CN105017329B - Tridentate anionic ligand-based europium complex luminescent material - Google Patents

Abstract

The invention discloses a rare earth europium complex luminescent material based on a tridentate anion ligand, a preparation method and an application thereof. The general structural formula of the europium complex is Eu(t-ND) ₃ , wherein t-ND is a 4-hydroxyl-1,5-naphthyridine tridentate anion ligand substituted by a phosphineoxy group, a sulfoxide group or a sulfone group . This type of europium complex has a more rigid structure, a high coordination stability constant, is not prone to ligand dissociation, and has a high thermal decomposition temperature; the phosphine atom and sulfur atom in it are sp3 hybridized without strong conjugation effect, It ensures that the ligand has a suitable energy level, and the complex also has high luminous efficiency; in addition, this type of europium complex also has good UV resistance and high mobility of electrons and holes, and can be used as a down-converter Photoluminescent materials and organic electroluminescent materials.

Description

A Class of Europium Complex Luminescent Materials Based on Tridentate Anionic Ligands

technical field

The invention relates to a rare earth europium complex luminescent material, a preparation method thereof, and an application in the fields of photoluminescence and electroluminescence.

Background technique

Rare earth complex luminescent materials have unique advantages such as high luminous efficiency, long life, and good color purity, and have important application prospects in the fields of lighting, display, light conversion film, and biomedicine. As a photoluminescent material, because the organic ligand has a large molar absorption coefficient, compared with pure inorganic materials (such as Y ₂ O ₃ : Eu ³⁺ ), the light absorption ability of rare earth complexes can be increased hundreds of times, The amount of rare earths can also be greatly reduced. Moreover, rare earth complexes have better compatibility with polymers, and are more suitable for use in functional light conversion films than inorganic materials, such as agricultural light conversion films and solar cell light conversion films. In addition, the application of rare earth complexes in electroluminescence (Organic Light-emitting Diode, OLED) is also a key research direction, and rare earth luminescence also has the opportunity to show its skills in the field of bright, ultra-thin, flexible OLED displays.

In rare earth complexes, organic ligands play a decisive role in the luminescent properties of the complexes. The chelation of organic ligands with rare earth ions can not only absorb and transmit energy as antenna molecules, but also protect the rare earth luminescence from being quenched by the external environment. The most commonly used ligands in traditional rare earth europium complexes are β-diketone compounds. This type of material has been extensively studied since the 1960s, and many materials with high luminous efficiency have also been developed so far. However, the application of rare earth complexes in lighting, display and light conversion film has not been widely promoted, and the main reason is that the light stability of the material is too poor. Usually rare earth complexes are excited by absorbing the energy of ultraviolet light, but β-diketone compounds themselves are easily destroyed by high-energy ultraviolet light, resulting in rapid decay of the luminescent properties of the material (Synth.Met.2011, 161, 964).

In a recent study, the inventors discovered and designed a class of 4-hydroxyl-1,5-naphthyridine (abbreviated as ND) ligands, and coordinated with europium ions to obtain a highly efficient rare earth luminescent material (CN 201110139842.1). This kind of ligand has rigid molecular structure and suitable sensitization energy level, and the obtained complex not only has high photoluminescence quantum efficiency (PLQY), but also exhibits excellent photostability. However, in practical applications, we found that such rare earth complexes still have defects in thermal stability. This type of ND ligand is mainly bidentate anion ligand, so when we synthesize the complex, in addition to using three ND ligands, we will also use some neutral ligands to make the rare earth ion reach coordination saturation and prevent solvent Coordination of molecules or water molecules results in quenching of the luminescence. However, due to the weak binding force between the neutral ligand and the rare earth ion, it is easy to dissociate under extreme conditions such as dilute solution or heating, resulting in the destruction of the complex and the attenuation of the luminescent properties. For example, in the process of preparing OLED devices by vacuum evaporation and thermal plating, the dissociation of neutral ligands will greatly reduce the device efficiency. Therefore, the luminescent materials of such rare earth complexes still need to make necessary improvements to make them have better technical effects and wider application prospects.

Contents of the invention

The purpose of the present invention is to solve the technical problems of easy dissociation and poor stability of neutral ligands of existing rare earth complexes, and obtain a rare earth luminescent material with high luminous efficiency, thermal stability and light stability.

As mentioned in the previous technical background, the synthesis of bidentate ND rare earth complexes usually requires the use of neutral ligands to improve their luminous efficiency, but this brings technical defects such as easy dissociation of neutral ligands and poor thermal stability of the complexes. . The solution idea of the present invention is to design and synthesize novel tridentate ND class anion ligands, by increasing the chelating sites of the ligands, after forming complexes with rare earth ions at a ratio of 3:1, the requirements of coordination saturation can be met ( The coordination number is 9), which avoids the problem of thermal stability caused by the introduction of neutral ligands, thereby obtaining a thermally stable, photostable and high-efficiency rare earth complex luminescent material.

Generally speaking, when people design groups that chelate with rare earth ions, azaaryl groups, amides, carboxyl groups, etc. are usually used. However, for ND ligands, it is not suitable to obtain tridentate ligands by adding the above groups, because these groups will be conjugated with the naphthyridine ring, which will greatly reduce the energy of the ligand, which may reduce the sensitivity. chemical efficiency and luminous efficiency. In order not to affect the energy level of the ligand, the present invention designs novel chelating groups, which are respectively phosphine-oxyl, sulfoxide- and sulfone-groups. Both the phosphorus atom and the sulfur atom in these groups adopt sp3 hybridization, so the conjugation effect with the naphthyridine ring is greatly weakened, and the influence on the energy level of the ligand will not be too great.

Specifically, the technical scheme of the present invention is as follows:

A rare earth complex based on a tridentate 4-hydroxyl-1,5-naphthyridine ligand, the general structural formula is Eu(t-ND) ₃ , wherein t-ND is phosphine-oxy-substituted as shown in formula I 4-hydroxyl-1,5-naphthyridine anionic ligand, 4-hydroxyl-1,5-naphthyridine anionic ligand substituted by sulfoxide group shown in formula II, or sulfone group substituted substituted by formula III 4-Hydroxy-1,5-naphthyridine anionic ligand.

The structure of the europium complex is shown in formula IV, formula V and formula VI:

In formulas I-VI, R ₁ , R ₂ , R ₃ , and R ₄ are each independently a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a halogen-substituted alkyl group, or a phenyl group. Wherein, the halogen atom refers to F, Cl, Br, I; the alkyl is preferably a C1-C8 straight or branched chain alkyl, more preferably a C1-C4 straight or branched chain alkyl, including methyl, Ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, particularly preferably methyl, ethyl and tert-butyl; said halogen-substituted alkyl is preferably halogen-substituted C1-C8 straight-chain or branched-chain alkyl, more preferably halogen-substituted C1-C4 straight-chain or branched-chain alkyl, especially preferably trifluoromethyl, pentafluoroethyl.

In formula I-VI, R ₅ is an alkyl group or an aryl group. Among them, the alkyl group is preferably a C1-C18 linear or branched chain alkyl group, particularly preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-octyl, n-dodecyl Alkyl, n-hexadecyl, n-octadecyl; the aryl is phenyl, naphthyl or substituted phenyl; the substituted phenyl is halogen atom, methyl, ethyl, isopropyl Base, tert-butyl, methoxy, ethoxy, trifluoromethyl, phenyl substituted by dimethylamino, the number and position of substituents can be determined according to the actual situation, preferably 2-fluorophenyl, 2-chlorophenyl, 2-bromophenyl, 3-fluorophenyl, 3-chlorophenyl, 3-bromophenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 2, 3-dichlorophenyl, 2,4-dichlorophenyl, 2,5-dichlorophenyl, 2,6-dichlorophenyl, 3,4-dichlorophenyl, 3,5-dichlorophenyl Base, 2-methylphenyl, 2-ethylphenyl, 2-isopropylphenyl, 2-tert-butylphenyl, 4-methylphenyl, 4-ethylphenyl, 4-isopropyl phenyl, 4-tert-butylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,5-dimethylbenzene Base, 2-methyl-5-tert-butylphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2-dimethylaminophenyl, 4-two Methylaminophenyl, particularly preferably 2-chlorophenyl, 2-methylphenyl, 4-methylphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl .

The novel tridentate anion ligands described in the present invention and the europium complexes based on such tridentate anion ligands are all within the scope of protection of this patent.

The form of the tridentate anion ligand described in the present invention can be neutral, salts formed by reacting with acids or bases, complexes containing crystal water or solvents, salts obtained by reacting with acids or bases containing solvents or A compound of crystal water.

The tridentate anion ligand described in the present invention has keto and enol tautomerism, and all tautomers in different forms are within the scope of protection of this patent. The tautomeric forms are as follows:

The form of the europium complex described in the present invention may be a pure product or a complex containing water of crystallization or a solvent.

The preparation method of the tridentate anion ligand in the present invention is to react the ND ligand substituted by the 6-position halogen shown in the formula VII with the organic phosphine chloride shown in the formula VIII or the thiol shown in the formula VIV. The first step is nucleophilic substitution for coupling, and the second step is oxidation.

The definitions of the R ₁ -R ₄ groups in formula VII are the same as described above, and X represents the halogen atoms F, Cl, Br, I; the definitions of the R ₅ groups in the formulas VIII and VIV are the same as described above.

Specifically, the synthesis steps of the phosphinooxy-substituted ND anionic ligand shown in formula I are as follows, which is defined as route a (Scheme a):

The sulfoxide and sulfone group-substituted ND anionic ligands represented by formula II and formula III and the synthesis steps are as follows, which are defined as route b (Scheme b):

In route a and route b, first, the 6-position halogen-substituted ND ligand reacts with the base to take the proton, and the organic phosphine chloride or thiol reacts with the alkali metal to obtain the corresponding salt, and then performs the coupling reaction; MOH means Hydroxide formed by alkali metal, such as lithium hydroxide, sodium hydroxide, potassium hydroxide; M means metal lithium, sodium, potassium.

In route a and route b, the solvent used in the coupling reaction includes diethyl ether, tetrahydrofuran, toluene, xylene, ethylene glycol dimethyl ether, etc.; the reaction temperature is from room temperature to the reflux temperature of the solvent; the reaction time is 1 to 24 hours.

In route a and route b, [O] in the oxidation reaction represents an oxidant, including oxygen, ozone, chlorine, chlorine water, sodium hypochlorite, peroxyacids (such as peroxybenzoic acid, m-chloroperoxybenzoic acid, peracetic acid ), hydrogen peroxide, etc.

In the preparation method of the europium complex in the present invention, the ND ligand of formula I (or II, III), alkali and europium salt are reacted in a solvent to prepare the europium complex shown in formula IV (or V, VI) . The base is preferably hydroxide, carbonate or amines, pyridine organic bases, more preferably sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonia water, triethylamine, tetramethylammonium hydroxide. The europium salt is preferably europium hydrochloride, nitrate, acetate, trifluorosulfonate and the like. In the method, the ND ligand of formula I (or II, III), the base and the europium salt are reacted in a molar ratio of 3:3:1, or close to the molar ratio. In the method, the temperature of the reaction is -10 to 120° C., and the reaction time is 10 minutes to 24 hours. The solvent is selected from water, ethanol, methanol, isopropanol, acetone, tetrahydrofuran, acetonitrile, toluene, methylene chloride, chloroform, ether, N, N-dimethylformamide, etc., can be any one of them species or a mixture of two or more.

The application of the europium complex in the present invention as a luminescent material includes two aspects of photoluminescence and electroluminescence.

In terms of photoluminescence, such europium complexes can be used to construct down-converting luminescent materials with practical applications. Its application methods include: (1) use in solid form, such as solid powder, or use solution spraying to remove solvent to form thin film, etc.; (2) doping in a certain matrix, such as in solution, ink, ionic liquid, high Molecular plastics, colloids, or other solid materials. This kind of luminescent material can obtain bright red light under the excitation of ultraviolet light or blue-violet light, or can obtain mixed-color luminescence after being mixed with other fluorescent agents.

In the field of electroluminescence, such europium complexes (in the form of pure compounds or doped in other host materials) are formed into ultra-thin films by vacuum evaporation, spin coating or inkjet printing, as organic electroluminescent devices. luminescent layer material. The electroluminescent device based on this kind of europium complex can emit characteristic red light under current driving, or it can be used together with other color luminescent materials to obtain luminescence of various colors or white light.

The europium complex described in the present invention has the following advantages: (1) no need to use other neutral ligands, which solves the unstable factors that neutral ligands are easy to dissociate; (2) tridentate chelation coordination, complexation The constant is large, the coordination ability is strong, and the ligand itself is not easy to dissociate; (3) the coordination saturation of rare earth ions does not have the quenching effect of other solvent molecules, and the luminescence quantum efficiency is high; (4) ND ligands have a rigid structure , the material has strong ultraviolet light resistance and high thermal decomposition temperature; (5) ND ligands have an aromatic heterocyclic structure and high carrier mobility, which has advantages in electroluminescent applications.

Specifically, the ND-type tridentate ligands described in the present invention have suitable sensitization energy levels and rigid structures, and the obtained europium complexes have very high photoluminescence quantum yields, for example, Example 3 obtained The PLQY of its solid powder is as high as 94%, which is among the highest levels compared with the europium complexes reported in the literature. The europium complex of the present invention also has a high coordination stability constant, and the solid powder of this type of europium complex is soaked in a strong acid or strong alkali solution for a long time without causing the disappearance of the luminescent property. In addition, the europium complex described in the present invention also has good thermal stability and photostability, for example, the europium complex Eu5 obtained in Example 5 has a thermal decomposition temperature as high as 440 degrees Celsius, and the 40-watt UVA340 type ultraviolet lamp 20 hours of irradiation did not cause significant photodegradation. Electroluminescent devices based on this type of europium complex (Eu3) also have good performance. Preliminary results show that the maximum brightness can reach 1180cdm ^-2 and the maximum current efficiency is 14cdA ^-1 . In a word, the europium complex of the present invention has very excellent luminescent properties and excellent stability, and has incomparable advantages over traditional or known europium complex luminescent materials. Both have very important application prospects, and are rare and excellent rare earth luminescent materials.

Description of drawings

Fig. 1 is the absorption spectrum of the europium complex Eu3 obtained in Example 3 of the present invention in dichloromethane solution.

Fig. 2 is the excitation and emission spectra of the europium complex Eu3 solid powder obtained in Example 3 of the present invention.

Fig. 3 is the structural formula of related materials used in the electroluminescent device of Example 12 of the present invention.

Fig. 4 is a graph of current density-brightness-voltage of the electroluminescence device of Example 12 of the present invention.

Fig. 5 is the emission spectrum of the electroluminescent device of Example 12 of the present invention at 100 cd·m ^-2 .

detailed description

The product, preparation method and application of the present invention will be further described below through specific examples, but these specific embodiments do not limit the protection scope of the present invention in any way.

The 6-position halogen-substituted ND ligands (1a, 2a, 3a) in the following examples can be synthesized using the method in the invention patent CN201110139842.1, and organic phosphine chlorides, thiols and other reagents used can be purchased from reagent companies . The solvents used are analytically pure, and other reagents are chemically pure.

<Synthesis of ligands and complexes>

Example 1.

The synthetic route involved in the present embodiment is as follows:

1.1 Synthesis of ligand 1f (4-hydroxy-6-diethylphosphoryl-1,5-naphthyridine, 4-hydroxy-6-(diethylphosphoryl)-1,5-naphthyridine)

Reaction of 4-hydroxy-6-chloro-1,5-naphthyridine (1a) with NaOH affords its sodium salt 1b. Heat 30mmol of diethylphosphine chloride (1c) and 60mmol of metal sodium in tetrahydrofuran solution to reflux for 24h to obtain the sodium salt of diethylphosphine (1d). Add 30mmol sodium salt 1b of chlorinated ND to the freshly prepared solution of sodium diethylphosphine (1d), heat to reflux for 24h, and obtain ND (1e) substituted by diethylphosphine through coupling reaction. After the reaction, an equivalent amount of m-chloroperoxybenzoic acid (mCPBA) was added, stirred for 1 h, and then the pH of the solution was adjusted to 7-8 with hydrochloric acid to obtain the oxidized product. The product was purified by vacuum sublimation, then recrystallized with ethanol, and vacuum-dried to obtain 1.13 g of white powder of ligand 1f, with a yield of 15%.

¹ H NMR (400MHz, MeOD) δ8.19-8.07(m, 2H), 8.01(d, J=7.2Hz, 1H), 6.51(d, J=7.2Hz, 1H), 2.10-1.90(m, 4H ), 1.02-0.90 (m, 6H). Mass Spectrometry (m/z, ESI): Calc. 250.1, Found 251.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 57.64 (57.60); H, 6.10 (6.04); N, 11.16 (11.19), the theoretical values in brackets.

1.2 Synthesis of complex Eu1

Heat 3 mmol of ligand 1f and 3 mmol of NaOH in a mixed solution of methanol and water 1:1 (volume ratio) to reflux for 30 minutes. Then, 1 mmol of an aqueous solution of europium trichloride hexahydrate was added dropwise to the above solution or suspension, and refluxed for 2 hours. Filtered, washed with water, washed with a small amount of methanol, and dried in vacuum. After recrystallization from methanol, 0.74 g of the white target europium complex was obtained with a yield of 82%. Mass Spectrometry (m/z, ESI): Calc. 900.1, Found 901.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 47.80 (47.69); H, 4.92 (4.87); N, 9.06 (9.14), the theoretical value of Eu1·0.5CH ₃ OH·0.2H ₂ O in brackets.

Example 2.

The synthetic route involved in the present embodiment is as follows:

2.1 Ligand 2f (3-methyl-4-hydroxy-6-diethylphosphinooxy-1,5-naphthyridine, 3-methyl-4-hydroxy-6-(diethylphosphoryl)-1,5-naphthyridine) Synthesis

The synthesis procedure is the same as in Example 1 (part 1.1), except that 4-hydroxyl-6-chloro-1,5-naphthyridine (1a) is replaced by 3-methyl 4-hydroxyl-6-chloro-1,5-naphthyridine (2a). Ligand 2f white powder 0.95 g was obtained with a yield of 12%.

¹ H NMR (400MHz, MeOD) δ8.15-8.03(m, 2H), 7.99(s, 1H), 2.68(s, 3H), 2.11-1.92(m, 4H), 1.03-0.90(m, 6H) . Mass Spectrometry (m/z, ESI): Calc. 264.1, Found 265.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 59.02 (59.09); H, 6.48 (6.48); N, 10.65 (10.60), the theoretical values in brackets.

2.2 Synthesis of complex Eu2

The synthesis steps are the same as in Example 1 (part 1.2), except that the ligand 1f is replaced with 2f. 0.73 g of the white target europium complex was obtained with a yield of 78%. Mass Spectrometry (m/z, ESI): Calc. 942.1, Found 943.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 49.48 (49.62); H, 5.33 (5.21); N, 8.78 (8.83), the theoretical value of Eu2·0.3CH ₃ OH in brackets.

Example 3.

The synthetic route involved in the present embodiment is as follows:

3.1 Ligand 3f (3-cyano-4-hydroxyl-6-diethylphosphinoxy-1,5-naphthyridine, 3-cyano-4-hydroxy-6-(diethylphosphoryl)-1,5-naphthyridine) Synthesis

The synthesis procedure is the same as in Example 1 (part 1.1), except that 4-hydroxyl-6-chloro-1,5-naphthyridine (1a) is replaced by 3-cyano 4-hydroxyl-6-chloro-1,5-naphthyridine (3a). Ligand 3f white powder 1.56g was obtained with a yield of 19%.

¹ H NMR (400 MHz, MeOD) δ 8.36-8.20 (m, 2H), 8.16 (s, 1H), 2.18-1.96 (m, 4H), 1.03-0.92 (m, 6H). Mass Spectrometry (m/z, ESI): Calc. 275.1, Found 276.1 (M+H) ⁺ . Elemental analysis (% by mass): C, 56.78 (56.73); H, 5.09 (5.13); N, 15.31 (15.27), the theoretical values in brackets.

3.2 Synthesis of complex Eu3

The synthesis steps are the same as in Example 1 (part 1.2), except that the ligand 1f is replaced with 3f. 0.83 g of the white target europium complex was obtained with a yield of 85%. Mass Spectrometry (m/z, ESI): Calc. 975.1, Found 976.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 47.68 (47.89); H, 4.33 (4.17); N, 12.67 (12.72), the theoretical value of Eu3·0.5CH ₃ OH is in brackets.

Example 4.

The synthetic route involved in the present embodiment is as follows:

4.1 Synthesis of ligand 4f (4-hydroxy-6-di-tert-butylphosphoryl-1,5-naphthyridine, 4-hydroxy-6-(di-tert-butylphosphoryl)-1,5-naphthyridine)

The synthesis procedure is the same as in Example 1 (part 1.1), except that diethylphosphine chloride (1c) is replaced by di-tert-butylphosphine chloride (4c). Ligand 4f white powder 1.28g was obtained with a yield of 14%. Mass spectrometry (m/z, ESI): Calc. 306.1, found 307.1 (M+H) ⁺ . Elemental analysis (% by mass): C, 62.74 (62.73); H, 7.51 (7.57); N, 9.14 (9.14), the theoretical values in brackets.

4.2 Synthesis of complex Eu4

The synthesis steps are the same as in Example 1 (part 1.2), except that the ligand 1f is replaced with 4f. 0.82 g of the white target europium complex was obtained with a yield of 77%. Mass spectrometry (m/z, ESI): Calc. 1068.3, found 1069.3 (M+H) ⁺ . Elemental analysis (mass percentage): C, 53.70 (53.53); H, 6.51 (6.27); N, 7.69 (7.80), the theoretical value of Eu4·0.5H ₂ O in brackets.

Example 5.

The synthetic route involved in the present embodiment is as follows:

5.1 Synthesis of ligand 5f (4-hydroxy-6-diphenylphosphinooxy-1,5-naphthyridine, 4-hydroxy-6-(diphenylphosphoryl)-1,5-naphthyridine)

The synthesis procedure is the same as in Example 1 (part 1.1), except that diethylphosphine chloride (1c) is replaced by diphenylphosphine chloride (5c). Ligand 5f white powder 1.98g was obtained with a yield of 19%.

¹ H NMR (400MHz, MeOD) δ8.43(d, J=4.4Hz, 1H), 8.22(dd, J=8.6, 3.0Hz, 1H), 8.05(d, J=7.4Hz, 1H), 7.99( dd, J = 21.8, 13.8 Hz, 4H), 7.61-7.53 (m, 2H), 7.54-7.44 (m, 4H), 6.54 (d, J = 7.2 Hz, 1H). Mass Spectrometry (m/z, ESI): Calc. 346.1, Found 347.1 (M+H) ⁺ . Elemental analysis (% by mass): C, 69.31 (69.36); H, 4.38 (4.37); N, 8.10 (8.09), the theoretical values in brackets.

5.2 Synthesis of complex Eu5

The synthesis steps are the same as in Example 1 (part 1.2), except that the ligand 1f is replaced with 5f. 0.97 g of the white target europium complex was obtained with a yield of 82%. Mass spectrometry (m/z, ESI): Calc. 1188.2, found 1189.2 (M+H) ⁺ . Elemental analysis (mass percentage): C, 60.10 (60.12); H, 3.74 (3.73); N, 6.90 (6.94), the theoretical value of Eu5·0.6CH ₃ OH·0.2H ₂ O in brackets.

Example 6.

The synthetic route involved in the present embodiment is as follows:

6.1 Ligand 6f (3-cyano-4-hydroxy-6-n-octylsulfoxide-1,5-naphthyridine, 3-cyano-4-hydroxy-6-(octylsulfiyl)-1,5-naphthyridine) Synthesis

Reaction of 3-cyano-4-hydroxy-6-chloro-1,5-naphthyridine (3a) with NaOH affords its sodium salt 3b. Heat 10 mmol of octyl thiol (6c) and 10 mmol of metal sodium in tetrahydrofuran solution to reflux for 24 h to obtain sodium octyl thiol (6d). Add 10 mmol of chlorinated ND sodium salt 3b to the freshly prepared sodium octylthiolate (6d) solution, heat to reflux for 24 hours, and obtain thioether (6e) through coupling reaction. After the reaction, an equivalent amount of m-chloroperoxybenzoic acid (mCPBA) was added, stirred for 1 h, and then the pH of the solution was adjusted to 7-8 with hydrochloric acid to obtain the oxidized product. Separation by column chromatography (eluent: dichloromethane:methanol=10:1) and recrystallization from ethanol afforded 1.80 g of white powder of ligand 6f with a yield of 55%.

¹ H NMR (400MHz, DMSO) δ8.82(s, 1H), 8.28(d, J=8.6Hz, 1H), 8.15(d, J=8.6Hz, 1H), 3.19-3.09(m, 1H), 3.02-2.90 (m, 1H), 1.73-1.63 (m, 1H), 1.39-1.28 (m, 3H), 1.26-1.10 (m, 8H), 0.84 (t, J=6.9Hz, 3H). Mass Spectrometry (m/z, ESI): Calc. 331.1, Found 332.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 61.60 (61.61); H, 6.40 (6.39); N, 12.66 (12.68), the theoretical values in brackets.

6.2 Synthesis of complex Eu6

3 mmol of ligand 6f and 3 mmol of NaOH were heated to reflux for 30 minutes in a mixed solution of methanol and water 1:1 (volume ratio). Then, 1 mmol of an aqueous solution of europium trichloride hexahydrate was added dropwise to the above solution or suspension, and refluxed for 2 hours. Filtered, washed with water, washed with a small amount of methanol, and dried in vacuum. 0.91 g of the white target europium complex was obtained with a yield of 80%. Mass spectrometry (m/z, ESI): Calc. 1143.3, found 1144.3 (M+H) ⁺ . Elemental analysis (mass percentage): C, 53.00 (53.07); H, 5.43 (5.44); N, 10.77 (10.79), the theoretical value of Eu6·0.6CH ₃ OH·0.3H ₂ O in brackets.

Example 7.

The synthetic route involved in the present embodiment is as follows:

7.1 Ligand 7 (3-cyano-4-hydroxy-6-n-octylsulfonyl-1,5-naphthyridine, 3-cyano-4-hydroxy-6-(octylsulfonyl)-1,5-naphthyridine) synthesis

An equivalent methanolic solution of m-chloroperoxybenzoic acid (mCPBA) was added dropwise to 5 mmol of ligand 6f, and stirred for 1 h. Separation by column chromatography (eluent: dichloromethane:methanol=10:1), recrystallization from methanol, and vacuum drying gave 1.07 g of white powder of Ligand 7 with a yield of 61%.

¹ H NMR (400MHz, DMSO) δ13.03(s, 1H), 8.81(s, 1H), 8.34-8.28(m, 2H), 3.58-3.43(m, 2H), 1.69-1.48(m, 2H) , 1.42-1.27 (m, 2H), 1.27-1.14 (m, 8H), 0.83 (t, J=6.9Hz, 3H). Mass Spectrometry (m/z, ESI): Calc. 347.1, Found 348.1 (M+H). Elemental analysis (% by mass): C, 58.77 (58.77); H, 6.08 (6.09); N, 12.05 (12.09), the theoretical values in brackets.

7.2 Synthesis of complex Eu7

The synthesis steps are the same as in Example 6 (part 6.2), except that the ligand 6f is replaced by 7. 1.04 g of the light yellow target europium complex was obtained with a yield of 88%. Mass spectrometry (m/z, ESI): Calc. 1191.3, found 1192.3 (M+H) ⁺ . Elemental analysis (mass percentage): C, 51.18 (51.19); H, 5.20 (5.10); N, 10.50 (10.53), the theoretical value of Eu7·0.3H ₂ O in brackets.

Example 8.

The synthetic route involved in the present embodiment is as follows:

8.1 Ligand 8f (3-cyano-4-hydroxy-6-p-tolylsulfoxide-1,5-naphthyridine, 3-cyano-4-hydroxy-6-(p-tolylsulfinyl)-1,5- Naphthyridine) synthesis

The synthesis procedure is the same as in Example 6 (part 6.1), except that octylthiol (6c) is replaced by p-cresylthiol (8c). Ligand 8f white powder 1.98g was obtained with a yield of 51%.

Mass Spectrometry (m/z, ESI): Calc. 309.1, Found 310.1 (M+H) ⁺ . Elemental analysis (% by mass): C, 62.09 (62.12); H, 3.61 (3.58); N, 13.57 (13.58), the theoretical values in brackets.

8.2 Synthesis of complex Eu8

The synthesis steps are the same as in Example 6 (part 6.2), except that the ligand 6f is replaced with 8f. 0.88 g of the white target europium complex was obtained with a yield of 82%. Mass Spectrometry (m/z, ESI): Calc. 1077.1, Found 1078.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 53.11 (53.03); H, 3.01 (2.99); N, 11.37 (11.48), the theoretical value of Eu8·0.5CH ₃ OH·0.3H ₂ O in brackets.

Example 9.

The synthetic route involved in the present embodiment is as follows:

9.1 Ligand 9 (3-cyano-4-hydroxy-6-p-methylsulfonyl-1,5-naphthyridine, 3-cyano-4-hydroxy-6-(p-tolylsulfonyl)-1,5-naphthyridine )Synthesis

The synthesis procedure is the same as in Example 7 (part 7.1), except that 6f is replaced by 8f. Ligand 9 white powder 1.04g was obtained with a yield of 64%. Mass Spectrometry (m/z, ESI): Calc. 325.1, Found 326.1 (M+H) ⁺ . Elemental analysis (% by mass): C, 59.09 (59.07); H, 3.39 (3.41); N, 12.91 (12.92), the theoretical values in brackets.

9.2 Synthesis of complex Eu9

The synthesis steps are the same as in Example 6 (part 6.2), except that the ligand 6f is replaced with 9. 0.96 g of the white target europium complex was obtained with a yield of 86%. Mass spectrometry (m/z, ESI): Calc. 1125.1, found 1126.1 (M+H) ⁺ . Elemental analysis (mass percentage): C, 51.18 (51.08); H, 2.69 (2.72); N, 11.20 (11.17), the theoretical value of Eu9·0.2H ₂ O in brackets.

Comparative example 1. The rare earth complex shown in the synthetic formula VV

Mix 3mmol of 8mCND (that is, 3-cyano-4-hydroxyl-8-methyl-1,5-naphthyridine, see the invention patent CN201110139842.1 for the synthesis method) and 3mmol of NaOH in ethanol and water 1:1 (volume ratio ) in the mixed solution and heated to reflux for 30 minutes, then the aqueous solution of 1 mmol europium trichloride hexahydrate was added dropwise to the above solution or suspension, and refluxed for 2 hours. After filtering, washing with water, washing with a small amount of ethanol, and vacuum drying, the complex Eu(8mCND) ₃ (H ₂ O) ₂ was obtained. The resulting complex was then mixed with 2 mmol of triphenylphosphine oxide (TPPO) in acetone solution and heated to reflux for 1 hour. After evaporating the solvent to dryness, 1.13 g of a yellowish powder of the target europium complex was obtained. Mass spectrometry (ESI-MS) analysis showed that the molecular ion peak M/Z=1262.3, [M+H] ⁺ .

Comparative example 2. the rare earth complex compound shown in synthetic formula VVI

4 mmol of TTA (2-thienoyltrifluoroacetone, 0.89 g) and 4 mmol of NaOH (0.16 g) were heated to reflux for 30 minutes in a mixed solution of ethanol and water (volume ratio, 50 mL). Then, an aqueous solution of 1 mmol of europium trichloride hexahydrate (0.37 g) was added dropwise to the above solution or suspension, and refluxed for 2 hours. Filtered, washed with water, washed with a small amount of ethanol, and dried in vacuum. Then recrystallized from ethanol/chlorobenzene to obtain 1.05 g of light yellow powder. Mass spectrometry (ESI-MS) analysis showed that the molecular ion peak M/Z=1036.9, [M-Na].

<Characterization of complexes>

Example 10. Characterization of Luminescent Properties, Thermal Stability, and Photostability

The technical effect of the present invention is mainly reflected by the emission spectrum, luminescence quantum yield, thermal stability and ultraviolet resistance of the rare earth complex in the examples. Among them, the luminescence quantum yield is tested by an integrating sphere, the thermal stability is measured by the thermal decomposition temperature obtained from the thermogravimetric analysis test under _N2 atmosphere, and the ultraviolet resistance is measured by testing the rare earth complex doped polymer The film (PMMA) is measured by the attenuation of luminous intensity under ultraviolet light irradiation. The quantum yield was tested on a Nanolog FL3-2iHR infrared spectrometer produced by France HORIBA JOBIN company. Thermogravimetric analysis was tested on a Q600SDT spectrometer produced by TA Company in the United States. The ultraviolet aging uses UVA340 type lamp tube, the power is 40 watts, and the radiation intensity during the test is 25-30 watts/square meter.

Only the test results of several representative complexes are listed, as shown in Table 1.

Firstly, the europium complex obtained in the present invention can see vivid and bright red light under the excitation of ultraviolet light. The ultraviolet-visible absorption spectrum of complex Eu3 in dichloromethane solution is shown in Figure 1, and the excitation and emission spectra of its solid powder are shown in Figure 2. The quantum yield of the solid powder is as high as 94%, which is among the highest levels compared with the europium complexes reported in the literature. The excitation and emission spectra of other complexes are similar to those of Eu3, and they also have good luminescence quantum efficiencies. It shows that such complexes have the potential to be used as efficient down-conversion luminescent materials.

Secondly, the europium complex obtained in the present invention has sufficient thermal stability. The thermal decomposition temperature of the complex Eu5 is as high as 440 degrees Celsius, indicating that this type of compound not only has a rigid structure, but also does not use neutral ligands, and there is no technical problem that neutral ligands are easily dissociated. As a control, the thermal decomposition temperature of the complex in Comparative Example 1 is only 230 °C, indicating that the dissociation of the neutral ligand TPPO can easily occur under heating conditions.

Again, the europium complex obtained in the present invention has sufficient photostability. The complex was irradiated under a 40W UVA340 ultraviolet lamp for 20 hours, and no obvious photodegradation was observed. As a contrast, the β-diketone rare earth complex [Eu(TTA) 4]Na (TTA is 2-thienoyltrifluoroacetone) in Comparative Example 2, after 20 hours of irradiation under the ultraviolet lamp, the luminous intensity has been reduced. greatly weakened.

In addition, the europium complex obtained in the present invention also has a high coordination stability constant, and soaking the solid powder of this type of europium complex in strong acid or strong alkali solution for a long time will not cause the disappearance of luminescent properties.

Table 1

a: Indicates the result measured in the integrating sphere of the solid powder sample. b: Test results after 20 hours of UV irradiation. c: Not tested.

<Applications of rare earth complexes>

Example 11. The complex Eu3 is dispersed in polymer PMMA as a luminescent film

The rare earth complex Eu3 and polymer PMMA resin are mixed at a mass ratio of 1:100, and dissolved in dichloromethane solution. Then, the obtained mixed solution is spin-coated to form a uniform polymer film on the surface of the cleaned quartz glass.

The obtained film can emit bright red light visible to the naked eye under the irradiation of ultraviolet light. The absolute quantum yield of photoluminescence measured by using an integrating sphere can reach 92%, and it is an efficient light-converting thin film material.

Example 12. Complex Eu3 is used as a light-emitting material in an electroluminescent device

The electroluminescent device structure of the rare earth europium complex in this embodiment can be expressed as ITO/MoO ₃ /TCTA (40nm)/Eu3:BCPO (1:15, 20nm)/TmPyPB (40nm)/LiF/Al, where ITO represents Indium tin conductive glass, MoO ₃ means molybdenum trioxide, LiF means lithium fluoride, Al means metal aluminum electrode. The structural formulas of other materials used are shown in Figure 3.

Electroluminescent devices can be fabricated by methods known in the art, such as those disclosed in references (Appl. Phys. Lett. 1987, 51, 913). The specific method is: under the condition of high vacuum (less than 8×10 ^-5 Pa), sequentially deposit hole transport material, luminescent material, electron transport material and metal cathode material on the cleaned conductive glass (ITO) substrate. The thickness of each layer was monitored with a quartz crystal oscillator.

When measuring the performance of the device, the ITO electrode is connected to the positive pole, and the metal electrode is connected to the negative pole. While applying a constant voltage (usually between 3-30 volts) to the device, record its voltage-current (IV) curve and voltage-brightness ( LV) curve, etc. The above measurements were made by a combination system of a computer-controlled Keithley 2400 analyzer and a PR650 spectrometer (see Figure 4). The emission spectrum of the device at 100cd·m ^-2 is shown in Fig. 5 .

Preliminary results show that the maximum brightness of the electroluminescence device can reach 1180cdm ^-2 , and the maximum current efficiency is 14cdA ^-1 . At 100cd·m ^-2 , the current efficiency is 2.7cd A ^-1 . Compared with electroluminescent devices based on europium complexes already disclosed in the literature, the performance of the electroluminescent device described in the present invention is at a higher level. It is believed that after optimization, there is still room for improvement in the efficiency of electroluminescent devices based on this type of europium complex.

Claims (12)

1. a kind of europium complex, its general structure is Eu (t-ND)₃, wherein t-ND is the later phosphine epoxide of deprotonation, sulfoxide group Or 4- hydroxyl -1,5- naphthyridine type anion ligands of sulfuryl substitution；The structure of the europium complex such as formula IV, Formula V and Formula IV institute Show：

Wherein, R₁、R₂、R₃、R₄Each stand alone as hydrogen atom, halogen atom, cyano group, C1-C8 straight or branched alkyl, C1-C8 Straight or branched halogen-substituted alkyl；R₅For C1-C18 straight or branched alkyl, phenyl, naphthyl or substituted phenyl, Described substituted phenyl be by halogen atom, methyl, ethyl, isopropyl, the tert-butyl group, methoxyl group, ethyoxyl, trifluoromethyl, The phenyl that dimethylamino is replaced.

2. europium complex as claimed in claim 1, it is characterised in that R₅For methyl, ethyl, n-propyl, isopropyl, normal-butyl, The tert-butyl group, n-octyl, dodecyl, n-hexadecyl, n-octadecane base, phenyl, naphthyl, 2- fluorophenyls, 2- chlorphenyls, 2- Bromophenyl, 3- fluorophenyls, 3- chlorphenyls, 3- bromophenyls, 4- fluorophenyls, 4- chlorphenyls, 4- bromophenyls, 2,3- dichlorophenyls, 2, 4- dichlorophenyls, 2,5- dichlorophenyls, 2,6- dichlorophenyls, 3,4- dichlorophenyls, 3,5- dichlorophenyls, 2- aminomethyl phenyls, 2- Ethylphenyl, 2- isopropyl phenyls, 2- tert-butyl-phenyls, 4- aminomethyl phenyls, 4- ethylphenyls, 4- isopropyl phenyls, the tertiary fourths of 4- Base phenyl, 2,4- 3,5-dimethylphenyls, 2,5- 3,5-dimethylphenyls, 2,6- 3,5-dimethylphenyls, 3,5- 3,5-dimethylphenyls, 2- methyl -5- Tert-butyl-phenyl, 2- methoxyphenyls, 3- methoxyphenyls, 4- methoxyphenyls, 2- dimethylamino phenyls, 4- Dimethylaminobenzenes Base.

3. europium complex as claimed in claim 1, it is characterised in that R₅For methyl, ethyl, n-propyl, isopropyl, normal-butyl, The tert-butyl group, n-octyl, dodecyl, n-hexadecyl, n-octadecane base, phenyl, naphthyl, p-methylphenyl.

4. europium complex as claimed in claim 1, it is characterised in that R₁、R₂、R₃、R₄Each stand alone as hydrogen atom, cyano group, first Base；R₅For ethyl, the tert-butyl group, n-octyl, phenyl, p-methylphenyl.

5. the tooth anion ligand of 4- hydroxyls -1,5- naphthyridine type three of a kind of phosphine epoxide, sulfoxide group or sulfuryl substitution, its structure such as formula Shown in I, Formula II and formula III：

Wherein, R₁、R₂、R₃、R₄Each stand alone as hydrogen atom, halogen atom, cyano group, C1-C8 straight or branched alkyl, C1-C8 Straight or branched halogen-substituted alkyl；R₅For C1-C18 straight or branched alkyl, phenyl, naphthyl or substituted phenyl, Described substituted phenyl be by halogen atom, methyl, ethyl, isopropyl, the tert-butyl group, methoxyl group, ethyoxyl, trifluoromethyl, The phenyl that dimethylamino is replaced.

6. anion ligand as claimed in claim 5, it is characterised in that R₁、R₂、R₃、R₄Each stand alone as hydrogen atom, cyano group, Methyl；R₅For ethyl, the tert-butyl group, n-octyl, phenyl, p-methylphenyl.

7. the preparation method of the europium complex in Claims 1 to 4 described in any one, cloudy using three teeth shown in Formulas I-III Ion ligand, alkali and rare earth salts react in a solvent, and the europium complex shown in formula IV-VI is made：

Wherein, the alkali is selected from hydroxide, carbonate, ammoniacal liquor, organic amine；The rare earth salts are selected from hydrochloride, the nitre of europium Hydrochlorate, acetate or trifluoro sulfonate；In Formulas I-VI, R₁、R₂、R₃、R₄And R₅Scope with described in claim 1-4.

8. preparation method as claimed in claim 7, it is characterised in that three tooth anion ligands, alkali shown in the Formulas I-III It is 3: 3: 1 with the mol ratio that rare earth salts react；One or more mixtures of the solvent in following solvent：Water, Ethanol, methanol, isopropanol, acetone, tetrahydrofuran, acetonitrile, toluene, dichloromethane, chloroform, ether, N, N- dimethyl methyls Acid amides；The temperature of reaction is -10~120 DEG C, and the time is 10 minutes~24 hours.

9. the preparation method of three tooth anion ligands described in claim 5, using the 4- hydroxyls of the 6- positions halogen substitution shown in Formula VII Base -1,5- naphthyridine type part and the organic chloride phosphine shown in Formula VIII or the thiol reactant shown in Formula IV V, it is even by the first step Connection reaction, second step oxidation reaction is obtained：

In Formula VII, X represents halogen atom, R₁、R₂、R₃、R₄Scope with described in claim 5；In Formula VIII and Formula IV V, R₅'s Scope is with described in claim 5.

10. preparation method as claimed in claim 9, it is characterised in that first, 4- hydroxyl -1,5- naphthalenes of 6- halogen substitutions Pyridine class part captures proton with alkali reaction, and organic chloride phosphine or mercaptan obtain corresponding salt, Ran Houjin with alkali metal reaction Row coupling reaction；Next, adding oxidant carries out oxidation reaction, the oxidant is selected from oxygen, ozone, chlorine, chlorine water, secondary Sodium chlorate, perbenzoic acid, m-chloro-benzoic acid peroxide, Peracetic acid, hydrogen peroxide；Eventually pass appropriate post processing and carry It is pure to obtain product.

11. europium complex in Claims 1 to 4 described in any one is used as the application of luminescent material.

12. application as claimed in claim 11, it is characterised in that the rare earth compounding shines through ultraviolet source or royal purple light source Penetrate and light, or the rare earth compounding is excited and lighted by electric energy.