Synthesis of Conjugated Carbazole Trimers and Pentamers by Suzuki Coupling

Abstract A series of N ‐alkylcarbazol‐3,6‐diyl trimers and pentamers has been synthesized by stepwise Suzuki coupling. The trimers with isopropyl and longer alkyl substituents at the nitrogen atom and all the pentamers form stable glasses with glass transition temperatures varying from 30 to 148 °C for the trimers and 65 to 104 °C for the pentamers. The ionization potential of the N ‐alkylcarbazol‐3,6‐diyl trimers is 5.25 eV and 5.20 eV for the pentamers. N ‐alkylcarbazol‐3,6‐diyl compounds typically exhibit hole‐drift mobilities in the range of 10 −4 –10 −6 cm 2 · V −1 · s −1 . The highest hole‐drift mobility observed in an amorphous film of N ‐octylcarbazol‐3,6‐diyl pentamer reached 10 −3 cm 2 · V −1 · s −1 at an applied electric field of 8.1 × 10 5 V · cm −1 . magnified image