The present invention provides compounds of formulae (1) (2) wherein R1 and R2 are C1-30alkyl, C2-3O-alkenyl, C2-30-alkynyl, C5-7-cycloalkyl, C6-14-aryl or 5 to 14 membered heteroaryl, wherein C1-30-alkyl, C2-3O-alkenyl and C2-3O-alkynyl can be substituted with one or more substituents selected from the group consisting of halogen, phenyl, O—C1-20-alkyl, O—C2-20-alkenyl and O—C2-2O-alkynyl, and wherein C5-7-cycloalkyl, C6-14-aryl and 5 to 14 membered heteroaryl can be substituted with one or more substituents selected from the group consisting of halogen, C1-20alkyl, C2-2O-alkenyl, C2-2O-alkynyl, O—C1-20-alkyl, O—C2-2o-alkenyl and O—C2-2o-alkynyl, Ra, Rb, Rc and Rd are independently and at each occurrence selected from the group consisting of C1-30alkyl, C2-30-alkenyl, C2-30-alkynyl, C6-14-aryl and 5 to 14 membered heteroaryl, wherein C1-30-alkyl, C2-3o-alkenyl and C2-3o-alkynyl can be substituted with one or more substituents selected from the group consisting of halogen, phenyl, O—C1-20-alkyl, O—C2-20-alkenyl and O—C2-20-alkynyl, and wherein C5-7-cycloalkyl, C6-14-aryl and 5 to 14 membered heteroaryl can be substituted with one or more substituents selected from the group consisting of halogen, C1-20alkyl, C2-2o-alkenyl, C2-20-alkynyl, O—C1-20-alkyl, O—C2-20-alkenyl and O—C2-2o-alkynyl, n and o are independently 0, 1, 2, 3, 4 or 5, and m and p are independently 0, 1, 2 or 3, and to electronic device comprising the compounds of formulae 1 or 2.