NOVELTY - (Hetero)cyclic compounds (I) are new.    USE - (I) are useful: for producing oligomer, polymer or dendrimer; and in an electronic device including organic integrated circuits, organic FETs, organic thin-film transistors, organic light-emitting transistors, organic solar cells, organic optical detectors, organic photoreceptors, organic field-quench devices, organic light-emitting electrochemical cells, organic laser diodes or organic electroluminescent devices (all claimed). The electronic device is useful in a display as a light source.    ADVANTAGE - (I) improve lifetime, stability and power efficiency of the electronic device.    DETAILED DESCRIPTION - (Hetero)cyclic compounds of formula (I) are new.    Z=CR1 (preferred) or N;    X=C(R2)2 (preferred), BR2, C(R2)2C(R2)2, R2C=CR2, R2C=N, Si(R2)2, Si(R2)2Si(R2)2, C(O), O, S, S(O), SO 2, NR2, PR2, or P(O)R2;    Ar1=aryl or heteroaryl ring system having 6-40 aryl ring atoms, substituted by one or more R1;    R1, R2=C(O)R3, CN, Si(R3) 3, N(R3) 2, P(O)(R3) 2, S(O)R3, SO2R3, linear-chain 1-20C-alkyl or -alkoxy, branched or cyclic 3-20C alkyl or alkoxy, 2-20C alkenyl or alkynyl (all optionally substituted by R3), H, D, F, aryl or heteroaryl ring system having 5-30C aromatic ring atoms that are substituted by one or more radicals R3, or aryloxy- or heteroaryloxy having 5-30C aromatic ring atoms (substituted by R3), where one or more CH 2 groups are replaced by R3C=CR3-, -CC-, Si(R3) 2, C(O), C=NR3, -C(O)O-, -C(O)NR3-, NR3, P(O)(R3), O, S, SO or SO 2, and one or more H atoms are replaced by D, F, Cl, Br or CN, where two or more radicals of R1 and R2 are joined together to form a ring;    R3=C(=O)R4, CN, Si(R4) 3, N(R4) 2, P(=O)(R4) 2, S(=O)R4, S(=O) 2R4, linear-chain 1-20C-alkyl or -alkoxy, branched or cyclic 3-20C-alkyl or -alkoxy, 2-20C-alkenyl or -alkynyl (all optionally substituted by R4), H, D, F, aryl or heteroaryl ring system having 5-30C aromatic ring atoms that are substituted by one or more radicals R3, or aryloxy- or heteroaryloxy having 5-30C aromatic ring atoms (substituted by R3), where one or more CH 2 groups are replaced by R3C=CR3-, -CC-, Si(R3) 2, C=O, C=NR3, -C(O)O-, -C(O)NR3-, NR3, P(O)(R3), O, S, SO or SO 2, and one or more H atoms are replaced by D, F, Cl, Br or CN, where two or more radicals of R1 are joined together to form a ring; and    R4=H, D, F, or aliphatic, aryl or heteroaryl organic radical having 1-20C (in which one or more H atoms are replaced by D or F), where two or more substituents R4 are linked to each other and form a ring.    (I) exclude the compounds, in which aryl or heteroaryl six-membered ring is optionally fused to both compounds A and A1a and does not comprise aryl or heteroaryl six-membered ring attached to one of the other four bonds comprising compounds B, C, B1a and C1a.    INDEPENDENT CLAIMS are included for:    (1) oligomer, polymer or dendrimer comprising (I), where the bond(s) to the polymer, oligomer or dendrimer is located in (I) with R1 or R2 substituted positions;    (2) a formulation comprising (I), the oligomer, polymer or dendrimer and at least one solvent; and    (3) an electronic device comprising (I).