Diaryliodonium Salts Enabled Arylation, Arylocyclization, and Aryl-Migration

Our research interest focusing on synthetic methodology with diaryliodonium salts, is summarized in this account. Besides employing a dual activation strategy of C-I and ortho C-H bonds, we have introduced vicinal functional groups at ortho-positions of diaryliodonium salts, in which their unique reactivities have been explored in various processes, including arylation, diarylation, cascade annulation, benzocyclization, arylocyclization, and intramolecular aryl migration. The variety of mechanisms of these reactions that involves either transition metals, especially palladium in organometallic catalysis, or transition-metal free conditions, were discussed in the context.

Pure Hydrocarbon Materials as Highly Efficient Host for White Phosphorescent Organic Light‐Emitting Diodes: A New Molecular Design Approach

To date, all efficient host materials reported for phosphorescent OLEDs (PhOLEDs) are constructed with heteroatoms, which have a crucial role in the device performance. However, it has been shown in recent years that the heteroatoms not only increase the design complexity but can also be involved in the instability of the PhOLED, which is nowadays the most important obstacle to overcome. Herein, we design pure aromatic hydrocarbon materials (PHC) as very efficient hosts in high‐performance white and blue PhOLEDs. With EQE of 27.7 %, the PHC‐based white PhOLEDs display similar efficiency as the best reported with heteroatom‐based hosts. Incorporated as a host in a blue PhOLED, which are still the weakest links of the technology, a very high EQE of 25.6 % is reached, surpassing, for the first time, the barrier of 25 % for a PHC and FIrpic blue emitter. This performance shows that the PHC strategy represents an effective alternative for the future development of the OLED industry.

Structurally Nontraditional Bipolar Hosts for RGB Phosphorescent OLEDs: Boosted by a "Butterfly-Shaped" Medium-Ring Acceptor

The emitting layer based on a host-guest system plays a crucial role in organic light-emitting diodes (OLEDs). While emitters have witnessed rapid progress in structural diversity, hosts still rely heavily on traditional structures and are underdeveloped. Herein a "medium-ring" strategy has been put forward to design structurally nontraditional host molecules, which are not only rotatable enough to suppress close π-π stacking, thus reducing exciton annihilation, but also rigid enough to prevent excessive conformational flipping, thus inhibiting non-radiative decay. Accordingly, a brand-new type of bipolar hosts with a twisted "butterfly-shaped heptagonal acceptor (EtBP), which features an electron-deficient benzophenone fragment with a flexible ethylidene bridge, has been developed. With satisfactory morphological stability and well-balanced hole- and electron-transporting properties, the EtBP-based bipolar hosts enable high-performance RGB phosphorescent OLEDs with small efficiency roll-off, which are superior to those of acyclic benzophenone-based devices.