COMPOUNDS HAVING FLUORENE STRUCTURES

Abstract

The present invention describes fluorene derivatives substituted by electron-transporting groups, especially for use as hole blocking materials, electron injection materials and/or electron transport materials in electronic devices. The invention further relates to a process for preparing the compounds of the invention and to electronic devices comprising these.

Claims

1. A compound comprising a structure of Formula (A), ##STR00227## wherein: Z.sup.a is Ar.sup.a or R.sup.x, wherein Ar.sup.a is an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms, each of which may be substituted by one or more R.sup.x radicals, wherein the groups Z.sup.a and Z.sup.b may form a mono- or polycyclic aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system with one another; Z.sup.b is Ar.sup.b or R.sup.w, wherein Ar.sup.b is an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms, each of which may be substituted by one or more R.sup.w radicals, wherein the groups Z.sup.a and Z.sup.b may form a mono- or polycyclic aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system with one another; Q is an electron transport group; L, L.sup.a, L.sup.b is the same or different at each instance and is a single bond, C(O) or an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R; R, R.sup.w, R.sup.x, R.sup.y, R.sup.z is the same or different at each instance and is H, D, F, Cl, Br, I, CN, Si(R.sup.1).sub.3, a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R.sup.1, wherein in each case one or more non-adjacent CH.sub.2 groups may be replaced by R.sup.1CCR.sup.1, CC, Si(R.sup.1).sub.2, CO, CS, CNR.sup.1, C(O)O, C(O)NR.sup.1, NR.sup.1, P(O)(R.sup.1), O, S, SO or SO.sub.2 and wherein one or more H atoms may be replaced by D, F, C, Br, I, CN or NO.sub.2, or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.1, or an aryloxy or heteroaryloxy group having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1, or an aralkyl group having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.1, or a combination of these systems; at the same time two or more adjacent substituents R, R.sup.w, R.sup.x, R.sup.y, R.sup.z may also form a ring system, preferably a mono- or polycyclic, aliphatic or aromatic ring system with one another, which may be substituted by one or more radicals R.sup.1; R.sup.1 is the same or different at each instance and is H, D, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more R.sup.2 radicals, where one or more non-adjacent CH.sub.2 groups may be replaced by R.sup.2CCR.sup.2, CC, Si(R.sup.2).sub.2, CO, CS, CNR.sup.2, C(O)O, C(O)NR.sup.2, NR.sup.2, P(O)(R.sup.2), O, S, SO or SO.sub.2 and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO.sub.2, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms, each of which may be substituted by one or more R.sup.2 radicals, or an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring atoms, each of which may be substituted by one or more R.sup.2 radicals, or a combination of these systems; at the same time, two or more adjacent R.sup.1 substituents may also form a ring system; R.sup.2 is the same or different at each instance and is H, D, F or an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, in which one or more hydrogen atoms may be replaced by D or F, or an aromatic or heteroaromatic ring system having 5 to 30 carbon atoms, in which one or more hydrogen atoms may be replaced by D or F; at the same time, two or more adjacent R.sup.2 substituents together may also form a ring system; R.sup.a, R.sup.b is the same or different at each instance and selected from (R.sup.a-1) to (R.sup.a-33): ##STR00228## ##STR00229## ##STR00230## ##STR00231## wherein one or more H atoms may be replaced by D and the dotted line denotes the bond to the corresponding group m1, m2 is the same or different at each instance and is 0, 1, 2, 3 or 4, preferably 1, 2, 3 or 4; n2, o2 is the same or different at each instance and is 0, 1, 2, 3 or 4; n1, o1 is the same or different at each instance and is 0, 1, 2 or 3; the sum of n1+o1 is 0, 1, 2 or 3; the sum of n2+o2 is 0, 1, 2, 3 or 4; and wherein the compound comprises at least one structure element of formulae (R.sup.a-1) to (R.sup.a-33).

2. The compound according to claim 1, wherein the compound has the structure of the Formula (I) or Formula (II), ##STR00232## in which the symbols Q, L, L.sup.a, L.sup.b, R, R.sup.w, R.sup.x, R.sup.y, R.sup.z, R.sup.a, R.sup.b, m1, m2, n1, n2, o1 and o2 have the definition given in claim 1 and L.sup.c, L.sup.d is the same or different at each instance and is a single bond, C(O) or an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R; R.sup.c, R.sup.d is the same or different at each instance and selected from (R.sup.a-1) to (R.sup.a-33) as given in claim 1; m3, m4 is the same or different at each instance and is 0, 1, 2, 3 or 4; n3, n4, o3, o4 is the same or different at each instance and is 0, 1, 2, 3 or 4; q3, q4, r3, r4 is the same or different at each instance and is 0, 1, 2, 3, 4 or 5; the sum of n3+o3 is 0, 1, 2, 3 or 4; the sum of n4+o4 is 0, 1, 2, 3 or 4; the sum of q3+r3 is 0, 1, 2, 3, 4 or 5; the sum of q4+r4 is 0, 1, 2, 3, 4 or 5; and wherein the compound comprises at least one structure element of formulae (R.sup.a-1) to (R.sup.a-33).

3. The compound according to claim 2, wherein the compound comprises at least one of the structures of the Formulae (Ia), (Ib), (Ic), (Id), (IIa), (IIb), (IIc) and/or (IId), ##STR00233## ##STR00234##

4. The compound according to claim 2, characterized in that the sum of the indices m1, m2, m3 and m4 is in the range of 1 to 6.

5. The compound according to claim 2, characterized in that the compound comprises at least one of the structures of the Formulae (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (II-1), (II-2), (II-3), (II-4), (II-5) and/or (II-6) ##STR00235## ##STR00236## ##STR00237## ##STR00238##

6. The compound according to claim 1, characterized in that the compound comprises at least one of the structures of the Formulae (Ia-3), (Ia-4), (Ib-4), (Ic-4) and/or (Id-4) ##STR00239##

7. The compound according to claim 1, characterized in that the Q group is a pyridine group, a pyrimidine group, or a triazine group, which may be substituted by one or more radicals R.

8. The compound according to claim 7, wherein the Q group is selected from the structures of the Formulae (Q-1), (Q-2), (Q-3), (Q-4), (Q-5), (Q-6), (Q-7) and/or (Q-8) ##STR00240## wherein the dotted bond marks the attachment position.

9. The compound according to claim 8, wherein (Q-1b), (Q-1c), (Q-1d), (Q-1e), (Q-1f), (Q-1g), (Q-1h), (Q-1i) and/or (Q-1j) ##STR00241## ##STR00242## wherein the dotted bond marks the attachment position and the index I is the same or different at each instance and is 0, 1, 2, 3, 4 or 5, the index h is the same or different at each instance and is 0, 1, 2, 3 or 4, the index j is the same or different at each instance and is 0, 1, 2 or 3.

10. The compound according to claim 2, wherein the symbol L, L.sup.a, L.sup.b, L.sup.c, L.sup.d, is a bond or an aryl group having 6 to 12 aromatic ring atoms, which may be substituted by one or more radicals R, which may be substituted by one or more radicals R.

11. The compound according to claim 10, wherein the symbol L, L.sup.a, L.sup.b, L.sup.c, L.sup.d, is a bond or is selected from the structures of the Formulae (L-1), (L-5), (L-6) and/or (L-7) ##STR00243## wherein the dotted bond marks the attachment positions, the index h is the same or different at each instance and is 0, 1, 2, 3 or 4, the index j is the same or different at each instance and is 0, 1, 2 or 3; the index i is the same or different at each instance and is 0, 1 or 2.

12. The compound according to claim 2, wherein the compound comprises at least one of the structures of the Formulae (Ia-3a), (Ia-4a), (Ib-4a) and/or (Ic-4a), ##STR00244## ##STR00245##

13. The compound according to claim 1, characterized in that the compound comprises exactly one triazine group.

14. An oligomer, polymer or dendrimer containing one or more compounds according to claim 1, wherein one or more bonds of the compound to the polymer, oligomer or dendrimer are present.

15. A composition comprising at least one compound according to claim 1 and at least one further compound selected from the group consisting of fluorescent emitters, phosphorescent emitters, TADF emitters, host materials, matrix materials, electron transport materials, electron injection materials, hole conductor materials, hole injection materials, electron blocking materials and hole blocking materials.

16. A formulation comprising at least one compound according to claim 1 and at least one solvent.

17. A process for preparing a compound according to claim 1 wherein, in a coupling reaction, a compound comprising at least one electron-transporting group is reacted with a compound comprising at least one fluorene or spirobifluorene radical.

18. (canceled)

19. An electronic device comprising at least one compound according to claim 1, wherein the electronic device is preferably selected from the group consisting of organic electroluminescent devices, organic integrated circuits, organic field-effect transistors, organic thin-film transistors, organic light-emitting transistors, organic solar cells, organic optical detectors, organic photoreceptors, organic field quench devices, light-emitting electrochemical cells and organic laser diodes.

20. An electronic device according to claim 19, wherein the device comprises at least one hole-blocking layer and at least one electron transport layer, wherein the hole-blocking layer is directly adjacent to an emitting layer and the at least one hole-blocking layer comprises the compound and the electron transport layer comprises at least one electron transport compound being different from the compound.

Description

EXAMPLES

A) Synthesis Examples

[0207] The syntheses which follow, unless stated otherwise, are conducted under a protective gas atmosphere in dried solvents. The reactants can be purchased from commercial sources (n-butyl lithium, trimethyl borate, tetrakis(triphenylphosphine)palladium(0)). 2,4-Diphenyl-6-(9,9-spirobi(9H-fluoren)-2-yl)-1,3,5-triazine (CAS 1207176-84-8) can be purchased from commercial sources as well. 2,4-Diphenyl-6-(9,9-spirobi(9H-fluoren)-4-yl)-1,3,5-triazine (1561044-71-0) can be made according to WO 2014/023388 A1.

a) (2,7-di-tert-butyl-9,9-spirobi(fluoren)-4-yl)boronic Acid

##STR00138##

[0208] A solution of 5-bromo-2,7-di-tert-butyl-9,9-spirobi(fluorene) (50.0 g, 98.5 mmol) in THF (1.00 L) is cooled down to 75 C. and n-butyl lithium (47.3 mL, 118 mmol) is added dropwise. The reaction mixture is stirred for 2.5 h at 75 C. before dropwise addition of trimethylborate (14.6 mL, 128 mmol). The mixture is stirred overnight and allowed to come to room temperature. Dest. water (150 mL) is added slowly followed by the addition of HCl (2 N, 30 mL) and dilution of the mixture with ethyl acetate. After phase separation, the aqueous solution is extracted with ethyl acetate. The combined organic layers are washed with dest. water and sat. NaCl-solution and dried over Na.sub.2SO.sub.4, subsequently. The solvent is removed under reduced pressure and the residue is separated by chromatography (heptane:ethyl acetate=4:1).

[0209] The yield is 23.1 g (48.9 mmol), corresponding to 50% of theory.

[0210] In an analogous manner, it is possible to obtain the following compounds:

TABLE-US-00002 TABLE 1 Examples for Boronic Acid formation [00139] [00140] 50% [00141] [00142] 84% CAS 393841-81-1 CAS 1241891-39-3 [00143] [00144] 82% CAS 2529935-30-4 [00145] [00146] 46% [00147] [00148] 51% CAS 2102016-91-9 [00149] [00150] 53% CAS 270741-67-5 [00151] [00152] 82% CAS 2768772-14-9 [00153] [00154] 42% CAS 2260634-40-8 [00155] [00156] 84% CAS 2413294-33-2 [00157] [00158] 43% CAS 1469898-65-4

b) 2-(2,7-di-tert-butyl-9,9-spirobi(fluoren)-2-yl)-4,6-diphenyl-1,3,5-triazine (2)

##STR00159##

[0211] 2-chloro-4,6-diphenyl-1,3,5-triazine (9.90 g, 37.0 mmol) and (2,7-di-tert-butyl-9,9-spiro(fluoren)4-yl)-boronic acid (19.2 g, 40.7 mmol) are solved in 1,4-dioxane (119 mL) and toluene (119 mL). The solution is warmed up to 40 C. and tetrakis(triphenylphosphine)palladium(0) (430 mg, 0.372 mmol) were added. Potassium carbonate (5.62 g, 41.0 mmol) is dissolved in dest. Water (44.2 mL) and added dropwise at 40 C. The reaction mixture is heated to reflux for 2.5 h. After cooling down to room temperature, ethyl acetate and water are added. The aqueous layer is extracted with ethyl acetate. The combined organic layers are washed with sat. aq. NaCl-solution and dried over Na.sub.2SO.sub.4. The solvent is removed under reduced pressure and the residue is separated by chromatography (heptane:toluene=1:1), followed by an additional recrystallization of the material from heptane.

[0212] The yield is 22.2 g (33.4 mmol), corresponding to 90% of theory.

[0213] In an analogous manner, it is possible to obtain the following compounds:

TABLE-US-00003 TABLE 2 Examples for Triazine formation [00160] [00161] CAS 3842-55-5 [00162] 90% 2 [00163] CAS 1241891-39-3 [00164] CAS 3842-55-5 [00165] 91% 1 [00166] [00167] CAS 3842-55-5 [00168] 76% 3 [00169] CAS 2641506-54-7 [00170] CAS 3842-55-4 [00171] 53% 4 [00172] [00173] CAS 3842-55-5 [00174] 92% 12 [00175] [00176] CAS 3842-55-5 [00177] 92% 51 [00178] [00179] CAS 3842-55-5 [00180] 90% 54 [00181] [00182] CAS 3842-55-5 [00183] 83% 18 [00184] [00185] CAS 3842-55-5 [00186] 75% 82 [00187] CAS 1241891-39-3 [00188] CAS 1300115-09-6 [00189] 90% 33 [00190] [00191] CAS 3842-55-5 [00192] 74% 114 [00193] CAS 1241891-39-3 [00194] CAS 1472062-94-4 [00195] 89% 20 [00196] [00197] CAS 3842-55-5 [00198] 84% 17 [00199] CAS 1241891-39-3 [00200] CAS 253158-13-3 [00201] 90% 40 [00202] [00203] CAS 1472062-95-5 [00204] 87% CAS 1241891-39-3 36 [00205] CAS 1241891-39-3 [00206] [00207] 67% 2074632-09-8 116 [00208] [00209] CAS 2142681-84-1 [00210] 72% 92 [00211] CAS 1241891-39-3 [00212] CAS 2915-16-4 [00213] 54% 61

B) Device Examples

1) General Production Process for the OLEDs and Characterization of the OLEDs

[0214] Glass plaques which have been coated with structured ITO (indium tin oxide) in a thickness of 50 nm form the substrates to which the OLEDs are applied.

[0215] The OLEDs basically have the following layer structure: substrate/optional interlayer (IL)/hole injection layer (HIL)/hole transport layer (HTL)/electron blocking layer (EBL)/emission layer (EML)/optional hole blocking layer (HBL)/electron transport layer (ETL)/optional electron injection layer (EIL) and finally a cathode. The cathode is formed by an aluminium layer of thickness 100 nm. The exact structure of the OLEDs can be found in the tables which follow. The structure of the OLEDs produced and the materials used for production of the OLEDs are shown in tables 3 and 4 below.

[0216] All materials are applied by thermal vapour deposition in a vacuum chamber. In this case, the emission layer consists of at least one matrix material (host material) and an emitting dopant which is added to the matrix material(s) in a particular proportion by volume by co-evaporation.

[0217] Details given in such a form as H:SEB (5%) mean here that the material H is present in the layer in a proportion by volume of 95% and SEB in a proportion of 5%. Analogously, the electron transport layer may also consist of a mixture of two materials.

[0218] The OLEDs are characterized in a standard manner. For this purpose, the electroluminescence spectra, the current efficiency (CE, measured in cd/A) and the external quantum efficiency (EQE, measured in %) are determined as a function of luminance, calculated from current-voltage-luminance characteristics assuming Lambertian emission characteristics, as is the lifetime. The electroluminescence spectra are determined at a luminance of 1000 cd/m.sup.2, and the CIE 1931 x and y colour coordinates are calculated therefrom. The parameter U1000 in table 5 refers to the voltage which is required for a luminance of 1000 cd/m.sup.2. CE1000 and EQE1000 respectively denotes the current efficiency and external quantum efficiency that is attained at 1000 cd/m.sup.2. Refractive indices are measured using a M-2000 spectroscopic ellipsometer from J. A, Woollam Co., Inc. using a Cauchy model.

2) Use and Benefit of the Inventive Compounds in OLEDs

[0219] Improved efficiency in blue OLED devices is found when the recombination (emission) zone is narrow and confined close to the EML:EBL interface. Blue OLED typically make use of the cavity effect (especially in Top Emission devices) to more efficiently outcouple the generated light. Electron transport or hole blocking materials with low refractive indices can further improve light outcoupling and hence improve EQE. Electron transport or hole blocking materials with high glass transition temperature Tg allow an easier and more reliable processing with less formation of defect devices. The glass transition temperature Tg is determined in accordance with DIN EN ISO 11357-2 (2014).

2a) Use of Compounds of the Invention as Electron Transport Material in the Electron Transport Layer of OLEDs

[0220] When the inventive compounds ETM-3, ETM 4 and ETM-5 are used as electron transport material, a better efficiency (examples E1.1, E2.1 and E2.2) is achieved than with the substances ETM-1 and ETM-2 according to the prior art (examples C1 to C2). When the inventive compounds ETM-3 to ETM-6 are used as hole blocking material, significantly better efficiency and a better driving voltage are observed (examples, E4.1, E4.2 and E4.3) compared to ETM-2 according to prior art (example C4). Additional performance improvement can be observed when ETM-3 to ETM-6 are used as hole blocking material (examples E5 and E6) as better efficiency and better driving voltage are observed compared to ETM-1 and ETM-2 according to the prior art (examples C5 to C6).

[0221] Table 5 collates the results for the performance data of the OLEDs from examples. Additional material parameters can be found in Table 6.

TABLE-US-00004 TABLE 3 Structure of the OLEDs HIL HTL EBL EML HBL ETL EIL Thick- Thick- Thick- Thick- Thick- Thick- Thick- Ex. ness/nm ness/nm ness/nm ness/nm ness/nm ness/nm ness/nm C1 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-1:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 30 nm 1 nm E1.1 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-3:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 30 nm 1 nm C2 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-2:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 30 nm 1 nm E2.1 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-4:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 30 nm 1 nm E2.2 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-5:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 30 nm 1 nm C3 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-1 ETM:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm E3.1 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-3 ETM:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm C4 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-2 ETM:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm E4.1 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-4 ETM:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm E4.2 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-5 ETM:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm E4.3 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-6 ETM:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm C5 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-1 ETM-1:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm E5.1 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-3 ETM-3:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm C6 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-2 ETM-2:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm E6.1 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-4 ETM-4:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm E6.2 HTM:p-Dopant (5%) HTM EBM H:SEB(5%) ETM-5 ETM-5:LiQ(50%) LiQ 10 nm 180 nm 10 nm 20 nm 10 nm 30 nm 1 nm

[0222] In Table 3, C denotes a Comparative Example and E denotes an Example of the present invention.

TABLE-US-00005 TABLE 4 Structural formulae of the materials for the OLEDs [00214] HTM [00215] P-dopant [00216] EBM [00217] H [00218] SEB [00219] ETM-1 (reference material) [00220] ETM-2 (reference material) [00221] ETM-3 (material of this invention) [00222] ETM-4 (material of this invention) [00223] ETM-5 (material of this invention) [00224] ETM-6 (material of this invention) [00225] ETM [00226] LiQ

TABLE-US-00006 TABLE 5 Data of the OLEDs U1000 CE1000 EQE 1000 CIE x/y at Examples (V) (cd/A) (cd/m.sup.2) 1000 cd/m.sup.2 C1 3.63 8.65 9.30 0.14/0.17 E1.1 3.74 8.57 9.60 0.14/0.11 C2 3.70 8.67 9.48 0.14/0.14 E2.1 3.96 8.96 9.52 0.14/0.14 E2.2 4.07 8.82 9.52 0.14/0.14 C3 3.72 8.82 9.26 0.14/0.17 E3.1 3.88 9.08 10.71 0.14/0.11 C4 3.82 8.48 9.52 0.14/0.14 E4.1 3.71 9.34 10.83 0.14/0.14 E4.2 3.71 9.75 11.01 0.14/0.14 E4.3 3.78 9.57 11.24 0.14/0.14 C5 3.77 8.73 9.35 0.14/0.14 E5.1 3.78 9.15 10.93 0.14/0.1 C6 3.80 9.13 9.91 0.14/0.14 E6.1 4.22 9.53 10.83 0.14/0.14 E6.2 4.43 9.36 10.65 0.14/0.14

TABLE-US-00007 TABLE 6 Data of the materials Ex. RI (620 nm) RI (550 nm) RI (460 nm) Tg ( C.) ETM-1 1.76 1.79 1.83 134 C. ETM-2 1.74 1.77 1.80 132 C. ETM-3 1.68 1.71 1.74 145 C. ETM-4 1.67 1.70 1.72 141 C. ETM-5 1.68 1.70 1.73 145 C. ETM-6 1.63 1.65 1.68 138 C.

[0223] The present Examples and Comparative Examples show an unexpected lowering in refractive indices (RI) over the whole range of wavelength as shown in Table 6. In addition thereto, the efficiency and external quantum efficiency are improved. Furthermore, the Examples E4.1, E4.2 and E4.3 show that also an improvement in operating voltage can be achieved with the compounds of the present invention.