A new series of pyrenyl-based triarylamines: syntheses, structures, optical properties, electrochemistry and electroluminescence

Abstract

Five dipyrenyl-based triarylamines N-p-(R)-phenyl-N,N-dipyrenyl-1-amine (R = H (2a), CH₃ (2b), OCH₃ (2c), F (2d), NO₂ (2e)) and one tripyrenyl-based triarylamine N,N-bis(7-tert-butylpyren-1-yl)-N-pyrenyl-1-amine (3py) were successfully synthesized by copper- and palladium-catalyzed coupling reactions in high yields. These compounds were structurally characterized and their photoelectric properties were analyzed by spectroscopy, electrochemical and theoretical studies. Moreover, the structures of 2b, 2c and 2d were determined by single-crystal X-ray diffraction analysis, indicating that the three compounds are all twisted paddle-like structures with a nitrogen atom as the linking center and the substituent attached to the para position of the benzene ring has an important effect on the intermolecular interactions. Compounds 2a–2d and 3py show green fluorescence emissions with excellent absolute fluorescence quantum yields in toluene (66.06–86.06%). Compound 2e displays a faint emission with a very low quantum yield because of the effect of the strong electron-withdrawing nitro group. They are thermally stable with decomposition temperatures above 355 °C. Organic light-emitting diodes incorporating the materials 2c and 2d as non-doped emitters were fabricated.