Synthesis and photophysical properties of fluorescent 8,9-diarylbenzo[def]carbazoles

Background: Benzocarbazole has attracted much attention from scientists in the past few decades for a variety of applications in materials science. Objective: Herein we report the synthesis and photophysical properties of N-acyl and N-free 8,9-diarylbenzo[def]carbazoles. Methods: These benzo[def]carbazoles were prepared by Pd(II)-catalyzed C-H bond activation and deacetylation as the key steps, and their photophysical properties were studied by measurement of absorption and emission spectra in chloroform at room temperature. Results: The 8,9-diarylbenzo[def]carbazoles show lower LUMO energy levels and smaller HOMO/LUMO gap compared to the parent benzo[def]carbazole, and the N-unprotected 8,9-diarylbenzo[def]carbazoles show more red-shifted fluorescent emission compared to the N-acyl ones. The absorption and emissionmaxima of these 8,9-diaryl-substituted benzo[def]carbazoles in CHCl₃ were in the ranges of 278–350 and 365–426 nm, respectively, and with quantum yields (Φ_F) up to 0.62. Conclusions: We have demonstrated the photophysical properties of 8,9-diaryl substituted benzo[def]carbazoles with or without N-acetyl group. These 8,9-diaryl substituted benzo[def]carbazoles could be good candidates for the future development of functional organic molecules.