Dibenzothiophene/Oxide and Quinoxaline/Pyrazine Derivatives Serving as Electron-Transport Materials


  • We thank the Academia Sinica, National Taiwan University, National Chiao Tung University and the National Science Council for supporting this work. Supporting Information is available from Wiley InterScience or from the authors.


A series of 2,8-disubstituted dibenzothiophene and 2,8-disubstituted dibenzothiophene-S,S-dioxide derivatives containing quinoxaline and pyrazine moieties are synthesized via three key steps: i) palladium-catalyzed Sonogashira coupling reaction to form dialkynes; ii) conversion of the dialkynes to diones; and iii) condensation of the diones with diamines. Single-crystal characterization of 2,8-di(6,7-dimethyl-3-phenyl-2-quinoxalinyl)-5H-5λ6-dibenzo[b,d]thiophene-5,5-dione indicates a triclinic crystal structure with space group P1 and a non-coplanar structure. These new materials are amorphous, with glass-transition temperatures ranging from 132 to 194 °C. The compounds (Cpd) exhibit high electron mobilities and serve as effective electron-transport materials for organic light-emitting devices. Double-layer devices are fabricated with the structure indium tin oxide (ITO)/Qn/Cpd/LiF/Al, where yellow-emitting 2,3-bis[4-(N-phenyl-9-ethyl-3-carbazolylamino)phenyl]quinoxaline (Qn) serves as the emitting layer. An external quantum efficiency of 1.41 %, a power efficiency of 4.94 lm W–1, and a current efficiency of 1.62 cd A–1 are achieved at a current density of 100 mA cm–2.