The invention relates to compounds of formula (1) which are suitable for use in electronic devices, and to electronic devices, in particular organic electroluminescent devices, containing said compounds. X is, identically or differently in each occurrence, CR or N, or two adjacent X stand for a group of the following formula (2), wherein the dashed bonds mark the bonding of said group in formula (1), with the stipulation that the compound of formula (1) contains one or two groups of formula (2); X1 is, identically or differently in each occurrence, CR or N; Y is, identically or differently in each occurrence, CR or N; Z1, Z2, Z3 are, identically or differently in each occurrence, O, S, N—Ar or CR2.