Crucial role of palladium(0/ii) catalysts in the synthesis of multi-resonance thermally activated delayed fluorescence emitters

Abstract

Boron and nitrogen/oxygen-based multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters represent cutting-edge OLED technology in both academic and industrial research, demonstrating high color purity and power efficiency. However, the advancement of these emitters is somewhat constrained due to limited synthetic methodologies and low yields of the emitters and their respective precursors. Therefore, comprehensive knowledge of synthetic approaches is necessary, particularly concerning the precursors for improved molecular development. Most precursors for the final emitter are synthesized by forming C–C/C–X bonds, involving palladium-based catalysts and additives as crucial reagents. In this review, we thoroughly discuss the synthetic approaches used to prepare the intermediates with the palladium catalyst alongside various ligands, along with most of the recent reports. We also outline the general criteria for selecting the Pd catalyst and ligand, their respective molar equivalents, and the corresponding yields.