Triphenylamine-functionalized tetraphenylpyrazine: facile preparation and multifaceted functionalities

Abstract

Aggregation-induced emission (AIE) is a unique photo-physical phenomenon and has become an emerging and hot research area. With the enthusiastic efforts paid by researchers, hundreds of AIE-active luminogens (AIEgens) have been generated but heterocyclic AIEgens are rarely reported. Recently, we enriched the family of AIEgens and reported a pyrazine-based AIEgen of tetraphenylpyrazine (TPP), which could be facilely functionalized by a post-synthetic strategy. In this work, we further expanded the TPP-based AIE system by covalently attaching one, two or four electron-donating triphenylamine moieties to the TPP core via Suzuki coupling, and TPP–TPA, TPP–2TPA and TPP–4TPA were produced, respectively. Thanks to their donor-π-acceptor structures, these luminogens exhibit multi-functional properties, such as excellent thermal stability (up to 504 °C), large molar absorptivity, bright emission in the solid state (quantum yields up to 35.2%), solvatochromism, and high two-photon absorption cross-sections (up to 480 GM). Furthermore, using TPP–TPA as the emitting layer, a triple-layer device was fabricated and a turn-on voltage, maximum luminance, current efficiency, power efficiency, and external quantum efficiency of 3.7 V, 17 459 cd m⁻², 5.49 cd A⁻¹, 3.18 lm W⁻¹ and 2.88% were realized, respectively. These results indicate a huge potential to develop high-tech applications based on these TPP-based AIEgens.