NL2036209A

NL2036209A - Use of cyano-modified pyridino imidazole derivative in preparing organic photoelectric devices

Info

Publication number: NL2036209A
Application number: NL2036209A
Authority: NL
Inventors: Huang Chou; Ji Shaomin; Chen Wencheng; Qiu Zhipeng; Fu Yu; Huo Yanping
Original assignee: Univ Guangdong Technology
Priority date: 2023-11-08
Filing date: 2023-11-08
Publication date: 2024-02-16

Abstract

The present disclosure discloses use of a cyano-modified pyridino imidazole derivative in preparing organic photoelectric devices. The cyano-modified pyridino imidazole derivative of the present invention has a better AIE effect, excellent thermally activated delayed fluorescence (TADF) property, and a good thermal stability and solubility. The cyano-modified pyridino imidazole derivative has an electron deficient property and can be 10 widely used as electron transport layers in OLED or organic solar cell devices. Moreover, the cyano-modified pyridino imidazole derivative also has lower LUIVIO energy levels, which can be used as the body material in OLED doped devices.

Description

USE OF CYANO-MODIFIED PYRIDINO IMIDAZOLE DERIVATIVE IN PREPARING ORGANIC

PHOTOELECTRIC DEVICES

TECHNICAL FIELD

The present disclosure belongs to the technical field of organic light-emitting materials and more specifically relates to use of a cyano-modified pyridino imidazole derivative in preparing organic photoelectric devices.

BACKGROUND

Since an organic light-emitting material has significant advantages of a large area, high-quality display and lighting, an ultrahigh resolution ratio, an ultrafast response speed, flexibility, and the like, a technology of using the organic light-emitting material as an organic light-emitting diode (OLED) has wide applications in the fields of flat panel displays, smart phones, solid-state lighting, and the like.

However, a red light-emitting material in the current organic light-emitting material has problems of a low solid-state fluorescence guantum yield, poor thermal stability and poor solubility because an inherent narrow band gap of the red light- emitting material can greatly enhance a non-radiative transition rate of molecules, thereby causing a large energy loss.

For example, Chinese patent CN102070632B discloses a pyridino imidazole derivative and its use thereof in an organic electroluminescent device. A luminescent position of the pyridino imidazole derivative is red-shifted to a visible light region by introducing a substituent group with a rigid structure, the luminescent efficiency is improved. At the same time, molecular coplanarity is destroyed and thus thermal stability of the compound is improved. However, the compound still has problems of poor solubility.

SUMMARY

The present disclosure aims to overcome the defects and shortcomings of poor solubility of the existing pyridino imidazole derivative luminescent material in the electron transport layer of OLED and/or organic solar cell devices, and provides use of a cyano-modified pyridino imidazole derivative in preparing organic photoelectric devices, which the cyano-modified pyridino imidazole derivative has relatively good thermal stability and solubility at the same time.

The foregoing object of the present disclosure is realized by the following technical solution:

Use of a cyano-modified pyridino imidazole derivative in preparing organic photoelectric devices, wherein the use is to prepare an electron transport layer for

OLED and/or organic solar cell devices, and the cyano-modified pyridino imidazole derivative has a molecular structure shown as formula (1):

Ri 0

AN, A — “wD 0 R

Formula (1) ‚ wherein R1 is a hydrogen or a cyano group,

R2 is a hydrogen or a cyano group, and R1 and R2 are not hydrogen at the same time.

The prepared cyano-modified pyridino imidazole derivative of the present invention has an advantage of good thermal stability due to the fact that the cyano- modified pyridino imidazole derivative has a relatively large molecular weight and an

N-containing heterocyclic structure {a pyridino imidazole group} and an N-containing aromatic anthryl structure are conjugated. In addition, the aromatic ring in the cyano- modified pyridino imidazole derivative has a relatively small volume structurally,

resulting in a better solubility.

Further, the cyano-modified pyridino imidazole derivative of the present invention structurally introduces a bridged benzene ring between a N-containing aromatic anthryl (or hydrogenated phenoxazinyl) and a carbonyl group, such that a larger conjugate plane is formed; and since a C.H... accumulation (provided by N atoms on hydrogenated phenoxazinyl and pyridino imidazole) exists, the structures are favorable for molecular luminescence and a higher fluorescence quantum yield is obtained. In addition, a cyano group is further introduced into the molecule, such that an electron donating capability of the molecule is enhanced, a spectrum is red-shifted, a red light is emitted, and differences between singlet state and triplet state energy levels are obviously reduced, such that a thermally activated delayed fluorescence (TADF) property is more excellent. Since the cyano-modified pyridino imidazole derivative further contains a carbonyl group, such that molecular vibration may be caused, an aggregation-induced emission (AlE) effect may be generated, exciton annihilation may be effectively inhibited, and molecules have stronger fluorescence emission in a high-concentration aggregation state than in a low-concentration state, and thus have a higher luminous intensity and a better AlE performance.

Further, due to electron deficient nature of the cyano-modified pyridino imidazole derivative, it can be used as electron transport layers in OLED or organic solar cell devices.

Particularly, the use may further be to prepare a body material for OLED doped devices.

The cyano-modified pyridino imidazole derivative also has lower LUMO energy levels, which can be used as the body material in OLED doped devices.

Preferably, when the R1 is a cyano group and R2 is hydrogen, the cyano-modified pyridino imidazole derivative is crystallized in an orthorhombic system, and has a space group of P21/n and cell parameters of a = 11.2742(2) A, b = 8.1358(2) A, c = 26.7059(6) A, and 8 = 95.651(2)°;

or when the R1 is a hydrogen and R2 is a cyano group, the cyano-modified pyridino imidazole derivative is crystallized in an orthorhombic system, and has a space group of P21/c and cell parameters of a = 18.3098(5) A, b = 7.6172(2) A, c = 17.5761(4) A, and 8 = 102.328(2)".

A preparation method for the cyano-modified pyridino imidazole derivative includes the following step: subjecting the pyridino imidazole derivative and 10- hydrogen-phenoxazine to a Buchwald-Hartwig cross-coupling reaction to prepare a compound of formula {1}; wherein the pyridino imidazole derivative is one of 4-{2-(4- bromobenzene)imidazo{1, al}pyridine-3-yl}benzonitrile, 4-(2-{4- bromobenzene)imidazofl, al)pyridine-3-yljpyridine nitrile, and 4-(2-(4- bromobenzene}imidazo{1, a])pyridine-3-yl)benzyl-pyridine nitrile.

Preferably, the pyridino imidazole derivative and the 10-hydrogen-phenoxazine have a molar ratio of 1:(1-2).

More preferably, the pyridino imidazole derivative and the 10-hydrogen- phenoxazine have a molar ratio of 1:(1-1.2).

Further preferably, the pyridino imidazole derivative and the 10-hydrogen- phenoxazine have a molar ratio of 1:1.1.

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

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

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

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

Preferably, a catalyst used in 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 performed under an inert atmosphere.

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

Preferably, the 4-(2-{4-bromobenzene)imidazo{l, a])pyridine-3-yl}benzonitrile is 5 obtained by a Michael cyclization reaction of (E)-4-(3-(4- bromophenylhydrazine}benzyinitrile and 2-aminopyridine in the presence of iodine.

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

More preferably, the (E)-4-(3-(4-bromophenylhydrazine)benzylnitrile, 2- aminopyridine, and iodine have a molar ratioof 1 . 2 © 0.23.

Preferably, the 4-(2-{4-bromobenzene)imidazo{l, a])pyridine-3-yl)pyridine nitrile is obtained by a Michael cyclization reaction of (E)-4-(3-(4- bromophenylhydrazine)benzyl and 2-amino-4-cyanopyridine in the presence of iodine.

Preferably, the (E)-4-(3-(4-bromophenylthydrazine)benzyl, 2-amino-4- cyanopyridine, and iodine have a molar ratio of (1-1.1) © (2-2.2) : (0.23-0.25).

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

Preferably, a solvent of 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 comprises post treatment of cooling, distillation, extraction, drying, concentration and separation.

Specifically, the post treatment comprises steps of performing cooling and collecting to obtain a yellow turbid liquid, distilling the turbid liquid under a reduced pressure to remove toluene, extracting a remaining solid with dichloromethane for three times, combining three obtained organic phases, performing drying with anhydrous magnesium sulfate, distilling the organic phase under a reduced pressure to obtain a crude product, and finally performing silica gel column chromatography using ethyl acetate and petroleum ether as eluents to separate out a compound of formula (1).

Preferably, the method further comprises steps of dissolving a cyano-modified pyridino imidazole derivative in an organic solvent to obtain a saturated solution, then adding n-hexane, and separating out a cyano-modified pyridino imidazole derivative crystal sample at 20-30°C.

Since the cyano-modified pyridino imidazole derivative has a relatively low solubility in n-hexane, the n-hexane is slowly added to facilitate precipitation of a crystal.

More preferably, the crystallization is performed at a temperature of 25°C. If a crystallization temperature is too low, volatilization of an organic solvent and an n- hexane solvent is not facilitated, and precipitation of a crystal is not facilitated. If the temperature is too high, the volatilization of the organic solvent is too fast, a needle- shaped polycrystal is easy to grow, and a crystal form is not good.

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

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

Preferably, the n-hexane is added at a speed of 0.5-1.0 mL/min.

Preferably, after the cyano-modified pyridino imidazole derivative crystal sample is precipitated, the method further comprises post treatments of filtration, washing and drying.

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

The present disclosure further protects use of the cyano-modified pyridino imidazole derivative in an organic light-emitting material.

Specifically, the present disclosure protects use of the cyano-modified pyridino imidazole derivative in an organic red light-emitting material.

The cyano-modified pyridino imidazole derivative prepared by the present disclosure can be assembled into a single-layer luminescent device in a practical application, has a better luminescent property, simplifies a process and reduces a cost.

Compared with the prior art, the present disclosure has the beneficial effects that:

The cyano-modified pyridino imidazole derivative provided by the present disclosure has a better AIE effect, an excellent TADF property, and a good thermal stability and solubility, can be used as a novel soluble light-emitting molecule with a good performance and a relatively low cost, can be used as a red light-emitting material, a light-emitting device or a light-emitting intelligent material and the like, and can be used in the fields of full-color display, solid-state lighting and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a H nuclear magnetic resonance of a cyano-modified pyridino imidazole derivative Ben-CN prepared in example 1;

FIG. 2 is a mass spectrum of a cyano-modified pyridino imidazole derivative Ben-

CN prepared in example 1;

FIG. 3 shows a H nuclear magnetic resonance of a cyano-modified pyridino imidazole derivative Bd-CN prepared in example 2;

FIG. 4 is a mass spectrum of a cyano-modified pyridino imidazole derivative Bd-

CN prepared in example 2;

FIG. 5 is an ultraviolet-visible absorption spectrum of a cyano-modified pyridino imidazole derivative Ben-CN prepared in example 1;

FIG. 6 shows an ultraviolet-visible absorption spectrum and a fluorescence emission diagram of a cyano-modified pyridino imidazole derivative Bd-CN prepared in example 2;

FIG. 7 is an AIE spectrum of a cyano-modified pyridino imidazole derivative Ben-

CN prepared in example 1 in solutions with different water contents;

FIG. 8 is an AIE spectrum of a cyano-modified pyridino imidazole derivative Bd-

CN prepared in example 2 in solutions with different water contents;

FIG. 9 shows a solvation effect of a cyano-modified pyridino imidazole derivative

Ben-CN prepared in example 1;

FIG. 10 is a cyclic voltammogram of a cyano-modified pyridino imidazole derivative Ben-CN prepared in example 1;

FIG. 11 is a cyclic voltammogram of a cyano-modified pyridino imidazole derivative Bd-CN prepared in example 2;

FIG. 12 shows a single crystal result of a cyano-modified pyridino imidazole derivative Ben-CN prepared in example 1;

FIG. 13 shows a single crystal result of a cyano-modified pyridino imidazole derivative Bd-CN prepared in example 2;

FIG. 14 shows a fluorescence emission of a single crystal and a pure film of a cyano-modified pyridino imidazole derivative Ben-CN prepared in example 1;

FIG. 15 shows a fluorescence emission of a single crystal and a pure film of a cyano-modified pyridino imidazole derivative Bd-CN prepared in example 2;

FIG. 16 shows thermal stability of cyano-modified pyridino imidazole derivatives

Ben-CN and Bd-CN prepared in examples 1 and 2;

FIG. 17 shows normaltemperature fluorescence and low-temperature phosphorescence test spectra of a cyano-modified pyridino imidazole derivative Ben-

CN prepared in example 1; and

FIG. 18 shows normal-temperature fluorescence and low-temperature phosphorescence test spectra of a cyano-modified pyridino imidazole derivative Bd-

CN prepared in example 2.

DETAILED DESCRIPTION OF EMBODIMENTS

The present disclosure is further described with reference to the specific embodiments, but the examples are not intended to limit the present disclosure in any form. Unless otherwise stated, the raw material reagents used in the examples of the present disclosure are purchased conventional raw material reagents.

Example 1

A cyano-modified pyridino imidazole derivative is named as Ben-CN and has a molecular structure shown as follows:

CN

A en

NT NT SNF N Ne! 5 A

A preparation method of the Ben-CN comprises the following steps: 150 mg (E}-4-(3-(4-bromophenylhydrazine))benzonitrile, 80 mg 2-aminopyridine, 60 mg iodine, and 3 mL dichloroethane were weighed in a 10 mL sealed tube, a mixture was subjected to a Michael cyclization reaction at a temperature of 120°C, and after the treatment, {(4-(2-{4-bromophenyl}imidazo{1,al)pyridin-3-yl)benzonitrile was obtained; and DCE was dichloroethane;

A reaction equation is as follows:

CN

0 0 )

A N NH: + (7 I2DCE,120°C,12h ® =

Br CN N=

Br mn 180 mg the prepared (4-(2-(4-bromophenyl)imidazo{1,a])pyridin-3- vlijbenzonitrile, 115 mg 10-hydrogen-phenoxazine, 80 mg potassium tert-butoxide, 4 mg tri-tert-butylphosphine, 5.5 mg palladium acetate and 5 mL toluene were weighed in a sealed tube, the materials were stirred, air in a device was pumped out and nitrogen was filled as protective atmosphere. Then, heating, stirring, refluxing and reacting were performed at 130°C under the protective atmosphere of nitrogen for 15 hours, after the reaction was finished, a crude product was subjected to cooling, distilling, extracting, drying, concentrating and separating; a yellow turbid liquid was obtained by cooling and collecting, the turbid liquid was distilled under a reduced pressure to remove toluene, a remaining solid was extracted with dichloromethane for three times, three obtained organic phases were combined and dried with anhydrous magnesium sulfate, the organic phase was distilled under a reduced pressure to obtain a crude product; finally silica gel column chromatography was performed using ethyl acetate and petroleum ether as eluents; an obtained pure product was distilled under a reduced pressure and dried in vacuum to obtain 90 mg a yellow solid, namely Ben-CN with a purity of 99% and a yield of 50%; and the product was further added to a mixed solution of tetrahydrofuran and n-hexane at 1:1, and a crystal was obtained after a solvent was slowly volatilized at a room temperature.

The reaction equation is as follows:

ED OE t-Bu3P t-BuOK, 130°C od oY ION ee OY OY

A TAA ALS dd b=)

ONT wen No Pd(OAc)2 N2 Tol WT Na

FL ed ON de

Be” Nf Ind B: >

Example 2

A cyano-modified pyridino imidazole derivative is named as Bd-CN and has a molecular structure shown as follows:

O

OT EN

(J

N en

A preparation method of the Bd-CN is the same as that in example 1 except that

(E)-4-(3-{4-bromophenylhydrazine})benzonitrile is replaced with (E)-4-(3-(4- bromophenylhydrazine})nitrile and 2-aminopyridine is replaced with 2-amino-4- cyano-pyridine to prepare {4-(2-(4-bromophenyl)imidazo{l,a])pyridin-3-yl)pyridine nitrile.

The reaction equation is as follows: 0 0 _ el Ny NH ; + (7 1,,DCE, 120°C, 12h (2 = ;

Br ee

CN

J

0 DD O0 tBu3P,t-BuOK,130 °C © AN + ee Ke ® CON 0 Pd(OAc)2 N2 Tol N 2 2 “0 CN

Br en

CN

Example 3

A cyano-modified pyridino imidazole derivative, has a molecular structure shown as follows:

CN o

OLA oN

A preparation method of the cyano-modified pyridino imidazole derivative is the same as that in example 1 except that {(4-(2-(4-bromobenzen)imidazo[1,a}) pyridin-3- yl)benzonitrile is replaced with (4-(2-(4-bromobenzene)imidazo[l,al)pyridin-3- yl)benzyl-pyridine nitrile.

The reaction equation is as follows:

CN

9 0 _

Ny NH2 P + | P 1, DCE, 120°C, 12h NTA

Br CN N=

Br ee

CN

: ® ’ 0

N t-Bu3P,t-BuOK,130 °C oO N + CT DD D N= ON 0 ZN \ 0 Pd(OAc)2 N2 Tol N ee ) 0) CN

Br wen

CN

Comparative example 1

A cyano-modified pyridino imidazole derivative of the present comparative example, having a molecular structure shown as follows: ° ~~

EN Rg rd A AN oo OM TONS

ETN

Rl AT N== /

Ww hl Nee

Oo. A

A preparation method of the cyano-modified pyridino imidazole derivative is the same as that in example 1 except that (E}-4-(3-(4- bromophenylhydrazine)}benzophenone is replaced with (E)-4-(3-{4- bromophenylhydrazine}}benzonitrile.

The reaction eguation is as follows: ? 0 _ 7 N, NH; Pp + o (TJ 1,,DCE,120°C, 12h NN

Br Br N

Structural characterization and performance test 1. Nuclear magnetic resonance and mass spectrometry

A hydrogen signal of Ben-CN prepared in example 1 was scanned by nuclear magnetic resonance; and the cyano-modified pyridino imidazole derivatives prepared in examples 1 and 2 were dissolved in acetonitrile to prepare a solution having a concentration of 1 mg/mL and subjected to mass spectrometry using a liquid chromatograph-mass spectrometer LCMS-2020.

A nuclear magnetic resonance spectrum (FIG. 1) 6 {ppm) of Ben-CN obtained in example 1 is *H NMR {400 MHz, Chloroform-d) 6 8.55-8.46 (m, 2H), 8.07 (d, J = 7.0 Hz, 1H), 7.84 (dd, J = 19.1, 8.6 Hz, 3H), 7.75 (d, J = 8.1 Hz, 2H), 7.51-7.45 (m, 2H), 7.39 (ddd, 1 =9.1, 6.6, 1.1 Hz, 1H), 6.96 (td, } = 6.9, 1.1 Hz, 1H), 6.75-6.64 {m, 4H), 6.61 (td,

J= 7.5, 1.9 Hz, 2H), and 6.01 (1 = 7.8, 1.5, 2H). From the mass spectrum of Ben-CN (FIG. 3), it can be seen that the relative molecular mass in the figure is 505.17 and after one

H is subtracted, the relative molecular mass of the substance is consistent with the relative molecular mass of the synthesized Ben-CN. Combined with the results of the above nuclear magnetic resonance and mass spectrometry, it can be seen that the product prepared in example 1 is Ben-CN.

A nuclear magnetic resonance spectrum of Bd-CN prepared in example 2 (FIG. 2) & (ppm) is tH NMR (400 MHz, Chloroform-d) 6 8.40 (d, J = 8.4 Hz, 2H), 8.19 (d, 1 = 7.6

Hz, 1H), 7.74 (d, } = 8.3 Hz, 1H), 7.61-7.51 {m, 4H), 7.44 (t, 1 = 7.9 Hz, 2H), 7.15 (t, J = 7.8 Hz, 1H), 7.01 (dd, J = 7.1, 1.7 Hz, 1H), 6.73-6.58 {m, 6H), and 5.97 (dd, J = 7.9, 1.4

Hz, 2H). From the mass spectrum of Bd-CN (FIG. 4), it can be seen that the relative molecular mass in the figure is 505.17 and after one H is subtracted, the relative molecular mass of the substance is consistent with the relative molecular mass of the synthesized Bd-CN. Combined with the results of the above nuclear magnetic resonance and mass spectrometry, it can be seen that the product prepared in example 2 is Bd-CN. 2. Ultraviolet-visible absorption spectrum

The cyano-modified pyridino imidazole derivatives prepared in examples 1 and 2 were dissolved in THF to prepare a mother solution of 1x10 mol/L and the mother solution was diluted to 1x10% mol/L for testing using a Shimadzu UV-visible spectrophotometer UV-2700.

As seen in FIG. 5, Ben-CN has a main absorption peak position of 334 nm, an emission wavelength of 601 nm, and a red emission.

As seen from FIG. 6, Bd-CN has a main absorption peak position of 334 nm, an emission wavelength of 610 nm, and a red emission. However, a molecule of comparative example 1 has an emission wavelength of 574 nm and fails to produce a red light. 3. AIE performance

A cyano-modified pyridino imidazole derivative was dissolved in tetrahydrofuran to prepare a 1x10 mol/L mother solution and a total volume of a test solution was maintained to be 3 mL. A concentration of the cyano-modified pyridino imidazole derivative in the test solution was kept at 1x10 mol/L and a ratio of tetrahydrofuran to water in the test solution was adjusted. For example, when a water content was 90%, a ratio of an addition amount of each component was as follows: a mother solution to water to tetrahydrofuran = 30 uL:2700 uL:270 ul. An AIE spectrum of the cyano-modified pyridino imidazole derivative was tested by an FLS980 luminoscope.

Fluorescence spectra of the cyano-modified pyridino imidazole derivative Ben-

CN in a tetrahydrofuran-water solution with a water content of 0%-99% were respectively tested. As shown in FIG. 7, a direction indicated by an arrow is a direction in which the water content of the solution corresponding to 6 fluorescence figure lines increases in sequence and an emission wavelength of the Ben-CN is 600 nm. When the water content is lower than 95%, a fluorescence emission wavelength of the Ben-

CN in the solution shows an obvious red shift. When the water content exceeds 95%, the spectrum is blue-shifted, molecules are precipitated and aggregated in the solution, and the corresponding fluorescence intensity is greatly enhanced, and it can be known that the Ben-CN has a significant AIE phenomenon.

Fluorescence spectra of the Bd-CN in a tetrahydrofuran-water solution with a water content of 0%-99% were respectively tested. As shown in FIG. 8, a direction indicated by an arrow is a direction in which the water content of the solution corresponding to 4 fluorescence figure lines increases in sequence and an emission wavelength of the Bd-CN is 610 nm. When the water content is lower than 95%, a fluorescence emission wavelength of the Bd-CN in the solution shows an obvious red shift. When the water content exceeds 95%, the spectrum is blue-shifted, molecules are precipitated and aggregated in the solution, and the corresponding fluorescence intensity is greatly enhanced, and it can be known that the Bd-CN has a significant AIE phenomenon. 4. Solvation effect

Normalized spectra of the cyano-modified pyridino imidazole derivative in different solvents were tested using an FLS980 fluorometer. As can be seen from FIG. 9, the spectra of the cyano-modified pyridino imidazole derivative Ben-CN in different solvents {arranged from according to a polarity of the solvents from strong to weak: n-hexane n-hex, toluene Tol, dichloromethane DCM, tetrahydrofuran THF, and ethyl acetate EtaOH) show an obvious solvation discoloration effect along with the increase of the polarity of the solvents. This is caused by an intramolecular charge transfer {ICT) effect, namely, a charge transfer excited state. 5. Cyclic voltammogram

Cyclic voltammograms of the cyano-modified pyridino imidazole derivatives Ben-

CN and Bd-CN prepared in examples 1 and 2 were tested by an electrochemical workstation PGSTAT302.

The cyano-modified pyridino imidazole derivatives were dissolved in acetonitrile to prepare into a 1 mg/mL solution, and oxidation potentials of the Ben-CN and Bd-

CN were measured by cyclic voltammetry under the electrochemical workstation as E =0.74 eV and E = 0.75 eV {see FIGs. 10 and 11). The Ben-CN and Bd-CN have stronger oxidation potential values than E = 0.67V of comparative example 1 and are more favorable for generating a red light. 6. Solubility

The Ben-CN prepared in example 1 was dissolved in acetone, ethyl acetate, tetrahydrofuran, and dichloromethane solvents. Specifically, 10 mg the sample was dissolved in 1 mi of the solvent. The results are shown in Table 1, wherein “+” indicates solubility in the corresponding solvent and the more number of “+” indicates greater solubility in the corresponding solvent.

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

The results in Table 1 above show that the Ben-CN and Bd-CN have relatively good solubility. 7. X-ray diffraction of single crystal

A crystal structure was determined using a German bruker X single crystal diffractometer. A test method is as follows: a single crystal with a proper size and a good crystal quality is selected as a sample, X-rays are used for irradiating one single crystal to generate diffraction, an arrangement rule of atoms in the crystal can be analyzed through analyzing diffraction lines, diffraction data is collected, a diffraction diagram is indexed, a cell constant is solved, an extinction rule is summarized according to diffraction indexes of all the diffraction lines, and a space group to which the crystal belongs is deduced. A measured diffraction intensity is subjected to various treatments such as absorption correction, LP correction and the like to obtain a structure amplitude |F]. A phase angle and an initial structure are estimated using a

Patterson function method.

As shown in FIG. 12, single crystal X-ray diffraction data indicate that the Ben-CN of example 1 belongs to an orthorhombic system, and has a space group of P21/n and cell parameters of 0 = 11.2742(2) A, b = 8.1358(2) A, c = 26.7059(6) A, 8 = 95.651(2)°,

V =2437.68(9) Â3, and Z = 4. From an acting force diagram of crystal, it can be seen that the existences of C..H...O/N and C.H... accumulation between molecules are beneficial to luminescence of the molecules. Besides, an absolute quantum yield is tested by an integrating sphere of FLS980 and the results show that the Ben-CN obtains a high fluorescence quantum yield of more than 50%.

As shown in FIG. 13, single crystal X-ray diffraction data indicate that the Bd-CN of example 2 belongs to an orthorhombic system, and has a space group of P21/c and cell parameters of a = 18.3098(5) A, b= 7.6172(2) A, c = 17.5761(4) A, 8 = 102.328(2)°,

V = 2394.80(11) A3, and Z = 4. From an acting force diagram of crystal, it can be seen that existences of C..H..O/N and C..H..m accumulation between molecules are beneficial to luminescence of the molecules. Besides, an absolute quantum yield is tested by an integrating sphere of FLS980 and the results show that the Bd-CN obtains a high fluorescence quantum yield of more than 50%. 8. Single crystal fluorescence emission test

Fluorescence spectra: a solid fluorescence spectrum test was performed using an

Edinburgh FL980 transient steady-state fluorescence phosphorescence spectrometer; and an excitation wavelength was set to 370 nm, a slit width was set to enable an ordinate value to be close to one million, and then spectrograms were obtained by a spectrum test.

As shown in FIGs. 14 and 15, the Ben-CN and Bd-CN crystals and pure films {thin films prepared by vacuum-evaporating the Ben-CN and Bd-CN on a quartz plate respectively) prepared in examples 1 and 2 exhibit maximum emission peaks at 600 nm under 370 nm optical excitation. By comparison, it can be found that a crystal emission wave peak is relatively broad, which may be attributed to compared with the amorphous pure film, in a crystal structure, a relatively obvious C..H..n accumulation exists among molecules. The Ben-CN and Bd-CN prepared in examples 1 and 2 in the pure films both obtain a fluorescence emission of more than 600 nm.

Compared with a fluorescence emission of 574 nm of comparative example 1, the molecules prepared by the present disclosure show superiority in red emission.

Besides, the Ben-CN and Bd-CN prepared in examples 1 and 2 in the pure films both obtain a fluorescence quantum yield close to 40%, while the thin film of comparative example 1 has a fluorescence quantum yield of 30.2%, indicating that the Ben-CN and

Bd-CN in the thin film state have a better luminescent property compared to the molecule of comparative example 1.

As shown in FIG. 16, with a temperature increased by a temperature gradient of 20°C under a nitrogen atmosphere, it is found that thermal decomposition temperatures of the Ben-CN and Bd-CN obtained in examples 1 and 2 both exceed 400°C and the thermal decomposition temperature of the molecule of comparative example 1 is 369.1°C, which indicates that the molecules in examples 1 and 2 have a more excellent thermal stability.

As shown in FIGs, 17 and 18, the Ben-CN and Bd-CN prepared in examples 1 and 2 are subjected to a room-temperature fluorescence and low-temperature phosphorescence test with the FLS980 instrument under the nitrogen atmosphere.

Energy level differences of a lowest singlet state Si and a lowest triplet state Ti calculated according to the spectra are as low as 0.03 and 0.02 electron volts, respectively, and the energy level difference is 0.05 eV of comparative example 1, which indicates that the two molecules of the present disclosure have a more efficient

TADF performance. lt is apparent that the above examples are merely intended to describe the present disclosure clearly, rather than to limit the implementations of the present disclosure. Different forms of variations or alterations may also be made by those of ordinary skill in the art based on the above descriptions. There are no need and no way to exhaust all the embodiments.

Any modification, equivalent replacement and improvement made within the spirit and principle of the present disclosure shall be included in the protection scope of the claims of the present disclosure.

Claims

CONCLUSIONS

1. Use of a cyano-modified pyridino-imidazole derivative in the preparation of organic photoelectric devices, characterized in that an electron transport layer for OLED and/or organic solar cell devices is prepared using the cyano-modified pyridino-imidazole derivative with a molecular structure shown in formula (1): R4 0 “ ™y - NS 7 DEN i { i : oe / Ny a SN AN N=={ / OND = Oet > R Formula (1) where R1 is a hydrogen or a cyano group, R2 is hydrogen or is a cyano group and R1 and R2 are not hydrogen at the same time.

The use of claim 1, wherein the use comprises the preparation of a body material for OLED doped devices.

The use according to claim 1 or 2, wherein when R1 is a cyano group and R2 is hydrogen, the cyano-modified pyridinoimidazole derivative is crystallized in an orthorhombic system and has a space group of P21/n and cell parameters of a =11.2742( 2) A, b = 8.1358(2) A, c = 26.7059(6) A, and B = 95.651(2)°; or when R1 is hydrogen and R2 is a cyano group, the cyano-modified pyridinoimidazole derivative is crystallized in an orthorhombic system and has a space group of P21/c and cell parameters of a = 18.3098(5) A, b = 7.6172 (2) A, c = 17.5761(4) A, and B = 102.328(2)°.

The use according to claim 1 or 2, wherein a method of preparing the cyano-modified pyridino-imidazole derivative comprises the following step: subjecting the pyridino-imidazole derivative and 10-hydrogen-phenoxazine to a Buchwald-Hartwig cross-coupling reaction to prepare a compound with formula {1}; wherein the pyridinoimidazole derivative is one of 4-{2-{4-bromobenzene}imidazole[1, a])pyridin-3-yl}benzonitrile, 4-(2-{(4-bromobenzene}imidazo]1, a]) pyridin-3-yl}pyridinitrile and 4-(2-(4-bromobenzene}imidazo{[1, a])pyridin-3-yl}benzyl-pyridinenitrile.

The use according to claim 4, wherein the pyridinoimidazole derivative and the 10-hydrogen-phenoxazine have a molar ratio of 1:(1-2).

The use according to claim 4, wherein the Buchwald-Hartwig cross-coupling reaction is carried out at 120 - 130°C for 12 - 15 hours.

The use according to claim 4, wherein the Buchwald-Hartwig cross-coupling reaction is carried out at a pH value of 10 - 14.

The use according to claim 4, wherein a catalyst used in the Buchwald-Hartwig cross-coupling reaction is a palladium catalyst.

The use according to claim 4, wherein the Buchwald-Hartwig cross-coupling reaction is carried out in an inert atmosphere.

The use according to claim 4, wherein the preparation method further comprises dissolving the cyano-modified pyridino-imidazole derivative in an organic solvent to obtain a saturated solution, and then adding n-hexane to form a cyano-modified pyridino-imidazole derivative crystal sample to precipitate at 20 - 30 °C.