))benzyl, 2-amino-4-cyanopyridine and iodine element is 1～1.1:2～2.2:0.23 ~0.25.

More preferably, the molar ratio of ((E)-4-(3-(4-bromophenylhydrazine))benzyl, 2-amino-4-cyanopyridine and iodine is 1:2:0.23.

Preferably, the solvent for the Michael cyclization reaction is dichloroethane.

Preferably, the Michael cyclization reaction is performed in air at 115-120° C. for 10-13 hours.

More preferably, the Michael cyclization reaction is performed in air at 118-120° C. for 10-12 hours.

Further preferably, the Michael cyclization reaction is performed in air at 120° C. for 12 hours.

Preferably, the preparation method further includes post-processing steps of cooling, distillation, extraction, drying, concentration and separation.

Specifically, the post-processing step is cooling and collecting to obtain a yellow turbid liquid, the turbid liquid is distilled under reduced pressure to remove toluene, the remaining solid is extracted three times with dichloromethane, combined three times to obtain an organic phase, dried with anhydrous magnesium sulfate, and then reduced The organic phase is distilled under pressure to obtain a crude product, and finally the compound of formula (I) is isolated by silica gel column chromatography using ethyl acetate and petroleum ether as eluents.

Preferably, the method also includes dissolving the cyano-modified pyridoimidazole derivative in an organic solvent to obtain a saturated solution, and then adding n-hexane to precipitate a crystal sample of the cyano-modified pyridoimidazole derivative at 20-30°C.

Since the cyano-modified pyridoimidazole derivatives have low solubility in n-hexane, slow addition of n-hexane is beneficial to the precipitation of crystals.

More preferably, the temperature of the crystallization is 25°C. If the crystallization temperature is too low, it is not conducive to the volatilization of the organic solvent and the n-hexane solvent, and is not conducive to the precipitation of crystals. If the temperature is too high, the organic solvent volatilizes too quickly, and needle-like polycrystals are easy to grow, and the crystal form is not good.

Preferably, the organic solvent is one of tetrahydrofuran, dichloromethane and toluene.

Preferably, the volume ratio of the organic solvent to n-hexane is 1:1-2.

Preferably, the rate of adding n-hexane is 0.5-1.0 mL/min.

Preferably, after the cyano group-modified pyridoimidazole derivative crystal sample is precipitated, post-processing steps of filtration, washing and drying are further included.

Preferably, the washing uses n-hexane as a detergent.

The present invention also protects the application of the above-mentioned cyano group-modified pyridoimidazole derivatives in organic light-emitting materials.

Specifically, the application of cyano group-modified pyridoimidazole derivatives in organic red light-emitting materials.

In practical application, the cyano group-modified pyridoimidazole derivatives prepared by the invention can be assembled into a single-layer light-emitting device, have good light-emitting performance, simplify the process and reduce the cost.

Compared with the prior art, the beneficial effects of the present invention are:

The cyano group-modified pyridoimidazole derivatives provided by the present invention contain N aromatic anthracenyl groups, and a bridged benzene ring is introduced between the cyano group and the carbonyl group to form a larger conjugated plane. Fluorescence quantum yield, and the introduction of a cyano group enhances the electron-withdrawing ability of the acceptor group, the intramolecular charge transfer phenomenon is more prominent, the spectrum is red-shifted, and red light can be emitted, and the cyano group-modified pyridoimidazole derivatives of the present invention It also has good AIE effect, excellent TADF properties, good thermal stability and solubility, and can be used as a new type of soluble light-emitting molecule with good performance and low cost, which can be used as red light-emitting materials, light-emitting devices or Light-emitting smart materials, etc., can be applied to fields such as full-color display and solid-state lighting.

Description of drawings

Fig. 1 is the hydrogen spectrum of the cyano group-modified pyridoimidazole derivative Ben-CN prepared in Example 1.

FIG. 2 is the mass spectrum of the cyano group-modified pyridoimidazole derivative Ben-CN prepared in Example 1. FIG.

FIG. 3 is the hydrogen spectrum of the cyano group-modified pyridoimidazole derivative Bd-CN prepared in Example 2. FIG.

FIG. 4 is the mass spectrum of the cyano group-modified pyridoimidazole derivative Bd-CN prepared in Example 2. FIG.

FIG. 5 is the UV-Vis absorption spectrum of the cyano group-modified pyridoimidazole derivative Ben-CN prepared in Example 1. FIG.

FIG. 6 is the ultraviolet-visible absorption spectrum and fluorescence emission of the cyano group-modified pyridoimidazole derivative Bd-CN prepared in Example 2. FIG.

7 is the AIE spectrum of the cyano-modified pyridoimidazole derivative Ben-CN prepared in Example 1 in solutions with different water contents.

8 is the AIE spectrum of the cyano-modified pyridoimidazole derivative Bd-CN prepared in Example 2 in solutions with different water contents.

FIG. 9 is a diagram showing the solvation effect of the cyano-modified pyridoimidazole derivative Ben-CN prepared in Example 1. FIG.

10 is a cyclic voltammogram of the cyano group-modified pyridoimidazole derivative Ben-CN prepared in Example 1.

FIG. 11 is the cyclic voltammogram of the cyano group-modified pyridoimidazole derivative Bd-CN prepared in Example 2. FIG.

12 is a graph showing the single crystal result of the cyano group-modified pyridoimidazole derivative Ben-CN prepared in Example 1. FIG.

13 is a graph showing the single crystal result of the cyano group-modified pyridoimidazole derivative Bd-CN prepared in Example 2.

FIG. 14 is the single crystal and pure film fluorescence emission diagrams of the cyano group-modified pyridoimidazole derivative Ben-CN prepared in Example 1. FIG.

15 is the single crystal and pure film fluorescence emission diagrams of the cyano-modified pyridoimidazole derivative Bd-CN prepared in Example 2. FIG.

FIG. 16 is a thermal stability diagram of the cyano group-modified pyridoimidazole derivatives Ben-CN and Bd-CN prepared in Example 1 and Example 2. FIG.

17 is the test spectrum of room temperature fluorescence and low temperature phosphorescence of the cyano-modified pyridoimidazole derivative Ben-CN prepared in Example 1.

18 is the test spectrum of the room temperature fluorescence and low temperature phosphorescence of the cyano-modified pyridoimidazole derivative Bd-CN prepared in Example 2.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw material reagents used in the examples of the present invention are conventionally purchased raw material reagents.

Example 1

A cyano group-modified pyridoimidazole derivative, named Ben-CN, has the following molecular structure:

The preparation method of above-mentioned Ben-CN, comprises the steps:

Weigh (E)-4-(3-(4-bromophenylhydrazine)) benzonitrile 150mg, 2-aminopyridine 80mg iodine element 60mg and 3mL dichloroethane in a 10mL sealed tube, carry out Michael ring at 120℃ After treatment, (4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)benzonitrile is obtained; DCE is dichloroethane;

Its reaction equation is:

Weigh out 180 mg of (4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)benzonitrile prepared above, 115 mg of 10-hydro-phenoxazine, and 80 mg of potassium tert-butoxide. , 4 mg of tri-tert-butylphosphine, 5.5 mg of palladium acetate and 5 mL of toluene were placed in a sealed tube, and the air in the device was removed by stirring and filled with nitrogen protection. The product is cooled, distilled, extracted, dried, concentrated and separated; the yellow turbid liquid is obtained by cooling and collection, the turbid liquid is distilled under reduced pressure to remove toluene, the remaining solid is extracted three times with dichloromethane, and the organic phases obtained three times are combined, and anhydrous sulfuric acid is used. After drying over magnesium, the organic phase was distilled under reduced pressure to obtain a crude product; finally, ethyl acetate and petroleum ether were used as eluents for separation by silica gel column chromatography; the obtained pure product solution was distilled under reduced pressure and dried under vacuum to obtain 90 mg of a yellow solid, namely It is Ben-CN, with a purity of 99% and a yield of 50%; the product is further added to a 1:1 mixed solution of tetrahydrofuran and n-hexane, and the solvent is slowly evaporated at room temperature to obtain crystals;

Its reaction equation is as follows:

Example 2

A cyano group-modified pyridoimidazole derivative, named Bd-CN, has the following molecular structure:

The preparation method of the above-mentioned Bd-CN is the same as that in Example 1, except that (E)-4-(3-(4-bromophenylhydrazine))benzonitrile is replaced by (E)-4-(3-(4- Bromophenylhydrazine)) nitrile, 2-aminopyridine was replaced by 2-amino-4-cyano-pyridine to obtain (4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl ) pyridine nitrile;

Its reaction equation is as follows:

Example 3

A cyano group-modified pyridoimidazole derivative has the following molecular structure:

The preparation method of the above cyano group-modified pyridoimidazole derivatives is the same as that in Example 1, the difference is that (4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)benzyl The nitrile was replaced with (4-(2-(4-bromophenyl)imidazo[1,a])pyridin-3-yl)benzyl-pyridinecarbonitrile.

Its reaction equation is as follows:

Comparative Example 1

The cyano group-modified pyridoimidazole derivatives of this comparative example have the following molecular structures:

The preparation method of the above-mentioned cyano group-modified pyridoimidazole derivatives is the same as that in Example 1, except that (E)-4-(3-(4-bromophenylhydrazine))benzophenone is replaced by (E)-4- (3-(4-Bromophenylhydrazine))benzonitrile.

Its reaction equation is as follows:

Structural Characterization and Performance Testing

1. Nuclear Magnetic Resonance and Mass Spectrometry

The hydrogen signal of Ben-CN prepared in Example 1 was scanned by nuclear magnetic resonance; the cyano-modified pyridoimidazole derivatives prepared in Examples 1 and 2 were dissolved in acetonitrile to prepare a solution with a concentration of 1 mg/mL , using a liquid mass spectrometer LCMS-2020 for mass spectrometry.

The nuclear magnetic spectrum of Ben-CN prepared in Example 1 (Fig. 1) δ(ppm) is ¹ H NMR (400MHz, Chloroform-d) δ8.55-8.46(m, 2H), 8.07(d, J=7.0Hz ,1H),7.84(dd,J＝19.1,8.6Hz,3H),7.75(d,J＝8.1Hz,2H),7.51–7.45(m,2H),7.39(ddd,J＝9.1,6.6,1.1 Hz, 1H), 6.96 (td, J=6.9, 1.1Hz, 1H), 6.75–6.64 (m, 4H), 6.61 (td, J=7.5, 1.9Hz, 2H), 6.01 (dd, J=7.8, 1.5Hz, 2H). From the Ben-CN mass spectrum (Figure 3), it can be seen that the relative molecular mass in the figure is 505.17, minus one H, which is consistent with the relative molecular mass of the synthesized Ben-CN. Combining the above NMR and mass spectrometry results, it can be known that the product prepared in Example 1 is Ben-CN.

The nuclear magnetic spectrum of Bd-CN prepared in Example 2 (Fig. 2) δ (ppm) is ¹ H NMR (400MHz, Chloroform-d) δ 8.40 (d, J=8.4 Hz, 2H), 8.19 (d, J ＝7.6Hz,1H),7.74(d,J＝8.3Hz,1H),7.61–7.51(m,4H),7.44(t,J＝7.9Hz,2H),7.15(t,J＝7.8Hz,1H) ), 7.01 (dd, J=7.1, 1.7Hz, 1H), 6.73–6.58 (m, 6H), 5.97 (dd, J=7.9, 1.4Hz, 2H). From the Bd-CN mass spectrum (Fig. 4) It can be seen that the relative molecular mass in the figure is 505.17, minus one H, which is consistent with the relative molecular mass of the synthesized Bd-CN. Combining the above NMR and mass spectrometry results, it can be known that the product prepared in Example 2 is Bd-CN.

2. UV-Vis absorption spectrum

Using a Shimadzu UV-Vis spectrophotometer UV-2700, the cyano-modified pyridoimidazole derivatives prepared in Examples 1 and 2 were dissolved in THF to prepare a 1×10 ^-3 mol/L mother solution, and diluted to 1 ×10 ^-5 mol/L for testing.

It can be seen from Figure 5 that the main absorption peak position of Ben-CN is 334 nm, and the emission wavelength is 601 nm, which is red light emission.

It can be seen from Fig. 6 that the main absorption peak position of Bd-CN is 334 nm, and the emission wavelength is 610 nm, which is red light emission. In contrast, the molecule of Comparative Example 1 has an emission wavelength of 574 nm and cannot generate red light.

3. AIE performance

The cyano-modified pyridoimidazole derivatives were dissolved in tetrahydrofuran to prepare a 1×10 ^-3 mol/L mother solution, and the total volume of the test solution was maintained at 3 mL. Keep the concentration of cyano-modified pyridoimidazole derivatives in the test solution at 1×10 ^{- 5} mol/L, and adjust the ratio of tetrahydrofuran and water in the test solution. For example: when the water content is 90%, the addition amount of each component is mother liquor: water: tetrahydrofuran=30uL:2700uL:270uL. The AIE spectra of cyano-modified pyridoimidazole derivatives were measured by FLS980 fluorometer.

The fluorescence spectra of cyano-modified pyridoimidazole derivatives Ben-CN in tetrahydrofuran-water solution with water content of 0% to 99% were tested respectively, as shown in Figure 7, the direction indicated by the arrows corresponds to the 6 fluorescence graph lines The water content of the solution increases in turn, and the emission wavelength of Ben-CN is 600 nm; when the water content is lower than 95%, the fluorescence emission wavelength of Ben-CN in the solution has an obvious red shift; and when the water content exceeds 95% After that, the spectrum blue-shifted, the molecules precipitated and aggregated in the solution, and the corresponding fluorescence intensity was greatly enhanced. It can be seen that Ben-CN has obvious AIE phenomenon.

The fluorescence spectra of Bd-CN in tetrahydrofuran-water solution with water content of 0% to 99% were tested respectively; as shown in Figure 8, the direction indicated by the arrows is the direction in which the water content of the solution corresponding to the four fluorescence graph lines increases in turn, The emission wavelength of Bd-CN is 610 nm; when the water content is less than 95%, the fluorescence emission wavelength of Bd-CN in solution has a significant red shift; when the water content exceeds 95%, the spectrum is blue-shifted, and the molecule is in the solution. The precipitation and aggregation in Bd-CN were greatly enhanced, and the corresponding fluorescence intensity was greatly enhanced, indicating that Bd-CN had obvious AIE phenomenon.

4. Solvation effect

The normalized spectra of cyano-modified pyridoimidazole derivatives in different solvents were measured by FLS980 fluorometer.

It can be seen from Figure 9 that the cyano group-modified pyridoimidazole derivatives Ben-CN are in different solvents (in descending order of solvent polarity: n-hexane n-hex, toluene Tol, dichloromethane DCM, tetrahydrofuran THF, In ethyl acetate (EtaOH), with the enhancement of solvent polarity, the spectrum shows obvious solvatochromic effect, which is caused by the intramolecular charge transfer effect (ICT), that is, the charge transfer excited state.

5. Cyclic voltammogram

The cyclic voltammograms of the cyano group-modified pyridoimidazole derivatives Ben-CN and Bd-CN prepared in Example 1 and Example 2 were tested by electrochemical workstation PGSTAT302.

The cyano-modified pyridoimidazole derivatives were dissolved in acetonitrile to make a solution of 1 mg/mL. The oxidation potentials of Ben-CN and Bd-CN were measured by cyclic voltammetry under the electrochemical workstation. E=0.74 eV and E=0.75eV (as shown in Figure 10, Figure 11). Compared with E=0.67V of Comparative Example 1, Ben-CN and Bd-CN have stronger oxidation potential values, which are more conducive to the generation of red light.

6. Solubility

The Ben-CN prepared in Example 1 was dissolved in acetone, ethyl acetate, tetrahydrofuran, and dichloromethane solvent, specifically, 10 mg of the sample was dissolved in 1 ml of solvent. The results are shown in Table 1, where "+" indicates that it can be dissolved in the corresponding solvent, and the more "+", the greater the solubility in the corresponding solvent.

Table 1 Solubility of Ben-CN and Bd-CN prepared in Example 1 and Example 2

The results in Table 1 above show that Ben-CN and Bd-CN have better solubility.

7. Single crystal X-ray diffraction

The crystal structure was determined by Bruker X single crystal diffractometer in Germany. Test method: Select a single crystal with a moderate size and good crystal quality as a sample. When X-rays are irradiated on a single crystal, diffraction will occur. By analyzing the diffraction lines, the arrangement law of atoms in the crystal can be analyzed, and the diffraction data can be collected. Index the diffractogram, obtain the unit cell constant, sum up the extinction law according to the diffraction index of all diffraction lines, and infer the space group to which the crystal belongs. The measured diffraction intensity is subjected to absorption correction, LP correction and other processing to obtain the structural amplitude |F|. Using the Paterson function method, the phase angle and initial structure are inferred.

β＝95.651(2)°,

Z＝4。从晶体的作用力图可以看到，分子之间存在C…H…O/N及C…H…π堆积，这有利于分子的发光，并且，采用FLS980的积分球测试其绝对量子产率，结果显示Ben-CN获得大于50％的高荧光量子产率。As shown in Figure 12, the single crystal X-ray diffraction data shows that the Ben-CN of Example 1 belongs to the orthorhombic system, and the space group is P21/n,

β=95.651(2)°,

Z=4. It can be seen from the force diagram of the crystal that there are C…H…O/N and C…H…π stacking between the molecules, which is beneficial to the luminescence of the molecules, and the absolute quantum yield of the molecules was tested by using the integrating sphere of FLS980. The result It is shown that Ben-CN achieves high fluorescence quantum yields greater than 50%.

β＝102.328(2)°,

Z＝4。从晶体的作用力图可以看到，分子之间存在C…H…O/N及C…H…π堆积，这有利于分子的发光，并且，采用FLS980的积分球测试其绝对量子产率，结果显示Bd-CN获得大于50％的高荧光量子产率。As shown in Figure 13, the single crystal X-ray diffraction data shows that the Bd-CN of Example 2 belongs to the orthorhombic system, and the space group is P2 ₁ /c,

β=102.328(2)°,

Z=4. It can be seen from the force diagram of the crystal that there are C…H…O/N and C…H…π stacking between the molecules, which is beneficial to the luminescence of the molecules, and the absolute quantum yield of the molecules was tested by using the integrating sphere of FLS980. The result It is shown that Bd-CN achieves high fluorescence quantum yields greater than 50%.

8. Single crystal fluorescence emission test

Fluorescence spectrum: use Edinburgh FL980 transient steady-state fluorescence phosphorescence spectrometer for solid fluorescence spectrum test; set the excitation wavelength to 370nm, set the slit width so that the ordinate value is close to one million, and then perform the spectrum test to obtain the spectrum.

As shown in Figure 14 and Figure 15, under the light excitation of 370 nm, the crystals and pure films of Ben-CN and Bd-CN prepared in Example 1 and Example 2 (Ben-CN and Bd-CN were vacuum evaporated respectively Thin films prepared on quartz wafers) exhibit an emission maximum at 600 nm. By comparison, it can be found that the crystal emission peak is wider, which may be attributed to the obvious C…H…π stacking between molecules in the crystal structure compared with the pure amorphous film. In the pure film, Ben-CN and Bd-CN prepared in Example 1 and Example 2 both obtained fluorescence emission greater than 600 nm. Compared with the fluorescence emission of 574 nm in Comparative Example 1, it showed that the molecules prepared by the present invention were in Superiority in red light emission. Moreover, in the pure film, Ben-CN and Bd-CN prepared in Example 1 and Example 2 both obtained fluorescence quantum yield close to 40%, while the fluorescence quantum yield of the thin film of Comparative Example 1 was 30.2%, It shows that Ben-CN and Bd-CN have better luminescence properties than the molecules of Comparative Example 1 in the thin film state.

As shown in Fig. 16, the temperature was increased at a temperature gradient of 20°C under nitrogen atmosphere. It can be seen that the thermal decomposition temperatures of Ben-CN and Bd-CN prepared in Example 1 and Example 2 all exceeded 400°C, which was higher than that of Comparative Example 1. The thermal decomposition temperature was 369.1° C., which proved that Example 1 and Example 2 had better thermal stability.

As shown in Figure 17 and Figure 18, under nitrogen atmosphere, the Ben-CN and Bd-CN prepared in Example 1 and Example 2 were tested for room temperature fluorescence and low temperature phosphorescence with FLS980 instrument. The energy level difference of the singlet state S ₁ and the lowest triplet state T ₁ is as low as 0.03 and 0.02 electron volts, respectively, compared with the 0.05 eV energy level difference of the comparative example 1, indicating that the two molecules of the present invention have more efficient TADF performance.

Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. A cyano-modified pyridoimidazole derivative is characterized by having a molecular structure shown as a formula (I):

wherein R1 is hydrogen and R2 is cyano; or R1 is cyano and R2 is hydrogen.

2. The cyano-modified pyridoimidazole derivative according to claim 1, wherein R is ₁ When it is cyano, R ₂ When the crystal is hydrogen, the cyano-modified pyridoimidazole derivative is crystallized in an orthorhombic system, the space group is P21/n, and the unit cell parameter is

β＝95.651(2)°；

Or when R1 is hydrogen and R2 is cyano, the cyano-modified pyridoimidazole derivative is crystallized in an orthorhombic system, the space group is P21/c, and the unit cell parameter is

β＝102.328(2)°。

3. The method for preparing cyano-modified pyridoimidazole derivatives according to claim 1 or 2, characterized in that the compound of formula (i) is prepared by Buchwald-Hartwig cross-coupling reaction of the pyridoimidazole derivatives with 10-hydro-phenoxazine; the structural formula of the pyridoimidazole derivatives is shown in the specification

4. The preparation method according to claim 3, characterized in that the molar ratio of the pyridoimidazole derivative to the 10-hydro-phenoxazine is 1: 1-2.

5. The preparation method of claim 3, wherein the Buchwald-Hartwig cross-coupling reaction is carried out at 120-130 ℃ for 12-15 h.

6. The method of claim 3, wherein the Buchwald-Hartwig cross-coupling reaction is carried out at a pH of 10 to 14.

7. The method of claim 3, wherein the catalyst for the Buchwald-Hartwig cross-coupling reaction is a palladium catalyst.

8. The method of claim 3, wherein the Buchwald-Hartwig cross-coupling reaction is performed in an inert atmosphere.

9. The preparation method according to claim 3, characterized by further comprising dissolving the cyano-modified pyridoimidazole derivative in an organic solvent to obtain a saturated solution, adding n-hexane, and precipitating a cyano-modified pyridoimidazole derivative crystal sample at 20-30 ℃.

10. The application of the cyano-modified pyridoimidazole derivatives in organic luminescent materials according to claim 1 or 2.

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