Compounds of the formula, where the following applies to the symbols and indices used: X is on each occurrence, identically or differently, N, P, As, Sb, P=O, As=O or Sb=O; Y is, identically or differently on each occurrence, O, S, C(R 1) 2, C=O, C=S, C=NR 1, C=C(R 1) 2, Si(R 1) 2, BR 1, NR 1, PR 1, AsR 1, SbR 1, BiR 1, P(=O)R 1, As(=O)R 1, Sb(=O)R 1, Bi(=O)R 1, SO, SeO, TeO, SO 2, SeO 2, TeO 2 or a chemical bond; R 1 is on each occurrence, identically or differently, H, OH, F, CI, Br, I, CN, NO 2, N(Ar) 2, Si(R 2) 3, B(OR 2) 2, C(=O)Ar, P(=O)Ar 2, S(=O)Ar, S(=O)Ar 2, CR 2 =CR 2 Ar, C≡CAr, OSO 2 R 2, a straightchain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 2, where one or more non-adjacent CH 2 groups may be replaced by -R 2 C=CR 2 -, -C=C-, Si(R 2) 2, Ge(R 2) 2, Sn(R 2) 2, C=O, C=S, C=Se, C=NR 2, P(=O)R 2, S=O, SO 2, NR 2, -O-, -S- or -CONR 2 - and where one or more H atoms may be replaced by F, Cl, Br, I, CN or NO 2, or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 2, or an aryloxy or heteroaryloxy group having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2, or a combination of two, three, four or five of these systems; two or more substituents R 1 here, both on the same ring and also on different rings, may also form a mono- or polycyclic, aliphatic, aromatic or heteroaromatic ring system with one another; R is on each occurrence, identically or differently, F, Br, I, CHO, B(OR 2) 2, P(R 2) 2, N(Ar) 2, R 2 C=CR 2 Ar, C≡CAr or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more non-aromatic radicals R 1, or a combination of two, three, four or five of these radicals; R 2 is on each occurrence, identically or differently, H or an aliphatic, aromatic and/or heteroaromatic hydrocarbon radical having 1 to 20 C atoms, where two or more radicals R 2 may also form a ring system with one another; Ar is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5-30 aromatic ring atoms, which may be substituted by one or more non-aromatic radicals R 1; n is on each occurrence, identically or differently, 0, 1 or 2, where n = 0 means that a hydrogen or radical R 1 is present instead of Y, with the proviso that at least two indices n are not equal to 0; the following compound is excluded from the invention: X is on each occurrence, identically or differently, N, P, As, Sb, P=O, As=O or Sb=O; Y is, identically or differently on each occurrence, O, S, C(R 1) 2, C=O, C=S, C=NR 1, C=C(R 1) 2, Si(R 1) 2, BR 1, NR 1, PR 1, AsR 1, SbR 1, BiR 1, P(=O)R 1, As(=O)R 1, Sb(=O)R 1, Bi(=O)R 1, SO, SeO, TeO, SO 2, SeO 2, TeO 2 or a chemical bond; R 1 is on each occurrence, identically or differently, H, OH, F, CI, Br, I, CN, NO 2, N(Ar) 2, Si(R 2) 3, B(OR 2) 2, C(=O)Ar, P(=O)Ar 2, S(=O)Ar, S(=O)Ar 2, CR 2 =CR 2 Ar, C≡CAr, OSO 2 R 2, a straightchain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 2, where one or more non-adjacent CH 2 groups may be replaced by -R 2 C=CR 2 -, -C=C-, Si(R 2) 2, Ge(R 2) 2, Sn(R 2) 2, C=O, C=S, C=Se, C=NR 2, P(=O)R 2, S=O, SO 2, NR 2, -O-, -S- or -CONR 2 - and where one or more H atoms may be replaced by F, Cl, Br, I, CN or NO 2, or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 2, or an aryloxy or heteroaryloxy group having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2, or a combination of two, three, four or five of these systems; two or more substituents R 1 here, both on the same ring and also on different rings, may also form a mono- or polycyclic, aliphatic, aromatic or heteroaromatic ring system with one another; R is on each occurrence, identically or differently, F, Br, I, CHO, B(OR 2) 2, P(R 2) 2, N(Ar) 2, R 2 C=CR 2 Ar, C≡CAr or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more non-aromatic radicals R 1, or a combination of two, three, four or five of these radicals; R 2 is on each occurrence, identically or differently, H or an aliphatic, aromatic and/or heteroaromatic hydrocarbon radical having 1 to 20 C atoms, where two or more radicals R 2 may also form a ring system with one another; Ar is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5-30 aromatic ring atoms, which may be substituted by one or more non-aromatic radicals R 1; n is on each occurrence, identically or differently, 0, 1 or 2, where n = 0 means that a hydrogen or radical R 1 is present instead of Y, with the proviso that at least two indices n are not equal to 0;