Compound of the formula, where the following applies to the symbols and indices used: R 1, R 2 stand on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, N(R 3) 2, N(Ar) 2, C(=O)Ar, P(=O)(Ar) 2, S(=O)Ar, S(=O) 2 Ar, NO 2, Si(R 3) 3, B(OR 3) 2, OSO 2 R 3, a straight-chain alkyl, alkoxy or thioalkyl groups having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl groups having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 3, an aromatic or heteroaromatic ring systems having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3, or an aryloxy groups having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 3, where two adjacent substituents R 2 may form a mono- or polycyclic, aliphatic ring system or aromatic ring system, which may be substituted by one or more radicals R 3; R 3 stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, N(Ar) 2, C(=O)Ar, P(=O)(Ar) 2, S(=O)Ar, S(=O) 2 Ar, NO 2, Si(R 4) 3, B(OR 4) 2, OSO 2 R 4, a straight-chain alkyl, alkoxy or thioalkyl groups having 1 to 40 C atoms or branched or cyclic alkyl, alkoxy or thioalkyl groups having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 4, an aromatic or heteroaromatic ring systems having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 4, or an aryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 4, where two adjacent substituents R 3 may form a mono- or polycyclic, aliphatic ring system or aromatic ring system, which may be substituted by one or more radicals R 4; R 4 stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CN, a straight-chain alkyl, alkoxy or thioalkyl groups having 1 to 20 C atoms or branched or cyclic alkyl, alkoxy or thioalkyl groups having 3 to 20 C atoms, or an aromatic or heteroaromatic ring system having 5 to 24 C atoms; Ar is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case also be substituted by one or more radicals R 4; n is an integer from 0 to 4. R 1, R 2 stand on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, N(R 3) 2, N(Ar) 2, C(=O)Ar, P(=O)(Ar) 2, S(=O)Ar, S(=O) 2 Ar, NO 2, Si(R 3) 3, B(OR 3) 2, OSO 2 R 3, a straight-chain alkyl, alkoxy or thioalkyl groups having 1 to 40 C atoms or branched or a cyclic alkyl, alkoxy or thioalkyl groups having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 3, an aromatic or heteroaromatic ring systems having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3, or an aryloxy groups having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 3, where two adjacent substituents R 2 may form a mono- or polycyclic, aliphatic ring system or aromatic ring system, which may be substituted by one or more radicals R 3; R 3 stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CHO, CN, N(Ar) 2, C(=O)Ar, P(=O)(Ar) 2, S(=O)Ar, S(=O) 2 Ar, NO 2, Si(R 4) 3, B(OR 4) 2, OSO 2 R 4, a straight-chain alkyl, alkoxy or thioalkyl groups having 1 to 40 C atoms or branched or cyclic alkyl, alkoxy or thioalkyl groups having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 4, an aromatic or heteroaromatic ring systems having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 4, or an aryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 4, where two adjacent substituents R 3 may form a mono- or polycyclic, aliphatic ring system or aromatic ring system, which may be substituted by one or more radicals R 4; R 4 stands on each occurrence, identically or differently, for H, D, F, Cl, Br, I, CN, a straight-chain alkyl, alkoxy or thioalkyl groups having 1 to 20 C atoms or branched or cyclic alkyl, alkoxy or thioalkyl groups having 3 to 20 C atoms, or an aromatic or heteroaromatic ring system having 5 to 24 C atoms; Ar is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case also be substituted by one or more radicals R 4; n is an integer from 0 to 4.