Compounds of the formula where the following applies to the symbols and indices used: Y is N; Ar 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; X is on each occurrence, identically or differently, a group selected from C(R 1) 2 and Si(R 1) 2; Z is C if a group X is bonded to the group Z or is CR if no group X is bonded to the group Z; W is CH; R is on each occurrence, identically or differently, H, D, a straight-chain alkyl group having 1 to 10 C atoms or a branched or cyclic alkyl group having 3 to 10 C atoms, each of which may be substituted by one or more radicals R 2; E is on each occurrence, identically or differently, a single bond, N(R 1), O, S, C(R 1) 2, C(R 1) 2 -C(R 1) 2, Si(R 1) 2 or B(R 1); R 1 is on each occurrence, identically or differently, H, D, F, Cl, Br, I, CN, NO 2, B(OR 2) 2, Si(R 2) 3, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a straight-chain alkenyl or alkynyl group having 2 to 40 C atoms or a branched or cyclic alkyl, alkenyl, alkynyl, 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, -0-, -S-, -COO- 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 non-aromatic radicals R 1, or an aryloxy or heteroaryloxy group having 5 to 40 aromatic ring atoms, which may be substituted by one or more non-aromatic radicals R 1, or a combination of these systems; two or more substituents R 1 here may also form a mono- or polycyclic 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; m, n are 0 or 1, with the proviso that m + n = 1; q is on each occurrence 1; s is 1 or 2; t is on each occurrence, identically or differently, 0 or 1, where t = 0 means that radicals R 1 are bonded instead of the group E; furthermore, t = 0 if q = 0; v is 0 or 1, where, for v = 0, hydrogen or a radical R is bonded instead of the group Y; characterised in that at least one radical R represents a substituent other than H or D. Y is N; Ar 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; X is on each occurrence, identically or differently, a group selected from C(R 1) 2 and Si(R 1) 2; Z is C if a group X is bonded to the group Z or is CR if no group X is bonded to the group Z; W is CH; R is on each occurrence, identically or differently, H, D, a straight-chain alkyl group having 1 to 10 C atoms or a branched or cyclic alkyl group having 3 to 10 C atoms, each of which may be substituted by one or more radicals R 2; E is on each occurrence, identically or differently, a single bond, N(R 1), O, S, C(R 1) 2, C(R 1) 2 -C(R 1) 2, Si(R 1) 2 or B(R 1); R 1 is on each occurrence, identically or differently, H, D, F, Cl, Br, I, CN, NO 2, B(OR 2) 2, Si(R 2) 3, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a straight-chain alkenyl or alkynyl group having 2 to 40 C atoms or a branched or cyclic alkyl, alkenyl, alkynyl, 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, -0-, -S-, -COO- 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 non-aromatic radicals R 1, or an aryloxy or heteroaryloxy group having 5 to 40 aromatic ring atoms, which may be substituted by one or more non-aromatic radicals R 1, or a combination of these systems; two or more substituents R 1 here may also form a mono- or polycyclic 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; q is on each occurrence 1; s is 1 or 2; t is on each occurrence, identically or differently, 0 or 1, where t = 0 means that radicals R 1 are bonded instead of the group E; furthermore, t = 0 if q = 0; v is 0 or 1, where, for v = 0, hydrogen or a radical R is bonded instead of the group Y;