Under basic conditions, the electron-deficient 3-nitro-3'-bromo-6,6'-difluorodicyanobiphenyl undergoes an uncommon nucleophilic aromatic substitution (S_NAr) reaction with one equiv. of carbazole, in which the nitro group on the ring is replaced by a 9-carbazolyl, to afford compound 1, whereas in the same reactions with two equiv. of carbazole and ditertbutylcarbazole, respectively, the nitro group and the fluorine atom on the same benzene ring are substituted by 9-carbazolyl or 9-ditertbutylcarbazolyl to produce compounds 2a,b. Compound 2a undergoes a Pd-catalyzed Suzuki coupling with 3-formylphenylboronic acid to give compound 3. The structures and compositions of the products have been studied using spectroscopic methods, elemental analysis (2b), X-ray diffraction (2a and 3), as well as density functional theory (DFT) calculations, and the mechanism of the S_NAr reaction is discussed. Investigations on the emission properties show that compounds 1-3 exhibit thermally activated delayed fluorescence (TADF) properties. These results provide new ideas for the design and synthesis of unsymmetric biphenyl TADF compounds.

Key words: Biphenyl, Nucleophilic Aromatic Substitution (S_NAr), Electron-Deficient, Thermally Activated Delayed Fluorescence (TADF)