Materials for organic electroluminescent devices

1. An organic electroluminescent device which comprises a compound of the formula (2a)

where the following applies to the symbols and indices used:

Ar is on each occurrence, identically or differently, a phenylene group, which is optionally substituted by one or more radicals R; wherein the phenylene is identically or differently selected from the formulae (3), (4) or (5),

 where the dashed bond in each case indicates the linking of these groups and each of these groups is optionally substituted by one or more radicals R and wherein at least one of the phenylene groups is a group of formula (4) or formula (5),

Ar 1 is an aromatic ring system having 6 to 24 aromatic ring atoms which contains no condensed aryl groups having more than 10 aromatic ring atoms and which is optionally substituted by one or more radicals R 1 , or is a dibenzofuran or dibenzothiophene group, each of which is optionally substituted by one or more radicals R 1 ;

Ar 2 is on each occurrence, identically or differently, an aryl group, where the aryl group has 6 to 10 aromatic ring atoms and is optionally substituted by one or more non-aromatic radicals R 1 , or is a dibenzofuran or dibenzothiophene group, each of which is optionally substituted by one or more radicals R 1 ;

R is on each occurrence, identically or differently, H, D, F, CN, an aryl group, a biaryl group, a triaryl group or quateraryl group, where each individual aryl group in the above-mentioned groups has 6 to 10 aromatic ring atoms and is optionally substituted by one or more radicals R 1 , or a carbazole group which is linked via a carbon atom and which may also be substituted by one or more radicals R 1 ;

R 1 is on each occurrence, identically or differently, H, D, F, CN, a straight-chain alkyl or alkoxy group having 1 to 20 C atoms or a branched or cyclic alkyl or alkoxy group having 3 to 20 C atoms, where one or more non-adjacent CH 2 groups is optionally replaced by R 2 C═CR 2 , C≡C or O and where one or more H atoms is optionally replaced by D or F, or an aryl group having 6 to 10 C atoms, which is optionally substituted by one or more radicals R 2 , or is a dibenzofuran or dibenzothiophene group, each of which is optionally substituted by one or more radicals R 2 , or a carbazole group which is linked via a carbon atom and which may also be substituted by one or more radicals R 2 , or an aralkyl group having 6 to 10 aromatic ring atoms, which is optionally substituted by one or more radicals R 2 ; two adjacent substituents R 1 here, together with the atoms to which they are bonded, may also form a mono- or polycyclic, aliphatic ring system with one another;

R 2 is on each occurrence, identically or differently, H, D or an aliphatic hydrocarbon radical having 1 to 20 C atoms or an aryl group having 6 to 10 ring atoms;

n is 2, 3 or 4,

wherein the compound of the formula (2a) is employed as matrix material for phosphorescent emitters in an emitting layer.

2. The organic electroluminescent device according to claim 1 , wherein the group —(Ar) n — is selected from the formulae (9) to (18),

where the dashed bond in each case indicates the linking of these groups, each of these groups may also be substituted by one or more radicals R, and R and R 1 have the meanings given in claim 1 .

3. The organic electroluminescent device according to claim 1 , wherein the radical R is selected, identically or differently on each occurrence, from the group consisting of H, D, F, CN, phenyl, biphenyl or terphenyl, where each of the aryl groups in the above-mentioned groups is optionally substituted by one or more radicals R 1 , and R 1 stands, identically or differently on each occurrence, for H or an alkyl group having 1 to 5 C atoms; or a carbazole group which is linked via a carbon atom and which is optionally substituted by one or more radicals R 1 .

4. The organic electroluminescent device according to claim 1 , wherein Ar 1 is selected from the group consisting of phenyl, biphenyl, terphenyl or quaterphenyl, each of which is optionally substituted by one or more radicals R 1 .

5. The organic electroluminescent device according to claim 1 , wherein Ar 2 is selected, identically on each occurrence, from the group consisting of phenyl which is optionally substituted by one or more non-aromatic radicals R 1 .

6. The organic electroluminescent device according to claim 1 , wherein the following applies to the symbols and indices:

n=2 or 3;

R is selected, identically or differently on each occurrence, from the group consisting of H, D, F, CN, phenyl, biphenyl or terphenyl, where each of the aryl groups is optionally substituted by one or more radicals R 1 , and R 1 stands, identically or differently on each occurrence, for H or an alkyl group having 1 to 5 C atoms; or a carbazole group which is linked via a carbon atom and which may also be substituted by one or more radicals R 1 ;

Ar 1 is selected from the group consisting of phenyl, biphenyl, terphenyl or quaterphenyl, each of which is optionally substituted by one or more radicals R 1 ;

Ar 2 is selected, identically on each occurrence, from the group consisting of phenyl which is optionally substituted by one or more non-aromatic radicals R 1 ;

R 1 is selected on each occurrence, identically or differently, from the group consisting of H, D, F, a straight-chain alkyl group having 1 to 10 C atoms or a branched or cyclic alkyl group having 3 to 10 C atoms, where one or more non-adjacent CH 2 groups is optionally replaced by R 2 C═CR 2 and where one or more H atoms is optionally replaced by F, or an aryl group having 6 to 10 C atoms, which is optionally substituted by one or more radicals R 2 , or is a dibenzofuran or dibenzothiophene group, each of which is optionally substituted by one or more radicals R 2 , or a carbazole group which is linked via a carbon atom and which may also be substituted by one or more radicals R 2 .

7. The organic electroluminescent device according to claim 1 , wherein Ar is on each occurrence, identically or differently, a phenylene group, which is optionally substituted by one or more radicals R.

8. The organic electroluminescent device according to claim 1 , wherein n=2 or 3.

9. The organic electroluminescent device according to claim 1 , wherein Ar 2 are identical.