CN1317334C - A kind of intramolecular charge transfer fluorescent dye and its application - Google Patents

Abstract

An intramolecular charge-transfer fluorescent dye and its preparation method, using triphenylamine, carbazole and phenothiazine as electron donors, and nitrile groups with strong electrophilic ability as electron acceptors A series of P-type luminescent materials are prepared through the C=N conjugated π-bond connection formed by a simple condensation reaction. The fluorescent dye prepared by the invention is doped into the conjugated polymer as a red luminescent dye, and the experimental results show that this kind of material is a kind of red electroluminescent material with pure emission.

Description

A kind of intramolecular charge transfer fluorescent dye and its application

technical field

The invention relates to an intramolecular charge transfer fluorescent dye.

The present invention also relates to a preparation method of the above-mentioned fluorescent dye.

The present invention also relates to the application of the above-mentioned fluorescent dyes.

Background technique

Organic electroluminescent devices are a new type of display technology that is gradually becoming mature in the field of optoelectronic devices and has great practical prospects. Since Kodak Corporation (Tang, C.W.; Vanslyke, S.A. Appl. Phys. Lett. 1987, 51, 913.) introduced high-efficiency organic electroluminescent devices in 1987, with its adjustable luminous color, high brightness, high efficiency, Excellent characteristics such as wide viewing angle, low power consumption, simple preparation process, and the ability to prepare curved and flexible screens, as well as potential applications in the field of large-area flat-panel full-color displays, have attracted widespread attention from the scientific community and the active participation of internationally renowned companies and institutions. It is generally considered to be the most competitive technology in the new generation of display technology. At present, although organic electroluminescent displays have been sold commercially, the progress of commercialization is much lower than people's expectations. One of the key reasons is the lack of materials with excellent performance. Based on the full-color display scheme based on the three primary colors of red, green, and blue, high-performance greens are available in a wide variety and are already available for practical use. Blue luminescent materials are developing rapidly, while red luminescent materials are relatively lacking. Therefore, it is particularly important to develop red luminescent materials with excellent performance.

The intramolecular charge-transfer fluorescent dye is a conjugated structure formed by connecting an electron donor and an electron acceptor through a conjugation bridge. Charge transfer occurs between the electron donor and the acceptor, causing the dye to emit long-wavelength light. There are many kinds of electron donors and acceptors, and through proper chemical modification, the intrinsic properties of materials (such as luminous color) can be changed, so this kind of materials are widely designed and synthesized and applied in the field of optoelectronic devices, such as biological Fluorescent probes, nonlinear optics, solar cells, etc., especially occupy a more important position in the field of red electroluminescence. Kodak's Tang, C.W. et al. doped the intramolecular charge transfer red luminescent dye DCM into octahydroxyquinoline aluminum, and obtained the first organic red electroluminescent device (Tang, C.W.; VanSlyke, S.A.; Chen, C.H.J. Appl. Phys. 1989, 65, 3610.). Therefore, charge-transfer red light-emitting materials based on the DCM configuration have been continuously developed. At present, most of this type of dyes have a D-π-A asymmetric molecular structure containing only one charge donor and one charge acceptor (1: Chen, C.H.; Shi, J.; Tang, C.W.; et al. Thin Sold Films, 2000, 363, 327.2: Wang, P.F.; Xie, Z.Y.; Lee, S.T.Chem.Mater.2003, 15, 1913.), due to its strong charge transfer effect, the fluorescence quenching phenomenon is very serious; in order to overcome this The problem is that the preparation of the device adopts doping method, and aluminum octahydroxyquinoline is mostly used as the doping host material, but the incomplete energy transfer causes the device to show impure red light emission (590-615nm), and the emission band The half peak width is relatively wide (greater than 100nm), which makes it difficult to meet the strict requirements on chromaticity of organic electroluminescent devices. Adding co-doping substances for two energy transfers (Hamada, Y.; Kanno, H.; Tsujioka, T.; Takahashi, H.; Usuki, T.Appl.Phys.Lett.1999, 75, 1682.), Although the luminescence of the device is improved to a certain extent, it complicates the preparation process of the device and lacks operability.

Molecules with D-π-A-π-D symmetric configuration contain two charge donors and have two charge transfer channels with unique properties. However, they first appeared as by-products in the synthesis of DCM dyes, and previous views believed that symmetrical molecules had low autofluorescence efficiency, or even no fluorescence, and could not be used as luminescent materials (Chen, C.H.; Tang, C.W.; Shi, J.MacromoleculesSymp, 1998, 125, 49.), therefore, all efforts are made to avoid the generation of this type of compound in the design and synthesis of materials. However, the research of Shim et al. has obtained unexpected results (Jung, B.J.; Yoon, C.B.; Shim, H.K. Adv. Func. Mater. 2001, 11, 430.), with D-π-A-π-D symmetry The type compound DADB is a light-emitting layer, which produces bright red light, and it can be seen that molecules with symmetrical configurations can still be candidates for red light materials.

At present, materials that emit saturated red light are still lacking, and there are few literature and patent reports on charge-transfer fluorescent dyes with D-π-A-π-D configuration and their applications in organic electroluminescent diodes.

Contents of the invention

The object of the present invention is to provide an intramolecular charge transfer fluorescent dye.

Another object of the present invention is to provide a method for preparing the above-mentioned fluorescent dye,

The charge-transfer fluorescent dye with symmetrical molecular configuration provided by the present invention has a structural formula as shown in Formula 1:

(Formula 1)

In the formula, R is an aromatic heterocyclic electron donor: carbazole, phenothiazine or triphenylamine and their substituted derivatives.

When the electron donor is a structure of carbazoles as shown in formula 2;

(Formula 2)

In the formula, R' is an alkyl group, an aryl group or a substituted aryl group.

When the electron donor is a phenothiazine structure as shown in formula 3;

(Formula 3)

In the formula, R' is an alkyl group, an aryl group or a substituted aryl group.

When the electron donor is the structure of triphenylamines as shown in formula 4;

(Formula 4)

In the formula, R" is hydrogen or an alkyl group with 1 to 3 carbons

The method for preparing the above-mentioned fluorescent dye provided by the present invention uses three excellent hole transport groups of triphenylamine, carbazole and phenothiazine as electron donors, and a nitrile group with strong electrophilic ability as electron acceptors , A series of P-type luminescent materials were prepared through the C=N conjugated π bond connection formed by a simple condensation reaction.

The fluorescent dye prepared by the invention is doped into the conjugated polymer as a red luminescent dye, and the experimental results show that this kind of material is a kind of red electroluminescent material with pure emission.

The present invention prepares the method for fluorescent dye, main steps are:

(1) prepare the mixed solution a of phosphorus oxychloride and N, N-dimethyl-formamide by volume ratio 1: 1;

(2) the mixed solution b of N,N-dimethyl-formamide for preparation of electron donor, the concentration of electron donor is 1-3mol/L; Described electron donor is 9-alkylcarbazole, 9- Arylcarbazole, 9-substituted arylcarbazole, 10-alkylphenothiazine, 10-arylphenothiazine, 10-substituted arylphenothiazine or triphenylamine and their substitutes;

(3) Add 4-7 milliliters of solution a to every milliliter of solution b, and heat to reflux for 10-20 hours;

(4) Add the product of step 3 to a 33% aqueous sodium carbonate solution and stir for 0.5-2 hours, the volume ratio of the product of step 3 to the aqueous sodium carbonate solution is 1: 2-5;

(5) The product of step 4 is extracted with dichloromethane, separated and dried, and evaporated to remove the organic solvent to obtain an aldylated electron donor;

(6) The electron donor and diaminosuccinonitrile obtained in step 5 are dissolved in glacial acetic acid according to the ratio of 0.5-2mmol/ml, and the mol ratio of diaminosuccinonitrile and the electron donor of formylation is 1 : 1.5-3;

(7) Add acetic anhydride to the glacial acetic acid solution in step 6 as a catalyst, and the volume ratio of the catalyst to the glacial acetic acid solution is 0.15-0.4:5; under a nitrogen atmosphere, heat and reflux at 100-140° C. for 3-7 hours; cool, and place the reactant in cold water , extracted with dichloromethane, separated and dried, and evaporated to remove the organic solvent to obtain the target product.

The main advantages of the present invention are:

1. The selected raw materials and reagents are all commonly used reagents, and the synthesis of intermediates is simple; the double condensation reaction is easy to carry out without expensive catalysts; the by-products are easy to separate; the yield of the target product is high and the purity is good.

2. All three materials have good solubility and are completely soluble in common organic solvents such as toluene, chloroform, and tetrahydrofuran.

3. The highest occupied orbital (HOMO) energy level of the material is higher, which is beneficial to the injection and transport of holes.

4. The luminescent color of the material is controllable, the charge donor of the material is adjusted, the emission of the material is regulated, and a pure narrow-band red light emission is obtained.

The fluorescent dye prepared by the invention has a certain hole transport ability, and can be used as a red light-emitting material in organic electroluminescent devices.

Description of drawings

Figure 1a is the UV absorption of a series of dyes Dye1-3;

Figure 1b is the fluorescence spectrum of a series of dyes Dye1-3;

Fig. 2 is the cyclic voltammetry curve of dye Dye2;

Fig. 3 is the film ultraviolet absorption and fluorescence spectrum of dye Dye2 and host material;

Figure 4a is the fluorescence spectrum of the film under different doping ratios of dye Dye2 and host material;

Figure 4b is the electroluminescence spectrum of the light-emitting diode under different doping ratios of the dye Dye2 and the host material;

Fig. 5 is the current-voltage curve of the light emitting diode under different doping ratios of the dye Dye2 and the host material.

Detailed ways

The synthetic route is shown in Figure 1.

1. The specific embodiment of reaction process a (with synthetic 9-(2'-ethyl)-hexylcarbazole, compound 1 is example):

In a 100ml three-necked flask, under nitrogen protection, sodium hydroxide (0.18ml) was added to dimethyl sulfoxide (DMSO) solution (60ml), and after vigorous stirring for half an hour, carbazole (0.03mol) was added to In the above system; after stirring for 1 hour, 2-ethyl-hexyl bromide (0.03 mol) was slowly added dropwise; stirring at room temperature for 12 hours, the reaction was completed. The reaction solution was concentrated to remove part of DMSO, poured into water, and extracted several times with dichloromethane. The organic phases were combined and dried over anhydrous magnesium sulfate. The organic solvent was removed by vacuum rotary evaporation, and the crude product was purified by silica gel chromatography (eluent-petroleum ether), and the product was light yellow oil 9-(2'-ethyl)-hexylcarbazole (yield 73%) .

Using the same synthesis process, the 2-ethyl-hexyl bromide in the reaction can be replaced by other alkyl bromides, aryl bromides, and substituted aryl bromides to obtain the corresponding 9-alkylcarbazole and 9-arylcarbazole , 9-substituted aryl carbazole; then replace carbazole with phenothiazine to obtain the corresponding 9-alkyl phenothiazine, 9-aryl phenothiazine, 9-substituted aryl phenothiazine.

2. The specific implementation of reaction process b (taking synthetic aldehyde group triphenylamine, compound 3 is example):

In a 100ml three-necked flask, the N,N-dimethyl-formamide (DMF solution) of phosphorus oxychloride (0.12ml) was slowly added dropwise to the DMF solution of triphenylamine (0.04mol), after the addition was complete, heat Reflux for 15 hours; after the reaction is completed, the mixed solution becomes black and viscous, poured into 33% (w/w) sodium carbonate aqueous solution, and stirred for 1 hour; extracted with dichloromethane, combined organic phases, and dried over anhydrous magnesium sulfate; The organic solvent was removed by vacuum rotary evaporation, and the crude product was purified by silica gel column chromatography (eluent-dichloromethane/petroleum ether 1:2v/v), and the product was light yellow solid aldehyde triphenylamine (69% yield).

Using the same synthesis process, the corresponding 3-formyl-9-alkylcarbazole, 3-formyl-9- Arylcarbazole, 3-formyl-9-substituted arylcarbazole, 3-formyl-9-alkylphenothiazine, 3-formyl-9-arylphenothiazine, 3-formyl-9 - a substituted arylphenothiazine, or a substituted triphenylamino aldehyde.

3. The specific implementation of reaction process c:

Embodiment (1): N, N'-two-[9-(2'-ethyl-hexyl)-carbazole-vinyl]-succinonitrile (Dye 1)

In a 100ml three-necked flask, 3-formyl-9-(2'-ethyl-hexyl)-carbazole (42mmol) and diaminosuccinonitrile (20mmol) were placed in about 40ml of glacial acetic acid, and a few Drop acetic anhydride as a catalyst, heat and reflux at 120°C for 5 hours under a nitrogen atmosphere; after the reaction stops, cool to room temperature, pour the mixture into 150ml of water, leave it for 4 hours, and extract the aqueous phase with dichloromethane (60ml×2) ; The organic phases were combined, washed with water, and dried over anhydrous magnesium sulfate. The organic solvent was removed by vacuum rotary evaporation, and the crude product was purified by silica gel column chromatography (eluent-dichloromethane/petroleum ether 1:1 v/v) to obtain a dark red solid with metallic luster (yield 72%).

Mass Spectrum (MALDI-TOF-MS): m/z calculated 686.4, measured 687.6 (M ⁺ );

Proton nuclear magnetic spectrum ( ¹ H-NMR) (300MHz, CDCl ₃ , ppm): δ=0.87-0.99 (m, 12H), 1.31-1.44 (broad, 16H), 2.11-2.14 (broad, 2H), 4.17-4.25 (d, 4H), 7.37-7.40(t, 2H), 7.42-7.58(m, 6H), 8.19-8.24(d, 4H), 8.68(s, 2H), 8.95(s, 2H);

Elemental analysis calculated for _C46H50N6 (%): C 80.43, H 7.34 _, N 12.23; _found C 80.04, H 7.37, N 12.04.

Embodiment (2): N, N'-two-(triphenylamine)-vinyl-succinonitrile (Dye 2)

In a 100ml three-necked flask, put aldehyde triphenylamine (42mmol) and diaminosuccinonitrile (20mmol) in about 40ml of glacial acetic acid, add a few drops of acetic anhydride as a catalyst, and heat to reflux at 120°C under a nitrogen atmosphere 5 hours; after the reaction stopped, cooled to room temperature, the mixture was poured into 150ml of water, and after standing for 4 hours, the aqueous phase was extracted with dichloromethane (60ml×2); the organic phases were combined, washed with water, and dried over anhydrous magnesium sulfate. The organic solvent was removed by vacuum rotary evaporation, and the crude product was purified by silica gel column chromatography (eluent-dichloromethane/petroleum ether 1:1 v/v) to obtain a dark red solid with metallic luster (yield 72%).

Mass Spectrum (MALDI-TOF-MS): m/z calculated 618.3; measured 618.4.

Proton nuclear magnetic spectrum ( ¹ H-NMR) (300MHz, CDCl ₃ , ppm): δ=7.03(d, 4H), 7.19-7.22(t, 12H), 7.32-7.36(t, 8H), 7.78-7.80(d , 4H), 8.61(s, 2H);

Elemental analysis Calcd: _C42H30N6 ( _% ): C _81.53 , H 4.89, N 13.58; Measured: C 81.54, H 4.93, N 13.60.

Embodiment (3): N, N'-di-[9-(2'-ethyl-hexyl)-phenothiazine-vinyl]-succinonitrile (Dye3)

In a 100ml three-necked flask, put 3-formyl-9-(2'-ethyl-hexyl)-phenothiazine (42mmol) and diaminosuccinonitrile (20mmol) in about 40ml of glacial acetic acid, add A few drops of acetic anhydride were used as a catalyst, and heated to reflux at 120°C for 5 hours under nitrogen atmosphere; after the reaction stopped, cooled to room temperature, the mixture was poured into 150ml of water, and after standing for 4 hours, the aqueous phase was extracted with dichloromethane (60ml×2 ); the organic phases were combined, washed with water, and dried over anhydrous magnesium sulfate. The organic solvent was removed by vacuum rotary evaporation, and the crude product was purified by silica gel column chromatography (eluent-dichloromethane/petroleum ether 1:1 v/v) to obtain a dark red solid with metallic luster (yield 72%).

Mass Spectrum (MALDI-TOF-MS) m/z: Calculated 750.4; Measured 750.3;

Proton nuclear magnetic spectrum ( ¹ H-NMR) (300MHz, CDCl ₃ , ppm): δ=0.86-0.93(t, 12H), 1.25-1.29(t, 8H), 1.40-1.47(m, 8H), 1.96-1.98 (t, 2H), 3.84(s, 4H), 6.92-7.01(m, 6H), 7.18-7.22(d, 4H), 7.82(d, 4H), 8.64(s, 2H);

Elemental analysis calculated for _C46H50N6S2 ( _% ) _: C 73.56, H 6.71, N 11.19 _; calculated for C 72.94, H 6.66, N 11.10.

4. Photophysical Properties

The ultraviolet absorption and fluorescence spectra of dye Dye1-3 in chloroform solution are shown in Figure 2. With the increase of the power supply capacity of the charge donor in the molecular structure, the absorption and emission spectra of the dyes are red-shifted: the absorption peaks of the dyes are located at 506nm, 550nm and 556nm respectively; the emission peaks are located at 552nm, 628nm and 685nm respectively. Taking Rodin B as a reference (Parker, C.A.; Rees, W.T. Analyst, 1960, 85, 578.), the fluorescence quantum efficiency of the dye was measured, and the fluorescence quantum efficiency of the dye Dye2 was 39%.

5. Electrochemical properties

The electrochemical properties of the dye were tested by cyclic voltammetry, and the test was carried out on a computer-controlled EG&G Potentiostat/Galvanostat model 283 electrochemical analyzer. The traditional three-electrode test system is adopted, the platinum electrode is used as the working electrode, Ag/AgCl is used as the reference electrode, and the platinum wire is used as the counter electrode; the sample is dissolved in freshly distilled dichloromethane (1×10 ^-3 M), Bu ₄ NPF ₆ (0.1M) as a supporting electrolyte. Figure 3 is the volt-ampere characteristic curve of dye Dye2, in which there is a pair of reversible redox peaks in the positive direction, and an irreversible oxidation peak in the negative direction, indicating that this material is P-type. According to the literature method (Pommerehne, J.; Vestweber, H.; Guss, W.; et al., Adv. Mater. 1995, 7, 551.), the energy level of the dye was calculated based on ferrocene. The HOMO energy levels of the three dyes are -5.546eV, -5.351eV and -5.169eV, respectively, which can be compared with the HOMO energy levels of the classic hole transport material TPD, so they will be beneficial to the injection and transport of holes.

6. Luminous properties

Figure 4 shows the UV absorption and fluorescence spectra of the dye Dye2 and the polymer host material in the thin film state. There is sufficient overlap between the emission spectrum of the polymer host and the absorption bands of the dye, indicating efficient energy transfer. Figure 5a is the photoluminescence spectrum of the film under different doping ratios of dye Dye2 and the host material. It can be seen that with the increase of the doping ratio, the energy transfer effect gradually increases, and the emission of the polymer host decreases rapidly until it disappears completely. , indicating that efficient energy transfer occurs. We used conductive glass ITO as the anode, air-stable aluminum as the cathode, octahydroxyquinoline aluminum as the electron transport layer, dye Dye2 and polymer doping system as the light-emitting layer, and prepared a series of light-emitting devices with simple structures. With the increase of doping concentration, the luminescence of the device gradually approached pure red luminescence (as shown in Figure 5b). When the doping ratio is 5%, the pure luminescence of the device is at 619nm, and the half-maximum width is only 75nm. Fig. 6 shows the current-voltage curves of the device under different doping ratios, and the maximum external quantum efficiency of the device is 0.38%. It should be noted that this efficiency is the result of an unoptimized device. The fluorescent dye with symmetrical charge transfer configuration in the present invention will be a kind of pure red luminescent material.

Claims (8)

1. electric charge in molecule transfer type fluorescence dye, its structure be as shown in Equation 1:

Formula 1

R is the aromatic heterocyclic electron donor(ED) in the formula: carbazole, thiodiphenylamine or triphenylamine and substitutive derivative thereof.

2. fluorescence dye as claimed in claim 1 is characterized in that, the structure that described aromatic heterocyclic electron donor(ED) is a carbazoles as shown in Equation 2:

Formula 2

R ' is alkyl, aryl or substituted aryl in the formula.

3. fluorescence dye as claimed in claim 1 is characterized in that, the structure that described aromatic heterocyclic electron donor(ED) is a phenothiazines as shown in Equation 3:

Formula 3

R ' is alkyl, aryl or substituted aryl in the formula.

4. fluorescence dye as claimed in claim 1 is characterized in that, the structure that described aromatic heterocyclic electron donor(ED) is the triphen amine as shown in Equation 4:

Formula 4

R in the formula " be that hydrogen or carbon number are the alkyl of 1-3.

5. method for preparing each described fluorescence dye of claim 1-4, key step is:

(1) prepared phosphorus oxychloride and N, the mixing solutions a of N-dimethyl-methane amide in 1: 1 by volume;

(2) N of preparation electron donor(ED), the mixing solutions b of N-dimethyl-methane amide, the concentration of electron donor(ED) is 1-3mol/L; Described electron donor(ED) is 9-alkyl carbazole, 9-aryl carbazole, 9-substituted aryl carbazole, 10-alkyl thiodiphenylamine, 10-aryl thiodiphenylamine, 10-substituted aryl thiodiphenylamine, triphenylamine or its substituent;

(3) add 4-7 ml soln a, reflux 10-20 hour among every ml soln b;

(4) step 3 product is added in 33% the aqueous sodium carbonate and stirred 0.5-2 hour, the volume ratio of step 3 product and aqueous sodium carbonate is 1: 2-5;

(5) step 4 product dichloromethane extraction separates and drying, and organic solvent is removed in evaporation, gets the electron donor(ED) of aldehyde radicalization;

(6) the aldehyde radical electron donor(ED) and the diamino succinonitrile that obtain of step 5 is dissolved in the glacial acetic acid in the 0.5-2mmol/ml ratio, and the mol ratio of diamino succinonitrile and aldehyde radical electron donor(ED) is 1: 1.5-3;

(7) adding diacetyl oxide in the glacial acetic acid solution of step 6 is catalyzer, catalyzer and glacial acetic acid solution volume ratio 0.15-0.4: 5; Under the nitrogen atmosphere, 100-140 ℃ reflux 3-7 hour; Cool off, reactant places cold water, and dichloromethane extraction separates and drying, and organic solvent is removed in evaporation, gets target product.

6. method as claimed in claim 4 is characterized in that the product that step 5 obtains is purified through silica gel column chromatography.

7. method as claimed in claim 4 is characterized in that the product that step 7 obtains is purified through silica gel column chromatography.

8. as the application of the described fluorescence dye of above-mentioned each claim in organic electroluminescence device.

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