Compounds of the formula, where the following applies to the symbols and indices used: Y is on each occurrence N, P, P=O, PF 2, P=S, As, As=O, As=S, Sb, Sb=O, Sb=S, C=O, O, S, Se, Te, S=O, SO 2, Se=O, SeO 2, Te=O or TeO 2; Ar 1, Ar 2, Ar 3 are benzene, which may in each case be substituted by one or two radicals R 1; Ar 4 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 1; R 1 is on each occurrence, identically or differently, H, F, Cl, Br, I, CN, NO 2, Si(R 2) 3, a straight-chain 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, which may in each case 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, -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 40 aromatic ring atoms, which may be substituted by one or more radicals R 2, or a combination of these systems; two or more substituents R 1 may also form a mono- or polycyclic aliphatic ring system with one another; R 2 is on each occurrence, identically or differently, H or an aliphatic or aromatic hydrocarbon radical having 1 to 20 C atoms; X 1, X 4 are on each occurrence, identically or differently, a bridge which, with Ar 1 and Ar 2, forms a cyclic system, selected from C(R 1) 2, Si(R 1) 2, C=O, C=NR 1, C=C(R 1) 2, O, S, S=O, SO 2, N(R 1), P(R 1), P(=O)R 1, P(=S)R 1, B(R 1) or a combination of two, three or four of these groups; X 2, X 3 are on each occurrence, identically or differently, X 1 and, with Ar 2 and Ar 3, form a cyclic ring system; n, o, p are on each occurrence, identically or differently, 0 or 1, with the proviso that, if Y is from the fifth main group, n, p and o may only simultaneously be 0 if q = 3; n = 0 or o = 0 or p = 0 means that two H atoms or radicals R 1 are present instead of the bridge; q is 1, 2 or 3 if Y is bonded via an element from the fifth main group, and is 2 if Y is bonded via oxygen, and is 1 or 2 if Y is bonded via another element from the sixth main group; r is (3 - q) if Y is bonded via an element from the fifth main group, and is (2 - q) if Y is bonded via another element from the sixth main group. Y is on each occurrence N, P, P=O, PF 2, P=S, As, As=O, As=S, Sb, Sb=O, Sb=S, C=O, O, S, Se, Te, S=O, SO 2, Se=O, SeO 2, Te=O or TeO 2; Ar 1, Ar 2, Ar 3 are benzene, which may in each case be substituted by one or two radicals R 1; Ar 4 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 1; R 1 is on each occurrence, identically or differently, H, F, Cl, Br, I, CN, NO 2, Si(R 2) 3, a straight-chain 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, which may in each case 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, -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 40 aromatic ring atoms, which may be substituted by one or more radicals R 2, or a combination of these systems; two or more substituents R 1 may also form a mono- or polycyclic aliphatic ring system with one another; R 2 is on each occurrence, identically or differently, H or an aliphatic or aromatic hydrocarbon radical having 1 to 20 C atoms; X 1, X 4 are on each occurrence, identically or differently, a bridge which, with Ar 1 and Ar 2, forms a cyclic system, selected from C(R 1) 2, Si(R 1) 2, C=O, C=NR 1, C=C(R 1) 2, O, S, S=O, SO 2, N(R 1), P(R 1), P(=O)R 1, P(=S)R 1, B(R 1) or a combination of two, three or four of these groups; X 2, X 3 are on each occurrence, identically or differently, X 1 and, with Ar 2 and Ar 3, form a cyclic ring system; n, o, p are on each occurrence, identically or differently, 0 or 1, with the proviso that, if Y is from the fifth main group, n, p and o may only simultaneously be 0 if q = 3; n = 0 or o = 0 or p = 0 means that two H atoms or radicals R 1 are present instead of the bridge; q is 1, 2 or 3 if Y is bonded via an element from the fifth main group, and is 2 if Y is bonded via oxygen, and is 1 or 2 if Y is bonded via another element from the sixth main group; r is (3 - q) if Y is bonded via an element from the fifth main group, and is (2 - q) if Y is bonded via another element from the sixth main group.