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

Abstract 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.