Synthesis and characterization of efficient luminescent materials based on 2,1,3-benzothiadiazole with carbazole moieties

Two new luminescent materials named 4-bromo-7-carbazyl-[2,1,3]-benzothiadiazole (3) and 4,7-dicarbazyl-[2,1,3]-benzothiadiazole (4) were obtained by a modified Ullmann reaction in one step from 4,7-dibromo-[2,1,3]-benzothiadiazole (2) (based on 2,1,3-benzothiadiazole (1, BTD)) and carbazole. The structure and purity of them were characterized by crystal structures, 1H NMR and elemental analysis. Compared with compounds 1 and 2, the compounds 3 and 4 have better optical properties and thermostability due to the introduction of the carbazole moieties, and the compound 4 shows better performances than that of compound 3. For compound 4, a strong absorption peak at 236 nm with a high extinction coefficient up to 1.205 × 105 L·mol·cm−1 and bright green to orange photoluminescence with quantum yields of 9.0%, 48.4%, 51.0% and 75.6% in different solvents of acetonitrile, dichloromethane, ethyl acetate, and diethyl ether, respectively, were measured.