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.

The synthesis and characterization of novel dipolar fluorescent materials based on a quinoxaline core

“…Similarly, the optical edge was utilized to derive the band gap and the LUMO energies. As expected, these compounds by using quinoxaline as core possess lower LUMO energies and smaller band gaps compared to the simple quinoxaline derivatives [27]. The values (À2.32 to À2.80 eV) are slightly higher than that observed for quinoxaline monomers [23] and quinoxaline heterocycle hybrid polymers [38].…”

“…Similarly, quinoxaline is a useful n-type building block with high electron affinity (electronaccepting character) and good thermal stability. Moreover, quinoxaline has been successfully incorporated in small molecules and polymers as the electron-transport component of OLEDs [23][24][25][26][27].…”

Electropolymerization study of benzothiophenes and characterization of novel poly(dibenzothiophene-S,S-dioxide)

“…Now, research on TOs is growing rapidly [5] and TO-containing compounds [6][7][8][9][10][11][12] can emit light under UV excitation with frequencies covering the entire visible range (from the UV to the NIR) and display high photoluminescence efficiencies (some even up to 70%). In the last few years, extensive research has been also devoted to incorporation of benzothiophene-S,S-dioxide (BTO) [13][14][15] and dibenzothiophene-S,S-dioxide (DBTO) [16][17][18][19][20][21][22][23][24][25][26][27][28] units into various conjugated polymers. By employing BTO, Barbarella et al [13][14][15] designed a series of V-shaped thiophene oligomers, discovering a new family of amorphous molecular materials suitable for electroluminescent devices.…”

Halogen Bonding in the Design of Organic Phosphors

“…The SÁ Á ÁS interaction (assigned to π-π conjugation by σ-type overlap of π-orbitals of two different S atoms) [26] may make the gap between triplet and singlet ground states narrower and sequentially phosphorescence weaker compared with the case of cocrystal 9. It may also provide the cocrystal with additional functions, such as electron transport [45,46]. The phosphorescent decays of both 9 and 10 obey a monoexponential law with a lifetime of 2.75 ms for cocrystal 9 and 2.50 ms for 10, respectively (Figs.…”