MATERIALS FOR ORGANIC ELECTROLUMINESCENT DEVICES

Abstract

The present invention describes dibenzofuran derivatives substituted by electron-deficient heteroaryl groups, and electronic devices, especially organic electroluminescent devices, comprising these compounds as triplet matrix materials.

Claims

1.-15. (canceled)

16. A compound of formula (1) ##STR00244## where the symbols and indices used are as follows: Y.sup.1 is the same or different at each instance and is O or S; Y.sup.2 is the same or different at each instance and is NAr.sup.2, O, S or CR.sub.2; Z is the same or different at each instance and is CR or N, with the proviso that at least two Z are N; Ar.sup.1, Ar.sup.2 is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted by one or more R radicals; R is the same or different at each instance and is H, D, F, Cl, Br, I, N(Ar′).sub.2, N(R.sup.1).sub.2, OAr′, SAr′, CN, NO.sub.2, OR.sup.1, SR.sup.1, COOR.sup.1, C(═O)N(R.sup.1).sub.2, Si(R.sup.1).sub.3, B(OR.sup.1).sub.2, C(═O)R.sup.1, P(═O)(R.sup.1).sub.2, S(═O)R.sub.1, S(═O).sub.2R.sup.1, OSO.sub.2R.sup.1, a straight-chain alkyl group having 1 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, where the alkyl, alkenyl or alkynyl group may in each case be substituted by one or more R.sup.1 radicals, where one or more nonadjacent CH.sub.2 groups may be replaced by Si(R.sup.1).sub.2, C═O, NR.sup.1, O, S or CONR.sup.1, or an aromatic or heteroaromatic ring system which has 5 to 60 aromatic ring atoms, preferably 5 to 40 aromatic ring atoms, and may be substituted in each case by one or more R.sup.1 radicals; at the same time, two R radicals together may also form a ring system; Ar′ is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted by one or more R.sup.1 radicals; at the same time, two Ar′ radicals bonded to the same nitrogen atom may also be bridged to one another by a single bond or a bridge selected from N(R.sup.1), C(R.sup.1).sub.2, O and S; R.sup.1 is the same or different at each instance and is H, D, F, Cl, Br, I, N(R.sup.2).sub.2, CN, NO.sub.2, OR.sup.2, SR.sup.2, Si(R.sup.2).sub.3, B(OR.sup.2).sub.2, C(═O)R.sup.2, P(═O)(R.sup.2).sub.2, S(═O)R.sup.2, S(═O).sub.2R.sup.2, OSO.sub.2R.sup.2, a straight-chain alkyl group having 1 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, where the alkyl, alkenyl or alkynyl group may each be substituted by one or more R.sup.2 radicals, where one or more nonadjacent CH.sub.2 groups may be replaced by Si(R.sup.2).sub.2, C═O, NR.sup.2, O, S or CONR.sup.2 and where one or more hydrogen atoms in the alkyl, alkenyl or alkynyl group may be replaced by D, F, Cl, Br, I or CN, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R.sup.2 radicals; at the same time, two or more R.sup.1 radicals together may form an aliphatic ring system; R.sup.2 is the same or different at each instance and is H, D, F, CN or an aliphatic, aromatic or heteroaromatic organic radical having 1 to 20 carbon atoms, in which one or more hydrogen atoms may also be replaced by F; p, q, r is the same or different at each instance and is 0, 1, 2 or 3; s is the same or different at each instance and is 0, 1, 2, 3 or 4.

17. The compound according to claim 16, wherein the compound is of formula (2) ##STR00245## where the symbols and indices have the definitions given in claim 16.

18. The compound according to claim 16, wherein the compound is of formula (3) ##STR00246## where the symbols and indices have the definitions given in claim 16.

19. The compound according to claim 16, wherein the compound is of formula (4) ##STR00247## where the symbols and indices have the definitions given in claim 16.

20. The compound according to claim 16, wherein Y.sup.2 is NAr.sup.2 and the carbazole group has at least two adjacent R radicals that form a ring system with one another, so as to form a structure of one of the formulae (CARB-1) to (CARB-6) ##STR00248## where Ar.sup.2 and R.sup.1 have the definitions given in claim 16, the structures may be substituted by one or more R radicals on the carbazole and by one or more R.sup.1 radicals on the fused-on structure, Y.sup.3 is C(R.sup.1).sub.2, NR.sup.1, O or S, and the structures are joined to the dibenzofuran or dibenzothiophene via the dotted bond.

21. The compound according to claim 16, wherein the compound is of formula (5) ##STR00249## where the symbols and indices have the definitions given in claim 16.

22. The compound according to claim 16, wherein the compound is of one of the formulae (1a) to (5a) ##STR00250## where the symbols and indices have the definitions given in claim 16.

23. The compound according to claim 16, wherein the compound is of formula (6a) ##STR00251## where the symbols have the definitions given in claim 16 and s is the same or different at each instance and is 0 or 1.

24. The compound according to claim 16, wherein Ar.sup.1 and Ar.sup.2 are the same or different at each instance and are selected from the group consisting of phenyl, biphenyl, terphenyl, quaterphenyl, fluorene, spirobifluorene, naphthalene, indole, benzofuran, benzothiophene, carbazole, dibenzofuran, dibenzothiophene, indenocarbazole, indolocarbazole, phenanthrene, triphenylene or a combination of two or three of these groups, each of which may be substituted by one or more R radicals.

25. A process for preparing a compound according to claim 16 by reacting an Ar.sup.1-functionalized dichloropyrimidine or -triazine with a 1-dibenzofuranboronic acid or ester thereof or a 1-dibenzothiopheneboronic acid or ester thereof in a Suzuki coupling.

26. A formulation comprising at least one compound according to claim 16 and at least one further compound and/or a solvent.

27. A method comprising incorporating the compound according to claim 16 in an electronic device.

28. An electronic device comprising at least one compound according to claim 16.

29. The electronic device according to claim 28 which is an organic electroluminescent device, wherein the compound is used in an emitting layer as matrix material for phosphorescent emitters or for emitters that exhibit TADF (thermally activated delayed fluorescence) and/or in an electron transport layer and/or in a hole blocker layer.

30. The electronic device according to claim 29, wherein the compound is used in an emitting layer as matrix material for a phosphorescent emitter, wherein the compound is used in combination with one or more further matrix materials selected from the group consisting of aromatic ketones, aromatic phosphine oxides, aromatic sulfoxides, aromatic sulfones, triarylamines, carbazole derivatives, indolocarbazole derivatives, indenocarbazole derivatives, azacarbazole derivatives, bipolar matrix materials, azaboroles, boronic esters, triazine derivatives, zinc complexes, diazasilole or tetraazasilole derivatives, diazaphosphole derivatives, bridged carbazole derivatives, triphenylene derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, wide bandgap materials and/or phosphorescent compounds having shorter-wave emission than the actual emitter.

Description

EXAMPLES

[0105] The syntheses which follow, unless stated otherwise, are conducted under a protective gas atmosphere in dried solvents. The solvents and reagents can be purchased, for example, from Sigma-ALDRICH or ABCR. The respective figures in square brackets or the numbers quoted for individual compounds relate to the CAS numbers of the compounds known from the literature.

Stage 1: BB-1a

[0106] ##STR00142##

[0107] 100 g (26 mmol) of 1-bromo-8-iododibenzofuran (CAS: 1822311-11-4), 92.4 g (32 mmol) of (9-phenyl-9H-carbazol-3-yl)boronic acid, 85.2 g (61 mmol) of potassium carbonate and 15.5 g (13 mmol) of tetrakis(triphenylphosphine)palladium(0) are mixed in 1 l of ethylene glycol dimethyl ether/water (3:1) and heated under reflux overnight. The mixture is allowed to come to room temperature, and the precipitate is filtered off and washed with water and ethanol. Yield: 86 g (176 mmol; 66%).

[0108] The following compounds can be synthesized analogously:

TABLE-US-00002 Ex. Reactant 1 Reactant 2 BB-1b [00143] [00144] BB-1c [00145] [00146] BB-1d [00147] [00148] BB-1e [00149] [00150] BB-1f [00151] [00152] BB-1g [00153] [00154] BB-1h [00155] [00156] BB-1i [00157] [00158] BB-1j [00159] [00160] Ex. Product BB-1b [00161] BB-1c [00162] BB-1d [00163] BB-1e [00164] BB-1f [00165] BB-1g [00166] BB-1h [00167] BB-1i [00168] BB-1j [00169]

Stage 2: BB-2a

[0109] ##STR00170##

[0110] 86 g (176 mmol) of 3-(9-bromodibenzofuran-2-yl)-9-phenyl-9H-carbazole, 82.1 g (320 mmol) of 4,4,5,5,4′,4′,5′,5′-octamethyl-[2,2′]bi[[1,3,2]dioxaborolanyl], 52.4 g (530 mmol) of potassium acetate and 2.8 g (12 mmol) of palladium acetate are mixed in 1 l of DMF and stirred at 100° C. After 24 h, the reaction mixture is left to cool to room temperature and the mixture is concentrated to one third under reduced pressure. Water is added and the precipitated solids are filtered off, washed with water, ethanol and heptane, and purified further by filtration through silica with THE as eluent. The product is obtained by removing the solvents under reduced pressure. Yield: 58.2 g (109 mmol; 62%).

[0111] The following compounds can be synthesized analogously:

TABLE-US-00003 Ex. Reactant Product BB-2b [00171] [00172] BB-2c [00173] [00174] BB-2d [00175] [00176] BB-2e [00177] [00178] BB-2f [00179] [00180] BB-2g [00181] [00182] BB-2h [00183] [00184] BB-2i [00185] [00186] BB-2j [00187] [00188]

Stage 3: BB-3a

[0112] ##STR00189##

[0113] 21.1 g (85.4 mmol) of 1-bromodibenzofuran in 100 ml of THE is added dropwise to 2.27 g (93.5 mmol) of magnesium (with addition of iodine to start the Grignard reaction), and the mixture is heated under reflux for 2 h. 350 ml of THE is added, and the reaction mixture is left to come to room temperature. The Grignard reagent is added dropwise to 15 g (81 mmol) of 2,4,6-trichloro[1,3,5]triazine, dissolved in 150 ml of THF, at −10° C. The mixture is left to stir at room temperature overnight. Then the mixture is cooled to 0° C., and 8 ml of hydrochloric acid (1 M) is added dropwise. The mixture is stirred for 1 h, then 400 ml of water is added. The organic phase is removed and washed with water. The aqueous phase is extracted with ethyl acetate. The organic phases are combined and concentrated under reduced pressure. The crude product is purified by flash chromatography (heptane/dichloromethane 10:1). Yield: 24.0 g (75.9 mmol; 89%).

Stage 4 (Symmetric): Compound 1

[0114] ##STR00190##

[0115] 24 g (75.9 mmol) of 2,4-dichloro-6-dibenzofuran-1-yl-[1,3,5]triazine, 80.3 g (150 mmol) of 9-phenyl-3-[9-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-dibenzofuran-2-yl]-9H-carbazole, 2.2 g (1.9 mmol) of tetrakis(triphenylphosphine)palladium(0) and 15.7 g (113.9 mmol) of potassium carbonate are mixed in 500 ml of water/THF (1:3) and stirred at 70° C. overnight. Subsequently, the reaction mixture is allowed to come to room temperature, ethyl acetate is added and the phases are separated. The organic phase is washed with water, and the aqueous phase is extracted with ethyl acetate. The combined organic phases are concentrated under reduced pressure and purified by flash chromatography (heptane/THF 10:1). The product is purified by recrystallization from heptane/toluene. Further purification is effected by sublimation (430° C., 10.sup.−4 mbar). Yield: 22.6 g (21.28 mmol; 28%).

[0116] The following compounds can be synthesized analogously:

TABLE-US-00004 Ex. Reactant 1 Reactant 2 Product  2 BB-2b BB-3a [00191]  3 BB-2c BB-3a [00192]  4 BB-2d BB-3a [00193]  5 BB-2e BB-3a [00194]  6 BB-2a [00195] [00196]  7 BB-2b [00197] [00198]  8 BB-2c [00199] [00200]  9 BB-2b [00201] [00202] 10 BB-2a [00203] [00204] 11 BB-2f [00205] [00206] 12 BB-2g [00207] [00208] 13 BB-2h [00209] [00210] 14 BB-2i BB-3a [00211] 15 BB-2j BB-3a [00212]

Stage 5 (Asymmetric): BB-4a

[0117] ##STR00213##

[0118] 24 g (75.9 mmol) of 2,4-dichloro-6-dibenzofuran-1-yl-[1,3,5]triazine, 36.6 g (68.3 mmol) of 9-phenyl-3-[9-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-dibenzofuran-2-yl]-9H-carbazole, 2.2 g (1.9 mmol) of tetrakis(triphenylphosphine)palladium(0) and 15.7 g (113.9 mmol) of potassium carbonate are mixed in 500 ml of water/THF (1:3) and stirred at 70° C. overnight. The mixture is allowed to come to room temperature, ethyl acetate is added and the phases are separated. The organic phase is washed with water, and the aqueous phase is extracted with ethyl acetate. The combined organic phases are concentrated under reduced pressure and purified by flash chromatography (heptane/THF 10:1). Yield: 30 g (43.5 mmol; 58%).

[0119] The following compounds can be synthesized analogously:

TABLE-US-00005 Ex. Reactant 1 Reactant 2 Product BB-4b BB-2a [00214] [00215] BB-4c BB-2a [00216] [00217] BB-4d BB-2a [00218] [00219]

Stage 6 (Asymmetric): Compound 1.1

[0120] ##STR00220##

[0121] 29 g (42.1 mmol) of 3-[9-(4-chloro-6-dibenzofuran-1-yl-[1,3,5]triazin-2-yl)-dibenzofuran-2-yl]-9-phenyl-9H-carbazole, 33.6 g (44 mmol) of BB-2b, 1.2 g (1.1 mmol) of tetrakis(triphenylphosphine)palladium(0) and 8.7 g (63.1 mmol) of potassium carbonate are mixed in 500 ml of water/THF (1:3) and stirred at 70° C. overnight. The reaction mixture is allowed to come to room temperature, ethyl acetate is added and the phases are separated. The organic phase is washed with water, and the aqueous phase is extracted with ethyl acetate. The combined organic phases are concentrated under reduced pressure. The product is purified by flash chromatography (heptane/THF 10:1) and then purified by recrystallization (heptane/toluene). Yield: 20.6 g (16.0 mmol; 38%).

[0122] In an analogous manner, it is possible to synthesize the following compounds:

TABLE-US-00006 Ex. Reactant 1 Reactant 2 Product 1.2 BB-4b BB-2b [00221] 1.3 BB-4c BB-2c [00222] 1.4 BB-4d BB-2d [00223] 1.5 BB-4a BB-2e [00224] 1.6 BB-4a BB-2b [00225] 1.7 BB-4a BB-2c [00226]
Device Examples Processed from Solution: Production of the OLEDs

[0123] There are many descriptions of the production of vapour-deposited OLEDs in the literature, for example in WO 2004/058911. The production of solution-based OLEDs is detailed, for example, in WO 2004/037887 and WO 2010/097155. The examples that follow combine the two production processes, such that layers up to and including the emission layer are processed from solution and the subsequent layers (hole blocker layer/electron transport layer) are applied by vapour deposition under reduced pressure. For this purpose, the previously described general methods are matched to the circumstances described here (layer thickness variation, materials) and combined as follows.

[0124] The construction of the OLEDs used is as follows: [0125] substrate, [0126] ITO (50 nm), [0127] buffer (20 nm), [0128] hole transport layer (HTL, 20 nm), [0129] emission layer (EML, 50 nm), [0130] electron transport layer (ETL, 20 nm), [0131] electron injection layer (EIL, 3 nm), [0132] Al cathode (100 nm).

[0133] Substrates used are glass plaques coated with structured ITO (indium tin oxide) of thickness 50 nm. For better processing, they are coated with the buffer PEDOT:PSS (poly(3,4-ethylenedioxy-2,5-thiophene): polystyrenesulfonate) from Heraeus Precious Metals GmbH & Co. KG. Spin-coating is effected under air from water. The layer is subsequently baked at 180° C. for 10 minutes. The hole transport layer and the emission layer are applied to the glass plaques thus coated. The hole transport layer is the polymer of the structure shown in table 1, which can be synthesized according to WO 2010/097155. The polymer is dissolved in toluene, such that the solution typically has a solids content of about 5 g/l when, as is the case here, the layer thickness of 20 nm typical of a device is to be achieved by means of spin-coating. The layers are spun on in an inert gas atmosphere, nitrogen in the present case, and baked at 220° C. for 30 min.

[0134] The emission layer is always composed of at least one matrix material (host material) and an emitting dopant (emitter). Details given in such a form as H1 (92%):D1 (8%) mean here that the material H1 is present in the emission layer in a proportion by weight of 92% and the dopant D1 in a proportion by weight of 8%. The mixture for the emission layer is dissolved in toluene. The typical solids content of such solutions is about 14 g/l when, as here, the layer thickness of 50 nm which is typical of a device is to be achieved by means of spin-coating. The layers are spun on in an inert gas atmosphere, nitrogen in the present case, and baked for 10 minutes. The materials used are shown in table 1. The respective composition of the emission layer, the EML layer thickness and the baking temperature thereof are shown in table 2.

[0135] The materials for the electron transport layer and for the cathode are applied by thermal vapour deposition in a vacuum chamber. The electron transport layer, for example, may consist of more than one material, the materials being added to one another by co-evaporation in a particular proportion by volume. Details given in such a form as ETM:EIM (50%:50%) mean here that the ETM and EIM materials are present in the layer in a proportion by volume of 50% each. In the present case, the electron transport layer consists of the material ETM with a layer thickness of 20 nm. The electron injection layer is formed from 3 nm of the EIM material. Both materials are depicted in table 1. The concluding layer is a cathode layer of aluminium having a layer thickness of 100 nm.

[0136] The OLEDs are characterized in a standard manner. For this purpose, the electroluminescence spectra are recorded, and the current efficiency (measured in cd/A) and the external quantum efficiency (EQE, measured in percent) are calculated as a function of luminance, assuming Lambertian emission characteristics, from current-voltage-luminance characteristics (IUL characteristics), and finally the lifetime of the components is determined. The electroluminescence spectra are recorded at a luminance of 1000 cd/m.sup.2, and the CIE 1931 x and y colour coordinates are calculated therefrom. The parameter EQE @ 1000 cd/m.sup.2 refers to the external quantum efficiency at an operating luminance of 1000 cd/m.sup.2. The lifetime LT95 @ 4000 cd/m.sup.2 is the time that passes until the starting brightness of 4000 cd/m.sup.2 has fallen by 5% to 3800 cd/m.sup.2. The data for the various OLEDs are collated in table 3.

TABLE-US-00007 TABLE 1 Structures of the materials used [00227] HTL-A [00228] Host 2 [00229] TEG [00230] TER [00231] SdT1 [00232] Sdt2 [00233] EG1 [00234] EG2 [00235] EG3 [00236] EG4 [00237] EG5 [00238] EG6 [00239] EG7 [00240] EG8 [00241] EG9 [00242] ETM [00243] EIM

TABLE-US-00008 TABLE 2 Detailed device construction of the solution-processed OLEDs EML HIL HTL EML baking ETL EIL thickness thickness thickness temperature thickness thickness Ex. [nm] [nm] [nm] [° C.] [nm] [nm] C1 PEDOT:PSS HTL-A SdT1:Host2:TEG:TER 140 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm C2 PEDOT:PSS HTL-A SdT2:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I3 PEDOT:PSS HTL-A EG1:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I4 PEDOT:PSS HTL-A EG2:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I5 PEDOT:PSS HTL-A EG3:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I6 PEDOT:PSS HTL-A EG4:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I7 PEDOT:PSS HTL-A EG5:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I8 PEDOT:PSS HTL-A EG6:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I9 PEDOT:PSS HTL-A EG7:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I10 PEDOT:PSS HTL-A EG8:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm I11 PEDOT:PSS HTL-A EG9:Host2:TEG:TER 160 ETM EIM 80 nm 20 nm (40%:35%:17%:8%) 20 nm 3 nm 50 nm

TABLE-US-00009 TABLE 3 Data of the solution-processed OLEDs CIE x/y EQE @1000 LT95 @4000 @1000 cd/m.sup.2 cd/m.sup.2 Ex. cd/m.sup.2 (%) (hrs) C1 0.67 0.33 12.3 75 C2 0.67 0.33 12.8 70 I3 0.67 0.33 13.4 180 I4 0.67 0.33 13.1 200 I5 0.67 0.33 13.3 170 I6 0.67 0.33 13.2 190 I7 0.67 0.33 13.3 220 I8 0.67 0.33 13.4 180 I9 0.67 0.33 13.0 140 I10 0.67 0.33 13.5 190 I11 0.67 0.33 13.2 210

[0137] The results in table 3 show that it is possible to achieve not only a slight improvement in external quantum efficiency but also a distinct improvement in lifetime. The structures found are thus suitable as host for processing from solution and lead to excellent performance data.