Compounds of the formulae, and where the following applies to the symbols and indices used: R 2 is, identically or differently on each occurrence, H, D, F, Cl, Br, I, N(R 3) 2, CN, NO 2, Si(R 3) 3, B(OR 3) 2, C(=O)R 3, P(=O)(R 3) 2, S(=O)R 3, S(=O) 2 R 3, OSO 2 R 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, alkylalkoxy or thioalkoxy group having 3 to 40 C atoms, which may in each case be substituted by one or more radicals R 3, where one or more non-adjacent CH2 groups may be replaced by R 3 C=CR 3, C≡C, Si(R 3) 2, Ge(R 3) 2, Sn(R 3) 2, C=O, C=S, C=Se, C=NR 3, P(=O)(R 3), SO, SO 2, NR 3, O, S or CONR 3 and where one or more H atoms may be replaced by D, F, CI, Br, I, CN or NO 2, or an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3, or an aryloxy, arylalkoxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a combination of two or more of these groups; two or more adjacent radicals R 2 may form a mono- or polycyclic, aliphatic or aromatic ring system with one another; R 3 is, identically or differently on each occurrence, H, D, F or an aliphatic, aromatic and/or heteroaromatic hydrocarbon radical having 1 to 40 C atoms, in which, in addition, one or more H atoms may be replaced by F; two or more substituents R 3 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another. R 2 is, identically or differently on each occurrence, H, D, F, Cl, Br, I, N(R 3) 2, CN, NO 2, Si(R 3) 3, B(OR 3) 2, C(=O)R 3, P(=O)(R 3) 2, S(=O)R 3, S(=O) 2 R 3, OSO 2 R 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, alkylalkoxy or thioalkoxy group having 3 to 40 C atoms, which may in each case be substituted by one or more radicals R 3, where one or more non-adjacent CH2 groups may be replaced by R 3 C=CR 3, C≡C, Si(R 3) 2, Ge(R 3) 2, Sn(R 3) 2, C=O, C=S, C=Se, C=NR 3, P(=O)(R 3), SO, SO 2, NR 3, O, S or CONR 3 and where one or more H atoms may be replaced by D, F, CI, Br, I, CN or NO 2, or an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3, or an aryloxy, arylalkoxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a combination of two or more of these groups; two or more adjacent radicals R 2 may form a mono- or polycyclic, aliphatic or aromatic ring system with one another; R 3 is, identically or differently on each occurrence, H, D, F or an aliphatic, aromatic and/or heteroaromatic hydrocarbon radical having 1 to 40 C atoms, in which, in addition, one or more H atoms may be replaced by F; two or more substituents R 3 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another.