Dearomatizing [4+1] Spiroannulation of Naphthols: Discovery of Thermally Activated Delayed Fluorescent Materials

De(sulfon)amidative Cyclization: The Synthesis of Dibenzolactams and Dibenzosultams for Organic Light Emitting Diode Materials

This study addresses a challenge in organic synthetic chemistry: the direct cleavage of amide bonds, which is typically hampered by the thermodynamic stability of the C(Ar)-C(acyl) bond. Previous methods often rely on "CO" extrusion-jointing transition metal-catalyzed process and require activated tertiary amides, limiting their applicability due to incompatibility with reactive functional groups such as halogens. Herein, we report a transition metal-free approach for the deamidative cyclization of biaryl diamides via a radical process, yielding dibenzolactam derivatives. Along this line, we have developed the desulfonamidative cyclization of biaryl disulfonamides to produce dibenzosultams through direct nucleophilic aromatic substitution, demonstrating high selectivity for unsymmetrical structures. Additionally, unsymmetrical sulfamoyl biaryl amides, containing both amide and sulfonamide functionalities, can selectively undergo desulfonamidative coupling with the amide to form dibenzolactams, which offers a complementary synthetic pathway to unsymmetric dibenzolactams. These protocols exhibit excellent compatibility with reactive functional groups, including halogens, providing an innovative synthetic toolbox for the development of thermally activated delayed fluorescence (TADF) materials used in organic light emitting diodes (OLEDs). DMAC-PDO, incorporating a dibenzolactam as the acceptor unit, serves as an efficient blue TADF emitter with a maximum external quantum efficiency (EQEmax) of 23.4 %.

Structurally Nontraditional Benzo[c]cinnoline-Based Electron-Transporting Materials with 3D Molecular Interaction Architecture

The academically widely used electron-transporting materials (ETMs) typically suffer from low glass transition temperatures (T_g ) that could lead to poor device stability. Considering practical applications, we herein put forward a "3D molecular interaction architecture" strategy to design high-performance ETMs. As a proof-of-concept, a type of structurally nontraditional ETMs with the benzo[c]cinnoline (BZC) skeleton have been proposed and synthesized by the C-H/C-H homo-coupling of N-acylaniline as the key step. 2,9-diphenylbenzo[c]cinnoline (DPBZC) exhibits strong intermolecular interactions that feature a 3D architecture, which boosts T_g to exceedingly high 218 °C with a fast electron mobility (μ_e ) of 6.4×10^-4  cm²  V^-1  s^-1 . DPBZC-based fluorescent organic light-emitting diodes show outstanding electroluminescent performances with an external quantum efficiency of 20.1 % and a power efficiency as high as 70.6 lm W^-1 , which are superior to those of the devices with the commonly used ETMs.

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.